ci(release): scope cargo apk build to --lib to avoid post-sign panic

cargo-apk panics with "Bin is not compatible with Cdylib" after
successfully signing the APK, when cargo-subcommand's artifact
iterator walks the bin target after the cdylib has been produced.
The APK file survives the panic on disk, but the non-zero exit
fails the workflow step before the upload runs.

Passing --lib scopes the build to the cdylib target only.
SESSION_HANDOFF.md documented this as the canonical workaround.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - name: Install Rust stable
         uses: dtolnay/rust-toolchain@stable
@@ -33,7 +33,7 @@ jobs:
             libxkbcommon-dev
 
       - name: Cache cargo registry and build artifacts
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           path: |
             ~/.cargo/registry
@@ -59,7 +59,7 @@ jobs:
     needs: test
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - name: Install Rust stable
         uses: dtolnay/rust-toolchain@stable
@@ -74,7 +74,7 @@ jobs:
             libxkbcommon-dev
 
       - name: Cache cargo registry and build artifacts
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           path: |
             ~/.cargo/registry

.github/workflows/release.yml

@@ -0,0 +1,174 @@
+name: Release
+
+# Triggered by pushing a version tag, e.g. `git tag v0.22.0 && git push origin v0.22.0`.
+# Builds a Linux x86_64 tarball and a signed Android APK, then publishes
+# both as assets on a GitHub Release. Obtainium can track this repo's
+# releases and download the APK automatically.
+#
+# Required repository secrets (Settings → Secrets and variables → Actions):
+#   ANDROID_KEYSTORE_BASE64      base64-encoded .jks file (see README for gen command)
+#   ANDROID_KEYSTORE_PASSWORD    password used with -storepass when creating the keystore
+#   ANDROID_KEY_ALIAS            alias used with -alias when creating the keystore
+#   ANDROID_KEY_PASSWORD         password used with -keypass when creating the keystore
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+permissions:
+  contents: write   # gh release create needs write access
+
+env:
+  CARGO_TERM_COLOR: always
+  RUSTFLAGS: "-D warnings"
+
+# ---------------------------------------------------------------------------
+# Job 1: Linux x86_64 binary + assets tarball
+# ---------------------------------------------------------------------------
+jobs:
+  build-linux:
+    name: Build · Linux x86_64
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v5
+
+      - name: Install Rust stable
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Install system deps
+        run: |
+          sudo apt-get update -qq
+          sudo apt-get install -y --no-install-recommends \
+            libasound2-dev libudev-dev libwayland-dev libxkbcommon-dev
+
+      - name: Cache cargo registry + build artifacts
+        uses: actions/cache@v5
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: linux-release-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: linux-release-
+
+      - name: Build release binary
+        run: cargo build --release -p solitaire_app
+
+      - name: Package tarball
+        run: |
+          mkdir solitaire-quest
+          cp target/release/solitaire_app solitaire-quest/
+          cp -r assets solitaire-quest/
+          tar -czf solitaire-quest-linux-x86_64.tar.gz solitaire-quest
+
+      - uses: actions/upload-artifact@v5
+        with:
+          name: linux
+          path: solitaire-quest-linux-x86_64.tar.gz
+
+# ---------------------------------------------------------------------------
+# Job 2: Android APK (multi-arch) — release-built and signed via cargo-apk
+# ---------------------------------------------------------------------------
+  build-android:
+    name: Build · Android APK
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v5
+
+      - name: Install Rust stable + Android targets
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          targets: aarch64-linux-android,armv7-linux-androideabi,x86_64-linux-android
+
+      - name: Expose NDK root to cargo-apk
+        # ANDROID_NDK_LATEST_HOME is set by the GitHub-hosted runner.
+        # cargo-apk reads ANDROID_NDK_ROOT; write it to GITHUB_ENV so
+        # all subsequent steps in this job inherit it.
+        run: echo "ANDROID_NDK_ROOT=$ANDROID_NDK_LATEST_HOME" >> $GITHUB_ENV
+
+      - name: Cache cargo registry + cargo-apk binary + build artifacts
+        uses: actions/cache@v5
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            ~/.cargo/bin
+            target
+          key: android-release-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: android-release-
+
+      - name: Install cargo-apk
+        # --locked: use the dependency versions cargo-apk was tested with.
+        # cargo install is a no-op when the cached binary is already current.
+        run: cargo install --locked cargo-apk
+
+      - name: Inject release signing config
+        # cargo-apk --release requires [package.metadata.android.signing.release]
+        # in solitaire_app/Cargo.toml. Appended at CI time so secrets never
+        # live in the repo. printf keeps every line inside the YAML run block,
+        # avoiding the YAML parse error a heredoc with column-0 content causes.
+        env:
+          ANDROID_KEYSTORE_BASE64: ${{ secrets.ANDROID_KEYSTORE_BASE64 }}
+          ANDROID_KEYSTORE_PASSWORD: ${{ secrets.ANDROID_KEYSTORE_PASSWORD }}
+          ANDROID_KEY_ALIAS: ${{ secrets.ANDROID_KEY_ALIAS }}
+          ANDROID_KEY_PASSWORD: ${{ secrets.ANDROID_KEY_PASSWORD }}
+        run: |
+          echo "$ANDROID_KEYSTORE_BASE64" | base64 -d > release.keystore
+          {
+            printf '\n[package.metadata.android.signing.release]\n'
+            printf 'path = "%s"\n'             "${GITHUB_WORKSPACE}/release.keystore"
+            printf 'keystore_password = "%s"\n' "$ANDROID_KEYSTORE_PASSWORD"
+            printf 'key_alias = "%s"\n'        "$ANDROID_KEY_ALIAS"
+            printf 'key_password = "%s"\n'     "$ANDROID_KEY_PASSWORD"
+          } >> solitaire_app/Cargo.toml
+
+      - name: Build and sign APK (release profile)
+        # `--lib` scopes cargo-apk to the cdylib target only.
+        # Without it, cargo-apk panics post-sign with
+        # "Bin is not compatible with Cdylib" (cargo-subcommand
+        # artifact iteration walks the bin target after the
+        # cdylib APK is already produced). See SESSION_HANDOFF.md
+        # "Cosmetic cargo apk build --lib workaround."
+        run: cargo apk build -p solitaire_app --lib --release
+
+      - name: Stage APK for upload
+        run: |
+          cp target/release/apk/solitaire-quest.apk \
+             "solitaire-quest-${{ github.ref_name }}.apk"
+          rm release.keystore
+
+      - uses: actions/upload-artifact@v5
+        with:
+          name: android
+          path: solitaire-quest-${{ github.ref_name }}.apk
+
+# ---------------------------------------------------------------------------
+# Job 3: Create the GitHub Release once both builds succeed
+# ---------------------------------------------------------------------------
+  release:
+    name: Publish GitHub Release
+    runs-on: ubuntu-latest
+    needs: [build-linux, build-android]
+
+    steps:
+      - uses: actions/download-artifact@v5
+        with:
+          name: linux
+
+      - uses: actions/download-artifact@v5
+        with:
+          name: android
+
+      - name: Create GitHub Release
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          gh release create "${{ github.ref_name }}" \
+            --repo "${{ github.repository }}" \
+            --title "Solitaire Quest ${{ github.ref_name }}" \
+            --generate-notes \
+            "solitaire-quest-linux-x86_64.tar.gz" \
+            "solitaire-quest-${{ github.ref_name }}.apk"

.gitignore

@@ -7,3 +7,6 @@
 *.tmp
 data/
 .claude/
+
+# IDE project files
+.idea/

CHANGELOG.md

@@ -6,8 +6,688 @@ project follows [Semantic Versioning](https://semver.org/).
 
 ## [Unreleased]
 
-No threads in flight. v0.21.2 cut on 2026-05-08; CHANGELOG accumulates
+## [0.22.0] — 2026-05-08
-the next cycle here.
+
+Adds difficulty-tier game selection, Android JNI bridges for keystore and
+clipboard, Play-by-Seed dialog, and double-tap auto-move on touch screens.
+Also closes the Prev/Next replay-selector spawn-site item carried since v0.19.0.
+
+### Added
+
+- **Difficulty-tier game mode** (this release).
+  `DifficultyLevel` enum (`Easy / Medium / Hard / Expert / Grandmaster /
+  Random`) added to `solitaire_core::game_state` alongside a new
+  `GameMode::Difficulty(DifficultyLevel)` variant. Five pre-verified seed
+  catalogs (40 seeds each, 200 total) are generated by the new
+  `gen_difficulty_seeds` binary in `solitaire_assetgen`; each catalog
+  contains seeds proven winnable at progressively larger solver budgets
+  (1 K → 200 K moves). `DifficultyPlugin` resolves `StartDifficultyRequestEvent`
+  → catalog seed → `NewGameRequestEvent`; the `Random` tier uses a
+  system-time seed and intentionally bypasses the winnable-only filter.
+  The home overlay gains an expandable `▶ Difficulty` section between the
+  Draw Mode row and the mode-card grid; the last-played tier is persisted
+  in `Settings::last_difficulty` and pre-expands/highlights on re-open.
+  Difficulty wins pool into Classic stats (no separate buckets).
+- **Prev/Next replay selector in the Stats overlay** (`a449f60`).
+  `ReplayPrevButton`, `ReplayNextButton`, `ReplaySelectorCaption`, and
+  `ReplaySelectorDetail` nodes now spawn inside `spawn_stats_screen`
+  as a flex row of two bordered chips flanking a `"Replay N / M"`
+  caption, with a detail line below showing the selected replay's
+  duration + date and an optional `"· Shareable"` badge. Both chips
+  carry `ModalButton(Secondary)` so the existing `repaint_modal_buttons`
+  paint loop gives them hover/press feedback at zero extra cost.
+  `repaint_replay_selector_detail` is wired into the existing
+  `.chain()` alongside `handle_replay_selector_buttons` and
+  `repaint_replay_selector_caption`. The click handler and repaint
+  systems have been registered (and dormant) since v0.19.0; this
+  commit is purely the missing spawn site.
+- **6 new selector unit tests** (`a449f60`). Covers: spawn-site
+  presence (Prev, Next, Caption, Detail all spawn with the screen),
+  caption initial text ("Replay 1 / 1"), detail initial text
+  ("{dur} win on {date}"), Shareable badge when `share_url` is set,
+  empty-history "No replays" caption, and ordinal wrapping.
+  `make_test_replay(time_seconds, share_url)` helper encapsulates
+  `Replay::new(...)` + `chrono::NaiveDate`.
+
+### Fixed
+
+- **`const { assert!() }` for dim-layer z-order test** (`a449f60`).
+  Converted `assert!(Z_REPLAY_DIM < Z_REPLAY_OVERLAY, …)` in
+  `replay_overlay` tests to `const { assert!(…) }` to satisfy
+  `clippy::assertions_on_constants` (constant-fold at compile time
+  rather than a runtime no-op).
+
+### Added (post-cut, same pending release)
+
+- **Double-tap auto-move on touch screens** (`395a322`).
+  `handle_double_tap` fires `MoveRequestEvent` (single card to
+  foundation/tableau, or a whole face-up stack via
+  `best_tableau_destination_for_stack`) when two `TouchPhase::Ended`
+  events on the same card arrive within `DOUBLE_TAP_WINDOW` (0.5 s,
+  slightly wider than the mouse `DOUBLE_CLICK_WINDOW` to account for
+  touch latency). If no legal destination exists, fires
+  `MoveRejectedEvent` (audio + visual rejection feedback).  The system
+  is inserted into the touch drag chain immediately before
+  `touch_end_drag` so `DragState.active_touch_id` and `committed` are
+  still readable; the tap timestamp is tracked in a `Local<HashMap<u32,
+  f32>>` keyed by card ID.
+- **Play-by-Seed dialog** (`0cb1587`).
+  `PlayBySeedPlugin` adds a numeric-input modal that accepts a decimal
+  seed, runs a solver preview in the background (debounced 500 ms via
+  `AsyncComputeTaskPool`), and shows a win/no-win verdict before
+  dealing.  A new `HomeMode::PlayBySeed` card in the home overlay fires
+  `StartPlayBySeedRequestEvent`; the handler in `PlayBySeedPlugin`
+  spawns the dialog.  Digit, Backspace, Enter (confirm), and Escape
+  (cancel) are handled via `ButtonInput<KeyCode>`.  Five unit tests
+  cover spawn, digit append, buffer read, confirm, and cancel paths.
+- **75 new challenge seeds** (`2062bd0`).
+  New `gen_seeds` binary in `solitaire_assetgen` brute-searches seeds
+  in the `0xCAFEBABE…` namespace and filters for hands solvable in
+  ≤250 moves via the core solver.  The 75 confirmed-win seeds are
+  appended to `CHALLENGE_SEEDS` in `solitaire_data::challenge`.
+
+### Fixed (post-cut, same pending release)
+
+- **Gate `handle_fullscreen` to non-Android** (`45436d0`).
+  F11 fullscreen toggle makes no sense on Android (the OS owns window
+  sizing); the fn and its `MonitorSelection`/`WindowMode` imports are
+  now `#[cfg(not(target_os = "android"))]`-gated.  The `add_systems`
+  call is extracted as a separate statement so `#[cfg]` can annotate it
+  (attributes cannot appear mid-chain in Rust).
+- **Android APK launch: export `android_main`** (`202a64d`).
+  `NativeActivity` dlopen-s `libsolitaire_app.so` and calls
+  `android_main` as its entry point. Without the symbol the app
+  crashed immediately with `UnsatisfiedLinkError`. The new function
+  sets `bevy::android::ANDROID_APP` (required by `WinitPlugin`) then
+  delegates to `run()` — equivalent to what `#[bevy_main]` would
+  generate, but usable on an arbitrary entry point name.
+- **Android APK launch: gate `resize_constraints` to non-Android**
+  (`202a64d`). On Android `max_width/max_height` default to `0.0`;
+  Bevy's clamp panicked with `min=800 > max=0`.
+- **Android APK launch: gate `apply_smart_default_window_size` to
+  non-Android** (`202a64d`). The system calls `.clamp(800.0,
+  logical_w)` which panics when the emulator reports zero window
+  dimensions during early Android lifecycle events. The OS controls
+  window size on Android; the system is irrelevant there.
+- **Ignore `.idea/` IDE project files** (`16242e6`). Android Studio
+  created `.idea/` when the project was opened during APK
+  verification; added to `.gitignore` and removed the accidentally-
+  committed files.
+
+### Android verification result
+
+APK boots on `x86_64-linux-android` in a Pixel_7 AVD (Android 14 /
+API 34, SwiftShader Vulkan). App runs for 2+ minutes without crashing.
+Bevy renderer initialises, splash screen loads. This is the first
+confirmed end-to-end device run.
+
+### Stats
+
+- Tests: **1300+ passing** / 0 failing
+- Clippy: clean
+- Crates touched: `solitaire_core` (game_state), `solitaire_data`
+  (settings, stats, difficulty_seeds, challenge), `solitaire_engine`
+  (events, difficulty_plugin, home_plugin, hud_plugin, win_summary_plugin,
+  input_plugin, play_by_seed_plugin, lib), `solitaire_app` (lib.rs),
+  `solitaire_assetgen` (gen_difficulty_seeds + gen_seeds binaries)
+
+## [0.21.8] — 2026-05-08
+
+Patch release for replay-overlay polish. Through-line:
+**notch-label centering + WIN MOVE HC legibility + HC system extension**.
+All three items were "optional polish" flagged in the v0.21.7 handoff;
+all three ship in two commits.
+
+### Added
+
+- **`STATE_SUCCESS_HC` constant** (`c50eaf8`). Brighter lime
+  (`#c8e862`, L≈0.73) in `ui_theme` for use wherever the
+  standard `STATE_SUCCESS` (`#acc267`, L≈0.51) needs extra
+  luminance under HC mode. Sits above the bumped notch ticks
+  (`BORDER_SUBTLE_HC` gray, L≈0.60) so a WIN MOVE marker at
+  this colour is unambiguous.
+- **`HighContrastBackground::with_hc(default, hc)` constructor**
+  (`c50eaf8`). Extends `HighContrastBackground` with an
+  `hc_color: Color` field (default = `BORDER_SUBTLE_HC` via
+  `with_default()`). `update_high_contrast_backgrounds` now
+  reads `marker.hc_color` instead of the hardcoded constant —
+  backwards-compatible; all existing `with_default()` usages
+  continue to bump to gray.
+- **WIN MOVE scrub-bar marker HC bump** (`c50eaf8`). Marker
+  now carries `HighContrastBackground::with_hc(STATE_SUCCESS,
+  STATE_SUCCESS_HC)` so the lime stays lime under HC (brighter
+  lime rather than gray). Pin test locks both the default and
+  HC colour fields on the spawned entity.
+
+### Fixed
+
+- **Scrub-bar notch-label centering** (`b44d277`). Middle
+  three labels ("25%", "50%", "75%") previously had their
+  left edge at the notch; now their text centre coincides
+  with the notch tick. Implemented using the CSS
+  `translateX(-50%)` pattern for Bevy 0.18 UI: a fixed
+  `SCRUB_LABEL_CENTER_WIDTH = 36 px` container with
+  `margin.left = -18 px` is placed at `left: Percent(pct)`,
+  and `Justify::Center` centres the text within it. Endpoint
+  labels ("0%", "100%") keep their flush-left / flush-right
+  anchoring. `with_default()` remains one-argument.
+
+### Stats
+
+- Tests: 1276 passing / 0 failing (engine: 831)
+- Clippy: clean
+- Crates touched: `solitaire_engine` (replay_overlay.rs,
+  ui_theme.rs, settings_plugin.rs)
+
+## [0.21.7] — 2026-05-08
+
+Patch release closing the last major B-2 sub-piece. Through-line:
+**mini-tableau preview dim layer**. The mockup's "Game Peek Band at
+50 % opacity" is now implemented as a full-screen UI scrim that darkens
+the card world during replay so the chrome (banner + move-log panel)
+reads clearly against the scene.
+
+### Added
+
+- **Full-screen tableau dim layer** (`da3e542`). Spawns a
+  `ReplayTableauDimLayer` UI node (100 % × 100 %, 50 % opacity
+  black) at `Z_REPLAY_DIM = Z_REPLAY_OVERLAY − 1 = 54` whenever
+  a replay starts; despawned alongside the banner and move-log
+  panel when the replay ends. Bevy's UI/world compositor means
+  no changes to `card_plugin` are needed — UI nodes always
+  render above world-space sprites regardless of `Transform.z`.
+  The dim layer carries no `Interaction` component (purely
+  visual; pointer events pass through). Adds `Z_REPLAY_DIM`
+  and `TABLEAU_DIM_ALPHA` constants plus two new tests:
+  lifecycle (spawn/despawn mirrors the floating-chip pattern)
+  and z-ordering invariant (`Z_REPLAY_DIM < Z_REPLAY_OVERLAY`
+  pinned). 1275 tests pass / 0 failing.
+
+### Stats
+
+- Tests: 1275 passing / 0 failing
+- Clippy: clean
+- Crates touched: `solitaire_engine` (replay_overlay.rs)
+
+## [0.21.6] — 2026-05-08
+
+Patch release for the post-v0.21.5 work. Through-line:
+**Move Log panel + scrub-UX polish**. v0.21.5 closed out the
+keyboard-accelerator surface (Space / Esc / ← / →) and the
+keybind footer; v0.21.6 builds on that with two parallel
+threads — accessibility + scrub-on-hold polish for the v0.21.5
+surfaces, plus a brand-new Move Log panel anchored to the
+viewport's bottom edge that gives players a 5-row recent-and-
+upcoming move history alongside the existing top-edge banner.
+
+The Move Log panel is the first replay-overlay surface that
+*isn't* attached to the banner — it lives at a separate screen
+anchor (bottom: 0) with its own spawn/despawn lifecycle.
+Establishes the pattern for "multi-anchor replay UI" that the
+remaining B-2 sub-piece (mini-tableau preview) will inherit.
+
+### Added
+
+- **HC-mode coverage for the scrub track + quarter-mark notch
+  ticks** (`d3cb1a5`). Adds parallel primitive
+  `HighContrastBackground` to `ui_theme` and a paint system
+  `update_high_contrast_backgrounds` in `settings_plugin` that
+  mirrors the existing border-marker pattern but targets
+  `BackgroundColor` instead of `BorderColor`. Tags the 1 px
+  scrub track Node and all five quarter-mark notch ticks so
+  they bump from `BORDER_SUBTLE` (`#505050`) →
+  `BORDER_SUBTLE_HC` (`#a0a0a0`) under HC mode. Scrub fill
+  (`ACCENT_PRIMARY`) and WIN MOVE marker (`STATE_SUCCESS`)
+  don't get the marker — accent and state colours are already
+  saturated and don't need an HC luminance variant.
+- **Continuous scrub on key-held arrow keys** (`2e25476`).
+  Holding ← or → triggers continuous step at 100 ms cadence
+  (10 steps/sec) — matches the mockup's `[← →] scrub`
+  terminology while keeping single-press = single-step
+  semantics. Per-key accumulators in a new
+  `ReplayScrubKeyHold` resource; `just_pressed` events bypass
+  the accumulator and fire immediately. Release resets to 0
+  so the next fresh press fires immediately rather than at
+  half-interval.
+- **Move Log panel** (`d6f32d3` + `140251b` + `e7345ae` +
+  `4437a1a`). New bottom-edge UI panel showing a 5-row window
+  onto recent + upcoming moves: 2 prev rows above the active
+  row + active row highlighted in `ACCENT_PRIMARY` + 2 next
+  rows below. Header reads `▌ MOVE LOG · N/M` (or
+  `▌ MOVE LOG · COMPLETE` when finished). Active row carries
+  a `▶` focus prefix and `TEXT_PRIMARY_HC` text colour for
+  legible contrast against the brick-red highlight. Prev /
+  next rows render in `TEXT_SECONDARY` so the active row
+  stays the focal point.
+  - Sibling-of-banner pattern (separate root entity anchored
+    at viewport bottom, not a banner child) — same
+    spawn/despawn lifecycle as `ReplayFloatingProgressChip`,
+    different screen anchor.
+  - Five pure helpers handle the formatting:
+    `format_pile`, `format_move_body`,
+    `format_move_log_header`, `format_kth_recent_row` (active
+    + prev), `format_kth_next_row` (next). 1-indexed display
+    numbers throughout (`Foundation(2)` reads as "foundation
+    3" rather than the enum's 0-index).
+  - Panel grows from 56 → 84 → 112 px across the four
+    move-log commits. `MOVE_LOG_PREV_ROWS` and
+    `MOVE_LOG_NEXT_ROWS` constants (both = 2) parameterise
+    the row count; `format_kth_recent_row` and
+    `format_kth_next_row` return empty for out-of-range k so
+    panels gracefully under-fill at the start (cursor=1) and
+    end (cursor=N-1) of a replay.
+  - HC marker on the panel's top border so the 1 px edge
+    bumps under HC mode (same pattern as the keybind footer).
+
+### Changed
+
+- **`react_to_state_change` despawns the Move Log panel** on
+  `Playing → Inactive` alongside the banner root and floating
+  progress chip. Third query in the same defer-and-despawn
+  cycle.
+- **Move Log panel height grew 56 → 84 → 112 px** across the
+  prev-rows and next-rows commits. The panel is sized to fit
+  the chosen row count + header + padding; tunable via the
+  `MOVE_LOG_PANEL_HEIGHT` const.
+- **`format_active_move_row` now prefixes the `▶` focus
+  marker** (`e7345ae`). Wraps `format_kth_recent_row(state, 1)`
+  and prepends the prefix when the body is non-empty. Empty
+  case still returns empty — cursor=0 doesn't paint a stray
+  `▶` on an otherwise-empty row.
+
+### Documentation
+
+- `SESSION_HANDOFF.md` refreshed twice this cycle — once
+  recording the HC paint + continuous-scrub polish, then
+  again as the Move Log arc shipped commit-by-commit. The
+  Resume menu's B option now traces the full arc:
+  notches → labels → footer → ESC → HC → arrow keys →
+  HC paint → continuous scrub → move log.
+
+### Stats
+
+- **1273 passing tests / 0 failing** across the workspace
+  (net +23 from v0.21.5's 1250 baseline):
+  - 2 from `d3cb1a5` (HC marker on track + notches).
+  - 2 from `2e25476` (continuous-scrub repeat-while-held +
+    release-resets-accumulator).
+  - 8 from `d6f32d3` (move-log panel init + 5 helpers + 3
+    spawn / lifecycle scenarios).
+  - 4 from `140251b` (prev rows: helper k coverage + spawn
+    cardinality + spawn texts + repaint on cursor advance).
+  - 3 from `e7345ae` (active row highlight: wrapper bg +
+    text colour + focus prefix + cursor=0 stays empty).
+  - 4 from `4437a1a` (next rows: helper k coverage + spawn
+    cardinality + spawn texts + under-fill at replay end).
+- Clippy clean across the workspace.
+
+## [0.21.5] — 2026-05-08
+
+Patch release for the post-v0.21.4 work. One through-line:
+**replay-overlay scrubbing affordances + accessibility**. v0.21.4
+shipped pause / resume / step + the WIN MOVE marker as the first
+*scrubbing-shaped* additions to the replay overlay; v0.21.5
+fills out the rest of the scrubbing UX so the player has both
+visual anchor points (notches + labels) and a complete keyboard
+control surface (Space / Esc / ← / →) for navigating a paused
+replay.
+
+Two of the six commits in this cycle are layout-changing — they
+grow the banner height from 60 px → 76 px → 92 px to make room
+for the notch labels and keybind footer. Banner geometry was
+fixed for every prior B-2 commit; this release establishes the
+"grow the container, add a flex-column child" pattern that the
+remaining B-2 sub-pieces (move-log scroller, mini-tableau
+preview) will inherit when they land.
+
+### Added
+
+- **Quarter-mark scrub-bar notches** (`fe68861`). Five 1 px
+  vertical ticks at 0 / 25 / 50 / 75 / 100 % give the player
+  visual anchor points without needing to mentally bisect the
+  bar. Pure helper `scrub_notch_positions()` returns the fixed
+  array; spawn loop sits next to the WIN MOVE marker spawn so
+  the lifecycles match. Notches paint in `BORDER_SUBTLE` (same
+  as the unfilled track) and rely on extending past the 1 px
+  track (5 px tall, anchored 2 px above the track top) for
+  visibility — same trick the WIN MOVE marker uses. Spawned
+  *after* the WIN MOVE marker so a notch and the marker
+  landing on the same percentage paint the marker on top.
+- **Percentage labels under each notch** (`d322abf`). Five
+  `0%` / `25%` / `50%` / `75%` / `100%` labels in a new 16 px
+  row beneath the 1 px scrub track give the player explicit
+  quarter-mark readouts. Banner grew from 60 → 76 px to
+  accommodate the row — first **layout-changing** commit in
+  the B-2 arc. Pure helper `scrub_notch_labels()` returns the
+  fixed array, paired index-for-index with
+  `scrub_notch_positions()`. Spawn loop applies an "endpoints
+  flush, middle three percent-anchored" positioning pattern:
+  leftmost label gets `left: 0`, rightmost gets `right: 0`,
+  middle three anchor at `left: Val::Percent(p)` since Bevy
+  0.18 UI lacks a clean CSS-style `translate-x: -50%`
+  centering primitive. Label colour is `TEXT_SECONDARY`
+  rather than the mockup's `BORDER_SUBTLE` (the latter would
+  match the notches but is too low-contrast against
+  `BG_ELEVATED_HI` to read at 12 px).
+- **Keybind-hint footer** (`1873b3f`). Vim-style mode line on
+  the left (`▌ NORMAL │ replay`) plus a keybind hint on the
+  right at the bottom edge of the banner. Banner grew from
+  76 → 92 px to fit the 16 px footer row. Surfaces every
+  wired keyboard accelerator visually so CLAUDE.md §3.3's
+  UI-first contract holds for keyboard accelerators too. The
+  footer lists *only* keybinds that are actually wired —
+  the only-wired-keybinds discipline means each release
+  cycle's hint string is a precise honest contract with the
+  player. Two pure helpers (`keybind_footer_mode_text`,
+  `keybind_footer_hint_text`) keep the static text testable.
+  1 px top border in `BORDER_SUBTLE` separates the footer
+  from the labels row.
+- **ESC keyboard accelerator for replay-stop** (`90e24d9`).
+  New `handle_stop_keyboard` system parallels
+  `handle_pause_keyboard` in shape — fires only when state
+  is `Playing`, calls `stop_replay_playback`. Cross-plugin
+  coordination via `pause_plugin::toggle_pause`: added a
+  fourth defer-if check
+  (`replay_state.is_some_and(|s| s.is_playing())`) right
+  after the existing `other_modal_scrims` check so ESC
+  during active replay belongs to the replay overlay, not
+  the pause modal.
+- **HC-mode coverage for the keybind-footer top border**
+  (`23902cd`).
+  `HighContrastBorder::with_default(BORDER_SUBTLE)` marker
+  on the footer's border-carrying Node so the existing
+  `apply_high_contrast_borders` system bumps the 1 px top
+  border from `#505050` → `#a0a0a0` when
+  `Settings::high_contrast_mode` is on. Without the marker
+  the footer reads as floating loose under HC because the
+  border that anchors it to the labels row is
+  near-invisible.
+- **← / → keyboard accelerators for paused stepping**
+  (`e5c4f51`). New `step_backwards_replay_playback` in
+  `replay_playback.rs` decrements the cursor and dispatches
+  `UndoRequestEvent`; the game's `handle_undo` reads it
+  next frame to reverse its most-recent move. Hooks the
+  existing undo system rather than replaying-forward-from-
+  zero — every replay-applied move pushes to the undo stack
+  the same way a player move would, so undo is the right
+  reversal primitive. Both arrow keys are paused-only via
+  the same destructure-gate pattern the forward step uses.
+  The mockup labels these `[← →] scrub`; single-move step
+  is the closest behaviour shippable today, so the footer
+  hint reads `[← →] step` — only-wired-keybinds discipline.
+
+### Changed
+
+- **Banner height grew 60 → 76 → 92 px** across two
+  layout-changing commits (`d322abf` then `1873b3f`). Top
+  row's `flex_grow: 1.0` still consumes 59 px so the
+  existing content (label / progress chip / buttons) has
+  the same vertical space; the new rows (16 px labels +
+  16 px footer) extend the banner downward into the
+  gameplay area. Banner geometry is now mutable — every
+  prior B-2 commit fit inside fixed 60 px space.
+- **Keybind-footer hint text grew alongside the wirings**:
+  `[SPACE] pause/resume` →
+  `[SPACE] pause/resume · [ESC] stop` →
+  `[SPACE] pause/resume · [ESC] stop · [← →] step`.
+- **`pause_plugin::toggle_pause` now defers when a replay
+  is active** (`90e24d9`). Adds a fourth defer-if check to
+  the existing modal-stack pattern.
+- **`ReplayOverlayPlugin` registers
+  `add_message::<UndoRequestEvent>()`** (`e5c4f51`).
+  Defensive registration so the plugin runs cleanly under
+  `MinimalPlugins` without `GamePlugin` attached.
+
+### Documentation
+
+- `SESSION_HANDOFF.md` refreshed five times this cycle.
+  The B option in the Resume menu now traces the full arc:
+  notches → labels → footer → ESC → HC → arrow keys.
+- The pre-existing `daily_challenge` warning test that
+  fails when wall-clock UTC is within 30 minutes of
+  midnight is documented in this cycle's handoff. Same
+  shape as the earlier `winnable_seed_search` flake —
+  time-dependent, deterministically passes outside the
+  trigger window.
+
+### Stats
+
+- **1250 total tests / 1249 passing / 1 pre-existing
+  time-dependent flake** across the workspace (net +22 from
+  v0.21.4's 1228 baseline):
+  - 4 from `fe68861` (scrub-notch coverage)
+  - 4 from `d322abf` (notch-label coverage)
+  - 4 from `1873b3f` (keybind-footer coverage)
+  - 3 from `90e24d9` (ESC-accelerator coverage)
+  - 1 from `23902cd` (HC-marker coverage)
+  - 6 from `e5c4f51` (arrow-keyboard coverage)
+- **Pre-existing flake**:
+  `daily_challenge_plugin::tests::check_system_fires_warning_event_only_once_per_day`
+  fails when wall-clock UTC is within 30 minutes of
+  midnight. Verified pre-existing by stash-and-retest
+  before each commit. Will pass deterministically outside
+  the trigger window. Not introduced by this release.
+- Clippy clean across the workspace.
+
+## [0.21.4] — 2026-05-08
+
+Patch release for the post-v0.21.3 work. One through-line:
+**replay-scrubbing accessibility**. The replay overlay used to be
+pure-passive — the player started a replay, watched it execute,
+and waited for it to end. v0.21.4 adds the scaffolding for
+*navigating within* a replay: a WIN MOVE marker on the scrub bar
+so the player can see at a glance where the winning move sits,
+and pause / resume / step controls so they can stop on any move
+and inspect the board.
+
+The work is also the first three commits on the B-2 replay
+screen-takeover redesign arc. The remaining pieces (screen-
+takeover layout, move-log scroller, mini-tableau preview) are
+deferred to a future cycle because they need a layout reflow
+that the existing banner-only overlay can't carry.
+
+### Added
+
+- **`Replay::win_move_index: Option<usize>` data field**
+  (`ab857bb`). Additive optional field on the persisted
+  `Replay` shape. `#[serde(default)]` keeps older
+  `latest_replay.json` / `replays.json` files loadable without
+  bumping `REPLAY_SCHEMA_VERSION` — this is purely additive.
+  Populated at the live recording site
+  (`game_plugin::handle_game_won`) via a new builder-style
+  setter `Replay::with_win_move_index`. For fresh recordings
+  the value is always `Some(moves.len() - 1)` because recording
+  freezes on win, but storing it explicitly lets the playback
+  UI read the WIN MOVE position directly without re-deriving
+  on every render.
+- **WIN MOVE scrub-bar marker** (`52befa6`). New
+  `ReplayOverlayWinMoveMarker` component spawned as a sibling
+  to `ReplayOverlayScrubFill` under the 1px scrub track,
+  absolute-positioned at `replay.win_move_index / total %` of
+  the bar. Painted in `STATE_SUCCESS` (green) so the marker
+  reads as "this is where the win lives." Pure helper
+  `win_move_marker_pct` returns `None` for any state where the
+  marker shouldn't draw (Inactive, Completed, replay missing
+  the field, empty move list); percentage clamps to `[0, 100]`
+  defensively. Spawn-time only — the position never changes
+  during a single playback because the underlying `Replay` is
+  immutable while `Playing`.
+- **Pause / Resume / Step playback controls** (`fbe48ac`). New
+  `paused: bool` field on `ReplayPlaybackState::Playing`.
+  `tick_replay_playback` skips the `secs_to_next` decrement
+  entirely while paused so cursor and timer freeze together;
+  resuming starts the next move from a full interval. New
+  public API: `toggle_pause_replay_playback` and
+  `step_replay_playback` (the latter hard-gated to `Playing {
+  paused: true }` via the destructure pattern itself, so
+  manual stepping can't race the tick loop). On-screen Pause
+  and Step buttons sit alongside the existing Stop button;
+  `Space` keyboard accelerator toggles pause / resume.
+- **`Replay::with_win_move_index` builder** (`ab857bb`).
+  Chainable setter so the recording site can write
+  `Replay::new(...).with_win_move_index(idx)`. Keeps
+  `Replay::new`'s signature stable across the 13+ existing
+  test-fixture call sites that don't care about the field.
+
+### Changed
+
+- **`Replay::new` writes `win_move_index: None`** (`ab857bb`).
+  Existing canonical constructor stays signature-compatible
+  with all existing callers. The field is opt-in via the
+  builder.
+- **`game_plugin::handle_game_won` populates the new field**
+  (`ab857bb`). The recording site computes
+  `recording.moves.len().checked_sub(1)` as the win-move
+  index. `checked_sub` rather than direct subtraction guards
+  the unreachable empty-recording branch (which is also
+  guarded earlier in the function).
+- **`tick_replay_playback` honors the new `paused` flag**
+  (`fbe48ac`). Skipping the timer decrement is the only
+  behavior change; the loop body and Completed-detection are
+  unchanged. Stepping fires moves directly via
+  `step_replay_playback`, bypassing the tick path entirely.
+- **Pause / Resume button label is reactive** (`fbe48ac`).
+  `update_pause_button_label` walks `Children` from the
+  marked button to its inner `Text` and repaints the label
+  whenever `ReplayPlaybackState` changes. Pure helper
+  `pause_button_label` covers all four state arms (running,
+  paused, inactive, completed).
+- **25 existing `Playing { ... }` construction sites gained
+  `paused: false`** (`fbe48ac`). Mechanical edit across
+  `replay_overlay`, `achievement_plugin`, and
+  `replay_playback` tests to satisfy the new field
+  requirement. No behavioral change.
+
+### Documentation
+
+- `SESSION_HANDOFF.md` refreshed three times this cycle —
+  once after each post-cut feature commit. The B-2 entry in
+  the Visual-identity follow-ups list now points at the
+  remaining sub-pieces (screen-takeover layout, move-log
+  scroller, mini-tableau preview) as a single multi-session
+  arc rather than three independent ones, since they share a
+  layout-reflow prerequisite.
+
+### Stats
+
+- **1228 passing tests / 0 failing** across the workspace
+  (net +21 from v0.21.3's 1207 baseline):
+  - 5 from `ab857bb`'s `win_move_index` coverage: default
+    constructor, builder set / set-None, on-disk round-trip,
+    legacy-JSON-loads-with-None backward-compat. The last
+    test pins the no-schema-bump claim — if a future refactor
+    drops the `#[serde(default)]`, that test catches it.
+  - 8 from `52befa6`'s WIN MOVE marker: pure-helper truth
+    table (Inactive / Completed / no-field / correct-position
+    / clamp) + spawn-presence-with-field /
+    spawn-absence-without / despawn-with-overlay observables.
+  - 8 from `fbe48ac`'s playback controls: label truth table,
+    label repaint on state change, click-toggles-paused,
+    step advances cursor by exactly one with paused
+    preserved, step-while-running no-op, Space toggles
+    paused.
+- Zero clippy warnings under `cargo clippy --workspace
+  --all-targets -- -D warnings`.
+- `cargo test --workspace` clean.
+
+## [0.21.3] — 2026-05-08
+
+Patch release for the post-v0.21.2 work. One through-line:
+**accessibility arc closure**. v0.21.2 explicitly carved out
+"dynamic-paint sites" (HUD action buttons, modal buttons, radial
+menu rim) on the assumption that their existing paint cycles would
+race the central `update_high_contrast_borders` system. v0.21.3
+walks the actual code, finds the carve-out was over-cautious, and
+closes it. Bonus: the first real consumer of `ToastVariant::Warning`
+also lands here, making the `ToastVariant` enum fully load-bearing
+(every variant has at least one driver).
+
+### Added
+
+- **`WarningToastEvent(String)` — first `ToastVariant::Warning`
+  consumer** (`279e23d`). Generic carrier message that any system
+  can fire to spawn a 4 s amber-bordered fire-and-forget toast.
+  Mirrors the v0.21.2 `MoveRejectedEvent` → `Error` toast wiring:
+  domain message crosses the plugin boundary, the animation
+  plugin's `handle_warning_toast` system reads it and spawns. Not
+  queued (Warning is alert-shaped, not info-shaped — should never
+  block on a queue).
+- **Daily-challenge-expiry warning** (`279e23d`). First in-engine
+  driver of `WarningToastEvent`. New
+  `daily_challenge_plugin::check_daily_expiry_warning` system
+  fires at most once per `DailyChallengeResource::date` when the
+  player is within 30 min of UTC midnight reset and today's
+  challenge isn't yet complete. Suppression decided by a pure
+  helper (`compute_expiry_warning_minutes`) covering: already-
+  completed-today, already-shown-for-this-date, outside the
+  threshold window, post-midnight rollover. Pure-helper-plus-
+  thin-system shape because `Utc::now()` can't be pinned without
+  injecting a clock resource — overkill for one consumer.
+- **`radial_rim_outline` pure helper** (`c153363`). Decision
+  logic for the radial-menu rim outline colour. Resting outlines
+  always carry `BORDER_SUBTLE`; focused outlines carry
+  `BORDER_STRONG` normally and `BORDER_SUBTLE_HC` under HC. Naive
+  marker substitution would invert the focused-vs-resting
+  hierarchy because `BORDER_SUBTLE_HC` (`#a0a0a0`) is *lighter*
+  than `BORDER_STRONG` (`#505050`); folding the choice in here
+  keeps the focused rim more visible under HC, not less.
+
+### Changed
+
+- **HC marker pattern extended to HUD action buttons + modal
+  buttons** (`c153363`). Re-reading the code revealed both sites'
+  paint systems (`paint_action_buttons`, `paint_modal_buttons`)
+  only mutate `BackgroundColor` — `BorderColor` is set once at
+  spawn and never touched. So the existing
+  `HighContrastBorder::with_default(BORDER_SUBTLE)` marker
+  pattern works cleanly for both, no race. v0.21.2's carve-out
+  comment was based on assumed-but-not-actual race risk; this
+  cycle treats it as the doc-vs-implementation drift pattern in
+  the wild and verifies before trusting.
+- **Radial menu rim folds HC into per-frame respawn**
+  (`c153363`). The rim is the only true dynamic-painter of the
+  three carved-out sites — `radial_redraw_overlay` despawns and
+  respawns all rim sprites every frame the radial is `Active`.
+  The `HighContrastBorder` marker can't apply (entities don't
+  persist across frames) so HC is read directly in the system
+  via `Option<Res<SettingsResource>>` and routed through
+  `radial_rim_outline`. The `Option<Res<...>>` shape preserves
+  test compatibility under `MinimalPlugins`.
+- **Animation plugin registers `WarningToastEvent`** (`279e23d`).
+  Joins `InfoToastEvent`, `MoveRejectedEvent` etc. in
+  `AnimationPlugin::build`. Daily-challenge plugin also
+  registers it (idempotent) so the message exists when running
+  the daily plugin under `MinimalPlugins` without the animation
+  plugin attached.
+
+### Documentation
+
+- `SESSION_HANDOFF.md` refreshed twice this cycle — once after
+  the Toast Warning wiring (menu trimmed 5 → 4 options), and
+  again after the HC dynamic-paint rollout (menu trimmed 4 → 3,
+  with all remaining options now flagged as multi-session). The
+  `High-contrast accessibility mode` entry in the Visual-identity
+  follow-ups list is updated to reflect that no "un-tagged
+  because race-risk" surfaces remain.
+
+### Stats
+
+- **1207 passing tests / 0 failing** across the workspace
+  (net +12 from v0.21.2's 1195 baseline):
+  - 7 tests for `compute_expiry_warning_minutes` (`279e23d`)
+    covering each suppression rule + the inclusive boundary at
+    exactly 30 min remaining.
+  - 1 in-Bevy test (`check_system_fires_warning_event_only_once_per_day`)
+    pinning `DailyExpiryWarningShown`'s once-per-date
+    suppression and the symmetric "already-completed-today"
+    suppression.
+  - 4 truth-table tests for `radial_rim_outline` (`c153363`):
+    focused × HC. The "resting stays subtle under HC" test
+    explicitly documents *why* — it's the hierarchy-preservation
+    invariant a future refactor might be tempted to break.
+- Zero clippy warnings under `cargo clippy --workspace
+  --all-targets -- -D warnings`.
+- `cargo test --workspace` clean.
 
 ## [0.21.2] — 2026-05-08
 

Cargo.lock

@@ -6967,6 +6967,8 @@ version = "0.1.0"
 dependencies = [
  "ab_glyph",
  "png 0.17.16",
+ "solitaire_core",
+ "solitaire_data",
 ]
 
 [[package]]
@@ -6986,6 +6988,7 @@ dependencies = [
  "axum",
  "chrono",
  "dirs",
+ "jni 0.21.1",
  "jsonwebtoken",
  "keyring-core",
  "reqwest",
@@ -7009,6 +7012,7 @@ dependencies = [
  "bevy",
  "chrono",
  "dirs",
+ "jni 0.21.1",
  "kira",
  "resvg",
  "ron",

Cargo.toml

@@ -31,6 +31,7 @@ keyring     = "4"
 keyring-core = "1"
 reqwest     = { version = "0.13", features = ["json", "rustls", "rustls-native-certs"], default-features = false }
 arboard     = { version = "3", default-features = false }
+jni         = { version = "0.21", default-features = false }
 
 solitaire_core   = { path = "solitaire_core" }
 solitaire_sync   = { path = "solitaire_sync" }

SESSION_HANDOFF.md

@@ -1,65 +1,98 @@
 # Solitaire Quest — Session Handoff
 
-**Last updated:** 2026-05-08 — **v0.21.1 cut and tagged at `daa655a`**,
+**Last updated:** 2026-05-08 — **v0.21.8 tagged at `c50eaf8`**;
-working tree clean, all post-tag work pushed to origin.
+nine post-cut commits on master. Push pending.
 
-v0.21.1 is a patch release for the post-v0.21.0 work: closes
+v0.21.8 closes the last optional polish items in the B-2
-Resume-prompt Options A (app icon — runtime `Window::icon` plus
+replay screen-takeover arc: **notch-label centering** (middle
-the 9-size PNG hierarchy) and F (high-contrast + reduce-motion
+three scrub-bar labels now centred on their notch ticks via the
-accessibility modes — Settings flags wired through engine and
+CSS `translateX(-50%)` pattern for Bevy 0.18 UI) and **WIN
-UI). Plus a card-visual iteration cycle that moved through three
+MOVE HC legibility** (lime stays lime under HC mode via the
-states (v0.21.0 Terminal pink/gray → brief 4-colour-deck
+extended `HighContrastBackground::with_hc` constructor and a
-experiment → traditional 2-colour Microsoft-Solitaire-on-dark-mode
+new `STATE_SUCCESS_HC` brighter-lime constant). The replay
-red/near-white) and two visible-bug fixes (suit-coloured border
+overlay arc is now fully closed with no known open items.
-anti-aliasing artifact at rounded corners, pile-marker
-bleed-through producing "gray L" shapes at occupied piles —
-the latter implemented the previously-documented-but-not-enforced
-"markers visible only at empty piles" invariant).
 
-Full v0.21.1 detail lives in `CHANGELOG.md` § [0.21.1]. This
+Full v0.21.8 detail lives in `CHANGELOG.md` § [0.21.8]. This
 file from here on focuses on what's *open* post-cut and how to
 resume.
 
 ## Status at pause
 
-- **HEAD locally:** see `git rev-parse HEAD`. The cut commit is
+- **HEAD locally:** `f281425` (Android Keystore JNI).
-  `daa655a`; any post-cut docs edits ride on top of that.
+  Docs ride on top; push pending.
-- **HEAD on origin:** matches local. v0.21.1 is fully on origin.
+- **HEAD on origin:** `395a322` (double-tap commit — last pushed).
-- **Working tree:** clean. No WIP outstanding.
+- **Working tree:** clean (docs uncommitted). No WIP outstanding.
 - **`artwork/` directory:** still untracked. Intentional.
 - **Build:** `cargo clippy --workspace --all-targets -- -D warnings`
   clean.
-- **Tests:** **1192 passing / 0 failing** across the workspace
+- **Tests:** **1292 passing / 0 failing** across the workspace.
-  (net +8 from v0.21.0's 1184 baseline). Detail in
+- **Tags on origin:** `v0.9.0` through `v0.21.8`.
-  `CHANGELOG.md` § [0.21.1] § Stats.
+- **Android:** APK verified booting on Pixel_7 AVD (Android 14,
-- **Tags on origin:** `v0.9.0` through `v0.21.1`. v0.21.1 is on
+  x86_64). All desktop-only systems (handle_fullscreen) now gated.
-  `daa655a`; v0.21.0 stays on `04f9bf9`; v0.20.0 stays on
+  See Phase Android punch list for remaining work.
-  `41a009a`.
 
-## Since the v0.21.1 cut
+## Since the v0.21.8 cut
 
-No threads in flight. Working tree clean as of 2026-05-08. New
+Seven commits since the v0.21.8 tag:
-work since the cut would land here as commit narratives; for
+- `a449f60` — Stats Prev/Next selector spawn site
-the v0.21.1 contents themselves, see `CHANGELOG.md` § [0.21.1].
+- `202a64d` — Android launch fixes (android_main, resize_constraints,
+  apply_smart_default_window_size) — **closes APK launch verification**
+- `16242e6` — Ignore .idea/ IDE files
+- `395a322` — double-tap auto-move for touch input
+- `0cb1587` — Play-by-Seed dialog + HomeMode card
+- `2062bd0` — 75 new challenge seeds + gen_seeds binary
+- `45436d0` — gate handle_fullscreen to non-Android
+- `2c822ba` — JNI clipboard bridge for Android Stats share-link
+- `f281425` — Android Keystore AES-GCM token storage via JNI
+
+CHANGELOG + SESSION_HANDOFF docs ride on top; push pending.
+
+Open next-step menu:
+1. **Phase 8 (sync)** — the biggest open arc. Local storage
+   scaffolding, self-hosted Axum server, GPGS stub.
+2. **Android follow-ups** — JNI ClipboardManager, Android Keystore,
+   GPGS. Launch verification and double-tap both closed; these
+   are the remaining Phase Android items.
+3. **Move Log auto-scroll** — only relevant if the panel
+   row count grows beyond the current 5-row fixed window.
 
 ## Open punch list
 
 ### Phase Android (build + persistence shipped; runtime gaps remain)
 
-- **APK launch verification on AVD / device.** `adb install` then
+- *APK launch verification — closed 2026-05-08 by `202a64d`.*
-  `adb logcat` against the `bevy_test` AVD or an x86_64 device.
+  Three fixes shipped: `android_main` export (missing NativeActivity
-  The build works and persistence is wired, but no end-to-end
+  entry point), `resize_constraints` gated to non-Android (max=0
-  device run has been logged. Shakes out runtime bugs the build +
+  panic), `apply_smart_default_window_size` gated to non-Android
-  unit tests can't catch.
+  (clamp panic on zero-dimension window event). Verified booting on
-- **JNI ClipboardManager bridge.** Replaces the Android stub for
+  Pixel_7 AVD (Android 14, x86_64, SwiftShader Vulkan), 2+ min
-  the Stats "Copy share link" toast. `arboard` doesn't ship an
+  runtime without crash. B0004 ECS hierarchy warnings remain
-  Android backend; small custom JNI call.
+  (non-fatal; entity parent/child component mismatch); investigate
-- **Android Keystore for credentials.** `keyring` is target-gated
+  if they surface gameplay bugs.
-  to a stub returning `KeychainUnavailable`; replace with Android
+- *Double-tap auto-move — closed 2026-05-08 by `395a322`.*
-  Keystore via JNI when sync auth ships on mobile.
+  `handle_double_tap` fires `MoveRequestEvent` on two rapid
-- **Google Play Games (gpgs) integration.** Listed as a
+  `TouchPhase::Ended` events within 0.5 s. Prefers foundation;
-  Phase-Android target since Phase 1; now unblocked by the build
+  falls back to tableau stack move. Fires `MoveRejectedEvent` when
-  target.
+  no legal destination exists. System runs before `touch_end_drag`
+  in the chain so drag state is readable.
+- *F11 fullscreen gate — closed 2026-05-08 by `45436d0`.*
+  `handle_fullscreen` and its `MonitorSelection`/`WindowMode`
+  imports are `#[cfg(not(target_os = "android"))]`-gated. The
+  `add_systems` call is a separate statement (not mid-chain).
+- *JNI ClipboardManager bridge — closed 2026-05-08 by `2c822ba`.*
+  `android_clipboard::set_text(url)` calls `ClipboardManager` via
+  JNI. Stats share-link button now writes to the clipboard with a
+  "Copied: {url}" toast; falls back to "Share link: {url}" on JNI
+  error. Requires AVD functional test (see verification steps in
+  the approved plan).
+- *Android Keystore for credentials — closed 2026-05-08 by `f281425`.*
+  `android_keystore` module: AES-256/GCM/NoPadding device-bound key,
+  tokens serialised to JSON and stored atomically at
+  `{data_dir}/auth_tokens.bin` as `[12-byte IV][ciphertext+tag]`.
+  `auth_tokens.rs` Android stubs now delegate to it. Key
+  invalidation (biometric reset) → `TokenError::KeychainUnavailable`.
+  Requires AVD functional test before Phase 8 sync goes live on
+  Android.
 - **Cosmetic `cargo apk build --lib` workaround.** Post-sign
   panic doesn't affect the APK on disk but produces noisy stderr.
   Either upstream a cargo-apk fix or document `--lib` as
@@ -72,34 +105,57 @@ chrome migration, splash boot screen, replay-overlay banner,
 card-face artwork (both rendering paths), and the `ACCENT_PRIMARY`
 palette refresh all shipped in v0.20.0 + v0.21.0. What stays open:
 
-- **Replay-overlay screen-takeover redesign.** The full mockup
+- *Replay-overlay screen-takeover redesign — closed 2026-05-08
-  (`docs/ui-mockups/replay-overlay-mobile.html`) calls for a
+  across 13 commits (v0.21.4–v0.21.7).* The full mockup
-  mini-tableau preview, playback controls, move-log scroll, and
+  (`docs/ui-mockups/replay-overlay-mobile.html`) has shipped:
-  a WIN MOVE marker on the scrub bar. Banner-local pieces all
+  banner chrome (v0.21.0), floating MOVE chip (v0.21.2), WIN
-  shipped in v0.21.0 (`c84d9f4` + `6204db8` + `54005d5` +
+  MOVE scrub-bar marker (post-v0.21.3), playback controls /
-  `e080b49`); the screen-takeover is a multi-session redesign
+  Space accelerator (post-v0.21.3), scrub notches + labels +
-  with data-layer impact (move-log scroller; WIN MOVE needs a
+  keybind footer + ESC / ← / → accelerators + HC border
-  `win_move_index` field on `Replay` that doesn't yet exist).
+  (v0.21.5), Move Log panel + HC scrub track + continuous
-- **Floating `MOVE N/M` chip above the focused card during
+  scrub (v0.21.6), and full-screen 50 % opacity dim layer
-  playback.** Cross-plugin work — `update_progress_text` writes
+  (v0.21.7). Every major B-2 sub-piece is now closed. The
-  the banner chip but the card-position lookup belongs in
+  only remaining items are minor polish: notch-label centering
-  `card_plugin`. Smaller scope than the screen-takeover.
+  and WIN MOVE HC contrast bump (see Open next-step menu).*
-- **Toast Warning / Error variants.** `ToastVariant` has slots
+- *Floating `MOVE N/M` chip above the focused card during
-  for `Warning` (gold) and `Error` (pink) but no in-engine
+  playback — closed 2026-05-08 by `2fb2d63`.* World-space
-  event uses them yet. Wire when a warning- or error-flavoured
+  `Text2d` entity sibling to the banner overlay; uses the same
-  toast event materialises.
+  `LayoutResource` pile coordinates so it survives window
+  resizes without UI/camera math.
+- *Toast Warning variant wiring — closed 2026-05-08 by `279e23d`.*
+  Daily-challenge-expiry toast fires once per `daily.date` when
+  within 30 min of UTC midnight reset and today is incomplete.
+  `ToastVariant` is now fully load-bearing (every variant has at
+  least one real driver). Future Warning drivers can either reuse
+  the generic `WarningToastEvent(String)` carrier or add their
+  own domain message + `animation_plugin` handler.
+- *Toast Error variant wiring — closed 2026-05-08 by `68d50b5`.*
+  `MoveRejectedEvent` now fires a 2-second pink-bordered
+  "Invalid move" toast as the third leg of the
+  audio + visual + text rejection-feedback stool.
 - *High-contrast accessibility mode — closed 2026-05-08 by
-  `c5787c6` + `07e0357`.* Card text rendering picks up
+  `c5787c6` + `07e0357` (engine + UI) + v0.21.2's HC chrome
-  `TEXT_PRIMARY_HC` (`#f5f5f5`) and `RED_SUIT_COLOUR_HC`
+  rollout (`c9af1ea` + `d87761d` + `ec804d5`) + post-cut
-  (`#ff8aa0`); Settings panel has a toggle. Future scope:
+  dynamic-paint rollout (`c153363`).* Card text rendering plus
-  extend HC through chrome borders (`BORDER_SUBTLE_HC` already
+  8 static-border chrome surfaces (modal scaffold, tooltip,
-  defined, not yet consumed), buttons, popover edges.
+  onboarding key chips, help panel key chips, stats panel
-- *Reduced-motion mode — closed 2026-05-08 by the same pair.*
+  cells, home Level/XP/Score row, home mode buttons, home
-  `effective_slide_secs` forces 0 when on, regardless of the
+  mode-hotkey chips, 4 settings panel surfaces) all boost
-  `AnimSpeed` setting. Future scope: gate splash scanline
+  borders to `BORDER_SUBTLE_HC` under HC via the
-  overlay + cursor pulse animation on the same flag, gate
+  `HighContrastBorder` marker. The previously-carved-out
-  warning-chip pulse, gate any future card-lift z-bump
+  dynamic-paint sites are now also covered: HUD action buttons
-  animation.
+  and modal buttons take the same marker (their paint cycles
+  only mutate `BackgroundColor`, so no race); the radial menu
+  rim folds HC into its per-frame spawn via
+  `radial_rim_outline` so the focused rim boosts to
+  `BORDER_SUBTLE_HC` under HC (preserving focused-vs-resting
+  hierarchy that naive marker substitution would invert).
+- *Reduced-motion mode — closed 2026-05-08 by `c5787c6` +
+  v0.21.2's `ed152e2`.* `effective_slide_secs` forces 0 on
+  card animations; `pulse_splash_cursor` skips the per-frame
+  pulse multiplier; `spawn_splash` skips the scanline overlay
+  entirely. Future scope: gate any future card-lift z-bump
+  animation, warning-chip pulse (when one materialises).
 
 ### Carried forward from v0.19.0
 
@@ -115,11 +171,19 @@ palette refresh all shipped in v0.20.0 + v0.21.0. What stays open:
 
 ### Other small candidates
 
-- **Prev/Next selector chips spawn site.** v0.19.0's `9b065e5`
+- *Play-by-Seed dialog — closed 2026-05-08 by `0cb1587`.*
-  noted Prev/Next markers exist in `stats_plugin` but no spawn
+  `PlayBySeedPlugin` adds a numeric-input modal with async solver
-  site renders them today — the Shareable badge therefore lands
+  preview (debounced 500 ms). `HomeMode::PlayBySeed` card fires
-  on the single-replay caption. If/when Prev/Next is plumbed,
+  `StartPlayBySeedRequestEvent`. 5 unit tests. 75 new verified-win
-  the badge will need to follow.
+  seeds (`2062bd0`) expand `CHALLENGE_SEEDS` via the new
+  `solitaire_assetgen::gen_seeds` binary.
+- *Prev/Next selector chips spawn site — closed 2026-05-08 by
+  `a449f60`.* `ReplayPrevButton` / `ReplayNextButton` /
+  `ReplaySelectorCaption` / `ReplaySelectorDetail` now spawn in
+  `spawn_stats_screen` as a compact chip row above the Watch
+  Replay action. The Shareable badge is in the detail line.
+  The click handler and repaint systems were already live since
+  v0.19.0; this was purely the missing spawn site.
 - **Toast queue / immediate unification.** The two toast paths
   (`spawn_queued_toast` for `InfoToastEvent` queue; `spawn_toast`
   for fire-and-forget) now share visual treatment but remain
@@ -203,19 +267,21 @@ into a v0.21.1 / v0.22.0 cut.
 ```
 You are a senior Rust + Bevy developer working on Solitaire Quest.
 Working directory: <Rusty_Solitaire clone path on this machine>.
-Branch: master. v0.21.1 is tagged at daa655a (cut 2026-05-08, a
+Branch: master. v0.21.8 is tagged at c50eaf8 (cut 2026-05-08,
-patch release rolling up app-icon, accessibility modes, and the
+replay-overlay polish). Seven post-cut commits are on master (see
-card-visual iteration cycle that closed Resume-prompt Options A
+"Since the v0.21.8 cut" above); push of the last four pending.
-and F). v0.21.0 stays at 04f9bf9. Working tree clean. See
+v0.21.7 stays at da3e542, v0.21.6 at f63db76, v0.21.5 at a2432df,
-CHANGELOG.md § [0.21.1] for full detail of what shipped in the
+v0.21.4 at 23ff62c, v0.21.3 at 3d92a91, v0.21.2 at f23df3b,
-patch release.
+v0.21.1 at daa655a, v0.21.0 at 04f9bf9.
+Working tree: uncommitted CHANGELOG + SESSION_HANDOFF docs; push
+pending. See CHANGELOG.md § [0.21.9] for full detail.
 
-State: HEAD locally — see `git rev-parse HEAD`. All workspace tests
+State: HEAD locally — see `git rev-parse HEAD`. Workspace
-pass (1192+; check with `cargo test --workspace`), clippy clean.
+tests: 1292 passing / 0 failing. Clippy clean.
 
 READ FIRST (in order, before doing anything):
   1. SESSION_HANDOFF.md  — this file
-  2. CHANGELOG.md        — [0.21.1] section is the most recent cut
+  2. CHANGELOG.md        — [0.21.9] section has the pending-cut items
   3. CLAUDE.md           — unified-3.0 rule set
   4. CLAUDE_SPEC.md      — formal architecture spec
   5. ARCHITECTURE.md     — crate responsibilities + data flow
@@ -230,34 +296,17 @@ READ FIRST (in order, before doing anything):
                            fresh machine)
 
 DECISION TO ASK THE PLAYER FIRST:
-  A. APK launch verification on AVD / device — `adb install` +
+  A. Android follow-ups — JNI ClipboardManager bridge (arboard
-     `adb logcat` to shake out runtime bugs the build / unit
+     has no Android backend), Android Keystore (blocked on Phase 8).
-     tests can't catch. Likely surfaces JNI ClipboardManager
+     Launch verification + double-tap are closed.
-     and Android Keystore stubs that need real bridges. Larger
+  B. Phase 8 (sync) — local storage scaffolding, self-hosted
-     scope; needs an Android device or emulator running.
+     Axum server, `SolitaireServerClient` impl. The biggest open
-     (Was Resume-prompt B before the post-v0.21.1 menu trim.)
+     arc by scope; rolls up Android dependencies (Keystore,
-  B. Replay-overlay extensions — either the floating `MOVE N/M`
-     chip above the focused card (smaller, cross-plugin; needs
-     cursor → card-position plumbing in `card_plugin`) or the
-     full screen-takeover redesign (multi-session: move-log
-     scroll, mini tableau preview, WIN MOVE marker, data-layer
-     impact for `Replay::win_move_index`).
-  C. Toast Warning / Error variant wiring. UI infrastructure
-     exists in `ToastVariant`; no in-engine event uses Warning
-     (gold) or Error (pink) yet. Wire when a real warning- or
-     error-flavoured event materialises.
-  D. Phase 8 (sync) — local storage scaffolding, self-hosted
-     Axum server, `SolitaireServerClient` impl, GPGS stub
-     wired into Settings. The biggest open arc by scope; rolls
-     up several Phase Android dependencies (Keystore,
      ClipboardManager).
-  E. Extend high-contrast through chrome — `BORDER_SUBTLE_HC`
+  C. Play-by-Seed polish — the dialog is functional but has no
-     was defined in v0.21.1 but isn't yet consumed; popover
+     visual preview of the solver verdict in the UI yet; the
-     edges, button borders, focus rings still use the default
+     HomeMode card is wired but the dialog spawn site and verdict
-     non-HC tokens. Plus reduce-motion still doesn't gate
+     display could use a second pass.
-     splash scanline / cursor pulse / warning-chip pulse —
-     v0.21.1 only gated card slide_secs. Both are small,
-     finite, half-day scope.
 
 WORKFLOW NOTES:
   - Use the system git config (already correct).
@@ -281,5 +330,9 @@ WORKFLOW NOTES:
     a "this does X" doc comment, verify the code actually does
     X and add a test if not. Two layers, two checks.
 
-OPEN AT THE START: ask which of A–E. Don't pick unilaterally.
+OPEN AT THE START: ask which of A–C. Don't pick unilaterally.
+Note: every remaining option is multi-session by nature (A is
+gated on Android tooling; B and C are explicitly multi-session
+arcs). A fresh session is a better fit for any of them than the
+tail of a long working stretch.
 ```

solitaire_app/src/lib.rs

@@ -18,21 +18,22 @@ use std::io::Write;
 use std::time::{SystemTime, UNIX_EPOCH};
 
 use bevy::prelude::*;
-use bevy::window::{
+use bevy::window::{MonitorSelection, PresentMode, WindowPosition};
-    Monitor, MonitorSelection, PresentMode, PrimaryMonitor, PrimaryWindow, WindowPosition,
+#[cfg(not(target_os = "android"))]
-};
+use bevy::window::{Monitor, PrimaryMonitor, PrimaryWindow};
 #[cfg(not(target_os = "android"))]
 use bevy::winit::WinitWindows;
 use solitaire_data::{load_settings_from, provider_for_backend, settings_file_path, Settings};
 use solitaire_engine::{
     register_theme_asset_sources, AchievementPlugin, AnimationPlugin, AssetSourcesPlugin,
     AudioPlugin, AutoCompletePlugin, CardAnimationPlugin, CardPlugin, ChallengePlugin,
-    CursorPlugin, DailyChallengePlugin, DiagnosticsHudPlugin, FeedbackAnimPlugin, FontPlugin,
+    CursorPlugin, DailyChallengePlugin, DiagnosticsHudPlugin, DifficultyPlugin, FeedbackAnimPlugin,
-    GamePlugin, HelpPlugin, HomePlugin, HudPlugin, InputPlugin, LeaderboardPlugin,
+    FontPlugin, GamePlugin, HelpPlugin, HomePlugin, HudPlugin, InputPlugin, LeaderboardPlugin,
-    OnboardingPlugin, PausePlugin, ProfilePlugin, ProgressPlugin, RadialMenuPlugin,
+    OnboardingPlugin, PausePlugin, PlayBySeedPlugin, ProfilePlugin, ProgressPlugin,
-    ReplayOverlayPlugin, ReplayPlaybackPlugin, SelectionPlugin, SettingsPlugin, SplashPlugin,
+    RadialMenuPlugin, ReplayOverlayPlugin, ReplayPlaybackPlugin, SelectionPlugin, SettingsPlugin,
-    StatsPlugin, SyncPlugin, TablePlugin, ThemePlugin, ThemeRegistryPlugin, TimeAttackPlugin,
+    SplashPlugin, StatsPlugin, SyncPlugin, TablePlugin, ThemePlugin, ThemeRegistryPlugin,
-    UiFocusPlugin, UiModalPlugin, UiTooltipPlugin, WeeklyGoalsPlugin, WinSummaryPlugin,
+    TimeAttackPlugin, UiFocusPlugin, UiModalPlugin, UiTooltipPlugin, WeeklyGoalsPlugin,
+    WinSummaryPlugin,
 };
 
 /// App entry point — builds and runs the Bevy app.
@@ -76,6 +77,7 @@ pub fn run() {
     // primary monitor) — `apply_smart_default_window_size` will resize
     // up to a monitor-relative target on the first frame so HiDPI / 4K
     // sessions don't end up with a comparatively tiny window.
+    #[cfg(not(target_os = "android"))]
     let had_saved_geometry = settings.window_geometry.is_some();
     let (window_resolution, window_position) = match settings.window_geometry {
         Some(geom) => (
@@ -116,6 +118,9 @@ pub fn run() {
                         // small enough that a few stray dropped frames from
                         // disabling vsync are imperceptible.
                         present_mode: PresentMode::AutoNoVsync,
+                        // Android windows always fill the screen; max_width/max_height
+                        // default to 0.0, which panics Bevy's clamp when min > max.
+                        #[cfg(not(target_os = "android"))]
                         resize_constraints: bevy::window::WindowResizeConstraints {
                             min_width: 800.0,
                             min_height: 600.0,
@@ -142,6 +147,13 @@ pub fn run() {
         .add_plugins(GamePlugin)
         .add_plugins(TablePlugin)
         .add_plugins(CardPlugin)
+        // Cursor-icon feedback is desktop-only; Android has no pointer cursor.
+        // The drop-target highlight systems (update_drop_highlights,
+        // update_drop_target_overlays) live in CursorPlugin but ARE useful
+        // on Android — they've been left running because their Bevy system
+        // params compile and function on Android; only the CursorIcon insert
+        // is inert. Gate the whole plugin if the cursor APIs ever cause
+        // Android linker issues; for now it's harmless to leave it registered.
         .add_plugins(CursorPlugin)
         .add_plugins(InputPlugin)
         .add_plugins(RadialMenuPlugin)
@@ -158,6 +170,8 @@ pub fn run() {
         .add_plugins(DailyChallengePlugin)
         .add_plugins(WeeklyGoalsPlugin)
         .add_plugins(ChallengePlugin)
+        .add_plugins(PlayBySeedPlugin)
+        .add_plugins(DifficultyPlugin)
         .add_plugins(TimeAttackPlugin)
         .add_plugins(HudPlugin)
         .add_plugins(HelpPlugin)
@@ -195,6 +209,8 @@ pub fn run() {
     // every fresh launch can flip `disable_smart_default_size` in
     // Settings to opt out. The flag is checked once at startup; a
     // mid-session change applies on the next launch.
+    // Android windows are always full-screen; the OS controls sizing.
+    #[cfg(not(target_os = "android"))]
     if !had_saved_geometry && !settings.disable_smart_default_size {
         app.add_systems(Update, apply_smart_default_window_size);
     }
@@ -215,6 +231,7 @@ pub fn run() {
 /// a dedicated resource. The Update tick is necessary because Bevy
 /// populates the `Monitor` entities asynchronously after winit's
 /// Resumed event fires; they may not exist on the first Startup pass.
+#[cfg(not(target_os = "android"))]
 fn apply_smart_default_window_size(
     mut applied: Local<bool>,
     monitors: Query<&Monitor, With<PrimaryMonitor>>,
@@ -335,6 +352,20 @@ fn set_window_icon(
     *applied = true;
 }
 
+/// Android entry point called by NativeActivity after dlopen-ing the `.so`.
+/// Sets the `AndroidApp` handle that Bevy's winit backend reads before
+/// constructing the event loop, then delegates to [`run`].
+///
+/// The `#[bevy_main]` proc-macro would generate the same code but only
+/// works on a function named `main`; our shared entry point is `run`, so
+/// we emit the equivalent expansion manually.
+#[cfg(target_os = "android")]
+#[unsafe(no_mangle)]
+fn android_main(android_app: bevy::android::android_activity::AndroidApp) {
+    let _ = bevy::android::ANDROID_APP.set(android_app);
+    run();
+}
+
 /// Wraps the default panic hook with one that also appends a crash log
 /// to `<data_dir>/crash.log` (next to `settings.json`). The default hook
 /// still runs afterwards, so stderr output and debugger integration are

solitaire_assetgen/Cargo.toml

@@ -12,6 +12,8 @@ publish = false
 [dependencies]
 png     = "0.17"
 ab_glyph = "0.2"
+solitaire_core = { path = "../solitaire_core" }
+solitaire_data = { path = "../solitaire_data" }
 
 [[bin]]
 name = "gen_sfx"
@@ -20,3 +22,11 @@ path = "src/bin/gen_sfx.rs"
 [[bin]]
 name = "gen_art"
 path = "src/bin/gen_art.rs"
+
+[[bin]]
+name = "gen_seeds"
+path = "src/bin/gen_seeds.rs"
+
+[[bin]]
+name = "gen_difficulty_seeds"
+path = "src/bin/gen_difficulty_seeds.rs"

solitaire_assetgen/src/bin/gen_difficulty_seeds.rs

@@ -0,0 +1,195 @@
+//! Generate difficulty-stratified seed catalogs for `EASY_SEEDS`, `MEDIUM_SEEDS`,
+//! `HARD_SEEDS`, `EXPERT_SEEDS`, and `GRANDMASTER_SEEDS` in
+//! `solitaire_data/src/difficulty_seeds.rs`.
+//!
+//! A seed's tier is determined by the **smallest** `SolverConfig` budget that
+//! returns `SolverResult::Winnable`. Seeds that are `Unwinnable` at any budget
+//! are discarded; `Inconclusive` at all budgets are also discarded (we only emit
+//! provably-winnable seeds).
+//!
+//! # Usage
+//!
+//! ```bash
+//! cargo run -p solitaire_assetgen --bin gen_difficulty_seeds --release -- \
+//!     --start 0xD1FF0000_00000000 --per-tier 40
+//! ```
+//!
+//! Flags:
+//!   --start     Starting seed (decimal or 0x-prefixed hex, default 0xD1FF000000000000)
+//!   --per-tier  Seeds to emit per tier (default 40)
+//!   --help      Print this message
+
+use solitaire_core::game_state::DrawMode;
+use solitaire_core::solver::{try_solve, SolverConfig, SolverResult};
+
+// Budget boundaries defining each tier. A seed belongs to the lowest tier
+// whose budget proves it Winnable.
+const BUDGETS: &[(&str, u64, usize)] = &[
+    ("Easy",        1_000,   1_000),
+    ("Medium",      5_000,   5_000),
+    ("Hard",       25_000,  25_000),
+    ("Expert",    100_000, 100_000),
+    ("Grandmaster", 200_000, 200_000),
+];
+
+fn main() {
+    let mut args = std::env::args().skip(1).peekable();
+    let mut start: u64 = 0xD1FF_0000_0000_0000;
+    let mut per_tier: usize = 40;
+
+    while let Some(arg) = args.next() {
+        match arg.as_str() {
+            "--start" => {
+                let val = args.next().unwrap_or_else(|| {
+                    eprintln!("error: --start requires a value");
+                    std::process::exit(1);
+                });
+                start = parse_u64(&val);
+            }
+            "--per-tier" => {
+                let val = args.next().unwrap_or_else(|| {
+                    eprintln!("error: --per-tier requires a value");
+                    std::process::exit(1);
+                });
+                per_tier = val.parse().unwrap_or_else(|_| {
+                    eprintln!("error: --per-tier must be a positive integer");
+                    std::process::exit(1);
+                });
+            }
+            "--help" | "-h" => {
+                eprintln!("gen_difficulty_seeds: generate tiered seed catalogs");
+                eprintln!("  --start <seed>     starting seed (hex or decimal)");
+                eprintln!("  --per-tier <n>     seeds per tier (default 40)");
+                return;
+            }
+            other => {
+                eprintln!("error: unknown argument: {other}");
+                std::process::exit(1);
+            }
+        }
+    }
+
+    if per_tier == 0 {
+        eprintln!("error: --per-tier must be > 0");
+        std::process::exit(1);
+    }
+
+    let draw_mode = DrawMode::DrawOne;
+    let num_tiers = BUDGETS.len();
+    let mut buckets: Vec<Vec<u64>> = vec![Vec::with_capacity(per_tier); num_tiers];
+    let mut tried: u64 = 0;
+    let mut seed = start;
+
+    eprintln!(
+        "gen_difficulty_seeds: finding {} seeds per tier from 0x{start:016X} (DrawOne) …",
+        per_tier
+    );
+    eprintln!(
+        "  Tiers: {}",
+        BUDGETS.iter().map(|(n, _, _)| *n).collect::<Vec<_>>().join(", ")
+    );
+
+    while buckets.iter().any(|b| b.len() < per_tier) {
+        tried += 1;
+        'tier: for (i, &(name, move_budget, state_budget)) in BUDGETS.iter().enumerate() {
+            if buckets[i].len() >= per_tier {
+                continue;
+            }
+            let cfg = SolverConfig { move_budget, state_budget };
+            match try_solve(seed, draw_mode.clone(), &cfg) {
+                SolverResult::Winnable => {
+                    buckets[i].push(seed);
+                    eprintln!(
+                        "  [{name}  {:>3}/{}]  0x{seed:016X}  (tried {tried})",
+                        buckets[i].len(),
+                        per_tier
+                    );
+                    break 'tier; // assign to the cheapest tier that proves it winnable
+                }
+                SolverResult::Unwinnable => {
+                    // Definitely unsolvable — skip all remaining tiers.
+                    break 'tier;
+                }
+                SolverResult::Inconclusive => {
+                    // Budget exhausted without proof — try the next larger tier.
+                    // If this is the last tier, the seed is discarded (Inconclusive
+                    // at max budget means "probably but not provably winnable").
+                    if i == num_tiers - 1 {
+                        break 'tier;
+                    }
+                }
+            }
+        }
+        seed = seed.wrapping_add(1);
+    }
+
+    eprintln!("\nDone ({tried} seeds examined). Paste the blocks below into difficulty_seeds.rs:\n");
+
+    let date = current_date();
+    for (i, (tier_name, _, _)) in BUDGETS.iter().enumerate() {
+        println!(
+            "    // Generated by solitaire_assetgen::gen_difficulty_seeds \
+             (tier={tier_name}, date={date})"
+        );
+        for chunk in buckets[i].chunks(5) {
+            for s in chunk {
+                println!(
+                    "    0x{:04X}_{:04X}_{:04X}_{:04X},",
+                    (s >> 48) & 0xFFFF,
+                    (s >> 32) & 0xFFFF,
+                    (s >> 16) & 0xFFFF,
+                    s & 0xFFFF,
+                );
+            }
+        }
+        println!();
+    }
+}
+
+fn parse_u64(s: &str) -> u64 {
+    let cleaned = s.replace('_', "");
+    if let Some(hex) = cleaned.strip_prefix("0x").or_else(|| cleaned.strip_prefix("0X")) {
+        u64::from_str_radix(hex, 16).unwrap_or_else(|_| {
+            eprintln!("error: could not parse '{s}' as a hex u64");
+            std::process::exit(1);
+        })
+    } else {
+        cleaned.parse().unwrap_or_else(|_| {
+            eprintln!("error: could not parse '{s}' as a decimal u64");
+            std::process::exit(1);
+        })
+    }
+}
+
+fn current_date() -> String {
+    use std::time::{SystemTime, UNIX_EPOCH};
+    let secs = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map(|d| d.as_secs())
+        .unwrap_or(0);
+    let days = secs / 86400;
+    let mut y = 1970u64;
+    let mut d = days;
+    loop {
+        let leap = (y.is_multiple_of(4) && !y.is_multiple_of(100)) || y.is_multiple_of(400);
+        let days_in_year = if leap { 366 } else { 365 };
+        if d < days_in_year {
+            break;
+        }
+        d -= days_in_year;
+        y += 1;
+    }
+    let leap = (y.is_multiple_of(4) && !y.is_multiple_of(100)) || y.is_multiple_of(400);
+    let month_days: [u64; 12] = [
+        31, if leap { 29 } else { 28 }, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31,
+    ];
+    let mut m = 0usize;
+    for &md in &month_days {
+        if d < md {
+            break;
+        }
+        d -= md;
+        m += 1;
+    }
+    format!("{y}-{:02}-{:02}", m + 1, d + 1)
+}

solitaire_assetgen/src/bin/gen_seeds.rs

@@ -0,0 +1,157 @@
+//! Generate provably-winnable Klondike seeds for `CHALLENGE_SEEDS`.
+//!
+//! Walks seeds incrementally from `--start`, calls the solver on each, and
+//! collects only those that return `SolverResult::Winnable` (Inconclusive is
+//! rejected — the curated list wants proof). Prints Rust source suitable for
+//! pasting into `solitaire_data/src/challenge.rs`.
+//!
+//! # Usage
+//!
+//! ```bash
+//! cargo run -p solitaire_assetgen --bin gen_seeds --release -- \
+//!     --start 0xCAFE_BABE_0000_0000 --count 75
+//! ```
+//!
+//! Flags:
+//!   --start  Starting seed (decimal or 0x-prefixed hex, default 0xCAFEBABE00000000)
+//!   --count  Number of Winnable seeds to emit (default 75)
+//!   --help   Print this message
+
+use solitaire_core::game_state::DrawMode;
+use solitaire_core::solver::{try_solve, SolverConfig, SolverResult};
+
+fn main() {
+    let mut args = std::env::args().skip(1).peekable();
+    let mut start: u64 = 0xCAFE_BABE_0000_0000;
+    let mut count: usize = 75;
+
+    while let Some(arg) = args.next() {
+        match arg.as_str() {
+            "--start" => {
+                let val = args.next().unwrap_or_else(|| {
+                    eprintln!("error: --start requires a value");
+                    std::process::exit(1);
+                });
+                start = parse_u64(&val);
+            }
+            "--count" => {
+                let val = args.next().unwrap_or_else(|| {
+                    eprintln!("error: --count requires a value");
+                    std::process::exit(1);
+                });
+                count = val.parse().unwrap_or_else(|_| {
+                    eprintln!("error: --count must be a positive integer");
+                    std::process::exit(1);
+                });
+            }
+            "--help" | "-h" => {
+                eprintln!("{}", include_str!(concat!(env!("CARGO_MANIFEST_DIR"), "/src/bin/gen_seeds.rs")).lines().take(20).collect::<Vec<_>>().join("\n"));
+                return;
+            }
+            other => {
+                eprintln!("error: unknown argument: {other}");
+                std::process::exit(1);
+            }
+        }
+    }
+
+    if count == 0 {
+        eprintln!("error: --count must be > 0");
+        std::process::exit(1);
+    }
+
+    let cfg = SolverConfig::default();
+    let draw_mode = DrawMode::DrawOne;
+    let mut found: Vec<u64> = Vec::with_capacity(count);
+    let mut tried: u64 = 0;
+    let mut seed = start;
+
+    eprintln!(
+        "gen_seeds: finding {count} Winnable seeds from 0x{start:016X} (DrawOne) …"
+    );
+
+    while found.len() < count {
+        tried += 1;
+        if matches!(
+            try_solve(seed, draw_mode.clone(), &cfg),
+            SolverResult::Winnable
+        ) {
+            found.push(seed);
+            eprintln!(
+                "  [{:>3}/{}]  0x{:016X}  ({} tried so far)",
+                found.len(),
+                count,
+                seed,
+                tried
+            );
+        }
+        seed = seed.wrapping_add(1);
+    }
+
+    eprintln!("\nDone. Paste the block below into CHALLENGE_SEEDS in solitaire_data/src/challenge.rs:\n");
+
+    println!(
+        "    // Generated by solitaire_assetgen::gen_seeds \
+         (start=0x{start:016X}, count={count}, date={date})",
+        date = current_date()
+    );
+    for chunk in found.chunks(5) {
+        for s in chunk {
+            println!(
+                "    0x{:04X}_{:04X}_{:04X}_{:04X},",
+                (s >> 48) & 0xFFFF,
+                (s >> 32) & 0xFFFF,
+                (s >> 16) & 0xFFFF,
+                s & 0xFFFF,
+            );
+        }
+        println!();
+    }
+}
+
+fn parse_u64(s: &str) -> u64 {
+    let cleaned = s.replace('_', "");
+    if let Some(hex) = cleaned.strip_prefix("0x").or_else(|| cleaned.strip_prefix("0X")) {
+        u64::from_str_radix(hex, 16).unwrap_or_else(|_| {
+            eprintln!("error: could not parse '{s}' as a hex u64");
+            std::process::exit(1);
+        })
+    } else {
+        cleaned.parse().unwrap_or_else(|_| {
+            eprintln!("error: could not parse '{s}' as a decimal u64");
+            std::process::exit(1);
+        })
+    }
+}
+
+fn current_date() -> String {
+    use std::time::{SystemTime, UNIX_EPOCH};
+    let secs = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map(|d| d.as_secs())
+        .unwrap_or(0);
+    let days = secs / 86400;
+    // Gregorian calendar computation (Tomohiko Sakamoto's algorithm variant)
+    let mut y = 1970u64;
+    let mut d = days;
+    loop {
+        let leap = (y.is_multiple_of(4) && !y.is_multiple_of(100)) || y.is_multiple_of(400);
+        let days_in_year = if leap { 366 } else { 365 };
+        if d < days_in_year {
+            break;
+        }
+        d -= days_in_year;
+        y += 1;
+    }
+    let leap = (y.is_multiple_of(4) && !y.is_multiple_of(100)) || y.is_multiple_of(400);
+    let month_days: [u64; 12] = [31, if leap { 29 } else { 28 }, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
+    let mut m = 0usize;
+    for &md in &month_days {
+        if d < md {
+            break;
+        }
+        d -= md;
+        m += 1;
+    }
+    format!("{y}-{:02}-{:02}", m + 1, d + 1)
+}

solitaire_core/src/game_state.rs

@@ -50,6 +50,35 @@ pub enum DrawMode {
     DrawThree,
 }
 
+/// Difficulty tier for `GameMode::Difficulty`. Controls which pre-verified seed
+/// catalog is drawn from. `Random` skips verification entirely and uses a
+/// system-time seed — deals may or may not be winnable.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize, Default)]
+pub enum DifficultyLevel {
+    #[default]
+    Easy,
+    Medium,
+    Hard,
+    Expert,
+    Grandmaster,
+    /// Unverified system-time seed — may or may not be winnable.
+    Random,
+}
+
+impl DifficultyLevel {
+    /// Short human-readable label shown in the HUD and win summary.
+    pub fn label(self) -> &'static str {
+        match self {
+            Self::Easy => "Easy",
+            Self::Medium => "Medium",
+            Self::Hard => "Hard",
+            Self::Expert => "Expert",
+            Self::Grandmaster => "Grandmaster",
+            Self::Random => "Random",
+        }
+    }
+}
+
 /// Top-level game mode. Affects scoring, undo, and (eventually) timer behaviour.
 ///
 /// - `Classic`: standard Klondike scoring, undo allowed.
@@ -59,6 +88,8 @@ pub enum DrawMode {
 /// - `TimeAttack`: standard scoring + undo; the engine wraps a 10-minute
 ///   countdown around the session and auto-deals a fresh game on every win
 ///   (see `solitaire_engine::TimeAttackPlugin`).
+/// - `Difficulty(DifficultyLevel)`: seed drawn from a pre-verified per-tier catalog
+///   (or system-time for `Random`). Rules identical to Classic.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, Default)]
 pub enum GameMode {
     #[default]
@@ -70,6 +101,8 @@ pub enum GameMode {
     Challenge,
     /// Play as many games as possible within 10 minutes.
     TimeAttack,
+    /// Seed drawn from a difficulty-tiered catalog; rules identical to Classic.
+    Difficulty(DifficultyLevel),
 }
 
 /// Snapshot of game state used for undo.

solitaire_data/Cargo.toml

@@ -26,6 +26,13 @@ tokio          = { workspace = true }
 [target.'cfg(not(target_os = "android"))'.dependencies]
 keyring-core   = { workspace = true }
 
+[target.'cfg(target_os = "android")'.dependencies]
+jni            = { workspace = true }
+# android_keystore.rs uses bevy::android::ANDROID_APP to obtain the
+# process-wide JavaVM handle for JNI. Must be listed here so the
+# symbol resolves when cross-compiling for Android targets.
+bevy           = { workspace = true }
+
 [dev-dependencies]
 solitaire_server = { path = "../solitaire_server" }
 solitaire_sync   = { workspace = true }

solitaire_data/src/android_keystore.rs

@@ -0,0 +1,409 @@
+/// Android Keystore token storage via JNI.
+///
+/// Tokens are serialised to JSON, encrypted with AES-256/GCM/NoPadding using a
+/// device-bound key from the Android Keystore, and written atomically to
+/// `{data_dir}/auth_tokens.bin` as `[12-byte IV][ciphertext+GCM-tag]`.
+///
+/// The Keystore key survives app restarts but is destroyed on uninstall (or if
+/// the user changes biometric/lock credentials, in which case decryption fails
+/// and we surface `TokenError::KeychainUnavailable` so the caller knows to
+/// prompt re-login — identical semantics to a Linux box without Secret Service).
+///
+/// Only compiled and linked on `target_os = "android"`.
+use jni::{
+    objects::{JByteArray, JObject, JObjectArray, JValue, JValueOwned},
+    JNIEnv, JavaVM,
+};
+use serde::{Deserialize, Serialize};
+use std::path::PathBuf;
+
+use crate::auth_tokens::TokenError;
+
+const KEY_ALIAS: &str = "solitaire_quest_token_key";
+
+#[derive(Serialize, Deserialize)]
+struct TokenBlob {
+    username: String,
+    access_token: String,
+    refresh_token: String,
+}
+
+// ---------------------------------------------------------------------------
+// JVM helper
+// ---------------------------------------------------------------------------
+
+fn with_jvm<F, R>(f: F) -> Result<R, TokenError>
+where
+    F: for<'env> FnOnce(&mut JNIEnv<'env>) -> Result<R, jni::errors::Error>,
+{
+    let app = bevy::android::ANDROID_APP
+        .get()
+        .ok_or_else(|| TokenError::KeychainUnavailable("ANDROID_APP not initialised".into()))?;
+
+    // SAFETY: vm_as_ptr() is the process-wide JavaVM* set by the Android runtime.
+    let vm = unsafe { JavaVM::from_raw(app.vm_as_ptr().cast()) }
+        .map_err(|e| TokenError::Keyring(format!("JavaVM: {e}")))?;
+
+    let mut env = vm
+        .attach_current_thread_permanently()
+        .map_err(|e| TokenError::Keyring(format!("attach: {e}")))?;
+
+    f(&mut env).map_err(|e| TokenError::Keyring(format!("JNI: {e}")))
+}
+
+// ---------------------------------------------------------------------------
+// Keystore key management
+// ---------------------------------------------------------------------------
+
+/// Load the existing AES key from the Android Keystore, or generate one if it
+/// doesn't exist yet. Returns a local reference valid for the current JNI frame.
+fn load_or_create_key<'local>(env: &mut JNIEnv<'local>) -> jni::errors::Result<JObject<'local>> {
+    // KeyStore ks = KeyStore.getInstance("AndroidKeyStore"); ks.load(null);
+    let ks_class = env.find_class("java/security/KeyStore")?;
+    let ks_type = JValueOwned::from(env.new_string("AndroidKeyStore")?);
+    let ks = env
+        .call_static_method(
+            &ks_class,
+            "getInstance",
+            "(Ljava/lang/String;)Ljava/security/KeyStore;",
+            &[ks_type.borrow()],
+        )?
+        .l()?;
+
+    let null = JObject::null();
+    env.call_method(
+        &ks,
+        "load",
+        "(Ljava/security/KeyStore$LoadStoreParameter;)V",
+        &[JValue::Object(&null)],
+    )?
+    .v()?;
+
+    // Key key = ks.getKey(ALIAS, null)  — char[] password is null for hardware keys
+    let alias = JValueOwned::from(env.new_string(KEY_ALIAS)?);
+    let null2 = JObject::null();
+    let key = env
+        .call_method(
+            &ks,
+            "getKey",
+            "(Ljava/lang/String;[C)Ljava/security/Key;",
+            &[alias.borrow(), JValue::Object(&null2)],
+        )?
+        .l()?;
+
+    if !env.is_same_object(&key, JObject::null())? {
+        return Ok(key);
+    }
+
+    // No key yet — generate AES-256 with GCM block mode.
+    let builder_class =
+        env.find_class("android/security/keystore/KeyGenParameterSpec$Builder")?;
+    let alias2 = JValueOwned::from(env.new_string(KEY_ALIAS)?);
+    // PURPOSE_ENCRYPT | PURPOSE_DECRYPT = 1 | 2 = 3
+    let purpose = JValueOwned::Int(3);
+    let builder = env.new_object(
+        &builder_class,
+        "(Ljava/lang/String;I)V",
+        &[alias2.borrow(), purpose.borrow()],
+    )?;
+
+    let str_class = env.find_class("java/lang/String")?;
+
+    // builder.setBlockModes(["GCM"])
+    let gcm_str = env.new_string("GCM")?;
+    let block_modes: JObjectArray = env.new_object_array(1, &str_class, &gcm_str)?;
+    let block_modes_val = JValueOwned::Object(block_modes.into());
+    let builder = env
+        .call_method(
+            &builder,
+            "setBlockModes",
+            "([Ljava/lang/String;)Landroid/security/keystore/KeyGenParameterSpec$Builder;",
+            &[block_modes_val.borrow()],
+        )?
+        .l()?;
+
+    // builder.setEncryptionPaddings(["NoPadding"])
+    let nopad_str = env.new_string("NoPadding")?;
+    let enc_pads: JObjectArray = env.new_object_array(1, &str_class, &nopad_str)?;
+    let enc_pads_val = JValueOwned::Object(enc_pads.into());
+    let builder = env
+        .call_method(
+            &builder,
+            "setEncryptionPaddings",
+            "([Ljava/lang/String;)Landroid/security/keystore/KeyGenParameterSpec$Builder;",
+            &[enc_pads_val.borrow()],
+        )?
+        .l()?;
+
+    // KeyGenParameterSpec spec = builder.build()
+    let spec = env
+        .call_method(
+            &builder,
+            "build",
+            "()Landroid/security/keystore/KeyGenParameterSpec;",
+            &[],
+        )?
+        .l()?;
+
+    // KeyGenerator kg = KeyGenerator.getInstance("AES", "AndroidKeyStore")
+    let kg_class = env.find_class("javax/crypto/KeyGenerator")?;
+    let aes = JValueOwned::from(env.new_string("AES")?);
+    let ks_name = JValueOwned::from(env.new_string("AndroidKeyStore")?);
+    let kg = env
+        .call_static_method(
+            &kg_class,
+            "getInstance",
+            "(Ljava/lang/String;Ljava/lang/String;)Ljavax/crypto/KeyGenerator;",
+            &[aes.borrow(), ks_name.borrow()],
+        )?
+        .l()?;
+
+    // kg.init(spec); return kg.generateKey()
+    let spec_val = JValueOwned::Object(spec);
+    env.call_method(
+        &kg,
+        "init",
+        "(Ljava/security/spec/AlgorithmParameterSpec;)V",
+        &[spec_val.borrow()],
+    )?
+    .v()?;
+
+    env.call_method(&kg, "generateKey", "()Ljavax/crypto/SecretKey;", &[])?
+        .l()
+}
+
+// ---------------------------------------------------------------------------
+// AES-GCM encrypt / decrypt
+// ---------------------------------------------------------------------------
+
+/// Returns `[12-byte IV][ciphertext+GCM-tag]`.
+fn encrypt_gcm(
+    env: &mut JNIEnv<'_>,
+    key: &JObject<'_>,
+    plaintext: &[u8],
+) -> jni::errors::Result<Vec<u8>> {
+    let cipher_class = env.find_class("javax/crypto/Cipher")?;
+    let transform = JValueOwned::from(env.new_string("AES/GCM/NoPadding")?);
+    let cipher = env
+        .call_static_method(
+            &cipher_class,
+            "getInstance",
+            "(Ljava/lang/String;)Ljavax/crypto/Cipher;",
+            &[transform.borrow()],
+        )?
+        .l()?;
+
+    // cipher.init(Cipher.ENCRYPT_MODE=1, key)
+    let mode = JValueOwned::Int(1);
+    env.call_method(
+        &cipher,
+        "init",
+        "(ILjava/security/Key;)V",
+        &[mode.borrow(), JValue::Object(key)],
+    )?
+    .v()?;
+
+    // IV is generated by Android's provider; read it back after init.
+    let iv_jobj = env.call_method(&cipher, "getIV", "()[B", &[])?.l()?;
+    // SAFETY: the method signature guarantees a byte array return.
+    let iv_arr = unsafe { JByteArray::from_raw(iv_jobj.into_raw()) };
+    let iv = env.convert_byte_array(&iv_arr)?;
+
+    let pt_arr = env.byte_array_from_slice(plaintext)?;
+    let pt_val = JValueOwned::Object(pt_arr.into());
+    let ct_jobj = env
+        .call_method(&cipher, "doFinal", "([B)[B", &[pt_val.borrow()])?
+        .l()?;
+    // SAFETY: doFinal([B) returns [B.
+    let ct_arr = unsafe { JByteArray::from_raw(ct_jobj.into_raw()) };
+    let ciphertext = env.convert_byte_array(&ct_arr)?;
+
+    let mut out = Vec::with_capacity(iv.len() + ciphertext.len());
+    out.extend_from_slice(&iv);
+    out.extend_from_slice(&ciphertext);
+    Ok(out)
+}
+
+/// Expects `data` as `[12-byte IV][ciphertext+GCM-tag]`.
+fn decrypt_gcm(
+    env: &mut JNIEnv<'_>,
+    key: &JObject<'_>,
+    data: &[u8],
+) -> jni::errors::Result<Vec<u8>> {
+    let (iv, ciphertext) = data.split_at(12);
+
+    let cipher_class = env.find_class("javax/crypto/Cipher")?;
+    let transform = JValueOwned::from(env.new_string("AES/GCM/NoPadding")?);
+    let cipher = env
+        .call_static_method(
+            &cipher_class,
+            "getInstance",
+            "(Ljava/lang/String;)Ljavax/crypto/Cipher;",
+            &[transform.borrow()],
+        )?
+        .l()?;
+
+    // GCMParameterSpec spec = new GCMParameterSpec(128, iv)
+    let spec_class = env.find_class("javax/crypto/spec/GCMParameterSpec")?;
+    let tag_len = JValueOwned::Int(128);
+    let iv_arr = env.byte_array_from_slice(iv)?;
+    let iv_val = JValueOwned::Object(iv_arr.into());
+    let spec = env.new_object(
+        &spec_class,
+        "(I[B)V",
+        &[tag_len.borrow(), iv_val.borrow()],
+    )?;
+
+    // cipher.init(Cipher.DECRYPT_MODE=2, key, spec)
+    let mode = JValueOwned::Int(2);
+    let spec_val = JValueOwned::Object(spec);
+    env.call_method(
+        &cipher,
+        "init",
+        "(ILjava/security/Key;Ljava/security/spec/AlgorithmParameterSpec;)V",
+        &[mode.borrow(), JValue::Object(key), spec_val.borrow()],
+    )?
+    .v()?;
+
+    let ct_arr = env.byte_array_from_slice(ciphertext)?;
+    let ct_val = JValueOwned::Object(ct_arr.into());
+    let pt_jobj = env
+        .call_method(&cipher, "doFinal", "([B)[B", &[ct_val.borrow()])?
+        .l()?;
+    // SAFETY: doFinal([B) returns [B.
+    let pt_arr = unsafe { JByteArray::from_raw(pt_jobj.into_raw()) };
+    env.convert_byte_array(&pt_arr)
+}
+
+// ---------------------------------------------------------------------------
+// File helpers
+// ---------------------------------------------------------------------------
+
+fn token_file_path() -> Option<PathBuf> {
+    crate::platform::data_dir().map(|d| d.join("auth_tokens.bin"))
+}
+
+fn read_file_bytes() -> Result<Vec<u8>, TokenError> {
+    let path = token_file_path()
+        .ok_or_else(|| TokenError::KeychainUnavailable("no data dir".into()))?;
+    if !path.exists() {
+        return Err(TokenError::NotFound(String::new()));
+    }
+    std::fs::read(&path).map_err(|e| TokenError::Keyring(format!("read auth_tokens.bin: {e}")))
+}
+
+fn write_file_bytes(data: &[u8]) -> Result<(), TokenError> {
+    let path = token_file_path()
+        .ok_or_else(|| TokenError::KeychainUnavailable("no data dir".into()))?;
+    let tmp = path.with_extension("tmp");
+    std::fs::write(&tmp, data)
+        .map_err(|e| TokenError::Keyring(format!("write auth_tokens.tmp: {e}")))?;
+    std::fs::rename(&tmp, &path)
+        .map_err(|e| TokenError::Keyring(format!("rename auth_tokens: {e}")))
+}
+
+fn load_blob(username: &str) -> Result<TokenBlob, TokenError> {
+    let data = read_file_bytes().map_err(|e| match e {
+        TokenError::NotFound(_) => TokenError::NotFound(username.to_string()),
+        other => other,
+    })?;
+
+    if data.len() < 12 {
+        return Err(TokenError::Keyring("auth_tokens.bin corrupt (too short)".into()));
+    }
+
+    let plaintext = with_jvm(|env| {
+        let key = load_or_create_key(env)?;
+        decrypt_gcm(env, &key, &data)
+    })?;
+
+    let blob: TokenBlob = serde_json::from_slice(&plaintext)
+        .map_err(|e| TokenError::Keyring(format!("JSON decode: {e}")))?;
+
+    if blob.username != username {
+        return Err(TokenError::NotFound(username.to_string()));
+    }
+
+    Ok(blob)
+}
+
+// ---------------------------------------------------------------------------
+// Public API — mirrors auth_tokens desktop surface exactly.
+// ---------------------------------------------------------------------------
+
+/// Encrypt and store `access_token` and `refresh_token` for `username`.
+///
+/// Overwrites any previously stored tokens.
+pub fn store_tokens(
+    username: &str,
+    access_token: &str,
+    refresh_token: &str,
+) -> Result<(), TokenError> {
+    let blob = TokenBlob {
+        username: username.to_string(),
+        access_token: access_token.to_string(),
+        refresh_token: refresh_token.to_string(),
+    };
+    let plaintext = serde_json::to_vec(&blob)
+        .map_err(|e| TokenError::Keyring(format!("JSON encode: {e}")))?;
+
+    let encrypted = with_jvm(|env| {
+        let key = load_or_create_key(env)?;
+        encrypt_gcm(env, &key, &plaintext)
+    })?;
+
+    write_file_bytes(&encrypted)
+}
+
+/// Return the stored access token for `username`.
+///
+/// Returns [`TokenError::NotFound`] if no token has been stored yet.
+pub fn load_access_token(username: &str) -> Result<String, TokenError> {
+    load_blob(username).map(|b| b.access_token)
+}
+
+/// Return the stored refresh token for `username`.
+///
+/// Returns [`TokenError::NotFound`] if no token has been stored yet.
+pub fn load_refresh_token(username: &str) -> Result<String, TokenError> {
+    load_blob(username).map(|b| b.refresh_token)
+}
+
+/// Delete stored tokens and remove the Keystore key for `username`.
+///
+/// Missing file or missing Keystore entry are silently ignored.
+pub fn delete_tokens(_username: &str) -> Result<(), TokenError> {
+    if let Some(path) = token_file_path() {
+        if path.exists() {
+            std::fs::remove_file(&path)
+                .map_err(|e| TokenError::Keyring(format!("delete auth_tokens.bin: {e}")))?;
+        }
+    }
+
+    // Remove the Keystore key so a future re-login generates a fresh key.
+    with_jvm(|env| {
+        let ks_class = env.find_class("java/security/KeyStore")?;
+        let ks_type = JValueOwned::from(env.new_string("AndroidKeyStore")?);
+        let ks = env
+            .call_static_method(
+                &ks_class,
+                "getInstance",
+                "(Ljava/lang/String;)Ljava/security/KeyStore;",
+                &[ks_type.borrow()],
+            )?
+            .l()?;
+
+        let null = JObject::null();
+        env.call_method(
+            &ks,
+            "load",
+            "(Ljava/security/KeyStore$LoadStoreParameter;)V",
+            &[JValue::Object(&null)],
+        )?
+        .v()?;
+
+        let alias = JValueOwned::from(env.new_string(KEY_ALIAS)?);
+        env.call_method(&ks, "deleteEntry", "(Ljava/lang/String;)V", &[alias.borrow()])?
+            .v()
+    })
+}

solitaire_data/src/auth_tokens.rs

@@ -131,35 +131,29 @@ pub fn delete_tokens(username: &str) -> Result<(), TokenError> {
 }
 
 // -------------------------------------------------------------------
-// Android stub — same public API, always returns KeychainUnavailable.
+// Android — delegate to the JNI Keystore bridge in android_keystore.
-// Lets `sync_client::*` compile unchanged on Android; the runtime
-// effect is "session login required every launch", same as a Linux
-// box without Secret Service.
 // -------------------------------------------------------------------
 
-#[cfg(target_os = "android")]
-const ANDROID_STUB_MSG: &str = "android stub: keychain not yet wired (Phase-Android task)";
-
 #[cfg(target_os = "android")]
 pub fn store_tokens(
-    _username: &str,
+    username: &str,
-    _access_token: &str,
+    access_token: &str,
-    _refresh_token: &str,
+    refresh_token: &str,
 ) -> Result<(), TokenError> {
-    Err(TokenError::KeychainUnavailable(ANDROID_STUB_MSG.to_string()))
+    crate::android_keystore::store_tokens(username, access_token, refresh_token)
 }
 
 #[cfg(target_os = "android")]
-pub fn load_access_token(_username: &str) -> Result<String, TokenError> {
+pub fn load_access_token(username: &str) -> Result<String, TokenError> {
-    Err(TokenError::KeychainUnavailable(ANDROID_STUB_MSG.to_string()))
+    crate::android_keystore::load_access_token(username)
 }
 
 #[cfg(target_os = "android")]
-pub fn load_refresh_token(_username: &str) -> Result<String, TokenError> {
+pub fn load_refresh_token(username: &str) -> Result<String, TokenError> {
-    Err(TokenError::KeychainUnavailable(ANDROID_STUB_MSG.to_string()))
+    crate::android_keystore::load_refresh_token(username)
 }
 
 #[cfg(target_os = "android")]
-pub fn delete_tokens(_username: &str) -> Result<(), TokenError> {
+pub fn delete_tokens(username: &str) -> Result<(), TokenError> {
-    Err(TokenError::KeychainUnavailable(ANDROID_STUB_MSG.to_string()))
+    crate::android_keystore::delete_tokens(username)
 }

solitaire_data/src/challenge.rs

@@ -40,6 +40,82 @@ pub const CHALLENGE_SEEDS: &[u64] = &[
     0xDDDD_EEEE_FFFF_0000,
     0x0101_0101_0101_0101,
     0xA1B2_C3D4_E5F6_0718,
+    // Generated by solitaire_assetgen::gen_seeds (start=0xCAFEBABE00000000, count=75, date=2026-05-09)
+    0xCAFE_BABE_0000_0000,
+    0xCAFE_BABE_0000_0002,
+    0xCAFE_BABE_0000_0004,
+    0xCAFE_BABE_0000_0008,
+    0xCAFE_BABE_0000_000B,
+    0xCAFE_BABE_0000_000D,
+    0xCAFE_BABE_0000_000E,
+    0xCAFE_BABE_0000_0010,
+    0xCAFE_BABE_0000_0011,
+    0xCAFE_BABE_0000_0014,
+    0xCAFE_BABE_0000_0016,
+    0xCAFE_BABE_0000_0019,
+    0xCAFE_BABE_0000_001A,
+    0xCAFE_BABE_0000_001F,
+    0xCAFE_BABE_0000_0020,
+    0xCAFE_BABE_0000_0021,
+    0xCAFE_BABE_0000_0024,
+    0xCAFE_BABE_0000_0025,
+    0xCAFE_BABE_0000_0027,
+    0xCAFE_BABE_0000_002B,
+    0xCAFE_BABE_0000_002D,
+    0xCAFE_BABE_0000_0030,
+    0xCAFE_BABE_0000_0034,
+    0xCAFE_BABE_0000_0036,
+    0xCAFE_BABE_0000_003A,
+    0xCAFE_BABE_0000_003B,
+    0xCAFE_BABE_0000_003D,
+    0xCAFE_BABE_0000_0042,
+    0xCAFE_BABE_0000_0043,
+    0xCAFE_BABE_0000_0044,
+    0xCAFE_BABE_0000_004C,
+    0xCAFE_BABE_0000_004D,
+    0xCAFE_BABE_0000_004F,
+    0xCAFE_BABE_0000_0050,
+    0xCAFE_BABE_0000_0051,
+    0xCAFE_BABE_0000_0054,
+    0xCAFE_BABE_0000_0055,
+    0xCAFE_BABE_0000_0056,
+    0xCAFE_BABE_0000_0059,
+    0xCAFE_BABE_0000_005B,
+    0xCAFE_BABE_0000_005C,
+    0xCAFE_BABE_0000_005E,
+    0xCAFE_BABE_0000_0060,
+    0xCAFE_BABE_0000_0062,
+    0xCAFE_BABE_0000_0064,
+    0xCAFE_BABE_0000_0067,
+    0xCAFE_BABE_0000_0069,
+    0xCAFE_BABE_0000_006A,
+    0xCAFE_BABE_0000_006B,
+    0xCAFE_BABE_0000_006C,
+    0xCAFE_BABE_0000_006D,
+    0xCAFE_BABE_0000_006E,
+    0xCAFE_BABE_0000_006F,
+    0xCAFE_BABE_0000_0072,
+    0xCAFE_BABE_0000_0073,
+    0xCAFE_BABE_0000_0074,
+    0xCAFE_BABE_0000_0079,
+    0xCAFE_BABE_0000_007A,
+    0xCAFE_BABE_0000_007D,
+    0xCAFE_BABE_0000_007E,
+    0xCAFE_BABE_0000_007F,
+    0xCAFE_BABE_0000_0082,
+    0xCAFE_BABE_0000_0083,
+    0xCAFE_BABE_0000_0084,
+    0xCAFE_BABE_0000_0085,
+    0xCAFE_BABE_0000_0089,
+    0xCAFE_BABE_0000_008A,
+    0xCAFE_BABE_0000_008D,
+    0xCAFE_BABE_0000_008E,
+    0xCAFE_BABE_0000_0090,
+    0xCAFE_BABE_0000_0094,
+    0xCAFE_BABE_0000_0095,
+    0xCAFE_BABE_0000_0098,
+    0xCAFE_BABE_0000_0099,
+    0xCAFE_BABE_0000_009F,
 ];
 
 /// Resolve a `challenge_index` to its corresponding seed, wrapping when

solitaire_data/src/difficulty_seeds.rs

@@ -0,0 +1,320 @@
+//! Pre-verified seed catalogs for each [`DifficultyLevel`] tier.
+//!
+//! Each slice contains seeds that are provably winnable in Draw-One mode and
+//! that required a specific solver-budget range to solve — the **smallest**
+//! budget that returns `Winnable` determines the tier. See
+//! `solitaire_assetgen/src/bin/gen_difficulty_seeds.rs` for the generator.
+//!
+//! # Tiers and budget boundaries
+//!
+//! | Tier        | move_budget | state_budget |
+//! |-------------|-------------|--------------|
+//! | Easy        | 1 000       | 1 000        |
+//! | Medium      | 5 000       | 5 000        |
+//! | Hard        | 25 000      | 25 000       |
+//! | Expert      | 100 000     | 100 000      |
+//! | Grandmaster | 200 000     | 200 000      |
+//!
+//! [`DifficultyLevel::Random`] has no catalog — the engine picks a system-time
+//! seed and skips verification.
+
+use solitaire_core::game_state::DifficultyLevel;
+
+// ---------------------------------------------------------------------------
+// Catalogs (populated by gen_difficulty_seeds)
+// ---------------------------------------------------------------------------
+
+/// 40 seeds proven winnable within the Easy budget (≤ 1 000 states).
+pub const EASY_SEEDS: &[u64] = &[
+    // Generated by solitaire_assetgen::gen_difficulty_seeds (tier=Easy, date=2026-05-09)
+    0xD1FF_0000_0000_0001,
+    0xD1FF_0000_0000_0002,
+    0xD1FF_0000_0000_0007,
+    0xD1FF_0000_0000_0008,
+    0xD1FF_0000_0000_0009,
+    0xD1FF_0000_0000_000E,
+    0xD1FF_0000_0000_0013,
+    0xD1FF_0000_0000_0015,
+    0xD1FF_0000_0000_0018,
+    0xD1FF_0000_0000_001D,
+    0xD1FF_0000_0000_0021,
+    0xD1FF_0000_0000_0022,
+    0xD1FF_0000_0000_0026,
+    0xD1FF_0000_0000_002C,
+    0xD1FF_0000_0000_002E,
+    0xD1FF_0000_0000_002F,
+    0xD1FF_0000_0000_0035,
+    0xD1FF_0000_0000_0036,
+    0xD1FF_0000_0000_003C,
+    0xD1FF_0000_0000_0045,
+    0xD1FF_0000_0000_0046,
+    0xD1FF_0000_0000_0048,
+    0xD1FF_0000_0000_0049,
+    0xD1FF_0000_0000_004D,
+    0xD1FF_0000_0000_004F,
+    0xD1FF_0000_0000_0050,
+    0xD1FF_0000_0000_0051,
+    0xD1FF_0000_0000_0053,
+    0xD1FF_0000_0000_0054,
+    0xD1FF_0000_0000_0057,
+    0xD1FF_0000_0000_0058,
+    0xD1FF_0000_0000_005A,
+    0xD1FF_0000_0000_005B,
+    0xD1FF_0000_0000_005C,
+    0xD1FF_0000_0000_005D,
+    0xD1FF_0000_0000_005F,
+    0xD1FF_0000_0000_0061,
+    0xD1FF_0000_0000_0062,
+    0xD1FF_0000_0000_0063,
+    0xD1FF_0000_0000_0069,
+];
+
+/// 40 seeds proven winnable within the Medium budget (≤ 5 000 states).
+pub const MEDIUM_SEEDS: &[u64] = &[
+    // Generated by solitaire_assetgen::gen_difficulty_seeds (tier=Medium, date=2026-05-09)
+    0xD1FF_0000_0000_0000,
+    0xD1FF_0000_0000_0012,
+    0xD1FF_0000_0000_0016,
+    0xD1FF_0000_0000_001B,
+    0xD1FF_0000_0000_001C,
+    0xD1FF_0000_0000_0020,
+    0xD1FF_0000_0000_002A,
+    0xD1FF_0000_0000_0034,
+    0xD1FF_0000_0000_003A,
+    0xD1FF_0000_0000_0041,
+    0xD1FF_0000_0000_0043,
+    0xD1FF_0000_0000_0060,
+    0xD1FF_0000_0000_006A,
+    0xD1FF_0000_0000_006C,
+    0xD1FF_0000_0000_006E,
+    0xD1FF_0000_0000_006F,
+    0xD1FF_0000_0000_0071,
+    0xD1FF_0000_0000_0072,
+    0xD1FF_0000_0000_0075,
+    0xD1FF_0000_0000_0076,
+    0xD1FF_0000_0000_007B,
+    0xD1FF_0000_0000_007E,
+    0xD1FF_0000_0000_0081,
+    0xD1FF_0000_0000_0083,
+    0xD1FF_0000_0000_0084,
+    0xD1FF_0000_0000_0087,
+    0xD1FF_0000_0000_0090,
+    0xD1FF_0000_0000_0092,
+    0xD1FF_0000_0000_0093,
+    0xD1FF_0000_0000_0098,
+    0xD1FF_0000_0000_0099,
+    0xD1FF_0000_0000_009A,
+    0xD1FF_0000_0000_009E,
+    0xD1FF_0000_0000_00A5,
+    0xD1FF_0000_0000_00A8,
+    0xD1FF_0000_0000_00AA,
+    0xD1FF_0000_0000_00AB,
+    0xD1FF_0000_0000_00AE,
+    0xD1FF_0000_0000_00AF,
+    0xD1FF_0000_0000_00B0,
+];
+
+/// 40 seeds proven winnable within the Hard budget (≤ 25 000 states).
+pub const HARD_SEEDS: &[u64] = &[
+    // Generated by solitaire_assetgen::gen_difficulty_seeds (tier=Hard, date=2026-05-09)
+    0xD1FF_0000_0000_001F,
+    0xD1FF_0000_0000_0024,
+    0xD1FF_0000_0000_0025,
+    0xD1FF_0000_0000_0031,
+    0xD1FF_0000_0000_0032,
+    0xD1FF_0000_0000_003E,
+    0xD1FF_0000_0000_004A,
+    0xD1FF_0000_0000_006D,
+    0xD1FF_0000_0000_0079,
+    0xD1FF_0000_0000_007C,
+    0xD1FF_0000_0000_0080,
+    0xD1FF_0000_0000_008A,
+    0xD1FF_0000_0000_0097,
+    0xD1FF_0000_0000_00B1,
+    0xD1FF_0000_0000_00B2,
+    0xD1FF_0000_0000_00B3,
+    0xD1FF_0000_0000_00B5,
+    0xD1FF_0000_0000_00B7,
+    0xD1FF_0000_0000_00B8,
+    0xD1FF_0000_0000_00B9,
+    0xD1FF_0000_0000_00BA,
+    0xD1FF_0000_0000_00BB,
+    0xD1FF_0000_0000_00BC,
+    0xD1FF_0000_0000_00BD,
+    0xD1FF_0000_0000_00C2,
+    0xD1FF_0000_0000_00C3,
+    0xD1FF_0000_0000_00C5,
+    0xD1FF_0000_0000_00CC,
+    0xD1FF_0000_0000_00CE,
+    0xD1FF_0000_0000_00D1,
+    0xD1FF_0000_0000_00D2,
+    0xD1FF_0000_0000_00D6,
+    0xD1FF_0000_0000_00D7,
+    0xD1FF_0000_0000_00DC,
+    0xD1FF_0000_0000_00DF,
+    0xD1FF_0000_0000_00E0,
+    0xD1FF_0000_0000_00E1,
+    0xD1FF_0000_0000_00E4,
+    0xD1FF_0000_0000_00E6,
+    0xD1FF_0000_0000_00E7,
+];
+
+/// 40 seeds proven winnable within the Expert budget (≤ 100 000 states).
+pub const EXPERT_SEEDS: &[u64] = &[
+    // Generated by solitaire_assetgen::gen_difficulty_seeds (tier=Expert, date=2026-05-09)
+    0xD1FF_0000_0000_0006,
+    0xD1FF_0000_0000_000B,
+    0xD1FF_0000_0000_0019,
+    0xD1FF_0000_0000_0082,
+    0xD1FF_0000_0000_00CB,
+    0xD1FF_0000_0000_00D5,
+    0xD1FF_0000_0000_00D8,
+    0xD1FF_0000_0000_00E8,
+    0xD1FF_0000_0000_00EA,
+    0xD1FF_0000_0000_00EB,
+    0xD1FF_0000_0000_00EC,
+    0xD1FF_0000_0000_00ED,
+    0xD1FF_0000_0000_00F2,
+    0xD1FF_0000_0000_00F3,
+    0xD1FF_0000_0000_00F4,
+    0xD1FF_0000_0000_00FE,
+    0xD1FF_0000_0000_00FF,
+    0xD1FF_0000_0000_0102,
+    0xD1FF_0000_0000_0103,
+    0xD1FF_0000_0000_0104,
+    0xD1FF_0000_0000_0105,
+    0xD1FF_0000_0000_0106,
+    0xD1FF_0000_0000_0109,
+    0xD1FF_0000_0000_010B,
+    0xD1FF_0000_0000_010C,
+    0xD1FF_0000_0000_0110,
+    0xD1FF_0000_0000_0113,
+    0xD1FF_0000_0000_0114,
+    0xD1FF_0000_0000_011B,
+    0xD1FF_0000_0000_011C,
+    0xD1FF_0000_0000_011E,
+    0xD1FF_0000_0000_0120,
+    0xD1FF_0000_0000_0121,
+    0xD1FF_0000_0000_0122,
+    0xD1FF_0000_0000_0123,
+    0xD1FF_0000_0000_0124,
+    0xD1FF_0000_0000_0126,
+    0xD1FF_0000_0000_012B,
+    0xD1FF_0000_0000_012C,
+    0xD1FF_0000_0000_012E,
+];
+
+/// 40 seeds proven winnable only within the Grandmaster budget (≤ 200 000 states).
+pub const GRANDMASTER_SEEDS: &[u64] = &[
+    // Generated by solitaire_assetgen::gen_difficulty_seeds (tier=Grandmaster, date=2026-05-09)
+    0xD1FF_0000_0000_0027,
+    0xD1FF_0000_0000_00A0,
+    0xD1FF_0000_0000_00C4,
+    0xD1FF_0000_0000_00D4,
+    0xD1FF_0000_0000_00DE,
+    0xD1FF_0000_0000_00F9,
+    0xD1FF_0000_0000_0107,
+    0xD1FF_0000_0000_0108,
+    0xD1FF_0000_0000_0130,
+    0xD1FF_0000_0000_0132,
+    0xD1FF_0000_0000_0133,
+    0xD1FF_0000_0000_0134,
+    0xD1FF_0000_0000_0135,
+    0xD1FF_0000_0000_0137,
+    0xD1FF_0000_0000_0139,
+    0xD1FF_0000_0000_013A,
+    0xD1FF_0000_0000_013D,
+    0xD1FF_0000_0000_013F,
+    0xD1FF_0000_0000_0140,
+    0xD1FF_0000_0000_0141,
+    0xD1FF_0000_0000_0142,
+    0xD1FF_0000_0000_0143,
+    0xD1FF_0000_0000_0145,
+    0xD1FF_0000_0000_0146,
+    0xD1FF_0000_0000_014A,
+    0xD1FF_0000_0000_014B,
+    0xD1FF_0000_0000_014C,
+    0xD1FF_0000_0000_014D,
+    0xD1FF_0000_0000_014F,
+    0xD1FF_0000_0000_0150,
+    0xD1FF_0000_0000_0151,
+    0xD1FF_0000_0000_0152,
+    0xD1FF_0000_0000_0153,
+    0xD1FF_0000_0000_0157,
+    0xD1FF_0000_0000_0158,
+    0xD1FF_0000_0000_015B,
+    0xD1FF_0000_0000_015C,
+    0xD1FF_0000_0000_015E,
+    0xD1FF_0000_0000_0162,
+    0xD1FF_0000_0000_0164,
+];
+
+// ---------------------------------------------------------------------------
+// Public API
+// ---------------------------------------------------------------------------
+
+/// Type alias for the catalog lookup return: a static slice or `None` for `Random`.
+pub type DifficultySeeds = Option<&'static [u64]>;
+
+/// Return the seed catalog for `level`, or `None` for `Random` (caller must
+/// use a system-time seed instead).
+pub fn seeds_for(level: DifficultyLevel) -> DifficultySeeds {
+    match level {
+        DifficultyLevel::Easy => Some(EASY_SEEDS),
+        DifficultyLevel::Medium => Some(MEDIUM_SEEDS),
+        DifficultyLevel::Hard => Some(HARD_SEEDS),
+        DifficultyLevel::Expert => Some(EXPERT_SEEDS),
+        DifficultyLevel::Grandmaster => Some(GRANDMASTER_SEEDS),
+        DifficultyLevel::Random => None,
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn all_difficulty_seeds_are_unique() {
+        let all: Vec<u64> = [
+            EASY_SEEDS,
+            MEDIUM_SEEDS,
+            HARD_SEEDS,
+            EXPERT_SEEDS,
+            GRANDMASTER_SEEDS,
+        ]
+        .iter()
+        .flat_map(|s| s.iter().copied())
+        .collect();
+
+        let mut sorted = all.clone();
+        sorted.sort_unstable();
+        let before = sorted.len();
+        sorted.dedup();
+        assert_eq!(sorted.len(), before, "duplicate seeds found across difficulty tiers");
+    }
+
+    #[test]
+    fn seeds_for_random_returns_none() {
+        assert!(seeds_for(DifficultyLevel::Random).is_none());
+    }
+
+    #[test]
+    fn seeds_for_non_random_returns_some() {
+        for level in [
+            DifficultyLevel::Easy,
+            DifficultyLevel::Medium,
+            DifficultyLevel::Hard,
+            DifficultyLevel::Expert,
+            DifficultyLevel::Grandmaster,
+        ] {
+            assert!(
+                seeds_for(level).is_some(),
+                "{level:?} should return Some catalog"
+            );
+        }
+    }
+}

solitaire_data/src/lib.rs

@@ -138,6 +138,9 @@ pub use weekly::{
 pub mod challenge;
 pub use challenge::{challenge_count, challenge_seed_for, CHALLENGE_SEEDS};
 
+pub mod difficulty_seeds;
+pub use difficulty_seeds::{seeds_for, DifficultySeeds};
+
 pub mod settings;
 pub use settings::{
     load_settings_from, save_settings_to, settings_file_path, AnimSpeed, Settings, SyncBackend,
@@ -147,6 +150,9 @@ pub use settings::{
     TOOLTIP_DELAY_MIN_SECS, TOOLTIP_DELAY_STEP_SECS,
 };
 
+#[cfg(target_os = "android")]
+mod android_keystore;
+
 pub mod auth_tokens;
 pub use auth_tokens::{
     delete_tokens, load_access_token, load_refresh_token, store_tokens, TokenError,

solitaire_data/src/replay.rs

@@ -147,12 +147,38 @@ pub struct Replay {
     /// [`REPLAY_SCHEMA_VERSION`].
     #[serde(default)]
     pub share_url: Option<String>,
+    /// Index into [`moves`](Self::moves) of the move that triggered
+    /// the win condition (i.e. completed the last foundation pile).
+    ///
+    /// For replays recorded by the live engine this is always
+    /// `Some(moves.len() - 1)` because recording freezes on win — but
+    /// the field is stored explicitly so the playback UI can read it
+    /// directly without re-deriving "the last move was the win" each
+    /// time, and to leave room for future recording semantics that
+    /// might capture post-win state.
+    ///
+    /// `None` for replays loaded from disk that pre-date this field.
+    /// `#[serde(default)]` keeps older `latest_replay.json` /
+    /// `replays.json` files loadable without bumping
+    /// [`REPLAY_SCHEMA_VERSION`] — this is an additive optional
+    /// field, not a schema-breaking change.
+    ///
+    /// Surfaced by the replay-overlay scrub bar's WIN MOVE marker
+    /// (B-2 screen-takeover redesign) when present.
+    #[serde(default)]
+    pub win_move_index: Option<usize>,
 }
 
 impl Replay {
     /// Construct a fresh replay with the current schema version. The
     /// caller fills in the recorded fields; this is the canonical
     /// constructor used by the engine on win.
+    ///
+    /// [`win_move_index`](Self::win_move_index) and
+    /// [`share_url`](Self::share_url) default to `None` — the engine
+    /// uses [`with_win_move_index`](Self::with_win_move_index) at the
+    /// recording site to set the former, and `sync_plugin` writes the
+    /// latter directly when the upload task resolves.
     pub fn new(
         seed: u64,
         draw_mode: DrawMode,
@@ -172,8 +198,24 @@ impl Replay {
             recorded_at,
             moves,
             share_url: None,
+            win_move_index: None,
         }
     }
+
+    /// Builder-style setter for [`win_move_index`](Self::win_move_index).
+    /// Returns `self` so the recording site can chain it onto
+    /// [`Replay::new`]:
+    ///
+    /// ```ignore
+    /// let replay = Replay::new(...).with_win_move_index(Some(recording.moves.len() - 1));
+    /// ```
+    ///
+    /// `None` is a valid input — useful for tests that don't care about
+    /// the WIN MOVE marker's scrub-bar position.
+    pub fn with_win_move_index(mut self, idx: Option<usize>) -> Self {
+        self.win_move_index = idx;
+        self
+    }
 }
 
 /// Rolling history of the player's most recent winning replays.
@@ -737,4 +779,71 @@ mod tests {
 
         let _ = fs::remove_file(&path);
     }
+
+    // -----------------------------------------------------------------------
+    // win_move_index — additive optional field for the WIN MOVE marker
+    // -----------------------------------------------------------------------
+
+    #[test]
+    fn replay_new_defaults_win_move_index_to_none() {
+        let r = sample_replay();
+        assert_eq!(r.win_move_index, None);
+    }
+
+    #[test]
+    fn with_win_move_index_sets_value() {
+        let r = sample_replay().with_win_move_index(Some(3));
+        assert_eq!(r.win_move_index, Some(3));
+    }
+
+    #[test]
+    fn with_win_move_index_accepts_none() {
+        // Passing None through the builder is a valid no-op — useful for
+        // tests / synthetic replays that don't care about the marker.
+        let r = sample_replay().with_win_move_index(None);
+        assert_eq!(r.win_move_index, None);
+    }
+
+    #[test]
+    fn replay_with_win_move_index_round_trips_on_disk() {
+        let path = tmp_path("win_move_index_round_trip");
+        let _ = fs::remove_file(&path);
+
+        let original = sample_replay().with_win_move_index(Some(3));
+        save_latest_replay_to(&path, &original).expect("save");
+        let loaded = load_latest_replay_from(&path).expect("load");
+        assert_eq!(loaded.win_move_index, Some(3));
+        assert_eq!(loaded, original);
+
+        let _ = fs::remove_file(&path);
+    }
+
+    /// Older replay files written before this field was added must still
+    /// load — `#[serde(default)]` keeps `win_move_index` optional and
+    /// defaults missing fields to `None`. This is the contract that lets
+    /// us add the field without bumping `REPLAY_SCHEMA_VERSION`.
+    #[test]
+    fn replay_without_win_move_index_loads_with_none() {
+        let path = tmp_path("legacy_no_win_move_index");
+        let _ = fs::remove_file(&path);
+
+        // Hand-rolled minimal v2 replay JSON with no win_move_index field.
+        let v2_no_field = r#"{
+            "schema_version": 2,
+            "seed": 1,
+            "draw_mode": "DrawOne",
+            "mode": "Classic",
+            "time_seconds": 60,
+            "final_score": 100,
+            "recorded_at": "2026-05-02",
+            "moves": []
+        }"#;
+        fs::write(&path, v2_no_field).expect("write fixture");
+
+        let loaded = load_latest_replay_from(&path).expect("load");
+        assert_eq!(loaded.win_move_index, None);
+        assert_eq!(loaded.schema_version, REPLAY_SCHEMA_VERSION);
+
+        let _ = fs::remove_file(&path);
+    }
 }

solitaire_data/src/settings.rs

@@ -9,7 +9,7 @@ use std::io;
 use std::path::{Path, PathBuf};
 
 use serde::{Deserialize, Serialize};
-use solitaire_core::game_state::DrawMode;
+use solitaire_core::game_state::{DifficultyLevel, DrawMode};
 
 const APP_DIR_NAME: &str = "solitaire_quest";
 const SETTINGS_FILE_NAME: &str = "settings.json";
@@ -224,6 +224,13 @@ pub struct Settings {
     /// `#[serde(default = "default_replay_move_interval_secs")]`.
     #[serde(default = "default_replay_move_interval_secs")]
     pub replay_move_interval_secs: f32,
+    /// Last difficulty tier the player selected. `None` means the player has
+    /// never used the difficulty picker. When `Some`, the difficulty section in
+    /// the home overlay opens pre-expanded and highlights this tier. Older
+    /// `settings.json` files written before this field existed deserialize
+    /// cleanly to `None` via `#[serde(default)]`.
+    #[serde(default)]
+    pub last_difficulty: Option<DifficultyLevel>,
 }
 
 fn default_draw_mode() -> DrawMode {
@@ -342,6 +349,7 @@ impl Default for Settings {
             winnable_deals_only: false,
             disable_smart_default_size: false,
             replay_move_interval_secs: default_replay_move_interval_secs(),
+            last_difficulty: None,
         }
     }
 }

solitaire_data/src/stats.rs

@@ -104,6 +104,13 @@ impl StatsExt for StatsSnapshot {
             // Time Attack uses its own session-level scoring; a per-game best
             // wouldn't compose with the other modes' single-game numbers.
             GameMode::TimeAttack => {}
+            // Difficulty games pool into the Classic best-score/time buckets per
+            // the user's stats preference.
+            GameMode::Difficulty(_) => {
+                self.classic_best_score = self.classic_best_score.max(score_u32);
+                self.classic_fastest_win_seconds =
+                    min_ignore_zero(self.classic_fastest_win_seconds, time_seconds);
+            }
         }
         self.last_modified = Utc::now();
     }

solitaire_engine/Cargo.toml

@@ -32,6 +32,9 @@ zip            = { workspace = true }
 [target.'cfg(not(target_os = "android"))'.dependencies]
 arboard        = { workspace = true }
 
+[target.'cfg(target_os = "android")'.dependencies]
+jni            = { workspace = true }
+
 [dev-dependencies]
 async-trait = { workspace = true }
 tempfile    = { workspace = true }

solitaire_engine/src/achievement_plugin.rs

@@ -1445,6 +1445,7 @@ mod tests {
                 replay: dummy_replay(),
                 cursor: 0,
                 secs_to_next: 0.0,
+                paused: false,
             };
         app.update();
         assert!(
@@ -1480,6 +1481,7 @@ mod tests {
                 replay: dummy_replay(),
                 cursor: 0,
                 secs_to_next: 0.0,
+                paused: false,
             };
         app.update();
 
@@ -1512,6 +1514,7 @@ mod tests {
                 replay: dummy_replay(),
                 cursor: 0,
                 secs_to_next: 0.0,
+                paused: false,
             };
         app.update();
         *app.world_mut().resource_mut::<ReplayPlaybackState>() =
@@ -1534,6 +1537,7 @@ mod tests {
                 replay: dummy_replay(),
                 cursor: 0,
                 secs_to_next: 0.0,
+                paused: false,
             };
         app.update();
         *app.world_mut().resource_mut::<ReplayPlaybackState>() =
@@ -1559,6 +1563,7 @@ mod tests {
                 replay: dummy_replay(),
                 cursor: 0,
                 secs_to_next: 0.0,
+                paused: false,
             };
         app.update();
         *app.world_mut().resource_mut::<ReplayPlaybackState>() =

solitaire_engine/src/android_clipboard.rs

@@ -0,0 +1,65 @@
+/// Android clipboard bridge via JNI.
+///
+/// Writes text to the system clipboard by calling into `ClipboardManager`
+/// through the JNI. Only compiled and linked on `target_os = "android"`.
+#[cfg(target_os = "android")]
+pub fn set_text(text: &str) -> Result<(), String> {
+    use bevy::android::ANDROID_APP;
+    use jni::{
+        objects::{JObject, JValueOwned},
+        JavaVM,
+    };
+
+    let app = ANDROID_APP
+        .get()
+        .ok_or_else(|| "ANDROID_APP not initialized".to_string())?;
+
+    // SAFETY: vm_as_ptr() returns the raw JavaVM* set up by the Android runtime.
+    let vm = unsafe { JavaVM::from_raw(app.vm_as_ptr().cast()) }
+        .map_err(|e| format!("JavaVM::from_raw: {e}"))?;
+
+    let mut env = vm
+        .attach_current_thread_permanently()
+        .map_err(|e| format!("attach_current_thread: {e}"))?;
+
+    // SAFETY: activity_as_ptr() is the NativeActivity jobject pointer —
+    // valid for the lifetime of the process.
+    let activity = unsafe { JObject::from_raw(app.activity_as_ptr() as _) };
+
+    (|| -> jni::errors::Result<()> {
+        // ClipboardManager cm = activity.getSystemService("clipboard")
+        let svc_name = JValueOwned::from(env.new_string("clipboard")?);
+        let cm = env
+            .call_method(
+                &activity,
+                "getSystemService",
+                "(Ljava/lang/String;)Ljava/lang/Object;",
+                &[svc_name.borrow()],
+            )?
+            .l()?;
+
+        // ClipData clip = ClipData.newPlainText("link", text)
+        let label = JValueOwned::from(env.new_string("link")?);
+        let java_text = JValueOwned::from(env.new_string(text)?);
+        let clip_class = env.find_class("android/content/ClipData")?;
+        let clip = env
+            .call_static_method(
+                &clip_class,
+                "newPlainText",
+                "(Ljava/lang/CharSequence;Ljava/lang/CharSequence;)Landroid/content/ClipData;",
+                &[label.borrow(), java_text.borrow()],
+            )?
+            .l()?;
+
+        // cm.setPrimaryClip(clip)
+        let clip_val = JValueOwned::Object(clip);
+        env.call_method(
+            &cm,
+            "setPrimaryClip",
+            "(Landroid/content/ClipData;)V",
+            &[clip_val.borrow()],
+        )?
+        .v()
+    })()
+    .map_err(|e| format!("clipboard JNI: {e}"))
+}

solitaire_engine/src/animation_plugin.rs

@@ -22,7 +22,8 @@ use crate::card_plugin::CardEntity;
 use crate::challenge_plugin::ChallengeAdvancedEvent;
 use crate::daily_challenge_plugin::{DailyChallengeCompletedEvent, DailyGoalAnnouncementEvent};
 use crate::events::{
-    AchievementUnlockedEvent, GameWonEvent, InfoToastEvent, MoveRejectedEvent, XpAwardedEvent,
+    AchievementUnlockedEvent, GameWonEvent, InfoToastEvent, MoveRejectedEvent, WarningToastEvent,
+    XpAwardedEvent,
 };
 use crate::game_plugin::GameMutation;
 use crate::layout::LayoutResource;
@@ -164,6 +165,7 @@ impl Plugin for AnimationPlugin {
             .add_message::<SettingsChangedEvent>()
             .add_message::<InfoToastEvent>()
             .add_message::<MoveRejectedEvent>()
+            .add_message::<WarningToastEvent>()
             .add_message::<XpAwardedEvent>()
             .init_resource::<EffectiveSlideDuration>()
             .init_resource::<ToastQueue>()
@@ -186,6 +188,7 @@ impl Plugin for AnimationPlugin {
                     handle_auto_complete_toast,
                     handle_xp_awarded_toast,
                     handle_move_rejected_toast,
+                    handle_warning_toast,
                     tick_toasts,
                     (enqueue_toasts, drive_toast_display).chain(),
                 )
@@ -651,6 +654,23 @@ fn handle_move_rejected_toast(
     }
 }
 
+/// Spawns a 4-second amber-bordered Warning toast for every incoming
+/// [`WarningToastEvent`]. First in-engine consumer of
+/// [`ToastVariant::Warning`] — exercises the variant's amber accent and
+/// the design-system "act soon" semantic.
+///
+/// Mirrors [`handle_move_rejected_toast`] but reads a generic carrier
+/// event (not a domain-specific one) because Warning has multiple
+/// candidate drivers and the call-site knows the message wording.
+fn handle_warning_toast(
+    mut commands: Commands,
+    mut events: MessageReader<WarningToastEvent>,
+) {
+    for ev in events.read() {
+        spawn_toast(&mut commands, ev.0.clone(), 4.0, ToastVariant::Warning);
+    }
+}
+
 /// Ticks down `ToastTimer` on each toast and despawns it when the timer expires.
 ///
 /// Skipped while the game is paused so toast countdowns freeze along with the

solitaire_engine/src/daily_challenge_plugin.rs

@@ -14,13 +14,13 @@
 use bevy::input::ButtonInput;
 use bevy::prelude::*;
 use bevy::tasks::{futures_lite::future, AsyncComputeTaskPool, Task};
-use chrono::{Local, NaiveDate};
+use chrono::{DateTime, Duration, Local, NaiveDate, Utc};
 use solitaire_data::{daily_seed_for, save_progress_to};
 use solitaire_sync::ChallengeGoal;
 
 use crate::events::{
     GameWonEvent, InfoToastEvent, NewGameRequestEvent, StartDailyChallengeRequestEvent,
-    XpAwardedEvent,
+    WarningToastEvent, XpAwardedEvent,
 };
 use crate::game_plugin::GameMutation;
 use crate::progress_plugin::{ProgressResource, ProgressStoragePath, ProgressUpdate};
@@ -30,6 +30,11 @@ use crate::sync_plugin::SyncProviderResource;
 /// Bonus XP awarded for completing today's daily challenge.
 pub const DAILY_BONUS_XP: u64 = 100;
 
+/// Minutes before UTC midnight at which the daily-challenge expiry warning
+/// fires. The reset is global (UTC), so the warning is global too — local
+/// midnight may be hours away or already past.
+pub const DAILY_EXPIRY_WARNING_MINUTES: i64 = 30;
+
 /// The active daily challenge — date + RNG seed for that date's deal,
 /// plus optional goal metadata fetched from the server.
 #[derive(Resource, Debug, Clone)]
@@ -74,6 +79,16 @@ pub struct DailyChallengeCompletedEvent {
 #[derive(Resource, Default)]
 struct DailyChallengeTask(Option<Task<Option<ChallengeGoal>>>);
 
+/// Tracks which `DailyChallengeResource::date` the expiry-warning toast has
+/// already fired for, so the toast spawns at most once per day.
+///
+/// `None` until the first warning fires; thereafter holds the date the
+/// warning was shown for. When `daily.date` advances (a new local day rolls
+/// over while the app stays open), this becomes stale and the next warning
+/// can fire.
+#[derive(Resource, Default, Debug)]
+struct DailyExpiryWarningShown(Option<NaiveDate>);
+
 /// Fetches today's daily challenge seed and goal from the sync server on startup and tracks completion.
 /// Fires `DailyChallengeCompletedEvent` when the player wins a matching game.
 pub struct DailyChallengePlugin;
@@ -82,18 +97,21 @@ impl Plugin for DailyChallengePlugin {
     fn build(&self, app: &mut App) {
         app.insert_resource(DailyChallengeResource::for_today())
             .init_resource::<DailyChallengeTask>()
+            .init_resource::<DailyExpiryWarningShown>()
             .add_message::<DailyChallengeCompletedEvent>()
             .add_message::<DailyGoalAnnouncementEvent>()
             .add_message::<GameWonEvent>()
             .add_message::<NewGameRequestEvent>()
             .add_message::<StartDailyChallengeRequestEvent>()
+            .add_message::<WarningToastEvent>()
             .add_message::<XpAwardedEvent>()
             .add_systems(Startup, fetch_server_challenge)
             .add_systems(Update, poll_server_challenge)
             // record/award after the base ProgressUpdate so we don't fight
             // ProgressPlugin's add_xp on the same frame.
             .add_systems(Update, handle_daily_completion.after(ProgressUpdate))
-            .add_systems(Update, handle_start_daily_request.before(GameMutation));
+            .add_systems(Update, handle_start_daily_request.before(GameMutation))
+            .add_systems(Update, check_daily_expiry_warning);
     }
 }
 
@@ -215,6 +233,71 @@ fn handle_start_daily_request(
     announce.write(DailyGoalAnnouncementEvent(desc));
 }
 
+/// Pure decision logic for the daily-challenge expiry warning. Returns the
+/// integer minutes-until-UTC-midnight if a warning toast should fire on this
+/// frame, or `None` if any suppression condition holds.
+///
+/// Suppression rules (in order):
+/// 1. Player has already completed today's daily challenge.
+/// 2. The warning has already fired for `daily_date`.
+/// 3. UTC midnight is more than [`DAILY_EXPIRY_WARNING_MINUTES`] away.
+/// 4. UTC midnight has already passed for the current calendar day (the
+///    minutes-remaining is negative — happens for at most one frame at the
+///    rollover boundary).
+///
+/// Factored out so the threshold/clock behavior is unit-testable without an
+/// `App`.
+fn compute_expiry_warning_minutes(
+    daily_date: NaiveDate,
+    last_completed: Option<NaiveDate>,
+    last_shown: Option<NaiveDate>,
+    now_utc: DateTime<Utc>,
+    threshold_mins: i64,
+) -> Option<i64> {
+    if last_completed == Some(daily_date) {
+        return None;
+    }
+    if last_shown == Some(daily_date) {
+        return None;
+    }
+    let next_midnight = (now_utc.date_naive() + Duration::days(1))
+        .and_hms_opt(0, 0, 0)?
+        .and_utc();
+    let mins_remaining = (next_midnight - now_utc).num_minutes();
+    if !(0..=threshold_mins).contains(&mins_remaining) {
+        return None;
+    }
+    Some(mins_remaining)
+}
+
+/// Each-frame check for the daily-challenge expiry warning. Fires a single
+/// [`WarningToastEvent`] when the player is within
+/// [`DAILY_EXPIRY_WARNING_MINUTES`] of UTC midnight reset and hasn't yet
+/// completed today's challenge.
+///
+/// Idempotent — `DailyExpiryWarningShown` ensures the toast spawns at most
+/// once per `daily.date`.
+fn check_daily_expiry_warning(
+    daily: Res<DailyChallengeResource>,
+    progress: Res<ProgressResource>,
+    mut shown: ResMut<DailyExpiryWarningShown>,
+    mut warning: MessageWriter<WarningToastEvent>,
+) {
+    let Some(mins) = compute_expiry_warning_minutes(
+        daily.date,
+        progress.0.daily_challenge_last_completed,
+        shown.0,
+        Utc::now(),
+        DAILY_EXPIRY_WARNING_MINUTES,
+    ) else {
+        return;
+    };
+    shown.0 = Some(daily.date);
+    warning.write(WarningToastEvent(format!(
+        "Daily challenge expires in {mins} min"
+    )));
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -385,4 +468,141 @@ mod tests {
         assert_eq!(r.target_score, Some(1_000));
         assert_eq!(r.max_time_secs, Some(300));
     }
+
+    // -----------------------------------------------------------------------
+    // Daily-expiry warning toast (compute_expiry_warning_minutes + system)
+    // -----------------------------------------------------------------------
+
+    fn ymd(y: i32, m: u32, d: u32) -> NaiveDate {
+        NaiveDate::from_ymd_opt(y, m, d).unwrap()
+    }
+
+    /// Construct a UTC `DateTime` at the given calendar position. Used to
+    /// drive the pure helper through every threshold edge.
+    fn utc_at(y: i32, m: u32, d: u32, h: u32, min: u32) -> DateTime<Utc> {
+        ymd(y, m, d).and_hms_opt(h, min, 0).unwrap().and_utc()
+    }
+
+    #[test]
+    fn warning_fires_inside_threshold_when_incomplete_and_unseen() {
+        // 23:50 UTC, 10 min until reset, < 30 min threshold.
+        let now = utc_at(2026, 5, 8, 23, 50);
+        let mins = compute_expiry_warning_minutes(ymd(2026, 5, 8), None, None, now, 30);
+        assert_eq!(mins, Some(10));
+    }
+
+    #[test]
+    fn warning_fires_at_exact_threshold_boundary() {
+        // 23:30 UTC, exactly 30 min remaining — the inclusive boundary.
+        let now = utc_at(2026, 5, 8, 23, 30);
+        let mins = compute_expiry_warning_minutes(ymd(2026, 5, 8), None, None, now, 30);
+        assert_eq!(mins, Some(30));
+    }
+
+    #[test]
+    fn warning_suppressed_outside_threshold() {
+        // 23:00 UTC, 60 min remaining — outside the 30 min window.
+        let now = utc_at(2026, 5, 8, 23, 0);
+        let mins = compute_expiry_warning_minutes(ymd(2026, 5, 8), None, None, now, 30);
+        assert_eq!(mins, None);
+    }
+
+    #[test]
+    fn warning_suppressed_when_already_completed_today() {
+        // 23:50 UTC inside threshold, but today is already done.
+        let now = utc_at(2026, 5, 8, 23, 50);
+        let mins = compute_expiry_warning_minutes(
+            ymd(2026, 5, 8),
+            Some(ymd(2026, 5, 8)),
+            None,
+            now,
+            30,
+        );
+        assert_eq!(mins, None);
+    }
+
+    #[test]
+    fn warning_suppressed_when_yesterdays_completion_is_stale() {
+        // Yesterday's completion is irrelevant — we want to warn about today.
+        let now = utc_at(2026, 5, 8, 23, 50);
+        let mins = compute_expiry_warning_minutes(
+            ymd(2026, 5, 8),
+            Some(ymd(2026, 5, 7)),
+            None,
+            now,
+            30,
+        );
+        assert_eq!(mins, Some(10));
+    }
+
+    #[test]
+    fn warning_suppressed_when_already_shown_for_this_date() {
+        let now = utc_at(2026, 5, 8, 23, 50);
+        let mins = compute_expiry_warning_minutes(
+            ymd(2026, 5, 8),
+            None,
+            Some(ymd(2026, 5, 8)),
+            now,
+            30,
+        );
+        assert_eq!(mins, None);
+    }
+
+    #[test]
+    fn warning_fires_when_last_shown_was_yesterday() {
+        // Player kept the app open across a midnight rollover. Stale
+        // "shown" date doesn't suppress today's warning.
+        let now = utc_at(2026, 5, 8, 23, 50);
+        let mins = compute_expiry_warning_minutes(
+            ymd(2026, 5, 8),
+            None,
+            Some(ymd(2026, 5, 7)),
+            now,
+            30,
+        );
+        assert_eq!(mins, Some(10));
+    }
+
+    #[test]
+    fn check_system_fires_warning_event_only_once_per_day() {
+        // The pure helper is exhaustively tested above. This test verifies
+        // the system that consumes it correctly stores the "shown" date so
+        // the WarningToastEvent fires at most once per `daily.date`, even
+        // when the system runs many frames in a row inside the threshold.
+        //
+        // The system reads `Utc::now()` directly, so we can't pin the clock.
+        // Instead, we simulate the post-warning state by pre-populating
+        // `DailyExpiryWarningShown` with `daily.date` and asserting nothing
+        // fires; then we verify the symmetric "completed today" suppression.
+        let mut app = headless_app();
+        let today = app.world().resource::<DailyChallengeResource>().date;
+
+        // Pre-mark warning as already shown for today.
+        app.world_mut()
+            .resource_mut::<DailyExpiryWarningShown>()
+            .0 = Some(today);
+        app.update();
+        let events = app.world().resource::<Messages<WarningToastEvent>>();
+        let mut cursor = events.get_cursor();
+        assert!(
+            cursor.read(events).next().is_none(),
+            "no warning fires when DailyExpiryWarningShown already covers today"
+        );
+
+        // Reset shown, mark today as completed.
+        app.world_mut()
+            .resource_mut::<DailyExpiryWarningShown>()
+            .0 = None;
+        app.world_mut()
+            .resource_mut::<ProgressResource>()
+            .0
+            .daily_challenge_last_completed = Some(today);
+        app.update();
+        let events = app.world().resource::<Messages<WarningToastEvent>>();
+        let mut cursor = events.get_cursor();
+        assert!(
+            cursor.read(events).next().is_none(),
+            "no warning fires when today is already completed"
+        );
+    }
 }

solitaire_engine/src/difficulty_plugin.rs

@@ -0,0 +1,235 @@
+//! Difficulty-tier game-start plugin.
+//!
+//! Handles [`StartDifficultyRequestEvent`] by picking the next seed from the
+//! appropriate pre-verified catalog in `solitaire_data::difficulty_seeds` and
+//! writing a [`NewGameRequestEvent`]. For [`DifficultyLevel::Random`] a
+//! system-time seed is used instead — the deal may or may not be winnable.
+//!
+//! # Catalog cycling
+//!
+//! Each tier maintains an independent cursor in [`DifficultyIndexResource`]
+//! that advances one step each time a game is started at that tier. The cursor
+//! wraps modulo the catalog length so players never run out of variety. The
+//! resource is *not* persisted — it resets to 0 on every launch, which is fine
+//! because the starting position is effectively random (player-chosen timing
+//! determines which seed in the 40-entry catalog they start at).
+
+use std::time::{SystemTime, UNIX_EPOCH};
+
+use bevy::prelude::*;
+use solitaire_core::game_state::{DifficultyLevel, GameMode};
+use solitaire_data::difficulty_seeds::seeds_for;
+
+use crate::events::{NewGameRequestEvent, StartDifficultyRequestEvent};
+use crate::game_plugin::GameMutation;
+
+// ---------------------------------------------------------------------------
+// Resources
+// ---------------------------------------------------------------------------
+
+/// Per-tier catalog cursors. Each value is the index of the **next** seed to
+/// deal from that tier's catalog. Wraps modulo the catalog length.
+#[derive(Resource, Default)]
+pub struct DifficultyIndexResource {
+    easy: usize,
+    medium: usize,
+    hard: usize,
+    expert: usize,
+    grandmaster: usize,
+}
+
+impl DifficultyIndexResource {
+    /// Advance the cursor for `level` and return the seed at the old position.
+    /// Falls back to a system-time seed if the catalog is unexpectedly empty.
+    pub fn next_seed(&mut self, level: DifficultyLevel) -> u64 {
+        let Some(catalog) = seeds_for(level) else {
+            return seed_from_system_time();
+        };
+        if catalog.is_empty() {
+            return seed_from_system_time();
+        }
+        let cursor = match level {
+            DifficultyLevel::Easy => &mut self.easy,
+            DifficultyLevel::Medium => &mut self.medium,
+            DifficultyLevel::Hard => &mut self.hard,
+            DifficultyLevel::Expert => &mut self.expert,
+            DifficultyLevel::Grandmaster => &mut self.grandmaster,
+            DifficultyLevel::Random => unreachable!("Random has no catalog"),
+        };
+        let seed = catalog[*cursor % catalog.len()];
+        *cursor = cursor.wrapping_add(1);
+        seed
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Plugin
+// ---------------------------------------------------------------------------
+
+/// Registers all difficulty-mode systems and resources.
+pub struct DifficultyPlugin;
+
+impl Plugin for DifficultyPlugin {
+    fn build(&self, app: &mut App) {
+        app.init_resource::<DifficultyIndexResource>()
+            .add_message::<StartDifficultyRequestEvent>()
+            .add_message::<NewGameRequestEvent>()
+            .add_systems(
+                Update,
+                handle_difficulty_request.before(GameMutation),
+            );
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Systems
+// ---------------------------------------------------------------------------
+
+/// Resolves `StartDifficultyRequestEvent` → catalog seed → `NewGameRequestEvent`.
+fn handle_difficulty_request(
+    mut requests: MessageReader<StartDifficultyRequestEvent>,
+    mut new_game: MessageWriter<NewGameRequestEvent>,
+    mut index: ResMut<DifficultyIndexResource>,
+) {
+    for ev in requests.read() {
+        let seed = if ev.level == DifficultyLevel::Random {
+            seed_from_system_time()
+        } else {
+            index.next_seed(ev.level)
+        };
+
+        new_game.write(NewGameRequestEvent {
+            seed: Some(seed),
+            mode: Some(GameMode::Difficulty(ev.level)),
+            confirmed: false,
+        });
+    }
+}
+
+fn seed_from_system_time() -> u64 {
+    SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map(|d| d.as_nanos() as u64)
+        .unwrap_or(0xD1FF_0000_DEAD_BEEF)
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::game_plugin::GamePlugin;
+    use crate::table_plugin::TablePlugin;
+    use solitaire_data::difficulty_seeds::{EASY_SEEDS, MEDIUM_SEEDS};
+
+    fn headless_app() -> App {
+        let mut app = App::new();
+        app.add_plugins(MinimalPlugins)
+            .add_plugins(GamePlugin)
+            .add_plugins(TablePlugin)
+            .add_plugins(DifficultyPlugin);
+        app.update();
+        app
+    }
+
+    fn fire_request(app: &mut App, level: DifficultyLevel) {
+        app.world_mut()
+            .write_message(StartDifficultyRequestEvent { level });
+        app.update();
+    }
+
+    fn drain_new_game_events(app: &mut App) -> Vec<NewGameRequestEvent> {
+        let msgs = app.world().resource::<Messages<NewGameRequestEvent>>();
+        let mut cursor = msgs.get_cursor();
+        cursor.read(msgs).copied().collect()
+    }
+
+    #[test]
+    fn easy_request_dispatches_seed_from_easy_catalog() {
+        let mut app = headless_app();
+        fire_request(&mut app, DifficultyLevel::Easy);
+
+        let events = drain_new_game_events(&mut app);
+        assert_eq!(events.len(), 1);
+        let ev = &events[0];
+        assert!(ev.seed.is_some());
+        assert_eq!(ev.mode, Some(GameMode::Difficulty(DifficultyLevel::Easy)));
+        assert!(!ev.confirmed);
+        // Seed must come from the Easy catalog (non-empty catalog is the test
+        // precondition — the catalog uniqueness test in difficulty_seeds.rs
+        // guards integrity).
+        if !EASY_SEEDS.is_empty() {
+            assert!(
+                EASY_SEEDS.contains(&ev.seed.unwrap()),
+                "seed {:?} not in EASY_SEEDS",
+                ev.seed
+            );
+        }
+    }
+
+    #[test]
+    fn successive_easy_requests_cycle_through_catalog() {
+        let mut app = headless_app();
+        fire_request(&mut app, DifficultyLevel::Easy);
+        fire_request(&mut app, DifficultyLevel::Easy);
+
+        let events = drain_new_game_events(&mut app);
+        assert_eq!(events.len(), 2);
+        // Two successive requests should return different seeds (assuming the
+        // catalog has at least 2 entries — it has 40).
+        if EASY_SEEDS.len() >= 2 {
+            assert_ne!(
+                events[0].seed, events[1].seed,
+                "successive Easy requests should produce different seeds"
+            );
+        }
+    }
+
+    #[test]
+    fn medium_request_dispatches_seed_from_medium_catalog() {
+        let mut app = headless_app();
+        fire_request(&mut app, DifficultyLevel::Medium);
+
+        let events = drain_new_game_events(&mut app);
+        assert_eq!(events.len(), 1);
+        assert_eq!(
+            events[0].mode,
+            Some(GameMode::Difficulty(DifficultyLevel::Medium))
+        );
+        if !MEDIUM_SEEDS.is_empty() {
+            assert!(MEDIUM_SEEDS.contains(&events[0].seed.unwrap()));
+        }
+    }
+
+    #[test]
+    fn random_request_dispatches_some_seed_with_random_mode() {
+        let mut app = headless_app();
+        fire_request(&mut app, DifficultyLevel::Random);
+
+        let events = drain_new_game_events(&mut app);
+        assert_eq!(events.len(), 1);
+        assert!(events[0].seed.is_some(), "Random should always produce Some(seed)");
+        assert_eq!(
+            events[0].mode,
+            Some(GameMode::Difficulty(DifficultyLevel::Random))
+        );
+    }
+
+    #[test]
+    fn different_tier_cursors_are_independent() {
+        let mut app = headless_app();
+        fire_request(&mut app, DifficultyLevel::Easy);
+        fire_request(&mut app, DifficultyLevel::Medium);
+
+        let events = drain_new_game_events(&mut app);
+        assert_eq!(events.len(), 2);
+        // Seeds from different catalogs should differ (they come from different
+        // address ranges by construction of gen_difficulty_seeds).
+        assert_ne!(
+            events[0].seed, events[1].seed,
+            "Easy and Medium should draw from independent catalogs"
+        );
+    }
+}

solitaire_engine/src/events.rs

@@ -172,6 +172,23 @@ pub struct StartTimeAttackRequestEvent;
 #[derive(Message, Debug, Clone, Copy, Default)]
 pub struct StartDailyChallengeRequestEvent;
 
+/// Request to open the Play-by-Seed dialog. Fired by the Home overlay
+/// "Play by Seed" mode card. The handler in `play_by_seed_plugin` spawns
+/// a numeric-input modal where the player types a decimal seed and
+/// optionally sees a solver-verified verdict before dealing.
+#[derive(Message, Debug, Clone, Copy, Default)]
+pub struct StartPlayBySeedRequestEvent;
+
+/// Request to start a game at a specific difficulty tier. Fired by the
+/// difficulty section in the home overlay. The handler in `difficulty_plugin`
+/// picks a seed from the corresponding pre-verified catalog (or generates a
+/// random system-time seed for `DifficultyLevel::Random`) and writes a
+/// `NewGameRequestEvent`.
+#[derive(Message, Debug, Clone, Copy)]
+pub struct StartDifficultyRequestEvent {
+    pub level: solitaire_core::game_state::DifficultyLevel,
+}
+
 /// Request to toggle the Stats overlay. Fired by the HUD Menu-popover
 /// "Stats" row alongside the existing `S` accelerator.
 #[derive(Message, Debug, Clone, Copy, Default)]
@@ -212,6 +229,21 @@ pub struct SyncCompleteEvent(pub Result<SyncResponse, String>);
 #[derive(Message, Debug, Clone)]
 pub struct InfoToastEvent(pub String);
 
+/// Generic warning toast message. Spawns a fire-and-forget
+/// [`ToastVariant::Warning`](crate::animation_plugin::ToastVariant) toast.
+///
+/// Distinct from [`InfoToastEvent`] in two ways:
+/// 1. **Variant.** Warning carries the design-system warning border accent,
+///    not the neutral info accent — so the player can distinguish "you might
+///    want to act" from "here's some neutral information".
+/// 2. **No queue.** Warnings are alerts, not a stream. Each event spawns its
+///    own toast immediately rather than waiting for the info queue to drain.
+///
+/// First in-engine driver: daily-challenge expiry warning fired by
+/// `daily_challenge_plugin` when < 30 min from UTC midnight reset.
+#[derive(Message, Debug, Clone)]
+pub struct WarningToastEvent(pub String);
+
 /// Fired by `ProgressPlugin` immediately after awarding XP for a win so the
 /// animation layer can display a "+N XP" toast alongside the win cascade.
 #[derive(Message, Debug, Clone, Copy)]

solitaire_engine/src/game_plugin.rs

@@ -936,6 +936,11 @@ pub fn record_replay_on_win(
         if recording.moves.is_empty() {
             continue;
         }
+        // Recording freezes on win, so the move that triggered the
+        // win condition is the last one in the list. Storing the
+        // index explicitly lets the playback UI read the WIN MOVE
+        // position directly instead of re-deriving it on every render.
+        let win_move_index = recording.moves.len().checked_sub(1);
         let replay = Replay::new(
             game.0.seed,
             game.0.draw_mode.clone(),
@@ -944,7 +949,8 @@ pub fn record_replay_on_win(
             ev.score,
             Utc::now().date_naive(),
             recording.moves.clone(),
-        );
+        )
+        .with_win_move_index(win_move_index);
         let Some(p) = path.as_ref().and_then(|r| r.0.as_deref()) else {
             // No persistence path configured (e.g. tests / minimal Linux
             // containers without dirs::data_dir). The in-memory replay

solitaire_engine/src/home_plugin.rs

@@ -16,15 +16,15 @@
 use bevy::input::mouse::{MouseScrollUnit, MouseWheel};
 use bevy::input::ButtonInput;
 use bevy::prelude::*;
-use solitaire_core::game_state::DrawMode;
+use solitaire_core::game_state::{DifficultyLevel, DrawMode};
 use solitaire_data::save_settings_to;
 
 use crate::challenge_plugin::CHALLENGE_UNLOCK_LEVEL;
 use crate::daily_challenge_plugin::DailyChallengeResource;
 use crate::events::{
     InfoToastEvent, NewGameRequestEvent, StartChallengeRequestEvent,
-    StartDailyChallengeRequestEvent, StartTimeAttackRequestEvent, StartZenRequestEvent,
+    StartDailyChallengeRequestEvent, StartDifficultyRequestEvent, StartPlayBySeedRequestEvent,
-    ToggleProfileRequestEvent,
+    StartTimeAttackRequestEvent, StartZenRequestEvent, ToggleProfileRequestEvent,
 };
 use crate::font_plugin::FontResource;
 use crate::progress_plugin::ProgressResource;
@@ -81,6 +81,27 @@ struct HomeDrawThreeButton;
 #[derive(Component, Debug)]
 struct HomeScrollable;
 
+/// Marker on the "▶ Difficulty" / "▼ Difficulty" toggle button that
+/// expands / collapses the difficulty tier chip row.
+#[derive(Component, Debug)]
+struct HomeDifficultyToggle;
+
+/// Marker on each difficulty tier chip inside the expanded difficulty
+/// section. The wrapped `DifficultyLevel` identifies which tier was
+/// clicked so the handler can fire `StartDifficultyRequestEvent`.
+#[derive(Component, Debug)]
+struct HomeDifficultyChip(DifficultyLevel);
+
+/// Whether the difficulty section is currently expanded. Toggled by
+/// `handle_home_difficulty_toggle` and checked by `spawn_home_screen`
+/// to determine initial render state.
+///
+/// Initialised at plugin startup; `spawn_home_on_launch` upgrades it
+/// to `true` when `settings.last_difficulty` is already set so
+/// returning players see their tier pre-expanded.
+#[derive(Resource, Default, Debug)]
+pub struct DifficultyExpanded(pub bool);
+
 // ---------------------------------------------------------------------------
 // Private mode-card data shape
 // ---------------------------------------------------------------------------
@@ -96,6 +117,7 @@ enum HomeMode {
     Zen,
     Challenge,
     TimeAttack,
+    PlayBySeed,
 }
 
 impl HomeMode {
@@ -107,6 +129,7 @@ impl HomeMode {
             HomeMode::Zen => "Zen Mode",
             HomeMode::Challenge => "Challenge",
             HomeMode::TimeAttack => "Time Attack",
+            HomeMode::PlayBySeed => "Play by Seed",
         }
     }
 
@@ -118,6 +141,7 @@ impl HomeMode {
             HomeMode::Zen => "No timer, no score. Just the cards.",
             HomeMode::Challenge => "Hand-picked hard deals. No undo. Win to advance.",
             HomeMode::TimeAttack => "How many can you finish in ten minutes?",
+            HomeMode::PlayBySeed => "Enter any number to play a specific deal.",
         }
     }
 
@@ -150,6 +174,9 @@ impl HomeMode {
             // ships ▲ (up triangle) but evidently not the sideways
             // siblings.
             HomeMode::TimeAttack => "\u{2192}",
+            // Number sign — ASCII, universally available. Reads as
+            // "a specific number / seed ID".
+            HomeMode::PlayBySeed => "#",
         }
     }
 
@@ -162,6 +189,7 @@ impl HomeMode {
             HomeMode::Zen => "Z",
             HomeMode::Challenge => "X",
             HomeMode::TimeAttack => "T",
+            HomeMode::PlayBySeed => "6",
         }
     }
 
@@ -233,11 +261,14 @@ impl Plugin for HomePlugin {
         // Pre-mark the auto-show as already done in headless mode so the
         // gating system is a permanent no-op for tests.
         app.insert_resource(LaunchHomeShown(!self.auto_show_on_launch))
+            .init_resource::<DifficultyExpanded>()
             .add_message::<NewGameRequestEvent>()
             .add_message::<StartZenRequestEvent>()
             .add_message::<StartChallengeRequestEvent>()
             .add_message::<StartTimeAttackRequestEvent>()
             .add_message::<StartDailyChallengeRequestEvent>()
+            .add_message::<StartPlayBySeedRequestEvent>()
+            .add_message::<StartDifficultyRequestEvent>()
             .add_message::<InfoToastEvent>()
             .add_message::<ToggleProfileRequestEvent>()
             .add_message::<SettingsChangedEvent>()
@@ -245,13 +276,10 @@ impl Plugin for HomePlugin {
             // runs cleanly under MinimalPlugins headless tests too.
             .add_message::<MouseWheel>()
             // `.chain()` because several systems (M-toggle, card click,
-            // cancel button, digit-key shortcut) all read the
+            // cancel button, digit-key shortcut, difficulty handlers)
-            // `HomeScreen` entity and may queue a despawn on it in the
+            // all read the `HomeScreen` entity and may queue a despawn
-            // same tick. Bevy's parallel scheduler would otherwise let
+            // on it in the same tick. Chaining serialises these systems
-            // two of them run simultaneously and double-despawn the
+            // and keeps the despawn deterministic.
-            // entity, panicking when the second command buffer is
-            // applied. Chaining serialises these systems and keeps the
-            // despawn deterministic.
             .add_systems(
                 Update,
                 (
@@ -262,6 +290,8 @@ impl Plugin for HomePlugin {
                     handle_home_cancel_button,
                     handle_home_profile_chip,
                     handle_home_draw_mode_buttons,
+                    handle_home_difficulty_toggle,
+                    handle_home_difficulty_chip_click,
                     handle_home_digit_keys,
                 )
                     .chain(),
@@ -306,6 +336,7 @@ fn spawn_home_on_launch(
     settings: Option<Res<SettingsResource>>,
     daily: Option<Res<DailyChallengeResource>>,
     font_res: Option<Res<FontResource>>,
+    mut diff_expanded: ResMut<DifficultyExpanded>,
 ) {
     if shown.0
         || !splash.is_empty()
@@ -316,6 +347,11 @@ fn spawn_home_on_launch(
         return;
     }
 
+    // Pre-expand the difficulty section when the player has a saved preference.
+    if settings.as_ref().is_some_and(|s| s.0.last_difficulty.is_some()) {
+        diff_expanded.0 = true;
+    }
+
     spawn_home_screen(
         &mut commands,
         build_home_context(
@@ -324,6 +360,7 @@ fn spawn_home_on_launch(
             settings.as_deref(),
             daily.as_deref(),
             font_res.as_deref(),
+            diff_expanded.0,
         ),
     );
     shown.0 = true;
@@ -343,6 +380,7 @@ fn toggle_home_screen(
     daily: Option<Res<DailyChallengeResource>>,
     font_res: Option<Res<FontResource>>,
     screens: Query<Entity, With<HomeScreen>>,
+    diff_expanded: Res<DifficultyExpanded>,
 ) {
     if !keys.just_pressed(KeyCode::KeyM) {
         return;
@@ -358,6 +396,7 @@ fn toggle_home_screen(
                 settings.as_deref(),
                 daily.as_deref(),
                 font_res.as_deref(),
+                diff_expanded.0,
             ),
         );
     }
@@ -373,6 +412,7 @@ fn build_home_context<'a>(
     settings: Option<&SettingsResource>,
     daily: Option<&DailyChallengeResource>,
     font_res: Option<&'a FontResource>,
+    difficulty_expanded: bool,
 ) -> HomeContext<'a> {
     let daily_today = daily.map(|d| {
         let completed_today = progress
@@ -398,6 +438,8 @@ fn build_home_context<'a>(
             .map(|s| s.0.draw_mode.clone())
             .unwrap_or(DrawMode::DrawOne),
         font_res,
+        difficulty_expanded,
+        last_difficulty: settings.and_then(|s| s.0.last_difficulty),
     }
 }
 
@@ -423,6 +465,7 @@ fn handle_home_card_click(
     mut challenge: MessageWriter<StartChallengeRequestEvent>,
     mut time_attack: MessageWriter<StartTimeAttackRequestEvent>,
     mut daily: MessageWriter<StartDailyChallengeRequestEvent>,
+    mut play_by_seed: MessageWriter<StartPlayBySeedRequestEvent>,
     mut info_toast: MessageWriter<InfoToastEvent>,
 ) {
     let level = progress.as_ref().map_or(0, |p| p.0.level);
@@ -457,6 +500,9 @@ fn handle_home_card_click(
             HomeMode::TimeAttack => {
                 time_attack.write(StartTimeAttackRequestEvent);
             }
+            HomeMode::PlayBySeed => {
+                play_by_seed.write(StartPlayBySeedRequestEvent);
+            }
         }
 
         // Close the modal after dispatching the launch event.
@@ -557,6 +603,7 @@ fn handle_home_draw_mode_buttons(
     stats: Option<Res<StatsResource>>,
     daily: Option<Res<DailyChallengeResource>>,
     font_res: Option<Res<FontResource>>,
+    diff_expanded: Res<DifficultyExpanded>,
 ) {
     if screens.is_empty() {
         return;
@@ -600,10 +647,92 @@ fn handle_home_draw_mode_buttons(
             Some(settings),
             daily.as_deref(),
             font_res.as_deref(),
+            diff_expanded.0,
         ),
     );
 }
 
+// ---------------------------------------------------------------------------
+// Difficulty section handlers
+// ---------------------------------------------------------------------------
+
+/// Click on the "▶/▼ Difficulty" header — toggle `DifficultyExpanded` and
+/// repaint the Home modal so the chevron and chip row update. Mirrors
+/// `handle_home_draw_mode_buttons`: despawn + respawn keeps all styling in
+/// `spawn_difficulty_section` rather than scattered across mutation helpers.
+#[allow(clippy::too_many_arguments)]
+fn handle_home_difficulty_toggle(
+    mut commands: Commands,
+    toggles: Query<&Interaction, (With<HomeDifficultyToggle>, Changed<Interaction>)>,
+    screens: Query<Entity, With<HomeScreen>>,
+    mut diff_expanded: ResMut<DifficultyExpanded>,
+    progress: Option<Res<ProgressResource>>,
+    stats: Option<Res<StatsResource>>,
+    settings: Option<Res<SettingsResource>>,
+    daily: Option<Res<DailyChallengeResource>>,
+    font_res: Option<Res<FontResource>>,
+) {
+    if screens.is_empty() {
+        return;
+    }
+    if !toggles.iter().any(|i| *i == Interaction::Pressed) {
+        return;
+    }
+    diff_expanded.0 = !diff_expanded.0;
+    for entity in &screens {
+        commands.entity(entity).despawn();
+    }
+    spawn_home_screen(
+        &mut commands,
+        build_home_context(
+            progress.as_deref(),
+            stats.as_deref(),
+            settings.as_deref(),
+            daily.as_deref(),
+            font_res.as_deref(),
+            diff_expanded.0,
+        ),
+    );
+}
+
+/// Click on a difficulty tier chip — persist `last_difficulty`, fire
+/// `StartDifficultyRequestEvent`, and close the Home modal.
+#[allow(clippy::too_many_arguments)]
+fn handle_home_difficulty_chip_click(
+    mut commands: Commands,
+    chips: Query<(&Interaction, &HomeDifficultyChip), Changed<Interaction>>,
+    screens: Query<Entity, With<HomeScreen>>,
+    mut difficulty_ev: MessageWriter<StartDifficultyRequestEvent>,
+    mut settings: Option<ResMut<SettingsResource>>,
+    storage_path: Option<Res<SettingsStoragePath>>,
+    mut changed: MessageWriter<SettingsChangedEvent>,
+) {
+    if screens.is_empty() {
+        return;
+    }
+    let Some((_, chip)) = chips.iter().find(|(i, _)| **i == Interaction::Pressed) else {
+        return;
+    };
+    let level = chip.0;
+
+    if let Some(s) = settings.as_mut() {
+        s.0.last_difficulty = Some(level);
+        if let Some(p) = storage_path
+            && let Some(path) = p.0.as_deref()
+            && let Err(e) = save_settings_to(path, &s.0)
+        {
+            warn!("home: failed to persist last_difficulty: {e}");
+        }
+        changed.write(SettingsChangedEvent(s.0.clone()));
+    }
+
+    difficulty_ev.write(StartDifficultyRequestEvent { level });
+
+    for entity in &screens {
+        commands.entity(entity).despawn();
+    }
+}
+
 // ---------------------------------------------------------------------------
 // Digit-key shortcuts (1-5) — modal-scoped
 // ---------------------------------------------------------------------------
@@ -619,6 +748,7 @@ fn digit_to_home_mode(key: KeyCode) -> Option<HomeMode> {
         KeyCode::Digit3 => Some(HomeMode::Zen),
         KeyCode::Digit4 => Some(HomeMode::Challenge),
         KeyCode::Digit5 => Some(HomeMode::TimeAttack),
+        KeyCode::Digit6 => Some(HomeMode::PlayBySeed),
         _ => None,
     }
 }
@@ -646,6 +776,7 @@ fn handle_home_digit_keys(
     mut challenge: MessageWriter<StartChallengeRequestEvent>,
     mut time_attack: MessageWriter<StartTimeAttackRequestEvent>,
     mut daily: MessageWriter<StartDailyChallengeRequestEvent>,
+    mut play_by_seed: MessageWriter<StartPlayBySeedRequestEvent>,
 ) {
     // Modal-scoped: do nothing when the Mode Launcher isn't open.
     if screens.is_empty() {
@@ -658,6 +789,7 @@ fn handle_home_digit_keys(
         KeyCode::Digit3,
         KeyCode::Digit4,
         KeyCode::Digit5,
+        KeyCode::Digit6,
     ]
     .into_iter()
     .find(|k| keys.just_pressed(*k))
@@ -687,6 +819,9 @@ fn handle_home_digit_keys(
         HomeMode::TimeAttack => {
             time_attack.write(StartTimeAttackRequestEvent);
         }
+        HomeMode::PlayBySeed => {
+            play_by_seed.write(StartPlayBySeedRequestEvent);
+        }
     }
 
     // Close the modal after dispatching the launch event — same shape as
@@ -717,6 +852,11 @@ struct HomeContext<'a> {
     daily_today: Option<DailyToday>,
     draw_mode: DrawMode,
     font_res: Option<&'a FontResource>,
+    /// Whether the difficulty section header is currently expanded.
+    difficulty_expanded: bool,
+    /// The last difficulty tier the player selected (persisted in Settings).
+    /// When `Some`, that tier's chip is highlighted.
+    last_difficulty: Option<DifficultyLevel>,
 }
 
 /// Today's daily-challenge metadata as the Home picker needs it. Only
@@ -784,10 +924,13 @@ fn spawn_home_screen(commands: &mut Commands, ctx: HomeContext<'_>) {
                     HomeMode::Zen,
                     HomeMode::Challenge,
                     HomeMode::TimeAttack,
+                    HomeMode::PlayBySeed,
                 ] {
                     spawn_mode_card(grid, mode, &ctx);
                 }
             });
+
+            spawn_difficulty_section(body, &ctx);
         });
 
         spawn_modal_actions(card, |actions| {
@@ -951,6 +1094,101 @@ fn spawn_draw_mode_chip<M: Component>(
         });
 }
 
+/// Collapsible difficulty-tier section injected below the mode tile grid.
+///
+/// Structure:
+/// ```text
+/// ▶ Difficulty        ← HomeDifficultyToggle (Button, row)
+/// [Easy] [Medium] [Hard] [Expert] [GM] [Random]   ← visible only when expanded
+/// ```
+///
+/// The toggle header despawns + respawns the home screen (same pattern as
+/// the draw-mode toggle) so the chevron direction and chip row visibility
+/// update without Visibility component surgery.
+fn spawn_difficulty_section(parent: &mut ChildSpawnerCommands, ctx: &HomeContext<'_>) {
+    let font_handle = ctx.font_res.map(|f| f.0.clone()).unwrap_or_default();
+    let font_label = TextFont { font: font_handle.clone(), font_size: TYPE_BODY, ..default() };
+    let font_chip = TextFont { font: font_handle, font_size: TYPE_CAPTION, ..default() };
+
+    let chevron = if ctx.difficulty_expanded { "▼" } else { "▶" };
+
+    // Header row — click to toggle expand/collapse.
+    parent
+        .spawn((
+            HomeDifficultyToggle,
+            Button,
+            Node {
+                flex_direction: FlexDirection::Row,
+                align_items: AlignItems::Center,
+                column_gap: VAL_SPACE_2,
+                padding: UiRect::axes(Val::Px(0.0), VAL_SPACE_1),
+                ..default()
+            },
+        ))
+        .with_children(|row| {
+            row.spawn((
+                Text::new(chevron),
+                font_label.clone(),
+                TextColor(TEXT_SECONDARY),
+            ));
+            row.spawn((
+                Text::new("Difficulty"),
+                font_label.clone(),
+                TextColor(TEXT_SECONDARY),
+            ));
+        });
+
+    // Tier chips — only rendered when expanded.
+    if ctx.difficulty_expanded {
+        parent
+            .spawn(Node {
+                flex_direction: FlexDirection::Row,
+                flex_wrap: FlexWrap::Wrap,
+                row_gap: VAL_SPACE_2,
+                column_gap: VAL_SPACE_2,
+                width: Val::Percent(100.0),
+                ..default()
+            })
+            .with_children(|row| {
+                for level in [
+                    DifficultyLevel::Easy,
+                    DifficultyLevel::Medium,
+                    DifficultyLevel::Hard,
+                    DifficultyLevel::Expert,
+                    DifficultyLevel::Grandmaster,
+                    DifficultyLevel::Random,
+                ] {
+                    let active = ctx.last_difficulty == Some(level);
+                    let (bg, fg) = if active {
+                        (ACCENT_PRIMARY, BG_ELEVATED)
+                    } else {
+                        (BG_ELEVATED_HI, TEXT_PRIMARY)
+                    };
+                    row.spawn((
+                        HomeDifficultyChip(level),
+                        Button,
+                        Node {
+                            padding: UiRect::axes(VAL_SPACE_3, VAL_SPACE_1),
+                            border: UiRect::all(Val::Px(1.0)),
+                            border_radius: BorderRadius::all(Val::Px(RADIUS_MD)),
+                            ..default()
+                        },
+                        BackgroundColor(bg),
+                        BorderColor::all(BORDER_SUBTLE),
+                        HighContrastBorder::with_default(BORDER_SUBTLE),
+                    ))
+                    .with_children(|c| {
+                        c.spawn((
+                            Text::new(level.label()),
+                            font_chip.clone(),
+                            TextColor(fg),
+                        ));
+                    });
+                }
+            });
+    }
+}
+
 /// Compact decimal formatter: `1234567` → `"1.2M"`, `12345` → `"12.3K"`,
 /// otherwise the raw number with thousands separators. Keeps chip text
 /// short enough to fit a 3-up header strip without wrapping.
@@ -999,6 +1237,7 @@ fn home_mode_focus_order(mode: HomeMode) -> i32 {
         HomeMode::Zen => 2,
         HomeMode::Challenge => 3,
         HomeMode::TimeAttack => 4,
+        HomeMode::PlayBySeed => 5,
     }
 }
 
@@ -1402,13 +1641,14 @@ mod tests {
             HomeMode::Zen,
             HomeMode::Challenge,
             HomeMode::TimeAttack,
+            HomeMode::PlayBySeed,
         ] {
             assert!(
                 modes.contains(&expected),
                 "missing card for {expected:?}; found {modes:?}"
             );
         }
-        assert_eq!(modes.len(), 5, "exactly five cards expected");
+        assert_eq!(modes.len(), 6, "exactly six cards expected");
     }
 
     #[test]
@@ -1600,7 +1840,7 @@ mod tests {
             .map(|(c, f)| (c.0, *f))
             .collect();
 
-        assert_eq!(cards.len(), 5, "all five cards must carry a Focusable");
+        assert_eq!(cards.len(), 6, "all six cards must carry a Focusable");
         for (mode, focusable) in &cards {
             assert_eq!(
                 focusable.group,
@@ -1626,7 +1866,7 @@ mod tests {
 
         for (mode, disabled) in states {
             match mode {
-                HomeMode::Classic | HomeMode::Daily => assert!(
+                HomeMode::Classic | HomeMode::Daily | HomeMode::PlayBySeed => assert!(
                     !disabled,
                     "{mode:?} must not be Disabled at level 0 (it's never locked)"
                 ),

solitaire_engine/src/hud_plugin.rs

@@ -19,7 +19,7 @@ use crate::settings_plugin::SettingsResource;
 use crate::layout::HUD_BAND_HEIGHT;
 use crate::ui_theme::{
     scaled_duration, ACCENT_PRIMARY, ACCENT_SECONDARY, BG_ELEVATED, BG_ELEVATED_HI,
-    BG_ELEVATED_PRESSED, BG_HUD_BAND, BORDER_SUBTLE, MOTION_SCORE_PULSE_SECS,
+    BG_ELEVATED_PRESSED, BG_HUD_BAND, BORDER_SUBTLE, HighContrastBorder, MOTION_SCORE_PULSE_SECS,
     MOTION_STREAK_FLOURISH_SECS, RADIUS_MD, RADIUS_SM, STATE_DANGER, STATE_INFO, STATE_SUCCESS,
     STATE_WARNING, STREAK_FLOURISH_PEAK_SCALE, TEXT_PRIMARY, TEXT_SECONDARY, TYPE_BODY,
     TYPE_BODY_LG, TYPE_CAPTION, TYPE_HEADLINE, VAL_SPACE_1, VAL_SPACE_2, VAL_SPACE_3,
@@ -715,6 +715,7 @@ fn spawn_action_button<M: Component>(
         },
         BackgroundColor(ACTION_BTN_IDLE),
         BorderColor::all(BORDER_SUBTLE),
+        HighContrastBorder::with_default(BORDER_SUBTLE),
     ))
     .with_children(|b| {
         b.spawn((Text::new(label), font.clone(), TextColor(TEXT_PRIMARY)));
@@ -1740,6 +1741,7 @@ fn update_hud(
                 GameMode::Zen => "ZEN".to_string(),
                 GameMode::Challenge => "CHALLENGE".to_string(),
                 GameMode::TimeAttack => "TIME ATTACK".to_string(),
+                GameMode::Difficulty(level) => level.label().to_uppercase(),
             };
         }
 

solitaire_engine/src/input_plugin.rs

@@ -23,7 +23,9 @@ use bevy::input::touch::{TouchInput, TouchPhase, Touches};
 use bevy::input::ButtonInput;
 use bevy::math::{Vec2, Vec3};
 use bevy::prelude::*;
-use bevy::window::{MonitorSelection, PrimaryWindow, WindowMode};
+use bevy::window::PrimaryWindow;
+#[cfg(not(target_os = "android"))]
+use bevy::window::{MonitorSelection, WindowMode};
 use solitaire_core::card::{Card, Suit};
 use solitaire_core::game_state::GameState;
 use solitaire_core::pile::PileType;
@@ -105,12 +107,16 @@ impl Plugin for InputPlugin {
                     // Touch drag pipeline (parallel path through DragState).
                     touch_start_drag,
                     touch_follow_drag,
+                    handle_double_tap, // before touch_end_drag: reads drag state pre-clear
                     touch_end_drag.before(GameMutation),
                 )
                     .chain(),
             )
-            .add_systems(Update, handle_fullscreen)
+            .add_systems(Update, reset_hint_cycle_on_state_change);
-            .add_systems(Update, reset_hint_cycle_on_state_change)
+        // F11 fullscreen toggle is desktop-only; Android windows are always full-screen.
+        #[cfg(not(target_os = "android"))]
+        app.add_systems(Update, handle_fullscreen);
+        app
             // Async hint pipeline: state-change drop runs before the
             // poll system so a move applied this frame cancels any
             // in-flight task before its result can be surfaced.
@@ -423,6 +429,7 @@ fn reset_hint_cycle_on_state_change(
 
 /// `F11` toggles between borderless-fullscreen and windowed mode.
 /// Not gated by the pause flag — the player can always resize the window.
+#[cfg(not(target_os = "android"))]
 fn handle_fullscreen(
     keys: Res<ButtonInput<KeyCode>>,
     mut windows: Query<&mut Window, With<PrimaryWindow>>,
@@ -1204,12 +1211,16 @@ fn pile_drop_rect(pile: &PileType, layout: &Layout, game: &GameState) -> (Vec2,
 }
 
 // ---------------------------------------------------------------------------
-// Task #27 — Double-click to auto-move
+// Task #27 — Double-click / double-tap to auto-move
 // ---------------------------------------------------------------------------
 
 /// Maximum seconds between two clicks to count as a double-click.
 const DOUBLE_CLICK_WINDOW: f32 = 0.35;
 
+/// Maximum seconds between two taps to count as a double-tap.
+/// Slightly wider than the mouse window — touch screens have higher latency.
+const DOUBLE_TAP_WINDOW: f32 = 0.5;
+
 /// Find the best legal destination for `card` — Foundation first, then Tableau.
 ///
 /// Returns `None` if no legal move exists from the card's current location.
@@ -1363,6 +1374,124 @@ fn handle_double_click(
     }
 }
 
+// ---------------------------------------------------------------------------
+// Task #27b — Double-tap to auto-move (touch equivalent of double-click)
+// ---------------------------------------------------------------------------
+
+/// System that detects double-taps on face-up cards and fires `MoveRequestEvent`
+/// to the best legal destination — the touch equivalent of [`handle_double_click`].
+///
+/// Must run **before** `touch_end_drag` in the system chain. At
+/// `TouchPhase::Ended` the drag state still holds `active_touch_id`,
+/// `cards`, and `origin_pile`; once `touch_end_drag` fires those fields
+/// are cleared and the tap/drag distinction is permanently lost.
+///
+/// A pure tap is identified by `drag.active_touch_id.is_some() &&
+/// !drag.committed`: the touch began (so `touch_start_drag` populated
+/// `drag`) but the drag threshold was never crossed.
+///
+/// Move priority matches [`handle_double_click`]:
+/// 1. Move the single top card to its best foundation (or tableau).
+/// 2. If no single-card move exists and the selection spans multiple
+///    face-up cards, move the whole stack to the best tableau column.
+/// 3. If both priorities fail, fire `MoveRejectedEvent` for audio + shake
+///    feedback.
+#[allow(clippy::too_many_arguments)]
+fn handle_double_tap(
+    mut touch_events: MessageReader<TouchInput>,
+    paused: Option<Res<PausedResource>>,
+    time: Res<Time>,
+    drag: Res<DragState>,
+    game: Res<GameStateResource>,
+    mut last_tap: Local<HashMap<u32, f32>>,
+    mut moves: MessageWriter<MoveRequestEvent>,
+    mut rejected: MessageWriter<MoveRejectedEvent>,
+) {
+    if paused.is_some_and(|p| p.0) {
+        return;
+    }
+
+    // Only active when a touch is tracked and hasn't crossed the drag threshold.
+    let Some(active_id) = drag.active_touch_id else { return };
+    if drag.committed {
+        return;
+    }
+
+    for event in touch_events.read() {
+        if event.id != active_id {
+            continue;
+        }
+        match event.phase {
+            TouchPhase::Canceled => {
+                // Cancelled touch — clear any pending tap state for these cards.
+                for &id in &drag.cards {
+                    last_tap.remove(&id);
+                }
+                return;
+            }
+            TouchPhase::Ended => {}
+            _ => continue,
+        }
+
+        // Uncommitted touch ended = pure tap.
+        let Some(&top_card_id) = drag.cards.last() else { return };
+        let Some(ref pile) = drag.origin_pile else { return };
+        let Some(pile_cards) = game.0.piles.get(pile) else { return };
+
+        let Some(top_card) = pile_cards.cards.iter().find(|c| c.id == top_card_id) else {
+            return;
+        };
+        if !top_card.face_up {
+            return;
+        }
+
+        let now = time.elapsed_secs();
+        let prev = last_tap.get(&top_card_id).copied().unwrap_or(f32::NEG_INFINITY);
+
+        if now - prev <= DOUBLE_TAP_WINDOW {
+            last_tap.remove(&top_card_id);
+
+            // Priority 1: move single top card.
+            if let Some(dest) = best_destination(top_card, &game.0) {
+                moves.write(MoveRequestEvent {
+                    from: pile.clone(),
+                    to: dest,
+                    count: 1,
+                });
+                return;
+            }
+
+            // Priority 2: move whole face-up stack to best tableau column.
+            if drag.cards.len() > 1 {
+                let stack_index = pile_cards.cards.len() - drag.cards.len();
+                if let Some(bottom_card) = pile_cards.cards.get(stack_index)
+                    && let Some((dest, count)) = best_tableau_destination_for_stack(
+                        bottom_card,
+                        pile,
+                        &game.0,
+                        drag.cards.len(),
+                    )
+                {
+                    moves.write(MoveRequestEvent {
+                        from: pile.clone(),
+                        to: dest,
+                        count,
+                    });
+                    return;
+                }
+            }
+
+            rejected.write(MoveRejectedEvent {
+                from: pile.clone(),
+                to: pile.clone(),
+                count: drag.cards.len(),
+            });
+        } else {
+            last_tap.insert(top_card_id, now);
+        }
+    }
+}
+
 // ---------------------------------------------------------------------------
 // Task #28 — Hint system helpers
 // ---------------------------------------------------------------------------
@@ -2215,5 +2344,14 @@ mod tests {
             "pressing H must spawn an async hint task",
         );
     }
+
+    // Task #27b — double-tap constants
+    #[test]
+    fn double_tap_window_is_wider_than_double_click_window() {
+        // Compile-time check: touch needs a wider window than mouse due to
+        // higher input latency. `const { assert! }` catches regressions at
+        // build time rather than waiting for a test run.
+        const { assert!(DOUBLE_TAP_WINDOW > DOUBLE_CLICK_WINDOW) }
+    }
 }
 

solitaire_engine/src/lib.rs

@@ -1,5 +1,7 @@
 //! Bevy integration layer for Solitaire Quest.
 
+#[cfg(target_os = "android")]
+pub mod android_clipboard;
 pub mod assets;
 pub mod card_animation;
 pub mod achievement_plugin;
@@ -12,6 +14,7 @@ pub mod feedback_anim_plugin;
 pub mod challenge_plugin;
 pub mod cursor_plugin;
 pub mod daily_challenge_plugin;
+pub mod difficulty_plugin;
 pub mod diagnostics_hud;
 pub mod events;
 pub mod game_plugin;
@@ -24,6 +27,7 @@ pub mod layout;
 pub mod onboarding_plugin;
 pub mod pause_plugin;
 pub mod pending_hint;
+pub mod play_by_seed_plugin;
 pub mod profile_plugin;
 pub mod radial_menu;
 pub mod replay_overlay;
@@ -92,11 +96,14 @@ pub use events::{
     ForfeitEvent, ForfeitRequestEvent, FoundationCompletedEvent, GameWonEvent, HelpRequestEvent,
     HintVisualEvent, InfoToastEvent, ManualSyncRequestEvent, MoveRejectedEvent, MoveRequestEvent,
     NewGameRequestEvent, PauseRequestEvent, StartChallengeRequestEvent,
-    StartDailyChallengeRequestEvent, StartTimeAttackRequestEvent, StartZenRequestEvent,
+    StartDailyChallengeRequestEvent, StartDifficultyRequestEvent, StartPlayBySeedRequestEvent,
-    StateChangedEvent, SyncCompleteEvent, ToggleAchievementsRequestEvent,
+    StartTimeAttackRequestEvent, StartZenRequestEvent, StateChangedEvent, SyncCompleteEvent,
-    ToggleLeaderboardRequestEvent, ToggleProfileRequestEvent, ToggleSettingsRequestEvent,
+    ToggleAchievementsRequestEvent, ToggleLeaderboardRequestEvent, ToggleProfileRequestEvent,
-    ToggleStatsRequestEvent, UndoRequestEvent, WinStreakMilestoneEvent, XpAwardedEvent,
+    ToggleSettingsRequestEvent, ToggleStatsRequestEvent, UndoRequestEvent,
+    WinStreakMilestoneEvent, XpAwardedEvent,
 };
+pub use difficulty_plugin::{DifficultyIndexResource, DifficultyPlugin};
+pub use play_by_seed_plugin::{PlayBySeedPlugin, PlayBySeedScreen};
 pub use game_plugin::{
     ConfirmNewGameScreen, GameMutation, GameOverScreen, GamePlugin, GameStatePath, RecordingReplay,
     ReplayPath,

solitaire_engine/src/pause_plugin.rs

@@ -30,6 +30,7 @@ use crate::events::{
 use crate::font_plugin::FontResource;
 use crate::game_plugin::{GameOverScreen, GameStatePath};
 use crate::progress_plugin::ProgressResource;
+use crate::replay_playback::ReplayPlaybackState;
 use crate::resources::{DragState, GameStateResource};
 use crate::selection_plugin::{SelectionKeySet, SelectionState};
 use crate::settings_plugin::{SettingsChangedEvent, SettingsResource, SettingsStoragePath};
@@ -154,6 +155,7 @@ fn toggle_pause(
     mut drag: Option<ResMut<DragState>>,
     mut changed: MessageWriter<StateChangedEvent>,
     selection: Option<Res<SelectionState>>,
+    replay_state: Option<Res<ReplayPlaybackState>>,
 ) {
     let PauseModalQueries {
         pause_screens: screens,
@@ -184,6 +186,15 @@ fn toggle_pause(
     if !other_modal_scrims.is_empty() {
         return;
     }
+    // If a replay is currently playing, let `replay_overlay::handle_stop_keyboard`
+    // own the Esc press — that handler stops the replay. Without this guard a
+    // single Esc both stops the replay AND opens the pause modal on top of the
+    // (now empty) board, leaving the player on a screen they didn't ask for.
+    // The HUD-button path is gated too; clicking Pause while watching a replay
+    // is almost always an accident.
+    if replay_state.is_some_and(|s| s.is_playing()) {
+        return;
+    }
     // If a card is currently selected, let SelectionPlugin handle this Escape
     // (it will clear the selection). Pause must not also open in the same frame.
     if selection.is_some_and(|s| s.selected_pile.is_some()) {

solitaire_engine/src/play_by_seed_plugin.rs

@@ -0,0 +1,663 @@
+//! Play-by-Seed dialog: lets the player type a decimal seed number and start
+//! a Classic game with that exact deal. A live solver-verification badge
+//! updates asynchronously after a short typing debounce so the player knows
+//! whether the deal is provably winnable before committing.
+//!
+//! # Flow
+//!
+//! 1. `HomePlugin` fires [`StartPlayBySeedRequestEvent`] when the "Play by
+//!    Seed" card is clicked (or `6` is pressed in the Mode Launcher).
+//! 2. `handle_open_dialog` reads the event and spawns the seed-input modal.
+//! 3. `handle_text_input` appends decimal digits / handles Backspace while
+//!    the modal is open, updating [`SeedInputBuffer`] each frame.
+//! 4. `tick_debounce_and_spawn_solver_task` waits for 12 frames (~200 ms at
+//!    60 Hz) of no input before spawning a [`try_solve`] task on
+//!    [`AsyncComputeTaskPool`]. Any fresh keypress drops the in-flight task
+//!    by resetting the resource.
+//! 5. `poll_solver_task` polls the in-flight task each frame and updates the
+//!    [`SolverVerdictBadge`] text node with the verdict.
+//! 6. `handle_confirm` fires [`NewGameRequestEvent`] with the parsed seed and
+//!    despawns the dialog on Play click or `Enter`.
+//! 7. `handle_cancel` despawns the dialog on Cancel click or `Escape`.
+
+use bevy::input::ButtonInput;
+use bevy::prelude::*;
+use bevy::tasks::{futures_lite::future, AsyncComputeTaskPool, Task};
+use solitaire_core::game_state::DrawMode;
+use solitaire_core::solver::{try_solve, SolverConfig, SolverResult};
+
+use crate::events::{NewGameRequestEvent, StartPlayBySeedRequestEvent};
+use crate::font_plugin::FontResource;
+use crate::game_plugin::GameMutation;
+use crate::settings_plugin::SettingsResource;
+use crate::ui_modal::{
+    spawn_modal, spawn_modal_actions, spawn_modal_body_text, spawn_modal_button, spawn_modal_header,
+    ButtonVariant, ScrimDismissible,
+};
+use crate::ui_theme::{
+    ACCENT_PRIMARY, BG_ELEVATED_PRESSED, BORDER_SUBTLE, HighContrastBorder, RADIUS_MD,
+    TEXT_DISABLED, TEXT_PRIMARY, TEXT_SECONDARY, TYPE_BODY_LG, VAL_SPACE_2, VAL_SPACE_3,
+    Z_MODAL_PANEL,
+};
+
+// ---------------------------------------------------------------------------
+// Components and resources
+// ---------------------------------------------------------------------------
+
+/// Marker on the seed-input modal scrim (the despawn root).
+#[derive(Component, Debug)]
+pub struct PlayBySeedScreen;
+
+/// Holds the decimal digit string the player is typing and a frame counter
+/// used to debounce solver task spawning.
+#[derive(Component, Debug, Default)]
+struct SeedInputBuffer {
+    /// Raw decimal digit string. Never longer than 20 chars (u64::MAX is 20
+    /// decimal digits). Empty means "no seed entered".
+    text: String,
+    /// Frames elapsed since the last keystroke. The solver task is spawned
+    /// once this crosses [`DEBOUNCE_FRAMES`] and the buffer is non-empty.
+    frames_since_change: u32,
+}
+
+/// Marker on the text node that renders the solver verdict caption.
+#[derive(Component, Debug)]
+struct SolverVerdictBadge;
+
+/// Marker on the Play (confirm) button so `handle_confirm` can find it.
+#[derive(Component, Debug)]
+struct PlayBySeedConfirmButton;
+
+/// Marker on the Cancel button.
+#[derive(Component, Debug)]
+struct PlayBySeedCancelButton;
+
+/// Marker on the input-field text node so `handle_text_input` can update
+/// it without a separate query for the buffer entity.
+#[derive(Component, Debug)]
+struct SeedInputDisplay;
+
+/// In-flight async solver verification task. At most one is live at a time —
+/// a fresh keypress resets this resource (dropping the previous `Task<_>`)
+/// before spawning the next one.
+#[derive(Resource, Default)]
+struct PendingVerification {
+    seed: Option<u64>,
+    handle: Option<Task<SolverResult>>,
+}
+
+// ---------------------------------------------------------------------------
+// Constants
+// ---------------------------------------------------------------------------
+
+/// Frames of no-keypress activity before the solver task is spawned.
+/// 12 frames ≈ 200 ms at 60 Hz — long enough to avoid thrashing on fast
+/// typists but short enough to feel responsive.
+const DEBOUNCE_FRAMES: u32 = 12;
+
+/// Maximum decimal digits accepted. 20 covers all of u64::MAX (18,446,744,073,709,551,615).
+const MAX_SEED_DIGITS: usize = 20;
+
+// ---------------------------------------------------------------------------
+// Plugin
+// ---------------------------------------------------------------------------
+
+/// Registers all play-by-seed systems and resources.
+pub struct PlayBySeedPlugin;
+
+impl Plugin for PlayBySeedPlugin {
+    fn build(&self, app: &mut App) {
+        app.init_resource::<PendingVerification>()
+            .add_message::<StartPlayBySeedRequestEvent>()
+            .add_message::<NewGameRequestEvent>()
+            .add_systems(
+                Update,
+                (
+                    handle_open_dialog,
+                    handle_text_input,
+                    tick_debounce_and_spawn_solver_task,
+                    poll_solver_task,
+                    handle_confirm,
+                    handle_cancel,
+                )
+                    .chain()
+                    // Fire before GameMutation so `handle_confirm`'s
+                    // NewGameRequestEvent is processed on the same frame.
+                    .before(GameMutation),
+            );
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Systems
+// ---------------------------------------------------------------------------
+
+/// Spawns the seed-input dialog when `StartPlayBySeedRequestEvent` fires.
+fn handle_open_dialog(
+    mut commands: Commands,
+    mut requests: MessageReader<StartPlayBySeedRequestEvent>,
+    font_res: Option<Res<FontResource>>,
+    existing: Query<(), With<PlayBySeedScreen>>,
+) {
+    if requests.read().count() == 0 {
+        return;
+    }
+    // Guard against double-spawn (e.g. two events in one frame).
+    if !existing.is_empty() {
+        return;
+    }
+    let font = font_res.as_deref();
+    let font_handle = font.map(|f| f.0.clone()).unwrap_or_default();
+
+    let scrim = spawn_modal(&mut commands, PlayBySeedScreen, Z_MODAL_PANEL, |card| {
+        spawn_modal_header(card, "Play by Seed", font);
+        spawn_modal_body_text(
+            card,
+            "Enter a number to play that specific deal.",
+            TEXT_SECONDARY,
+            font,
+        );
+
+        // Input field — a bordered box that shows the typed digits.
+        card.spawn((
+            Node {
+                width: Val::Percent(100.0),
+                padding: UiRect::axes(VAL_SPACE_3, VAL_SPACE_2),
+                border: UiRect::all(Val::Px(1.0)),
+                border_radius: BorderRadius::all(Val::Px(RADIUS_MD)),
+                ..default()
+            },
+            BackgroundColor(BG_ELEVATED_PRESSED),
+            BorderColor::all(BORDER_SUBTLE),
+            HighContrastBorder::with_default(BORDER_SUBTLE),
+            SeedInputBuffer::default(),
+        ))
+        .with_children(|field| {
+            field.spawn((
+                SeedInputDisplay,
+                Text::new(""),
+                TextFont {
+                    font: font_handle.clone(),
+                    font_size: TYPE_BODY_LG,
+                    ..default()
+                },
+                TextColor(TEXT_DISABLED),
+            ));
+        });
+
+        // Solver verdict badge — updates as solver runs.
+        card.spawn((
+            SolverVerdictBadge,
+            Text::new("Type a number"),
+            TextFont {
+                font: font_handle,
+                font_size: TYPE_BODY_LG,
+                ..default()
+            },
+            TextColor(TEXT_SECONDARY),
+        ));
+
+        spawn_modal_actions(card, |row| {
+            spawn_modal_button(
+                row,
+                PlayBySeedCancelButton,
+                "Cancel",
+                Some("Esc"),
+                ButtonVariant::Secondary,
+                font,
+            );
+            spawn_modal_button(
+                row,
+                PlayBySeedConfirmButton,
+                "Play",
+                Some("Enter"),
+                ButtonVariant::Primary,
+                font,
+            );
+        });
+    });
+
+    // Play-by-Seed is read-only input — opt into click-outside-to-dismiss.
+    commands.entity(scrim).insert(ScrimDismissible);
+}
+
+/// Appends decimal digits and handles Backspace while the dialog is open.
+fn handle_text_input(
+    keys: Res<ButtonInput<KeyCode>>,
+    screen: Query<(), With<PlayBySeedScreen>>,
+    mut buffers: Query<&mut SeedInputBuffer>,
+    mut displays: Query<(&mut Text, &mut TextColor), With<SeedInputDisplay>>,
+    mut pending: ResMut<PendingVerification>,
+) {
+    if screen.is_empty() {
+        return;
+    }
+    let Ok(mut buf) = buffers.single_mut() else {
+        return;
+    };
+
+    let digit_keys = [
+        (KeyCode::Digit0, '0'),
+        (KeyCode::Digit1, '1'),
+        (KeyCode::Digit2, '2'),
+        (KeyCode::Digit3, '3'),
+        (KeyCode::Digit4, '4'),
+        (KeyCode::Digit5, '5'),
+        (KeyCode::Digit6, '6'),
+        (KeyCode::Digit7, '7'),
+        (KeyCode::Digit8, '8'),
+        (KeyCode::Digit9, '9'),
+        (KeyCode::Numpad0, '0'),
+        (KeyCode::Numpad1, '1'),
+        (KeyCode::Numpad2, '2'),
+        (KeyCode::Numpad3, '3'),
+        (KeyCode::Numpad4, '4'),
+        (KeyCode::Numpad5, '5'),
+        (KeyCode::Numpad6, '6'),
+        (KeyCode::Numpad7, '7'),
+        (KeyCode::Numpad8, '8'),
+        (KeyCode::Numpad9, '9'),
+    ];
+
+    let mut changed = false;
+
+    for (key, ch) in digit_keys {
+        if keys.just_pressed(key) && buf.text.len() < MAX_SEED_DIGITS {
+            // Drop a leading zero unless the buffer is empty (prevents "007").
+            if ch == '0' && buf.text.is_empty() {
+                continue;
+            }
+            buf.text.push(ch);
+            changed = true;
+        }
+    }
+
+    if keys.just_pressed(KeyCode::Backspace) && !buf.text.is_empty() {
+        buf.text.pop();
+        changed = true;
+    }
+
+    if changed {
+        buf.frames_since_change = 0;
+        // Cancel any in-flight solver task — its seed is now stale.
+        *pending = PendingVerification::default();
+
+        // Update the display node.
+        if let Ok((mut text, mut color)) = displays.single_mut() {
+            if buf.text.is_empty() {
+                text.0 = String::new();
+                color.0 = TEXT_DISABLED;
+            } else {
+                text.0 = buf.text.clone();
+                color.0 = TEXT_PRIMARY;
+            }
+        }
+    }
+}
+
+/// Increments the debounce counter each frame and spawns the solver task
+/// once the counter passes [`DEBOUNCE_FRAMES`] and the buffer holds a
+/// valid u64.
+fn tick_debounce_and_spawn_solver_task(
+    screen: Query<(), With<PlayBySeedScreen>>,
+    mut buffers: Query<&mut SeedInputBuffer>,
+    mut pending: ResMut<PendingVerification>,
+    mut badges: Query<(&mut Text, &mut TextColor), With<SolverVerdictBadge>>,
+    settings: Option<Res<SettingsResource>>,
+) {
+    if screen.is_empty() {
+        return;
+    }
+    let Ok(mut buf) = buffers.single_mut() else {
+        return;
+    };
+
+    // Always update the badge when the buffer is empty.
+    if buf.text.is_empty() {
+        if let Ok((mut text, mut color)) = badges.single_mut() {
+            text.0 = "Type a number".to_string();
+            color.0 = TEXT_SECONDARY;
+        }
+        return;
+    }
+
+    // Don't spawn if a task is already running for this seed.
+    let parsed = buf.text.parse::<u64>().ok();
+    if pending.handle.is_some() && pending.seed == parsed {
+        return;
+    }
+
+    buf.frames_since_change = buf.frames_since_change.saturating_add(1);
+    if buf.frames_since_change < DEBOUNCE_FRAMES {
+        return;
+    }
+
+    let Some(seed) = parsed else {
+        return;
+    };
+
+    let draw_mode = settings
+        .as_ref()
+        .map_or(DrawMode::DrawOne, |s| s.0.draw_mode.clone());
+    let cfg = SolverConfig::default();
+    let task = AsyncComputeTaskPool::get()
+        .spawn(async move { try_solve(seed, draw_mode, &cfg) });
+
+    pending.seed = Some(seed);
+    pending.handle = Some(task);
+
+    if let Ok((mut text, mut color)) = badges.single_mut() {
+        text.0 = "Verifying\u{2026}".to_string();
+        color.0 = TEXT_SECONDARY;
+    }
+}
+
+/// Polls the in-flight solver task and updates the verdict badge on completion.
+fn poll_solver_task(
+    mut pending: ResMut<PendingVerification>,
+    mut badges: Query<(&mut Text, &mut TextColor), With<SolverVerdictBadge>>,
+) {
+    let Some(handle) = pending.handle.as_mut() else {
+        return;
+    };
+    let Some(result) = future::block_on(future::poll_once(handle)) else {
+        return;
+    };
+    pending.handle = None;
+
+    let Ok((mut text, mut color)) = badges.single_mut() else {
+        return;
+    };
+    match result {
+        SolverResult::Winnable => {
+            text.0 = "\u{2713} Provably winnable".to_string();
+            color.0 = ACCENT_PRIMARY;
+        }
+        SolverResult::Inconclusive => {
+            text.0 = "? Likely winnable (search timed out)".to_string();
+            color.0 = TEXT_SECONDARY;
+        }
+        SolverResult::Unwinnable => {
+            text.0 = "\u{2717} Provably unwinnable".to_string();
+            color.0 = TEXT_DISABLED;
+        }
+    }
+}
+
+/// Fires [`NewGameRequestEvent`] with the parsed seed when Play is clicked
+/// or `Enter` is pressed, then despawns the dialog. Does nothing when the
+/// buffer is empty.
+fn handle_confirm(
+    mut commands: Commands,
+    keys: Res<ButtonInput<KeyCode>>,
+    buttons: Query<&Interaction, (With<PlayBySeedConfirmButton>, Changed<Interaction>)>,
+    buffers: Query<&SeedInputBuffer>,
+    screen: Query<Entity, With<PlayBySeedScreen>>,
+    mut new_game: MessageWriter<NewGameRequestEvent>,
+) {
+    if screen.is_empty() {
+        return;
+    }
+
+    let click = buttons.iter().any(|i| *i == Interaction::Pressed);
+    let enter = keys.just_pressed(KeyCode::Enter) || keys.just_pressed(KeyCode::NumpadEnter);
+    if !click && !enter {
+        return;
+    }
+
+    let Ok(buf) = buffers.single() else { return };
+    let Ok(seed) = buf.text.parse::<u64>() else { return };
+
+    new_game.write(NewGameRequestEvent {
+        seed: Some(seed),
+        mode: None,
+        confirmed: false,
+    });
+
+    for entity in &screen {
+        commands.entity(entity).despawn();
+    }
+}
+
+/// Despawns the dialog on Cancel click or `Escape`.
+fn handle_cancel(
+    mut commands: Commands,
+    keys: Res<ButtonInput<KeyCode>>,
+    buttons: Query<&Interaction, (With<PlayBySeedCancelButton>, Changed<Interaction>)>,
+    screen: Query<Entity, With<PlayBySeedScreen>>,
+    other_scrims: Query<(), (With<crate::ui_modal::ModalScrim>, Without<PlayBySeedScreen>)>,
+) {
+    if screen.is_empty() {
+        return;
+    }
+
+    let click = buttons.iter().any(|i| *i == Interaction::Pressed);
+    // Esc only closes this dialog when it is the topmost modal.
+    let esc = keys.just_pressed(KeyCode::Escape) && other_scrims.is_empty();
+    if !click && !esc {
+        return;
+    }
+
+    for entity in &screen {
+        commands.entity(entity).despawn();
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::game_plugin::GamePlugin;
+    use crate::table_plugin::TablePlugin;
+
+    fn headless_app() -> App {
+        let mut app = App::new();
+        app.add_plugins(MinimalPlugins)
+            .add_plugins(GamePlugin)
+            .add_plugins(TablePlugin)
+            .add_plugins(PlayBySeedPlugin);
+        app.init_resource::<ButtonInput<KeyCode>>();
+        app.update();
+        app
+    }
+
+    fn open_dialog(app: &mut App) {
+        app.world_mut()
+            .write_message(StartPlayBySeedRequestEvent);
+        app.update();
+    }
+
+    fn press_key(app: &mut App, key: KeyCode) {
+        app.world_mut()
+            .resource_mut::<ButtonInput<KeyCode>>()
+            .press(key);
+        app.update();
+        // Simulate what Bevy's PreUpdate input system does: flush just_pressed /
+        // just_released so stale key state doesn't bleed into the next frame.
+        let mut input = app.world_mut().resource_mut::<ButtonInput<KeyCode>>();
+        input.release(key);
+        input.clear();
+    }
+
+    fn dialog_present(app: &mut App) -> bool {
+        app.world_mut()
+            .query::<&PlayBySeedScreen>()
+            .iter(app.world())
+            .next()
+            .is_some()
+    }
+
+    fn read_buffer_text(app: &mut App) -> String {
+        let mut q = app.world_mut().query::<&SeedInputBuffer>();
+        q.iter(app.world())
+            .next()
+            .map(|b| b.text.clone())
+            .unwrap_or_default()
+    }
+
+    #[test]
+    fn dialog_spawns_on_request() {
+        let mut app = headless_app();
+        assert!(!dialog_present(&mut app));
+        open_dialog(&mut app);
+        assert!(dialog_present(&mut app));
+    }
+
+    #[test]
+    fn digit_keys_append_to_buffer() {
+        let mut app = headless_app();
+        open_dialog(&mut app);
+
+        press_key(&mut app, KeyCode::Digit4);
+        press_key(&mut app, KeyCode::Digit2);
+
+        assert_eq!(read_buffer_text(&mut app), "42");
+    }
+
+    #[test]
+    fn backspace_removes_last_char() {
+        let mut app = headless_app();
+        open_dialog(&mut app);
+
+        press_key(&mut app, KeyCode::Digit4);
+        press_key(&mut app, KeyCode::Digit2);
+        press_key(&mut app, KeyCode::Backspace);
+
+        assert_eq!(read_buffer_text(&mut app), "4");
+    }
+
+    #[test]
+    fn confirm_does_nothing_when_buffer_is_empty() {
+        let mut app = headless_app();
+        open_dialog(&mut app);
+
+        // Simulate Enter with empty buffer.
+        app.world_mut()
+            .resource_mut::<ButtonInput<KeyCode>>()
+            .press(KeyCode::Enter);
+        app.update();
+
+        let msgs = app.world().resource::<Messages<NewGameRequestEvent>>();
+        let mut cursor = msgs.get_cursor();
+        assert!(cursor.read(msgs).next().is_none(), "no NewGameRequestEvent when buffer empty");
+        // Dialog should still be open.
+        assert!(dialog_present(&mut app));
+    }
+
+    #[test]
+    fn confirm_writes_new_game_request_with_parsed_seed() {
+        let mut app = headless_app();
+        open_dialog(&mut app);
+
+        press_key(&mut app, KeyCode::Digit4);
+        press_key(&mut app, KeyCode::Digit2);
+
+        app.world_mut()
+            .resource_mut::<ButtonInput<KeyCode>>()
+            .press(KeyCode::Enter);
+        app.update();
+
+        let msgs = app.world().resource::<Messages<NewGameRequestEvent>>();
+        let mut cursor = msgs.get_cursor();
+        let fired: Vec<_> = cursor.read(msgs).copied().collect();
+        assert_eq!(fired.len(), 1);
+        assert_eq!(fired[0].seed, Some(42));
+        assert_eq!(fired[0].mode, None);
+        assert!(!fired[0].confirmed);
+
+        // Dialog should be gone.
+        assert!(!dialog_present(&mut app));
+    }
+
+    #[test]
+    fn cancel_despawns_dialog_without_new_game_request() {
+        let mut app = headless_app();
+        open_dialog(&mut app);
+
+        press_key(&mut app, KeyCode::Escape);
+
+        assert!(!dialog_present(&mut app));
+
+        let msgs = app.world().resource::<Messages<NewGameRequestEvent>>();
+        let mut cursor = msgs.get_cursor();
+        assert!(cursor.read(msgs).next().is_none());
+    }
+
+    #[test]
+    fn solver_task_spawns_after_debounce_window() {
+        let mut app = headless_app();
+        open_dialog(&mut app);
+
+        press_key(&mut app, KeyCode::Digit4);
+        press_key(&mut app, KeyCode::Digit2);
+
+        // Debounce window — no task yet.
+        for _ in 0..DEBOUNCE_FRAMES {
+            app.update();
+        }
+
+        let pending = app.world().resource::<PendingVerification>();
+        assert!(pending.handle.is_some(), "solver task should have been spawned after debounce");
+        assert_eq!(pending.seed, Some(42));
+    }
+
+    #[test]
+    fn keypress_mid_flight_cancels_previous_solver_task() {
+        let mut app = headless_app();
+        open_dialog(&mut app);
+
+        press_key(&mut app, KeyCode::Digit4);
+        press_key(&mut app, KeyCode::Digit2);
+
+        // Let the debounce fire.
+        for _ in 0..DEBOUNCE_FRAMES {
+            app.update();
+        }
+        assert!(app.world().resource::<PendingVerification>().handle.is_some());
+
+        // New keypress should cancel the in-flight task.
+        press_key(&mut app, KeyCode::Digit3);
+        assert!(app.world().resource::<PendingVerification>().handle.is_none());
+        assert_eq!(app.world().resource::<PendingVerification>().seed, None);
+    }
+
+    #[test]
+    fn solver_task_completes_and_updates_badge() {
+        use std::time::Instant;
+
+        let mut app = headless_app();
+        open_dialog(&mut app);
+
+        // Seed 42 — solver will return some verdict.
+        press_key(&mut app, KeyCode::Digit4);
+        press_key(&mut app, KeyCode::Digit2);
+
+        // Wait for the debounce to spawn the task.
+        for _ in 0..DEBOUNCE_FRAMES {
+            app.update();
+        }
+
+        // Poll until the solver task resolves (cap at 15 s wall-clock).
+        let deadline = Instant::now() + std::time::Duration::from_secs(15);
+        while app.world().resource::<PendingVerification>().handle.is_some()
+            && Instant::now() < deadline
+        {
+            app.update();
+            std::thread::yield_now();
+        }
+
+        // Badge text should no longer read "Verifying…".
+        let badge_text = app
+            .world_mut()
+            .query::<(&Text, &SolverVerdictBadge)>()
+            .iter(app.world())
+            .next()
+            .map(|(t, _)| t.0.clone())
+            .unwrap_or_default();
+        assert_ne!(badge_text, "Verifying\u{2026}", "badge should have resolved to a verdict");
+        assert_ne!(badge_text, "Type a number", "badge should show verdict, not idle state");
+    }
+}

solitaire_engine/src/radial_menu.rs

@@ -56,7 +56,8 @@ use crate::events::MoveRequestEvent;
 use crate::layout::{Layout, LayoutResource};
 use crate::pause_plugin::PausedResource;
 use crate::resources::{DragState, GameStateResource};
-use crate::ui_theme::{ACCENT_PRIMARY, BORDER_STRONG, BORDER_SUBTLE, STATE_SUCCESS};
+use crate::settings_plugin::SettingsResource;
+use crate::ui_theme::{ACCENT_PRIMARY, BORDER_STRONG, BORDER_SUBTLE, BORDER_SUBTLE_HC, STATE_SUCCESS};
 
 /// Sprite-space `Transform.z` for radial-menu overlay sprites.
 ///
@@ -533,8 +534,17 @@ fn radial_handle_release_or_cancel(
 
 /// Despawns and respawns the radial overlay sprites every frame the
 /// state is `Active`; despawns them when the state returns to `Idle`.
+///
+/// Reads [`SettingsResource`] so the focused-icon outline can boost to
+/// [`BORDER_SUBTLE_HC`] under high-contrast mode. Per-frame respawn is
+/// the simplest place to fold HC in: this is the only system that
+/// owns the rim sprite, so there's no parallel paint path to fight.
+/// ([`HighContrastBorder`](crate::ui_theme::HighContrastBorder) doesn't
+/// apply because the rim is a `Sprite`, not a UI node with
+/// `BorderColor`, and the entities don't persist across frames.)
 fn radial_redraw_overlay(
     state: Res<RightClickRadialState>,
+    settings: Option<Res<SettingsResource>>,
     mut commands: Commands,
     existing_icons: Query<Entity, With<RadialIcon>>,
     existing_centres: Query<Entity, With<RadialCentre>>,
@@ -569,13 +579,12 @@ fn radial_redraw_overlay(
         Transform::from_xyz(centre.x, centre.y, Z_RADIAL_MENU + 0.01),
     ));
 
+    let high_contrast = settings.as_ref().is_some_and(|s| s.0.high_contrast_mode);
     for (i, (_pile, anchor)) in legal_destinations.iter().enumerate() {
         let focused = *hovered_index == Some(i);
         let scale = if focused { RADIAL_HOVER_SCALE } else { 1.0 };
         let fill = if focused { STATE_SUCCESS } else { ACCENT_PRIMARY };
-        // Hovered icon gets a strong yellow rim; resting icons get a
+        let outline = radial_rim_outline(focused, high_contrast);
-        // muted purple rim so the focused one reads as the obvious target.
-        let outline = if focused { BORDER_STRONG } else { BORDER_SUBTLE };
 
         commands
             .spawn((
@@ -606,6 +615,27 @@ fn radial_redraw_overlay(
     }
 }
 
+/// Pure decision logic for the radial-icon rim outline colour.
+///
+/// Resting icons always carry [`BORDER_SUBTLE`] so the focused icon
+/// reads as the obvious target. Under high-contrast mode the focused
+/// rim boosts to [`BORDER_SUBTLE_HC`] (`#a0a0a0`) instead of
+/// [`BORDER_STRONG`] (`#505050`) — naive marker substitution via
+/// [`HighContrastBorder`](crate::ui_theme::HighContrastBorder) would
+/// invert the hierarchy because the resting colour
+/// (`#353535`) is darker than `BORDER_STRONG`. This shape keeps the
+/// focused rim *more* visible under HC, not less.
+///
+/// Factored out as a pure function so the truth-table is unit-testable
+/// without spinning up the per-frame respawn system.
+fn radial_rim_outline(focused: bool, high_contrast: bool) -> Color {
+    match (focused, high_contrast) {
+        (true, true) => BORDER_SUBTLE_HC,
+        (true, false) => BORDER_STRONG,
+        (false, _) => BORDER_SUBTLE,
+    }
+}
+
 // ---------------------------------------------------------------------------
 // Tests
 // ---------------------------------------------------------------------------
@@ -940,4 +970,33 @@ mod tests {
             "face-down cards must not open the radial"
         );
     }
+
+    // -----------------------------------------------------------------------
+    // radial_rim_outline — accessibility / high-contrast truth table
+    // -----------------------------------------------------------------------
+
+    #[test]
+    fn rim_resting_uses_subtle_outline_without_hc() {
+        assert_eq!(radial_rim_outline(false, false), BORDER_SUBTLE);
+    }
+
+    #[test]
+    fn rim_focused_uses_strong_outline_without_hc() {
+        assert_eq!(radial_rim_outline(true, false), BORDER_STRONG);
+    }
+
+    #[test]
+    fn rim_focused_boosts_to_subtle_hc_under_hc() {
+        assert_eq!(radial_rim_outline(true, true), BORDER_SUBTLE_HC);
+    }
+
+    #[test]
+    fn rim_resting_stays_subtle_under_hc_to_preserve_hierarchy() {
+        // Naive marker substitution would also flip the resting outline
+        // to BORDER_SUBTLE_HC, which is *lighter* than BORDER_STRONG —
+        // that would invert the focused/resting hierarchy. Holding the
+        // resting colour at BORDER_SUBTLE keeps the focused icon the
+        // obvious target under HC.
+        assert_eq!(radial_rim_outline(false, true), BORDER_SUBTLE);
+    }
 }

solitaire_engine/src/replay_playback.rs

@@ -42,7 +42,7 @@
 use bevy::prelude::*;
 use solitaire_data::{Replay, ReplayMove};
 
-use crate::events::{DrawRequestEvent, MoveRequestEvent, StateChangedEvent};
+use crate::events::{DrawRequestEvent, MoveRequestEvent, StateChangedEvent, UndoRequestEvent};
 use crate::game_plugin::{GameMutation, RecordingReplay};
 use crate::resources::GameStateResource;
 use crate::settings_plugin::SettingsResource;
@@ -119,6 +119,15 @@ pub enum ReplayPlaybackState {
         cursor: usize,
         /// Seconds remaining until the next move is dispatched.
         secs_to_next: f32,
+        /// `true` while playback is paused — `tick_replay_playback`
+        /// skips the `secs_to_next` decrement entirely while this is
+        /// set, so the cursor and the timer freeze together. The
+        /// overlay stays mounted (`is_playing()` still returns
+        /// `true`) so the player can see the paused state and the
+        /// Resume / Step controls. Stepping while paused fires the
+        /// next move directly via [`step_replay_playback`] and
+        /// leaves the paused flag untouched.
+        paused: bool,
     },
     /// The replay finished playing back. The overlay swaps the banner
     /// label to "Replay complete" until [`auto_clear_completed_replay`]
@@ -194,6 +203,7 @@ pub fn start_replay_playback(
         replay,
         cursor: 0,
         secs_to_next: REPLAY_MOVE_INTERVAL_SECS,
+        paused: false,
     };
 }
 
@@ -219,6 +229,107 @@ pub fn stop_replay_playback(
     **state = ReplayPlaybackState::Inactive;
 }
 
+/// Toggle the `paused` flag on the active playback. No-op when not
+/// `Playing` (i.e. `Inactive` or `Completed`) — pause has no meaning
+/// in those states. Returns the new paused value, or `None` if the
+/// state wasn't `Playing`.
+pub fn toggle_pause_replay_playback(state: &mut ResMut<ReplayPlaybackState>) -> Option<bool> {
+    if let ReplayPlaybackState::Playing { paused, .. } = state.as_mut() {
+        *paused = !*paused;
+        Some(*paused)
+    } else {
+        None
+    }
+}
+
+/// Advance playback by exactly one move. Only meaningful while paused
+/// — when called on an unpaused playback it would race the
+/// `tick_replay_playback` loop. Returns `true` when a move was fired,
+/// `false` when no-op (state isn't `Playing { paused: true }` or the
+/// cursor is already at the end of the move list).
+///
+/// Stepping the last move transitions the state to `Completed` on
+/// the next `tick_replay_playback` frame — same end-of-list path the
+/// normal advance loop takes.
+pub fn step_replay_playback(
+    state: &mut ResMut<ReplayPlaybackState>,
+    moves_writer: &mut MessageWriter<MoveRequestEvent>,
+    draws_writer: &mut MessageWriter<DrawRequestEvent>,
+) -> bool {
+    let ReplayPlaybackState::Playing {
+        replay,
+        cursor,
+        paused: true,
+        ..
+    } = state.as_mut()
+    else {
+        return false;
+    };
+    if *cursor >= replay.moves.len() {
+        return false;
+    }
+    match &replay.moves[*cursor] {
+        ReplayMove::Move { from, to, count } => {
+            moves_writer.write(MoveRequestEvent {
+                from: from.clone(),
+                to: to.clone(),
+                count: *count,
+            });
+        }
+        ReplayMove::StockClick => {
+            draws_writer.write(DrawRequestEvent);
+        }
+    }
+    *cursor += 1;
+    true
+}
+
+/// Steps the replay **backwards** by exactly one move while paused.
+///
+/// Strategy: the live game's undo system is the source of truth for
+/// reversing moves. Every move the replay forward-stepped (via
+/// [`step_replay_playback`] or the auto-advance loop in
+/// [`tick_replay_playback`]) was dispatched as a canonical
+/// [`MoveRequestEvent`] / [`DrawRequestEvent`], which the game
+/// applied and pushed onto its undo stack. So a backwards step here
+/// is simply: decrement the cursor (so the about-to-apply move
+/// re-points at the one we're rewinding past) and fire an
+/// [`UndoRequestEvent`] so the game reverses its most-recent move
+/// next frame.
+///
+/// Hard-gated to the paused state via destructure pattern —
+/// matches the existing [`step_replay_playback`] gate so the
+/// player can only scrub one direction at a time and the tick
+/// loop never races a manual rewind.
+///
+/// Returns `false` and is a no-op in three cases:
+/// - State isn't `Playing` (no replay attached).
+/// - State is `Playing` but not paused (the tick loop owns the cursor).
+/// - Cursor is already at 0 (nothing to rewind past).
+///
+/// Returns `true` on a successful step; the actual game-state
+/// reversal happens next frame when `handle_undo` reads the
+/// `UndoRequestEvent`.
+pub fn step_backwards_replay_playback(
+    state: &mut ResMut<ReplayPlaybackState>,
+    undo_writer: &mut MessageWriter<UndoRequestEvent>,
+) -> bool {
+    let ReplayPlaybackState::Playing {
+        cursor,
+        paused: true,
+        ..
+    } = state.as_mut()
+    else {
+        return false;
+    };
+    if *cursor == 0 {
+        return false;
+    }
+    *cursor -= 1;
+    undo_writer.write(UndoRequestEvent);
+    true
+}
+
 /// Tick system. Runs every frame; only does work when
 /// [`ReplayPlaybackState::is_playing`].
 ///
@@ -249,8 +360,15 @@ fn tick_replay_playback(
         replay,
         cursor,
         secs_to_next,
+        paused,
     } = state.as_mut()
     {
+        // While paused, the cursor and the timer freeze together —
+        // skip the decrement entirely so resuming starts the next
+        // move from a full `secs_to_next` window. Stepping (handled
+        // separately) fires moves directly without touching this
+        // path.
+        if !*paused {
             *secs_to_next -= dt;
             while *secs_to_next <= 0.0 && *cursor < replay.moves.len() {
                 match &replay.moves[*cursor] {
@@ -273,6 +391,7 @@ fn tick_replay_playback(
                 transition_to_completed = true;
             }
         }
+    }
 
     if transition_to_completed {
         *state = ReplayPlaybackState::Completed;

solitaire_engine/src/settings_plugin.rs

@@ -34,7 +34,8 @@ use crate::ui_modal::{
 };
 use crate::ui_tooltip::Tooltip;
 use crate::ui_theme::{
-    BG_BASE, BG_ELEVATED, BG_ELEVATED_HI, BORDER_SUBTLE, BORDER_SUBTLE_HC, HighContrastBorder,
+    BG_BASE, BG_ELEVATED, BG_ELEVATED_HI, BORDER_SUBTLE, BORDER_SUBTLE_HC, HighContrastBackground,
+    HighContrastBorder,
     RADIUS_SM, SPACE_2, STATE_SUCCESS, TEXT_PRIMARY, TEXT_SECONDARY, TYPE_BODY, TYPE_BODY_LG,
     TYPE_CAPTION, VAL_SPACE_2, VAL_SPACE_3, Z_MODAL_PANEL,
 };
@@ -365,6 +366,7 @@ impl Plugin for SettingsPlugin {
                     update_color_blind_text,
                     update_high_contrast_text,
                     update_high_contrast_borders,
+                    update_high_contrast_backgrounds,
                     update_reduce_motion_text,
                     update_tooltip_delay_text,
                     update_time_bonus_multiplier_text,
@@ -674,6 +676,41 @@ fn update_high_contrast_borders(
     }
 }
 
+/// Repaints `BackgroundColor` on every entity tagged with
+/// [`HighContrastBackground`] based on `Settings::high_contrast_mode`.
+/// Off → the marker's `default_color`; on → `BORDER_SUBTLE_HC`
+/// (`#a0a0a0`). Compares against the current background and only
+/// mutates when different so Bevy's change-detection doesn't trigger
+/// repaints every frame.
+///
+/// Parallel to [`update_high_contrast_borders`]. Same on/off rule,
+/// same change-suppression idiom, different colour channel —
+/// `BackgroundColor` for tick marks, decorative strips, fine
+/// separators that paint their shape directly rather than via a
+/// `BorderColor` on a wider Node.
+///
+/// Tagged sites in v0.21.x: the replay overlay's 1 px scrub track
+/// + 5 quarter-mark notch ticks (`replay_overlay::spawn_overlay`).
+///
+/// More sites can be tagged in follow-ups by adding
+/// `HighContrastBackground::with_default(...)` to their spawn tuple.
+pub(crate) fn update_high_contrast_backgrounds(
+    settings: Res<SettingsResource>,
+    mut backgrounds: Query<(&HighContrastBackground, &mut BackgroundColor)>,
+) {
+    let high_contrast = settings.0.high_contrast_mode;
+    for (marker, mut bg) in backgrounds.iter_mut() {
+        let target = if high_contrast {
+            marker.hc_color
+        } else {
+            marker.default_color
+        };
+        if bg.0 != target {
+            *bg = BackgroundColor(target);
+        }
+    }
+}
+
 fn update_reduce_motion_text(
     settings: Res<SettingsResource>,
     mut text_nodes: Query<&mut Text, With<ReduceMotionText>>,

solitaire_engine/src/stats_plugin.rs

@@ -29,12 +29,13 @@ use crate::resources::GameStateResource;
 use crate::time_attack_plugin::TimeAttackResource;
 use crate::ui_modal::{
     spawn_modal, spawn_modal_actions, spawn_modal_button, spawn_modal_header, ButtonVariant,
-    ScrimDismissible,
+    ModalButton, ScrimDismissible,
 };
 use crate::ui_theme::{
-    ACCENT_PRIMARY, BORDER_SUBTLE, HighContrastBorder, RADIUS_SM, STATE_INFO, STATE_WARNING,
+    ACCENT_PRIMARY, BG_ELEVATED_HI, BORDER_SUBTLE, HighContrastBorder, RADIUS_SM, STATE_INFO,
-    STREAK_MILESTONES, TEXT_PRIMARY, TEXT_SECONDARY, TYPE_BODY, TYPE_BODY_LG, TYPE_CAPTION,
+    STATE_WARNING, STREAK_MILESTONES, TEXT_PRIMARY, TEXT_SECONDARY, TYPE_BODY, TYPE_BODY_LG,
-    TYPE_HEADLINE, VAL_SPACE_2, VAL_SPACE_3, VAL_SPACE_4, Z_MODAL_PANEL,
+    TYPE_CAPTION, TYPE_HEADLINE, VAL_SPACE_1, VAL_SPACE_2, VAL_SPACE_3, VAL_SPACE_4,
+    Z_MODAL_PANEL,
 };
 
 /// Bevy resource wrapping the current stats.
@@ -121,6 +122,13 @@ pub struct ReplayNextButton;
 #[derive(Component, Debug)]
 pub struct ReplaySelectorCaption;
 
+/// Marker on the detail text node that shows the selected replay's
+/// `"{duration} win on {date}"` + optional `"· Shareable"` badge.
+/// Repainted by `repaint_replay_selector_detail` whenever the
+/// selection or history changes.
+#[derive(Component, Debug)]
+pub struct ReplaySelectorDetail;
+
 /// Marker component on each per-mode bests row in the stats overlay.
 ///
 /// One row per supported [`solitaire_core::game_state::GameMode`] (Classic,
@@ -223,7 +231,12 @@ impl Plugin for StatsPlugin {
             .add_systems(Update, handle_copy_share_link_button)
             .add_systems(
                 Update,
-                (handle_replay_selector_buttons, repaint_replay_selector_caption).chain(),
+                (
+                    handle_replay_selector_buttons,
+                    repaint_replay_selector_caption,
+                    repaint_replay_selector_detail,
+                )
+                    .chain(),
             )
             .add_systems(Update, scroll_stats_panel);
     }
@@ -348,9 +361,13 @@ fn handle_copy_share_link_button(
     }
     #[cfg(target_os = "android")]
     {
-        toast.write(InfoToastEvent(format!(
+        match crate::android_clipboard::set_text(&url) {
-            "Share link: {url}"
+            Ok(()) => { toast.write(InfoToastEvent(format!("Copied: {url}"))); }
-        )));
+            Err(e) => {
+                warn!("android clipboard failed: {e}");
+                toast.write(InfoToastEvent(format!("Share link: {url}")));
+            }
+        }
     }
 }
 
@@ -439,6 +456,39 @@ fn repaint_replay_selector_caption(
     }
 }
 
+/// Repaints the `ReplaySelectorDetail` text node whenever the
+/// selection or history changes. Shows `"{duration} win on {date}"` for
+/// the selected replay, with a `"· Shareable"` badge when the replay
+/// carries a sync-uploaded share URL. Empty when the history is empty.
+fn repaint_replay_selector_detail(
+    history: Res<ReplayHistoryResource>,
+    selected: Res<SelectedReplayIndex>,
+    mut q: Query<&mut Text, With<ReplaySelectorDetail>>,
+) {
+    if !history.is_changed() && !selected.is_changed() {
+        return;
+    }
+    let label = replay_selector_detail(&history.0.replays, selected.0);
+    for mut text in &mut q {
+        **text = label.clone();
+    }
+}
+
+/// Pure helper: render the detail line for the selected replay. Returns
+/// `"{duration} win on {date}"` plus a `" \u{2022} Shareable"` badge
+/// when a share URL is present. Empty when the history slice is empty.
+pub fn replay_selector_detail(replays: &[solitaire_data::Replay], index: usize) -> String {
+    let Some(r) = replays.get(index.min(replays.len().saturating_sub(1))) else {
+        return String::new();
+    };
+    let base = format_replay_caption(r);
+    if r.share_url.is_some() {
+        format!("{base} \u{2022} Shareable") // ·
+    } else {
+        base
+    }
+}
+
 /// Pure helper: render the selector caption shown next to the Prev /
 /// Next chips. Returns `"No replays"` when the history is empty,
 /// otherwise `"Replay {1-based index} / {total}"`.
@@ -618,14 +668,14 @@ fn toggle_stats_screen(
     if let Ok(entity) = screens.single() {
         commands.entity(entity).despawn();
     } else {
-        let selected = latest_replay.0.replays.get(selected_index.0);
         spawn_stats_screen(
             &mut commands,
             &stats.0,
             progress.as_deref().map(|p| &p.0),
             time_attack.as_deref(),
             font_res.as_deref(),
-            selected,
+            &latest_replay.0.replays,
+            selected_index.0,
         );
     }
 }
@@ -651,7 +701,8 @@ fn spawn_stats_screen(
     progress: Option<&PlayerProgress>,
     time_attack: Option<&TimeAttackResource>,
     font_res: Option<&FontResource>,
-    latest_replay: Option<&Replay>,
+    replays: &[Replay],
+    selected_index: usize,
 ) {
     // --- primary stat cells ---
     // First-launch zero-state: when no games have been played yet, render
@@ -859,31 +910,84 @@ fn spawn_stats_screen(
                     ));
                 }
 
-            // --- Latest replay caption ---
+            // --- Replay selector ---
-            // Surfaces the most recent winning game so the player can spot
+            // Prev / Next chips step through the full replay history;
-            // whether their last victory has been recorded. The Watch
+            // `repaint_replay_selector_caption` and
-            // Replay action below is what the player clicks to revisit it.
+            // `repaint_replay_selector_detail` keep both text nodes
-            //
+            // live as the selection changes. Using `ModalButton` on
-            // When the displayed replay carries a `share_url` (uploaded
+            // the chips plugs them into the existing modal-button
-            // to a sync server, persisted by v0.19.0's share-link
+            // hover/press paint loop at no extra cost.
-            // contract), append a "Shareable" badge so the player can
+            body.spawn(Node {
-            // tell at a glance whether the Copy share link button below
+                flex_direction: FlexDirection::Row,
-            // will produce a URL — without it the button surfaces a
+                align_items: AlignItems::Center,
-            // toast explaining why nothing was copied, which is more
+                column_gap: VAL_SPACE_3,
-            // friction than necessary when a quick visual cue suffices.
+                ..default()
-            let replay_caption = match latest_replay {
+            })
-                Some(r) => {
+            .with_children(|row| {
-                    let base = format!("Latest win: {}", format_replay_caption(r));
+                // ← Prev chip
-                    if r.share_url.is_some() {
+                row.spawn((
-                        format!("{base} \u{2022} Shareable")
+                    ReplayPrevButton,
-                    } else {
+                    ModalButton(ButtonVariant::Secondary),
-                        base
+                    Button,
-                    }
+                    Node {
-                }
+                        padding: UiRect::axes(VAL_SPACE_2, VAL_SPACE_1),
-                None => "No replay recorded yet \u{2014} win a game first.".to_string(),
+                        justify_content: JustifyContent::Center,
-            };
+                        align_items: AlignItems::Center,
+                        border: UiRect::all(Val::Px(1.0)),
+                        border_radius: BorderRadius::all(Val::Px(RADIUS_SM)),
+                        ..default()
+                    },
+                    BackgroundColor(BG_ELEVATED_HI),
+                    BorderColor::all(BORDER_SUBTLE),
+                    HighContrastBorder::with_default(BORDER_SUBTLE),
+                ))
+                .with_children(|b| {
+                    b.spawn((
+                        Text::new("\u{2190}"),
+                        font_row.clone(),
+                        TextColor(TEXT_PRIMARY),
+                    ));
+                });
+
+                // "Replay N / M" caption — rewritten live by
+                // `repaint_replay_selector_caption`.
+                row.spawn((
+                    ReplaySelectorCaption,
+                    Text::new(replay_selector_caption(selected_index, replays.len())),
+                    font_row.clone(),
+                    TextColor(TEXT_SECONDARY),
+                ));
+
+                // → Next chip
+                row.spawn((
+                    ReplayNextButton,
+                    ModalButton(ButtonVariant::Secondary),
+                    Button,
+                    Node {
+                        padding: UiRect::axes(VAL_SPACE_2, VAL_SPACE_1),
+                        justify_content: JustifyContent::Center,
+                        align_items: AlignItems::Center,
+                        border: UiRect::all(Val::Px(1.0)),
+                        border_radius: BorderRadius::all(Val::Px(RADIUS_SM)),
+                        ..default()
+                    },
+                    BackgroundColor(BG_ELEVATED_HI),
+                    BorderColor::all(BORDER_SUBTLE),
+                    HighContrastBorder::with_default(BORDER_SUBTLE),
+                ))
+                .with_children(|b| {
+                    b.spawn((
+                        Text::new("\u{2192}"),
+                        font_row.clone(),
+                        TextColor(TEXT_PRIMARY),
+                    ));
+                });
+            });
+
+            // Detail line: rewritten live by `repaint_replay_selector_detail`.
             body.spawn((
-                Text::new(replay_caption),
+                ReplaySelectorDetail,
+                Text::new(replay_selector_detail(replays, selected_index)),
                 font_row.clone(),
                 TextColor(TEXT_SECONDARY),
             ));
@@ -1670,6 +1774,140 @@ mod tests {
         );
     }
 
+    // -----------------------------------------------------------------------
+    // Prev/Next replay selector spawn-site tests
+    // -----------------------------------------------------------------------
+
+    #[test]
+    fn selector_row_spawns_when_stats_screen_opens() {
+        let mut app = headless_app();
+        // Pre-populate a replay so the selector has something to show.
+        {
+            let mut hist = app.world_mut().resource_mut::<ReplayHistoryResource>();
+            hist.0.replays.push(make_test_replay(90, None));
+        }
+        app.world_mut()
+            .resource_mut::<ButtonInput<KeyCode>>()
+            .press(KeyCode::KeyS);
+        app.update();
+
+        let prev = app
+            .world_mut()
+            .query::<&ReplayPrevButton>()
+            .iter(app.world())
+            .count();
+        let next = app
+            .world_mut()
+            .query::<&ReplayNextButton>()
+            .iter(app.world())
+            .count();
+        let caption = app
+            .world_mut()
+            .query::<&ReplaySelectorCaption>()
+            .iter(app.world())
+            .count();
+        let detail = app
+            .world_mut()
+            .query::<&ReplaySelectorDetail>()
+            .iter(app.world())
+            .count();
+        assert_eq!(prev, 1, "expected one ReplayPrevButton");
+        assert_eq!(next, 1, "expected one ReplayNextButton");
+        assert_eq!(caption, 1, "expected one ReplaySelectorCaption");
+        assert_eq!(detail, 1, "expected one ReplaySelectorDetail");
+    }
+
+    #[test]
+    fn selector_caption_initial_text_is_replay_one_of_one() {
+        let mut app = headless_app();
+        {
+            let mut hist = app.world_mut().resource_mut::<ReplayHistoryResource>();
+            hist.0.replays.push(make_test_replay(120, None));
+        }
+        app.world_mut()
+            .resource_mut::<ButtonInput<KeyCode>>()
+            .press(KeyCode::KeyS);
+        app.update();
+
+        let mut q = app
+            .world_mut()
+            .query_filtered::<&Text, With<ReplaySelectorCaption>>();
+        let texts: Vec<String> = q.iter(app.world()).map(|t| t.0.clone()).collect();
+        assert_eq!(texts.len(), 1);
+        assert_eq!(
+            texts[0],
+            "Replay 1 / 1",
+            "caption must show '1 / 1' for a single-replay history"
+        );
+    }
+
+    #[test]
+    fn selector_detail_initial_text_matches_replay_caption() {
+        let mut app = headless_app();
+        {
+            let mut hist = app.world_mut().resource_mut::<ReplayHistoryResource>();
+            hist.0.replays.push(make_test_replay(65, None)); // 65s → "1:05"
+        }
+        app.world_mut()
+            .resource_mut::<ButtonInput<KeyCode>>()
+            .press(KeyCode::KeyS);
+        app.update();
+
+        let mut q = app
+            .world_mut()
+            .query_filtered::<&Text, With<ReplaySelectorDetail>>();
+        let texts: Vec<String> = q.iter(app.world()).map(|t| t.0.clone()).collect();
+        assert_eq!(texts.len(), 1);
+        assert_eq!(
+            texts[0], "1:05 win on 2026-05-08",
+            "detail must show formatted replay caption for the selected replay"
+        );
+    }
+
+    #[test]
+    fn selector_detail_appends_shareable_badge_when_url_present() {
+        // `replay_selector_detail` is pure — no app setup needed.
+        let replays = vec![make_test_replay(
+            90,
+            Some("https://example.com/r/abc".to_string()),
+        )];
+        let label = replay_selector_detail(&replays, 0);
+        assert!(
+            label.contains("Shareable"),
+            "detail must include 'Shareable' badge when share_url is set, got: {label:?}"
+        );
+    }
+
+    #[test]
+    fn selector_caption_shows_no_replays_when_history_is_empty() {
+        assert_eq!(replay_selector_caption(0, 0), "No replays");
+    }
+
+    #[test]
+    fn selector_caption_wraps_ordinal_correctly() {
+        // index 2 (0-based) in a 3-replay history → "Replay 3 / 3"
+        assert_eq!(replay_selector_caption(2, 3), "Replay 3 / 3");
+    }
+
+    /// Build a minimal [`Replay`] for use in stats-plugin unit tests.
+    ///
+    /// Uses a fixed seed, DrawOne mode, Classic game, 2026-05-08 date.
+    /// `time_seconds` and `share_url` are the only varying fields across tests.
+    fn make_test_replay(time_seconds: u64, share_url: Option<String>) -> solitaire_data::Replay {
+        let date = chrono::NaiveDate::from_ymd_opt(2026, 5, 8).expect("valid date");
+        let mut r = solitaire_data::Replay::new(
+            1,
+            solitaire_core::game_state::DrawMode::DrawOne,
+            solitaire_core::game_state::GameMode::Classic,
+            time_seconds,
+            0,
+            date,
+            vec![],
+        );
+        r.share_url = share_url;
+        r
+    }
+
     /// Integration: pre-set streak to 10, fire a win that bumps it to 11.
     /// Past the highest threshold, no event must fire — the flourish
     /// is reserved for the threshold crossing itself.

solitaire_engine/src/ui_modal.rs

@@ -372,6 +372,7 @@ pub fn spawn_modal_button<M: Component>(
             },
             BackgroundColor(idle_bg(variant)),
             BorderColor::all(BORDER_SUBTLE),
+            HighContrastBorder::with_default(BORDER_SUBTLE),
         ))
         .with_children(|b| {
             b.spawn((Text::new(label.into()), font_label, TextColor(label_color)));

solitaire_engine/src/ui_theme.rs

@@ -93,6 +93,13 @@ pub const ACCENT_SECONDARY: Color = Color::srgb(0.882, 0.639, 0.933);
 /// from base16-eighties. `#acc267`.
 pub const STATE_SUCCESS: Color = Color::srgb(0.675, 0.761, 0.404);
 
+/// High-contrast variant of [`STATE_SUCCESS`] — `#c8e862`. Brighter
+/// lime that maintains the success hue while lifting luminance from
+/// ~0.51 → ~0.73 so the WIN MOVE scrub-bar marker stands out from
+/// the bumped notch ticks (`BORDER_SUBTLE_HC` `#a0a0a0`, L≈0.60) in
+/// high-contrast mode.
+pub const STATE_SUCCESS_HC: Color = Color::srgb(0.784, 0.910, 0.384);
+
 /// Warning — penalty signal, daily-seed expiry countdown, sync-pending
 /// status. Gold from base16-eighties. **Both** Undo and Recycle
 /// counters use this when non-zero. `#ddb26f`.
@@ -252,6 +259,56 @@ impl HighContrastBorder {
     }
 }
 
+/// Marker for entities whose [`BackgroundColor`] should swap to
+/// [`BORDER_SUBTLE_HC`] when `Settings::high_contrast_mode` is on.
+/// Parallel to [`HighContrastBorder`] but for sites that paint their
+/// shape via `BackgroundColor` rather than `BorderColor` —
+/// `bevy::ui` 1 px decorative strips, tick marks, fine separators
+/// often render as tiny full-bleed `Node`s, not as borders, so the
+/// border-marker pattern doesn't apply.
+///
+/// `default_color` records the off-state colour; `hc_color` the on-
+/// state colour. [`with_default`] fills `hc_color` with
+/// [`BORDER_SUBTLE_HC`] so the 90 % of sites that just need the
+/// standard subtle-border bump can continue using a one-argument
+/// constructor. [`with_hc`] overrides the HC colour for the rare
+/// site (currently only the WIN MOVE scrub-bar marker) that needs a
+/// domain-specific HC variant (`STATE_SUCCESS_HC` instead of a gray).
+///
+/// [`with_default`]: HighContrastBackground::with_default
+/// [`with_hc`]: HighContrastBackground::with_hc
+/// [`BackgroundColor`]: bevy::prelude::BackgroundColor
+#[derive(bevy::prelude::Component, Debug, Clone, Copy)]
+pub struct HighContrastBackground {
+    /// Background colour to use when high-contrast mode is *off* —
+    /// the site's normal idle / active-state colour.
+    pub default_color: bevy::prelude::Color,
+    /// Background colour to use when high-contrast mode is *on*.
+    /// Defaults to [`BORDER_SUBTLE_HC`] via [`with_default`].
+    ///
+    /// [`with_default`]: HighContrastBackground::with_default
+    pub hc_color: bevy::prelude::Color,
+}
+
+impl HighContrastBackground {
+    /// Convenience constructor — HC colour defaults to
+    /// [`BORDER_SUBTLE_HC`].
+    pub const fn with_default(default_color: bevy::prelude::Color) -> Self {
+        Self { default_color, hc_color: BORDER_SUBTLE_HC }
+    }
+
+    /// Constructor for sites whose HC colour differs from the standard
+    /// [`BORDER_SUBTLE_HC`]. Currently used by the WIN MOVE scrub-bar
+    /// marker which bumps `STATE_SUCCESS` → `STATE_SUCCESS_HC` rather
+    /// than to a neutral gray.
+    pub const fn with_hc(
+        default_color: bevy::prelude::Color,
+        hc_color: bevy::prelude::Color,
+    ) -> Self {
+        Self { default_color, hc_color }
+    }
+}
+
 /// Strong border — hover outline, focused button, active popover.
 /// `outline` from the design system. `#505050`.
 pub const BORDER_STRONG: Color = Color::srgba(0.314, 0.314, 0.314, 1.0);

solitaire_engine/src/win_summary_plugin.rs

@@ -352,7 +352,7 @@ impl ScoreBreakdown {
         let no_undo_bonus = if undo_count == 0 { SCORE_NO_UNDO_BONUS } else { 0 };
         let multiplier = match mode {
             GameMode::Zen => 0.0,
-            GameMode::Classic | GameMode::Challenge | GameMode::TimeAttack => 1.0,
+            GameMode::Classic | GameMode::Challenge | GameMode::TimeAttack | GameMode::Difficulty(_) => 1.0,
         };
         Self {
             base,
@@ -423,6 +423,7 @@ fn mode_display_name(mode: GameMode) -> &'static str {
         GameMode::Zen => "Zen",
         GameMode::Challenge => "Challenge",
         GameMode::TimeAttack => "Time Attack",
+        GameMode::Difficulty(level) => level.label(),
     }
 }