solitaire_engine/src/animation_plugin.rs

@@ -252,10 +252,17 @@ fn advance_card_anims(
     time: Res<Time>,
     paused: Option<Res<PausedResource>>,
     mut anims: Query<(Entity, &mut Transform, &mut CardAnim)>,
+    mut redraw: MessageWriter<RequestRedraw>,
 ) {
     if paused.is_some_and(|p| p.0) {
         return;
     }
+    // Keep the winit loop awake at full frame rate while slides (including
+    // staggered deals still in their delay phase) are in flight — required
+    // for Android's reactive_low_power focused_mode.
+    if !anims.is_empty() {
+        redraw.write(RequestRedraw);
+    }
     let dt = time.delta_secs();
     for (entity, mut transform, mut anim) in &mut anims {
         if anim.delay > 0.0 {
@@ -558,10 +565,17 @@ fn drive_toast_display(
     paused: Option<Res<PausedResource>>,
     mut queue: ResMut<ToastQueue>,
     mut active: ResMut<ActiveToast>,
+    mut redraw: MessageWriter<RequestRedraw>,
 ) {
     if paused.is_some_and(|p| p.0) {
         return;
     }
+    // Keep the loop ticking while a toast is displayed or queued so the
+    // countdown advances and the despawn frame isn't held hostage by
+    // Android's reactive_low_power wake ceiling.
+    if active.entity.is_some() || !queue.0.is_empty() {
+        redraw.write(RequestRedraw);
+    }
     let dt = time.delta_secs();
 
     // Tick down the active toast timer.

solitaire_engine/src/auto_complete_plugin.rs

@@ -147,6 +147,7 @@ fn drive_auto_complete(
     time: Res<Time>,
     paused: Option<Res<PausedResource>>,
     mut moves: MessageWriter<MoveRequestEvent>,
+    mut redraw: MessageWriter<RequestRedraw>,
 ) {
     if !state.active {
         return;
@@ -154,6 +155,10 @@ fn drive_auto_complete(
     if paused.is_some_and(|p| p.0) {
         return;
     }
+    // Keepalive: the step-interval cooldown only advances on frames that
+    // actually run, so keep the winit loop awake for the whole burst under
+    // Android's reactive_low_power focused_mode.
+    redraw.write(RequestRedraw);
 
     state.cooldown -= time.delta_secs();
     if state.cooldown > 0.0 {

solitaire_engine/src/card_animation/animation.rs

@@ -33,6 +33,7 @@
 use std::f32::consts::PI;
 
 use bevy::prelude::*;
+use bevy::window::RequestRedraw;
 
 use super::curves::{MotionCurve, sample_curve};
 use super::timing::compute_duration;
@@ -232,10 +233,18 @@ pub(crate) fn advance_card_animations(
     time: Res<Time>,
     paused: Option<Res<PausedResource>>,
     mut q: Query<(Entity, &mut Transform, &mut CardAnimation)>,
+    mut redraw: MessageWriter<RequestRedraw>,
 ) {
     if paused.is_some_and(|p| p.0) {
         return;
     }
+    // Keep the winit event loop awake while any animation (including one
+    // still in its delay phase) needs per-frame ticks. Without this,
+    // Android's reactive_low_power focused_mode only wakes at its 100 ms
+    // ceiling and card slides render at ~10 fps.
+    if !q.is_empty() {
+        redraw.write(RequestRedraw);
+    }
     let dt = time.delta_secs();
 
     for (entity, mut transform, mut anim) in &mut q {

solitaire_engine/src/card_animation/mod.rs

@@ -307,6 +307,49 @@ mod tests {
         );
     }
 
+    /// Regression test for the v0.40.0 Android animation-lag bug: commit
+    /// 38e4c03 switched Android to `reactive_low_power` focused_mode on the
+    /// premise that animation systems write `RequestRedraw` while active,
+    /// but the writers were never added — card slides rendered at the 100 ms
+    /// wake ceiling (~10 fps). Active animations MUST emit `RequestRedraw`
+    /// every frame; an idle board must not.
+    #[test]
+    fn active_card_animation_requests_redraw() {
+        let mut app = App::new();
+        app.add_plugins(MinimalPlugins)
+            .add_plugins(CardAnimationPlugin);
+
+        // Idle board: no redraw requests.
+        app.update();
+        assert!(
+            app.world().resource::<Messages<RequestRedraw>>().is_empty(),
+            "no RequestRedraw expected while no animation is active"
+        );
+
+        app.world_mut().spawn((
+            Transform::from_translation(Vec3::ZERO),
+            CardAnimation {
+                start: Vec2::ZERO,
+                end: Vec2::new(100.0, 0.0),
+                elapsed: 0.0,
+                duration: 1.0,
+                curve: MotionCurve::Responsive,
+                delay: 0.0,
+                start_z: 0.0,
+                end_z: 0.0,
+                z_lift: 0.0,
+                scale_start: 1.0,
+                scale_end: 1.0,
+            },
+        ));
+        app.update();
+        assert!(
+            !app.world().resource::<Messages<RequestRedraw>>().is_empty(),
+            "an active CardAnimation must write RequestRedraw each frame to \
+             sustain the reactive render loop"
+        );
+    }
+
     #[test]
     fn card_animation_instant_snaps_on_zero_duration() {
         let mut app = App::new();

solitaire_engine/src/feedback_anim_plugin.rs

@@ -276,10 +276,16 @@ fn tick_shake_anim(
     time: Res<Time>,
     paused: Option<Res<PausedResource>>,
     mut anims: Query<(Entity, &mut Transform, &mut ShakeAnim)>,
+    mut redraw: MessageWriter<RequestRedraw>,
 ) {
     if paused.is_some_and(|p| p.0) {
         return;
     }
+    // Sustain full-rate frames for the shake under Android's
+    // reactive_low_power focused_mode.
+    if !anims.is_empty() {
+        redraw.write(RequestRedraw);
+    }
     let dt = time.delta_secs();
     for (entity, mut transform, mut anim) in &mut anims {
         anim.elapsed += dt;
@@ -356,10 +362,16 @@ fn tick_settle_anim(
     time: Res<Time>,
     paused: Option<Res<PausedResource>>,
     mut anims: Query<(Entity, &mut Transform, &mut SettleAnim)>,
+    mut redraw: MessageWriter<RequestRedraw>,
 ) {
     if paused.is_some_and(|p| p.0) {
         return;
     }
+    // Sustain full-rate frames for the settle bounce under Android's
+    // reactive_low_power focused_mode.
+    if !anims.is_empty() {
+        redraw.write(RequestRedraw);
+    }
     let dt = time.delta_secs();
     for (entity, mut transform, mut anim) in &mut anims {
         anim.elapsed += dt;
@@ -581,10 +593,16 @@ fn tick_foundation_flourish(
         (Entity, &mut Sprite, &mut FoundationMarkerFlourish),
         Without<FoundationFlourish>,
     >,
+    mut redraw: MessageWriter<RequestRedraw>,
 ) {
     if paused.is_some_and(|p| p.0) {
         return;
     }
+    // Sustain full-rate frames for the flourish under Android's
+    // reactive_low_power focused_mode.
+    if !card_anims.is_empty() || !marker_anims.is_empty() {
+        redraw.write(RequestRedraw);
+    }
     let dt = time.delta_secs();
 
     // Advance the King's scale pulse.