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>

.gitignore

@@ -10,3 +10,8 @@ data/
 
 # IDE project files
 .idea/
+
+# Android signing keystores — never commit
+*.jks
+*.jks.bak
+*.keystore

Cargo.lock

@@ -6986,6 +6986,7 @@ version = "0.1.0"
 dependencies = [
  "async-trait",
  "axum",
+ "bevy",
  "chrono",
  "dirs",
  "jni 0.21.1",

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

@@ -30,7 +30,8 @@ use solitaire_engine::{
     CursorPlugin, DailyChallengePlugin, DiagnosticsHudPlugin, DifficultyPlugin, FeedbackAnimPlugin,
     FontPlugin, GamePlugin, HelpPlugin, HomePlugin, HudPlugin, InputPlugin, LeaderboardPlugin,
     OnboardingPlugin, PausePlugin, PlayBySeedPlugin, ProfilePlugin, ProgressPlugin,
-    RadialMenuPlugin, ReplayOverlayPlugin, ReplayPlaybackPlugin, SelectionPlugin, SettingsPlugin,
+    RadialMenuPlugin, ReplayOverlayPlugin, ReplayPlaybackPlugin, SafeAreaInsetsPlugin,
+    SelectionPlugin, SettingsPlugin,
     SplashPlugin, StatsPlugin, SyncPlugin, TablePlugin, ThemePlugin, ThemeRegistryPlugin,
     TimeAttackPlugin, UiFocusPlugin, UiModalPlugin, UiTooltipPlugin, WeeklyGoalsPlugin,
     WinSummaryPlugin,
@@ -131,11 +132,20 @@ pub fn run() {
                     ..default()
                 })
                 // The `assets/` directory lives at the workspace root, but
-                // Bevy resolves `AssetPlugin::file_path` relative to the
+                // on desktop Bevy resolves `AssetPlugin::file_path` relative
-                // binary package's `CARGO_MANIFEST_DIR` (`solitaire_app/`).
+                // to the binary package's `CARGO_MANIFEST_DIR`
-                // Point one level up so `cargo run -p solitaire_app` finds
+                // (`solitaire_app/`), so `cargo run -p solitaire_app` would
-                // card faces, backs, backgrounds, and the UI font.
+                // 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()
                 }),
@@ -173,6 +183,7 @@ pub fn run() {
         .add_plugins(PlayBySeedPlugin)
         .add_plugins(DifficultyPlugin)
         .add_plugins(TimeAttackPlugin)
+        .add_plugins(SafeAreaInsetsPlugin)
         .add_plugins(HudPlugin)
         .add_plugins(HelpPlugin)
         .add_plugins(HomePlugin::default())

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)),

solitaire_engine/src/layout.rs

@@ -21,9 +21,25 @@ pub enum LayoutSystem {
     UpdateOnResize,
 }
 
-/// Minimum supported window dimensions. Layout is still computed below this
+/// Minimum window dimensions used as a layout floor.
-/// size but cards will be small.
+///
-pub const MIN_WINDOW: Vec2 = Vec2::new(800.0, 600.0);
+/// `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

@@ -35,6 +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;
@@ -138,6 +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/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());
+    }
+}