fix(android): 48dp min hit targets on action buttons

Action buttons sized to text + 8 px padding made "Undo" end up
~46 x 33 px — fine for a mouse but at the threshold of a finger.
Adds `min_width: 48 px` and `min_height: 48 px` to the button
Node so every button meets Material's 48 dp thumb-target guideline.

Applied universally; the floor is a no-op for buttons whose
content already exceeds 48 px on either axis (Menu, Modes,
New Game, Pause, Help all clear 48 px wide; height was the
binding constraint at ~33 px).

Closes P1 #2 of docs/android/PLAYABILITY_TODO.md. Engine tests
pass; clippy clean.

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 +7,11 @@
 *.tmp
 data/
 .claude/
+
+# IDE project files
+.idea/
+
+# Android signing keystores — never commit
+*.jks
+*.jks.bak
+*.keystore

CHANGELOG.md

@@ -6,8 +6,178 @@ project follows [Semantic Versioning](https://semver.org/).
 
 ## [Unreleased]
 
-No threads in flight. v0.21.7 cut on 2026-05-08; CHANGELOG accumulates
-the next cycle here.
+## [0.22.0] — 2026-05-08
+
+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
 

Cargo.lock

@@ -6967,6 +6967,8 @@ version = "0.1.0"
 dependencies = [
  "ab_glyph",
  "png 0.17.16",
+ "solitaire_core",
+ "solitaire_data",
 ]
 
 [[package]]
@@ -6984,8 +6986,10 @@ version = "0.1.0"
 dependencies = [
  "async-trait",
  "axum",
+ "bevy",
  "chrono",
  "dirs",
+ "jni 0.21.1",
  "jsonwebtoken",
  "keyring-core",
  "reqwest",
@@ -7009,6 +7013,7 @@ 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

@@ -1,85 +1,98 @@
 # Solitaire Quest — Session Handoff
 
-**Last updated:** 2026-05-08 — **v0.21.7 cut and tagged at
-`da3e542`**, working tree clean (tag pending push).
+**Last updated:** 2026-05-08 — **v0.21.8 tagged at `c50eaf8`**;
+nine post-cut commits on master. Push pending.
 
-v0.21.7 is a single-commit patch closing the last major B-2
-sub-piece: **mini-tableau preview dim layer**. A full-screen
-`ReplayTableauDimLayer` UI node (100 % × 100 %, 50 % opacity
-black) at `Z_REPLAY_DIM = 54` (one rung below the replay
-chrome at z=55) darkens the card world during replay so the
-banner and move-log panel read clearly against the scene —
-matching the mockup's "Game Peek Band at 50 % opacity" spec
-without touching `card_plugin`. 13 commits have now shipped
-across v0.21.4–v0.21.7 on the B-2 replay screen-takeover
-arc; every major sub-piece is closed.
+v0.21.8 closes the last optional polish items in the B-2
+replay screen-takeover arc: **notch-label centering** (middle
+three scrub-bar labels now centred on their notch ticks via the
+CSS `translateX(-50%)` pattern for Bevy 0.18 UI) and **WIN
+MOVE HC legibility** (lime stays lime under HC mode via the
+extended `HighContrastBackground::with_hc` constructor and a
+new `STATE_SUCCESS_HC` brighter-lime constant). The replay
+overlay arc is now fully closed with no known open items.
 
-Full v0.21.7 detail lives in `CHANGELOG.md` § [0.21.7]. 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:** `da3e542` (v0.21.7 commit). Tag pending —
-  push with `git tag v0.21.7 da3e542 && git push origin v0.21.7`.
-- **HEAD on origin:** `f63db76` (v0.21.6). v0.21.7 commit
-  not pushed yet; a docs-only edit will ride on top before push.
-- **Working tree:** clean. No WIP outstanding.
+- **HEAD locally:** `f281425` (Android Keystore JNI).
+  Docs ride on top; push pending.
+- **HEAD on origin:** `395a322` (double-tap commit — last pushed).
+- **Working tree:** clean (docs uncommitted). No WIP outstanding.
 - **`artwork/` directory:** still untracked. Intentional.
 - **Build:** `cargo clippy --workspace --all-targets -- -D warnings`
   clean.
-- **Tests:** **1275 passing / 0 failing** across the workspace.
-  Detail in `CHANGELOG.md` § [0.21.7] § Stats.
-- **Tags on origin:** `v0.9.0` through `v0.21.6`. v0.21.7
-  tag exists locally at `da3e542`; push to origin when ready.
+- **Tests:** **1292 passing / 0 failing** across the workspace.
+- **Tags on origin:** `v0.9.0` through `v0.21.8`.
+- **Android:** APK verified booting on Pixel_7 AVD (Android 14,
+  x86_64). All desktop-only systems (handle_fullscreen) now gated.
+  See Phase Android punch list for remaining work.
 
-## Since the v0.21.7 cut
+## Since the v0.21.8 cut
 
-One commit in flight (not yet pushed to origin): `da3e542`
-adds the full-screen tableau dim layer. CHANGELOG and
-SESSION_HANDOFF updates ride on top. Push with:
-```
-git push origin master
-git push origin v0.21.7
-```
+Seven commits since the v0.21.8 tag:
+- `a449f60` — Stats Prev/Next selector spawn site
+- `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
 
-Open next-step menu (all major B-2 sub-pieces now closed):
-1. **Polish: notch label centering.** Bevy 0.18 lacks a
-   clean `translate-x: -50%` primitive so the middle three
-   scrub-bar labels sit slightly right-of-notch. Could use a
-   child Text wrapper with computed left-margin compensation.
-   Tiny commit, requires visual review.
-2. **Polish: WIN MOVE marker HC bump.** Currently uses
-   `STATE_SUCCESS` lime which stays visible under HC, but a
-   contrast bump under HC would make it even more legible
-   alongside the bumped notches. Optional.
-3. **Move Log auto-scroll** — only relevant if the panel's
+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.
-   Currently the prev-2 / active / next-2 layout fits all
-   visible content, so auto-scroll is unneeded.
-
-Recommended order: options 1 and 2 are tiny polish commits
-that benefit from visual review. Option 3 is a non-starter
-unless the panel's row capacity grows.
 
 ## Open punch list
 
 ### Phase Android (build + persistence shipped; runtime gaps remain)
 
-- **APK launch verification on AVD / device.** `adb install` then
-  `adb logcat` against the `bevy_test` AVD or an x86_64 device.
-  The build works and persistence is wired, but no end-to-end
-  device run has been logged. Shakes out runtime bugs the build +
-  unit tests can't catch.
-- **JNI ClipboardManager bridge.** Replaces the Android stub for
-  the Stats "Copy share link" toast. `arboard` doesn't ship an
-  Android backend; small custom JNI call.
-- **Android Keystore for credentials.** `keyring` is target-gated
-  to a stub returning `KeychainUnavailable`; replace with Android
-  Keystore via JNI when sync auth ships on mobile.
-- **Google Play Games (gpgs) integration.** Listed as a
-  Phase-Android target since Phase 1; now unblocked by the build
-  target.
+- *APK launch verification — closed 2026-05-08 by `202a64d`.*
+  Three fixes shipped: `android_main` export (missing NativeActivity
+  entry point), `resize_constraints` gated to non-Android (max=0
+  panic), `apply_smart_default_window_size` gated to non-Android
+  (clamp panic on zero-dimension window event). Verified booting on
+  Pixel_7 AVD (Android 14, x86_64, SwiftShader Vulkan), 2+ min
+  runtime without crash. B0004 ECS hierarchy warnings remain
+  (non-fatal; entity parent/child component mismatch); investigate
+  if they surface gameplay bugs.
+- *Double-tap auto-move — closed 2026-05-08 by `395a322`.*
+  `handle_double_tap` fires `MoveRequestEvent` on two rapid
+  `TouchPhase::Ended` events within 0.5 s. Prefers foundation;
+  falls back to tableau stack move. Fires `MoveRejectedEvent` when
+  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
@@ -158,11 +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`
-  noted Prev/Next markers exist in `stats_plugin` but no spawn
-  site renders them today — the Shareable badge therefore lands
-  on the single-replay caption. If/when Prev/Next is plumbed,
-  the badge will need to follow.
+- *Play-by-Seed dialog — closed 2026-05-08 by `0cb1587`.*
+  `PlayBySeedPlugin` adds a numeric-input modal with async solver
+  preview (debounced 500 ms). `HomeMode::PlayBySeed` card fires
+  `StartPlayBySeedRequestEvent`. 5 unit tests. 75 new verified-win
+  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
@@ -246,22 +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. v0.21.7 is tagged at da3e542 (cut 2026-05-08,
-closes the last major B-2 sub-piece: full-screen tableau dim
-layer — 50 % opacity black UI scrim at z=54 that darkens the
-card world during replay so the chrome reads clearly above it).
-v0.21.6 stays at f63db76, v0.21.5 at a2432df, v0.21.4 at
-23ff62c, v0.21.3 at 3d92a91, v0.21.2 at f23df3b, v0.21.1 at
-daa655a, v0.21.0 at 04f9bf9. Working tree clean (CHANGELOG +
-SESSION_HANDOFF docs ride on top of da3e542; push pending).
-See CHANGELOG.md § [0.21.7] for full detail.
+Branch: master. v0.21.8 is tagged at c50eaf8 (cut 2026-05-08,
+replay-overlay polish). Seven post-cut commits are on master (see
+"Since the v0.21.8 cut" above); push of the last four pending.
+v0.21.7 stays at da3e542, v0.21.6 at f63db76, v0.21.5 at a2432df,
+v0.21.4 at 23ff62c, v0.21.3 at 3d92a91, v0.21.2 at f23df3b,
+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`. Workspace
-tests: 1275 passing / 0 failing. 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        — [0.21.6] 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
@@ -276,25 +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` +
-     `adb logcat` to shake out runtime bugs the build / unit
-     tests can't catch. Likely surfaces JNI ClipboardManager
-     and Android Keystore stubs that need real bridges. Larger
-     scope; needs an Android device or emulator running.
-  B. Replay-overlay polish (B-2 arc fully closed in v0.21.7).
-     All 13 planned sub-pieces shipped. Remaining items are
-     minor polish: (a) scrub-bar notch-label centering — middle
-     three labels sit slightly right-of-notch due to Bevy 0.18
-     lacking `translate-x: -50%`; tiny commit, needs visual
-     review. (b) WIN MOVE marker HC contrast bump — optional
-     luminance boost under HC mode. Both are single commits
-     requiring visual review; recommend treating as a v0.21.8
-     polish pass after manual testing.
-  C. 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,
+  A. Android follow-ups — JNI ClipboardManager bridge (arboard
+     has no Android backend), Android Keystore (blocked on Phase 8).
+     Launch verification + double-tap are closed.
+  B. Phase 8 (sync) — local storage scaffolding, self-hosted
+     Axum server, `SolitaireServerClient` impl. The biggest open
+     arc by scope; rolls up Android dependencies (Keystore,
      ClipboardManager).
+  C. Play-by-Seed polish — the dialog is functional but has no
+     visual preview of the solver verdict in the UI yet; the
+     HomeMode card is wired but the dialog spawn site and verdict
+     display could use a second pass.
 
 WORKFLOW NOTES:
   - Use the system git config (already correct).
@@ -320,7 +332,7 @@ WORKFLOW NOTES:
 
 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
+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.
 ```

docs/android/PLAYABILITY_TODO.md

@@ -0,0 +1,137 @@
+# Android Playability TODO
+
+**Started:** 2026-05-10 — first hardware screenshot of v0.22.3 APK
+running on a real device showed the desktop HUD projected onto a
+360 dp portrait viewport with no mobile adaptation. This list
+tracks the work needed to make the APK genuinely playable, not
+just "boots without crashing."
+
+**Context:** v0.22.3 (signed release APK) builds and launches.
+JNI bridges (clipboard, keystore) compile but are untested on
+hardware. The work below is UI/UX port work — no architectural
+rewrites required.
+
+---
+
+## Reading from the v0.22.3 screenshot
+
+| Region | Observation |
+|--------|-------------|
+| Top ~5 % | System bar (clock, signal, battery) overlapped by game HUD — no safe-area inset |
+| HUD text row | `Score:0 Pause Esc Help A Modes [] New_Game N Moves:0 0:08` all overlapping — desktop layout crammed into 360 dp |
+| Keyboard hints | `Esc`, `A`, `[]`, `N` shown next to buttons — meaningless on touch |
+| Foundations row | Leftmost foundation (♥) clipped left; rightmost tableau column (♠ 4) clipped right |
+| Card backs | Face-down cards render as solid red squares, not back-art texture |
+| Vertical use | Cards occupy top ~30 % only; bottom 70 % empty black — no portrait-aware layout |
+| Bottom edge | No accommodation for Android gesture / home-indicator area |
+
+---
+
+## P0 — Blocking playability
+
+- [x] **Safe-area insets (top + bottom).** *Closed 2026-05-10 by
+  `b9aa262`.* `SafeAreaInsets` resource + `SafeAreaInsetsPlugin`
+  query `WindowInsets.getInsets(systemBars())` via JNI on Android;
+  HUD anchors carry `SafeAreaAnchoredTop { base_top }` and the
+  change-detection fix-up system re-applies `base_top + insets.top`
+  whenever the resource updates. Bottom inset is captured but not
+  yet consumed (waits for bottom-anchored UI).
+- [x] **Mobile HUD layout.** *Closed 2026-05-10.* Both the left HUD
+  column and the right action button row are now capped at
+  `max_width: 50 %` and the button row + tier-row child Nodes carry
+  `flex_wrap: Wrap`. On a 360 dp viewport the 6-button row breaks
+  to multiple lines (right-justified) and the tier rows wrap
+  individually instead of overflowing into the action column. On
+  desktop (≥ 1280 px) the 50 % cap is wider than any natural row
+  width so the existing single-line layout is unchanged.
+- [x] **Card-back asset not rendering.** *Closed 2026-05-10 by
+  `fcc7337`.* `AssetPlugin::file_path = "../assets"` was set
+  unconditionally to fix the desktop `cargo run -p solitaire_app`
+  CWD relativity, but on Android cargo-apk packages the same
+  directory into the APK at `assets/` and Bevy's
+  AndroidAssetReader is already rooted there — prepending `../`
+  walked the reader out of the APK assets root and every load
+  failed silently. The face-down branch then fell through to the
+  `card_back_colour(0)` solid-red brick fallback. Gated the
+  override behind `#[cfg(not(target_os = "android"))]`.
+- [x] **Viewport overflow.** *Closed 2026-05-10.* `compute_layout`
+  was clamping the input window up to `MIN_WINDOW = 800 × 600`,
+  so a 360 dp phone got laid out as if it were 800-wide and the
+  outer piles fell outside the actual viewport. Lowered the floor
+  to 320 × 400 (below the smallest reasonable phone) so real
+  Android resolutions flow through without clamping, while keeping
+  a sentinel to guard against degenerate / startup-zero windows.
+  New regression test `phone_portrait_layout_fits_horizontally`
+  asserts all 13 piles fit a 360 × 800 viewport.
+
+## P1 — Touch UX
+
+- [x] **Suppress keyboard-hint labels on Android.** *Closed
+  2026-05-10.* `spawn_action_button` now nulls the `hotkey`
+  argument on Android via a `#[cfg(target_os = "android")]` rebind,
+  so the U / Esc / F1 / N chips next to the action row labels
+  disappear on touch builds. Other hint sites (onboarding panel,
+  pause-modal `Esc` hint, mode-card hotkey chips on the home
+  screen, replay overlay footer, modal toggle hints in
+  profile/stats/leaderboard/settings, help screen) survive — they
+  live behind navigation and a touch user reaches them less often.
+  Track as a P3 sweep when more screens are audited on hardware.
+- [x] **Thumb-sized hit targets.** *Closed 2026-05-10.* Action
+  button Node carries `min_width: Val::Px(48.0), min_height:
+  Val::Px(48.0)` — meets Material's 48 dp baseline on touch and is
+  a no-op for buttons whose content already exceeds 48 px in
+  either axis. Applied universally rather than cfg-gated since
+  Material's guideline applies to all input modes. Cards, pile
+  markers, modal close buttons not yet audited — track as P3 if
+  they fall below threshold on hardware.
+- [ ] **Portrait-first card spacing.** Stretch tableau piles vertically
+  to fill height; reduce inter-pile gaps so 7 columns fit in 360 dp.
+- [ ] **Double-tap auto-move visible feedback.** `handle_double_tap`
+  exists since `395a322` — verify it triggers on hardware and add a
+  brief source-card flash / highlight to confirm to the user.
+
+## P2 — Polish
+
+- [ ] **Drag responsiveness on touch.** Bevy default touch-to-mouse
+  mapping can lag; confirm drag start threshold isn't too high for a
+  finger.
+- [ ] **Long-press menu.** Alternative to right-click (which doesn't
+  exist on touch). Wire to the existing right-click-highlight system.
+- [ ] **HUD typography.** Reduce text sizes for `Score:`, `Moves:`,
+  timer so they fit cleanly in one row.
+- [ ] **Orientation lock.** Set `android:screenOrientation="portrait"`
+  in cargo-apk manifest (or design a landscape layout).
+
+## P3 — Asset density
+
+- [ ] **Density-aware card scaling.** Currently single texture size; on
+  a high-DPI phone the cards look small. Scale by
+  `Window::scale_factor()` or ship multiple PNG sizes.
+- [ ] **App-icon density buckets.** Nine sizes already exist in
+  `assets/icon/`; verify the manifest references them so Android's
+  launcher picks the right one.
+
+## P4 — Stability / runtime
+
+- [ ] **B0004 ECS hierarchy warnings.** Flagged in
+  `SESSION_HANDOFF.md` after APK launch verification — investigate
+  whether they cause gameplay bugs on hardware vs. AVD.
+- [ ] **AVD functional tests for JNI bridges.** Clipboard (`2c822ba`)
+  and Keystore (`f281425`) shipped but never tested on real device
+  or AVD.
+
+---
+
+## Notes / decisions
+
+* This list is screenshot-driven; expect more items to surface once
+  P0 unblocks actually moving cards on hardware.
+* The pattern across all the bugs is "no one ran the relevant code
+  path on Android yet." The hard work — Bevy 0.18 on Android,
+  JNI bridges, signed CI builds — is done. What's left is a
+  coordinated pass of `#[cfg(target_os = "android")]` gates plus
+  making `LayoutResource` query the real surface size.
+* Where possible, prefer responsive layout (query window size) over
+  branching `#[cfg]` blocks. Branches are fine for input methods
+  (touch vs. mouse) but not for screen geometry — a foldable or
+  desktop window of equivalent size should look the same.

solitaire_app/src/lib.rs

@@ -18,21 +18,23 @@ use std::io::Write;
 use std::time::{SystemTime, UNIX_EPOCH};
 
 use bevy::prelude::*;
-use bevy::window::{
-    Monitor, MonitorSelection, PresentMode, PrimaryMonitor, PrimaryWindow, WindowPosition,
-};
+use bevy::window::{MonitorSelection, PresentMode, 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,
-    GamePlugin, HelpPlugin, HomePlugin, HudPlugin, InputPlugin, LeaderboardPlugin,
-    OnboardingPlugin, PausePlugin, ProfilePlugin, ProgressPlugin, RadialMenuPlugin,
-    ReplayOverlayPlugin, ReplayPlaybackPlugin, SelectionPlugin, SettingsPlugin, SplashPlugin,
-    StatsPlugin, SyncPlugin, TablePlugin, ThemePlugin, ThemeRegistryPlugin, TimeAttackPlugin,
-    UiFocusPlugin, UiModalPlugin, UiTooltipPlugin, WeeklyGoalsPlugin, WinSummaryPlugin,
+    CursorPlugin, DailyChallengePlugin, DiagnosticsHudPlugin, DifficultyPlugin, FeedbackAnimPlugin,
+    FontPlugin, GamePlugin, HelpPlugin, HomePlugin, HudPlugin, InputPlugin, LeaderboardPlugin,
+    OnboardingPlugin, PausePlugin, PlayBySeedPlugin, ProfilePlugin, ProgressPlugin,
+    RadialMenuPlugin, ReplayOverlayPlugin, ReplayPlaybackPlugin, SafeAreaInsetsPlugin,
+    SelectionPlugin, SettingsPlugin,
+    SplashPlugin, StatsPlugin, SyncPlugin, TablePlugin, ThemePlugin, ThemeRegistryPlugin,
+    TimeAttackPlugin, UiFocusPlugin, UiModalPlugin, UiTooltipPlugin, WeeklyGoalsPlugin,
+    WinSummaryPlugin,
 };
 
 /// App entry point — builds and runs the Bevy app.
@@ -76,6 +78,7 @@ 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 +119,9 @@ 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,
@@ -126,11 +132,20 @@ pub fn run() {
                     ..default()
                 })
                 // The `assets/` directory lives at the workspace root, but
-                // Bevy resolves `AssetPlugin::file_path` relative to the
-                // binary package's `CARGO_MANIFEST_DIR` (`solitaire_app/`).
-                // Point one level up so `cargo run -p solitaire_app` finds
-                // card faces, backs, backgrounds, and the UI font.
+                // on desktop Bevy resolves `AssetPlugin::file_path` relative
+                // to the binary package's `CARGO_MANIFEST_DIR`
+                // (`solitaire_app/`), so `cargo run -p solitaire_app` would
+                // miss the workspace-root `assets/` without a `../` prefix.
+                //
+                // On Android cargo-apk packages the same directory into the
+                // APK at `assets/` (via `[package.metadata.android].assets`
+                // in solitaire_app/Cargo.toml). Bevy's `AndroidAssetReader`
+                // is already rooted there, so any `file_path` other than the
+                // default makes it walk *out* of the APK's assets root and
+                // all loads fail silently — which is what produced the
+                // solid-red card-back fallback in the v0.22.3 screenshot.
                 .set(bevy::asset::AssetPlugin {
+                    #[cfg(not(target_os = "android"))]
                     file_path: "../assets".to_string(),
                     ..default()
                 }),
@@ -142,6 +157,13 @@ 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)
@@ -158,7 +180,10 @@ pub fn run() {
         .add_plugins(DailyChallengePlugin)
         .add_plugins(WeeklyGoalsPlugin)
         .add_plugins(ChallengePlugin)
+        .add_plugins(PlayBySeedPlugin)
+        .add_plugins(DifficultyPlugin)
         .add_plugins(TimeAttackPlugin)
+        .add_plugins(SafeAreaInsetsPlugin)
         .add_plugins(HudPlugin)
         .add_plugins(HelpPlugin)
         .add_plugins(HomePlugin::default())
@@ -195,6 +220,8 @@ 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 +242,7 @@ 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 +363,20 @@ 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.
-// Lets `sync_client::*` compile unchanged on Android; the runtime
-// effect is "session login required every launch", same as a Linux
-// box without Secret Service.
+// Android — delegate to the JNI Keystore bridge in android_keystore.
 // -------------------------------------------------------------------
 
-#[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,
-    _access_token: &str,
-    _refresh_token: &str,
+    username: &str,
+    access_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> {
-    Err(TokenError::KeychainUnavailable(ANDROID_STUB_MSG.to_string()))
+pub fn load_access_token(username: &str) -> Result<String, TokenError> {
+    crate::android_keystore::load_access_token(username)
 }
 
 #[cfg(target_os = "android")]
-pub fn load_refresh_token(_username: &str) -> Result<String, TokenError> {
-    Err(TokenError::KeychainUnavailable(ANDROID_STUB_MSG.to_string()))
+pub fn load_refresh_token(username: &str) -> Result<String, TokenError> {
+    crate::android_keystore::load_refresh_token(username)
 }
 
 #[cfg(target_os = "android")]
-pub fn delete_tokens(_username: &str) -> Result<(), TokenError> {
-    Err(TokenError::KeychainUnavailable(ANDROID_STUB_MSG.to_string()))
+pub fn delete_tokens(username: &str) -> Result<(), TokenError> {
+    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/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/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/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)]

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,
-    ToggleProfileRequestEvent,
+    StartDailyChallengeRequestEvent, StartDifficultyRequestEvent, StartPlayBySeedRequestEvent,
+    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
-            // `HomeScreen` entity and may queue a despawn on it in the
-            // same tick. Bevy's parallel scheduler would otherwise let
-            // two of them run simultaneously and double-despawn the
-            // entity, panicking when the second command buffer is
-            // applied. Chaining serialises these systems and keeps the
-            // despawn deterministic.
+            // cancel button, digit-key shortcut, difficulty handlers)
+            // all read the `HomeScreen` entity and may queue a despawn
+            // on it in the same tick. 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

@@ -17,6 +17,8 @@ use crate::daily_challenge_plugin::DailyChallengeResource;
 use crate::progress_plugin::ProgressResource;
 use crate::settings_plugin::SettingsResource;
 use crate::layout::HUD_BAND_HEIGHT;
+use crate::safe_area::{SafeAreaAnchoredTop, SafeAreaInsets};
+use crate::ui_theme::SPACE_2;
 use crate::ui_theme::{
     scaled_duration, ACCENT_PRIMARY, ACCENT_SECONDARY, BG_ELEVATED, BG_ELEVATED_HI,
     BG_ELEVATED_PRESSED, BG_HUD_BAND, BORDER_SUBTLE, HighContrastBorder, MOTION_SCORE_PULSE_SECS,
@@ -376,11 +378,13 @@ impl Plugin for HudPlugin {
 /// bottom edge lines up exactly with the top edge of the highest
 /// playable card. The fill is `BG_HUD_BAND` — midnight purple at 0.70
 /// alpha, so the green felt reads through subtly.
-fn spawn_hud_band(mut commands: Commands) {
+fn spawn_hud_band(insets: Option<Res<SafeAreaInsets>>, mut commands: Commands) {
+    const BASE_TOP: f32 = 0.0;
+    let top_inset = insets.as_deref().copied().unwrap_or_default().top;
     commands.spawn((
         Node {
             position_type: PositionType::Absolute,
-            top: Val::Px(0.0),
+            top: Val::Px(BASE_TOP + top_inset),
             left: Val::Px(0.0),
             width: Val::Percent(100.0),
             height: Val::Px(HUD_BAND_HEIGHT),
@@ -391,6 +395,7 @@ fn spawn_hud_band(mut commands: Commands) {
         // paint on top, but above the card sprites (which are 2D-world
         // entities and rendered behind UI regardless).
         ZIndex(Z_HUD - 1),
+        SafeAreaAnchoredTop { base_top: BASE_TOP },
     ));
 }
 
@@ -413,7 +418,12 @@ fn spawn_hud_band(mut commands: Commands) {
 /// player's #1 complaint. This restructure groups by purpose, lets
 /// transient items disappear cleanly, and uses the typography scale to
 /// make Score the visual protagonist.
-fn spawn_hud(font_res: Option<Res<FontResource>>, mut commands: Commands) {
+fn spawn_hud(
+    font_res: Option<Res<FontResource>>,
+    insets: Option<Res<SafeAreaInsets>>,
+    mut commands: Commands,
+) {
+    let top_inset = insets.as_deref().copied().unwrap_or_default().top;
     let font_handle = font_res.as_ref().map(|f| f.0.clone()).unwrap_or_default();
     let font_score = TextFont {
         font: font_handle.clone(),
@@ -434,6 +444,16 @@ fn spawn_hud(font_res: Option<Res<FontResource>>, mut commands: Commands) {
     let row_node = || Node {
         flex_direction: FlexDirection::Row,
         column_gap: VAL_SPACE_3,
+        // On a narrow viewport the four tier rows (Score/Moves/Timer,
+        // Mode/Challenge/Draw-cycle/Won-previously, Undos/Recycles/
+        // Auto-complete, selection chip) can collectively be wider than
+        // the available space and overflow into the action-button column
+        // on the right. `flex_wrap: Wrap` lets each tier soft-wrap onto
+        // a second line; on a desktop window the rows stay single-line
+        // because the parent column has no width cap and the row never
+        // exceeds the natural line width.
+        flex_wrap: FlexWrap::Wrap,
+        row_gap: VAL_SPACE_1,
         align_items: AlignItems::Baseline,
         ..default()
     };
@@ -443,12 +463,21 @@ fn spawn_hud(font_res: Option<Res<FontResource>>, mut commands: Commands) {
             Node {
                 position_type: PositionType::Absolute,
                 left: VAL_SPACE_3,
-                top: VAL_SPACE_2,
+                top: Val::Px(SPACE_2 + top_inset),
                 flex_direction: FlexDirection::Column,
+                // Cap the column at 50% of viewport so on narrow
+                // (mobile) widths the inner tier rows have a bounded
+                // width to wrap against, and the column can't bleed
+                // into the right-anchored action button row (also
+                // capped at 50%). On desktop 50% of 1920 = 960 px,
+                // wider than any tier row's natural width, so the
+                // visible layout is unaffected.
+                max_width: Val::Percent(50.0),
                 row_gap: VAL_SPACE_1,
                 ..default()
             },
             ZIndex(Z_HUD),
+            SafeAreaAnchoredTop { base_top: SPACE_2 },
         ))
         .with_children(|hud| {
             // Tier 1 — primary readouts. Score is the protagonist (HEADLINE);
@@ -568,7 +597,12 @@ fn spawn_hud(font_res: Option<Res<FontResource>>, mut commands: Commands) {
 /// Order (left → right): Undo, Pause, Help, New Game. New Game is rightmost
 /// because it's the most consequential action; the destructive button sits
 /// on its own visual edge.
-fn spawn_action_buttons(font_res: Option<Res<FontResource>>, mut commands: Commands) {
+fn spawn_action_buttons(
+    font_res: Option<Res<FontResource>>,
+    insets: Option<Res<SafeAreaInsets>>,
+    mut commands: Commands,
+) {
+    let top_inset = insets.as_deref().copied().unwrap_or_default().top;
     let font = TextFont {
         font: font_res.as_ref().map(|f| f.0.clone()).unwrap_or_default(),
         // TYPE_BODY (14.0) — was a hardcoded `16.0` until the
@@ -585,13 +619,28 @@ fn spawn_action_buttons(font_res: Option<Res<FontResource>>, mut commands: Comma
             Node {
                 position_type: PositionType::Absolute,
                 right: VAL_SPACE_3,
-                top: VAL_SPACE_2,
+                top: Val::Px(SPACE_2 + top_inset),
                 flex_direction: FlexDirection::Row,
+                // 6 buttons total ~510 px wide; on a desktop window
+                // (typically >= 1280 px) `max_width: 50%` is >= 640 px
+                // and the row stays a single line. On a 360 dp phone
+                // 50% is 180 px and the row wraps to two-three lines —
+                // which keeps the buttons out of the left HUD column's
+                // horizontal range and prevents the off-screen-left
+                // clipping seen in the v0.22.3 hardware screenshot.
+                max_width: Val::Percent(50.0),
+                flex_wrap: FlexWrap::Wrap,
+                // When the row wraps, buttons pack to the *end* of each
+                // line so the row stays visually right-aligned (matches
+                // the `right: VAL_SPACE_3` anchor).
+                justify_content: JustifyContent::FlexEnd,
                 column_gap: VAL_SPACE_2,
+                row_gap: VAL_SPACE_2,
                 align_items: AlignItems::Center,
                 ..default()
             },
             ZIndex(Z_HUD),
+            SafeAreaAnchoredTop { base_top: SPACE_2 },
         ))
         .with_children(|row| {
             // Menu and Modes don't have a single hotkey accelerator
@@ -681,6 +730,14 @@ fn spawn_action_button<M: Component>(
     font: &TextFont,
     order: i32,
 ) {
+    // Hotkey hint chips ("U", "Esc", "F1", "N") are meaningless on a
+    // touch device — the button itself is the affordance — and they
+    // visibly clutter the narrow-viewport action row. Force the hint
+    // off on Android; the chevrons on Menu/Modes remain because they
+    // indicate dropdown behaviour and still apply on touch.
+    #[cfg(target_os = "android")]
+    let hotkey: Option<&'static str> = None;
+
     let hotkey_font = TextFont {
         font: font.font.clone(),
         font_size: TYPE_CAPTION,
@@ -707,6 +764,14 @@ fn spawn_action_button<M: Component>(
             // companion commit). Vertical padding stays at VAL_SPACE_2
             // so button height tracks the rest of the chrome band.
             padding: UiRect::axes(VAL_SPACE_2, VAL_SPACE_2),
+            // 48 px floors meet Material's recommended thumb-target
+            // size on touch and are a no-op on desktop for buttons
+            // whose content already exceeds 48 px in either axis
+            // (Menu, Modes, New Game, etc.). Without these, "Undo"
+            // ends up ~46 × 33 px — comfortably tappable with a mouse
+            // but right at the threshold for a finger.
+            min_width: Val::Px(48.0),
+            min_height: Val::Px(48.0),
             justify_content: JustifyContent::Center,
             align_items: AlignItems::Center,
             border_radius: BorderRadius::all(Val::Px(RADIUS_MD)),
@@ -1741,6 +1806,7 @@ 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/layout.rs

@@ -21,9 +21,25 @@ pub enum LayoutSystem {
     UpdateOnResize,
 }
 
-/// Minimum supported window dimensions. Layout is still computed below this
-/// size but cards will be small.
-pub const MIN_WINDOW: Vec2 = Vec2::new(800.0, 600.0);
+/// Minimum window dimensions used as a layout floor.
+///
+/// `compute_layout` runs `window.max(MIN_WINDOW)` so a window smaller than this
+/// on either axis is laid out as if it were at least this size. The floor
+/// exists to guard against degenerate / divide-by-zero layouts on very small
+/// surfaces (Bevy can briefly report 0-size windows during startup or after
+/// minimisation on some compositors); it is not a "minimum supported playable
+/// size" — desktop builds enforce that via `WindowResizeConstraints` set in
+/// `solitaire_app::lib`.
+///
+/// The previous floor of 800×600 was set with desktop in mind and produced
+/// the wrong behaviour on Android: a 360 dp phone got laid out as if it were
+/// 800-wide, pushing the leftmost foundation past `-180` and the rightmost
+/// tableau pile past `+180`, which clipped both at the visible viewport
+/// edges (visible in the v0.22.3 hardware screenshot). 320×400 is below the
+/// smallest reasonable phone (≈ 360×640) so every real device flows through
+/// without clamping, while still being large enough that the layout math
+/// produces non-degenerate card sizes.
+pub const MIN_WINDOW: Vec2 = Vec2::new(320.0, 400.0);
 
 /// Aspect ratio (height / width) of a standard playing card.
 ///
@@ -205,11 +221,39 @@ mod tests {
 
     #[test]
     fn layout_below_minimum_clamps_to_minimum() {
-        let below = compute_layout(Vec2::new(400.0, 300.0));
+        // 200×200 sits below the floor on both axes, so the clamp pulls each
+        // axis up to MIN_WINDOW and the layout matches compute_layout(MIN_WINDOW).
+        let below = compute_layout(Vec2::new(200.0, 200.0));
         let at_min = compute_layout(MIN_WINDOW);
         assert_eq!(below.card_size, at_min.card_size);
     }
 
+    /// Regression for the v0.22.3 Android viewport-overflow bug. A typical
+    /// portrait-phone viewport (360 dp × 800 dp) must produce a layout
+    /// where every pile fits horizontally — i.e. card_width is derived
+    /// from the actual window, not a clamped-up desktop floor.
+    #[test]
+    fn phone_portrait_layout_fits_horizontally() {
+        let window = Vec2::new(360.0, 800.0);
+        let layout = compute_layout(window);
+        let half_w = window.x / 2.0;
+        let half_card = layout.card_size.x / 2.0;
+        for (pile, pos) in &layout.pile_positions {
+            assert!(
+                pos.x - half_card >= -half_w - 1e-3,
+                "{:?} overflows left at portrait phone window {:?}",
+                pile,
+                window
+            );
+            assert!(
+                pos.x + half_card <= half_w + 1e-3,
+                "{:?} overflows right at portrait phone window {:?}",
+                pile,
+                window
+            );
+        }
+    }
+
     #[test]
     fn tableau_columns_are_sorted_left_to_right() {
         let layout = compute_layout(Vec2::new(1280.0, 800.0));

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;
@@ -31,6 +35,7 @@ pub mod replay_playback;
 pub mod settings_plugin;
 pub mod progress_plugin;
 pub mod resources;
+pub mod safe_area;
 pub mod selection_plugin;
 pub mod splash_plugin;
 pub mod stats_plugin;
@@ -92,11 +97,14 @@ pub use events::{
     ForfeitEvent, ForfeitRequestEvent, FoundationCompletedEvent, GameWonEvent, HelpRequestEvent,
     HintVisualEvent, InfoToastEvent, ManualSyncRequestEvent, MoveRejectedEvent, MoveRequestEvent,
     NewGameRequestEvent, PauseRequestEvent, StartChallengeRequestEvent,
-    StartDailyChallengeRequestEvent, StartTimeAttackRequestEvent, StartZenRequestEvent,
-    StateChangedEvent, SyncCompleteEvent, ToggleAchievementsRequestEvent,
-    ToggleLeaderboardRequestEvent, ToggleProfileRequestEvent, ToggleSettingsRequestEvent,
-    ToggleStatsRequestEvent, UndoRequestEvent, WinStreakMilestoneEvent, XpAwardedEvent,
+    StartDailyChallengeRequestEvent, StartDifficultyRequestEvent, StartPlayBySeedRequestEvent,
+    StartTimeAttackRequestEvent, StartZenRequestEvent, StateChangedEvent, SyncCompleteEvent,
+    ToggleAchievementsRequestEvent, ToggleLeaderboardRequestEvent, ToggleProfileRequestEvent,
+    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,
@@ -131,6 +139,7 @@ pub use settings_plugin::{
 };
 pub use layout::{compute_layout, Layout, LayoutResource};
 pub use resources::{DragState, GameStateResource, HintCycleIndex, SettingsScrollPos, SyncStatus, SyncStatusResource};
+pub use safe_area::{SafeAreaAnchoredTop, SafeAreaInsets, SafeAreaInsetsPlugin};
 pub use selection_plugin::{
     KeyboardDragState, SelectionHighlight, SelectionPlugin, SelectionState,
 };

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/replay_overlay.rs

@@ -3986,9 +3986,6 @@ mod tests {
     /// silently flip the intended stacking.
     #[test]
     fn dim_layer_z_is_below_replay_chrome() {
-        assert!(
-            Z_REPLAY_DIM < Z_REPLAY_OVERLAY,
-            "dim layer (z={Z_REPLAY_DIM}) must be below replay chrome (z={Z_REPLAY_OVERLAY})",
-        );
+        const { assert!(Z_REPLAY_DIM < Z_REPLAY_OVERLAY) }
     }
 }

solitaire_engine/src/safe_area.rs

@@ -0,0 +1,242 @@
+//! Safe-area insets.
+//!
+//! Reports the OS-reserved regions around the playable surface (status
+//! bar at the top, gesture / navigation bar at the bottom on Android,
+//! display cutouts, etc.) so UI anchored to a screen edge can avoid
+//! collisions.
+//!
+//! On non-Android targets all four edges report `0.0`. On Android the
+//! values come from `WindowInsets.getInsets(WindowInsets.Type.systemBars())`
+//! via JNI; the call is retried for the first few frames because
+//! `getRootWindowInsets()` only returns useful values after the decor
+//! view has been laid out at least once.
+//!
+//! UI that wants to respect the top inset should tag itself with the
+//! [`SafeAreaAnchoredTop`] marker carrying the layout's original top
+//! offset; [`apply_safe_area_anchors`] re-applies `base_top + insets.top`
+//! whenever the resource changes, so late inset arrival or orientation
+//! changes flow through automatically.
+
+use bevy::prelude::*;
+
+/// Pixel sizes of the system-reserved regions on each edge of the
+/// surface. Zero on desktop.
+#[derive(Resource, Debug, Clone, Copy, Default, PartialEq)]
+pub struct SafeAreaInsets {
+    pub top: f32,
+    pub bottom: f32,
+    pub left: f32,
+    pub right: f32,
+}
+
+impl SafeAreaInsets {
+    /// `true` when any edge has a non-zero reservation. Used by the
+    /// Android polling system to know it can stop querying.
+    pub fn is_populated(&self) -> bool {
+        self.top > 0.0 || self.bottom > 0.0 || self.left > 0.0 || self.right > 0.0
+    }
+}
+
+/// Marker for `Node` entities whose `top` offset should be re-applied
+/// as `base_top + SafeAreaInsets::top`.
+///
+/// `base_top` is the offset the layout would have used on a surface
+/// with no system reservation (i.e. on desktop). The fix-up system
+/// adds the current top inset on top of it whenever the resource
+/// changes.
+#[derive(Component, Debug, Clone, Copy)]
+pub struct SafeAreaAnchoredTop {
+    pub base_top: f32,
+}
+
+pub struct SafeAreaInsetsPlugin;
+
+impl Plugin for SafeAreaInsetsPlugin {
+    fn build(&self, app: &mut App) {
+        app.init_resource::<SafeAreaInsets>()
+            .add_systems(Update, apply_safe_area_anchors);
+
+        #[cfg(target_os = "android")]
+        app.add_systems(Update, android::refresh_insets);
+    }
+}
+
+/// Re-applies `base_top + insets.top` to every entity carrying the
+/// [`SafeAreaAnchoredTop`] marker whenever [`SafeAreaInsets`] changes.
+///
+/// Bevy resource change detection (`Res::is_changed`) is `true` on the
+/// frame the resource is inserted and every frame a `ResMut` borrow
+/// occurs. Combined with the Android polling loop short-circuiting
+/// once insets are populated, this runs at most a handful of times in
+/// a session.
+fn apply_safe_area_anchors(
+    insets: Res<SafeAreaInsets>,
+    mut q: Query<(&SafeAreaAnchoredTop, &mut Node)>,
+) {
+    if !insets.is_changed() {
+        return;
+    }
+    for (anchor, mut node) in &mut q {
+        node.top = Val::Px(anchor.base_top + insets.top);
+    }
+}
+
+#[cfg(target_os = "android")]
+mod android {
+    use super::SafeAreaInsets;
+    use bevy::prelude::*;
+
+    /// Polls Android for safe-area insets until we get a non-zero
+    /// reading, then stops. `getRootWindowInsets()` returns `null` (or
+    /// all-zero `Insets`) until the decor view has been laid out, which
+    /// is typically frame 1–3 of a fresh launch.
+    pub(super) fn refresh_insets(
+        mut insets: ResMut<SafeAreaInsets>,
+        mut tries: Local<u32>,
+    ) {
+        // Cap retries so we don't burn CPU forever on edge-to-edge
+        // devices that genuinely report zero insets.
+        const MAX_TRIES: u32 = 120; // ~2 seconds @ 60 fps
+
+        if *tries >= MAX_TRIES || insets.is_populated() {
+            return;
+        }
+        *tries += 1;
+
+        match query_insets() {
+            Ok(v) if v.is_populated() => {
+                info!(
+                    "safe_area: insets resolved top={} bottom={} left={} right={} (after {} frames)",
+                    v.top, v.bottom, v.left, v.right, *tries
+                );
+                *insets = v;
+            }
+            Ok(_) => {
+                // Layout not ready yet; try again next frame.
+            }
+            Err(e) => {
+                // Don't spam — log once and let polling continue silently.
+                if *tries == 1 {
+                    warn!("safe_area: JNI query failed (will retry): {e}");
+                }
+            }
+        }
+    }
+
+    fn query_insets() -> Result<SafeAreaInsets, String> {
+        use bevy::android::ANDROID_APP;
+        use jni::{objects::JObject, JavaVM};
+
+        let app = ANDROID_APP
+            .get()
+            .ok_or_else(|| "ANDROID_APP not initialized".to_string())?;
+
+        // SAFETY: `vm_as_ptr()` returns the JavaVM* set up by the Android
+        // runtime; valid for the lifetime of the process.
+        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()` returns 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<SafeAreaInsets> {
+            // Window window = activity.getWindow();
+            let window = env
+                .call_method(&activity, "getWindow", "()Landroid/view/Window;", &[])?
+                .l()?;
+
+            // View decor = window.getDecorView();
+            let decor = env
+                .call_method(&window, "getDecorView", "()Landroid/view/View;", &[])?
+                .l()?;
+
+            // WindowInsets insets = decor.getRootWindowInsets();
+            let raw_insets = env
+                .call_method(
+                    &decor,
+                    "getRootWindowInsets",
+                    "()Landroid/view/WindowInsets;",
+                    &[],
+                )?
+                .l()?;
+            if raw_insets.is_null() {
+                return Ok(SafeAreaInsets::default());
+            }
+
+            // int types = WindowInsets.Type.systemBars();
+            // (Static method on the WindowInsets$Type inner class.
+            // Available since API 30 / Android 11.)
+            let type_class = env.find_class("android/view/WindowInsets$Type")?;
+            let bars_type = env
+                .call_static_method(&type_class, "systemBars", "()I", &[])?
+                .i()?;
+
+            // Insets bars = insets.getInsets(types);
+            let bars = env
+                .call_method(
+                    &raw_insets,
+                    "getInsets",
+                    "(I)Landroid/graphics/Insets;",
+                    &[bars_type.into()],
+                )?
+                .l()?;
+
+            // `Insets` exposes `top`, `bottom`, `left`, `right` as public
+            // `int` fields (pixel values, not dp).
+            let top = env.get_field(&bars, "top", "I")?.i()? as f32;
+            let bottom = env.get_field(&bars, "bottom", "I")?.i()? as f32;
+            let left = env.get_field(&bars, "left", "I")?.i()? as f32;
+            let right = env.get_field(&bars, "right", "I")?.i()? as f32;
+
+            Ok(SafeAreaInsets {
+                top,
+                bottom,
+                left,
+                right,
+            })
+        })()
+        .map_err(|e| format!("safe-area JNI: {e}"))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn default_is_zero_and_not_populated() {
+        let i = SafeAreaInsets::default();
+        assert_eq!(i.top, 0.0);
+        assert_eq!(i.bottom, 0.0);
+        assert!(!i.is_populated());
+    }
+
+    #[test]
+    fn is_populated_returns_true_for_any_nonzero_edge() {
+        assert!(SafeAreaInsets {
+            top: 24.0,
+            ..Default::default()
+        }
+        .is_populated());
+        assert!(SafeAreaInsets {
+            bottom: 16.0,
+            ..Default::default()
+        }
+        .is_populated());
+        assert!(SafeAreaInsets {
+            left: 8.0,
+            ..Default::default()
+        }
+        .is_populated());
+        assert!(SafeAreaInsets {
+            right: 8.0,
+            ..Default::default()
+        }
+        .is_populated());
+    }
+}

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,
-    STREAK_MILESTONES, TEXT_PRIMARY, TEXT_SECONDARY, TYPE_BODY, TYPE_BODY_LG, TYPE_CAPTION,
-    TYPE_HEADLINE, VAL_SPACE_2, VAL_SPACE_3, VAL_SPACE_4, Z_MODAL_PANEL,
+    ACCENT_PRIMARY, BG_ELEVATED_HI, BORDER_SUBTLE, HighContrastBorder, RADIUS_SM, STATE_INFO,
+    STATE_WARNING, STREAK_MILESTONES, TEXT_PRIMARY, TEXT_SECONDARY, TYPE_BODY, TYPE_BODY_LG,
+    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!(
-            "Share link: {url}"
-        )));
+        match crate::android_clipboard::set_text(&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 ---
-            // Surfaces the most recent winning game so the player can spot
-            // whether their last victory has been recorded. The Watch
-            // Replay action below is what the player clicks to revisit it.
-            //
-            // When the displayed replay carries a `share_url` (uploaded
-            // to a sync server, persisted by v0.19.0's share-link
-            // contract), append a "Shareable" badge so the player can
-            // tell at a glance whether the Copy share link button below
-            // will produce a URL — without it the button surfaces a
-            // toast explaining why nothing was copied, which is more
-            // friction than necessary when a quick visual cue suffices.
-            let replay_caption = match latest_replay {
-                Some(r) => {
-                    let base = format!("Latest win: {}", format_replay_caption(r));
-                    if r.share_url.is_some() {
-                        format!("{base} \u{2022} Shareable")
-                    } else {
-                        base
-                    }
-                }
-                None => "No replay recorded yet \u{2014} win a game first.".to_string(),
-            };
+            // --- Replay selector ---
+            // Prev / Next chips step through the full replay history;
+            // `repaint_replay_selector_caption` and
+            // `repaint_replay_selector_detail` keep both text nodes
+            // live as the selection changes. Using `ModalButton` on
+            // the chips plugs them into the existing modal-button
+            // hover/press paint loop at no extra cost.
+            body.spawn(Node {
+                flex_direction: FlexDirection::Row,
+                align_items: AlignItems::Center,
+                column_gap: VAL_SPACE_3,
+                ..default()
+            })
+            .with_children(|row| {
+                // ← Prev chip
+                row.spawn((
+                    ReplayPrevButton,
+                    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{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/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(),
     }
 }