diff --git a/solitaire_app/src/main.rs b/solitaire_app/src/main.rs
index 239b62c..a71d87c 100644
--- a/solitaire_app/src/main.rs
+++ b/solitaire_app/src/main.rs
@@ -1,5 +1,5 @@
 use bevy::prelude::*;
-use solitaire_engine::{CardPlugin, GamePlugin, InputPlugin, TablePlugin};
+use solitaire_engine::{AnimationPlugin, CardPlugin, GamePlugin, InputPlugin, TablePlugin};
 
 fn main() {
     App::new()
@@ -17,5 +17,6 @@ fn main() {
         .add_plugins(TablePlugin)
         .add_plugins(CardPlugin)
         .add_plugins(InputPlugin)
+        .add_plugins(AnimationPlugin)
         .run();
 }
diff --git a/solitaire_engine/src/animation_plugin.rs b/solitaire_engine/src/animation_plugin.rs
new file mode 100644
index 0000000..a7c699b
--- /dev/null
+++ b/solitaire_engine/src/animation_plugin.rs
@@ -0,0 +1,293 @@
+//! Smooth animations: card slide (linear lerp), win cascade, achievement toast.
+//!
+//! `CardAnim` is the only animation component used by other plugins — import
+//! it directly when adding animations outside this file.
+
+use bevy::prelude::*;
+
+use crate::card_plugin::CardEntity;
+use crate::events::{AchievementUnlockedEvent, GameWonEvent};
+use crate::game_plugin::GameMutation;
+use crate::layout::LayoutResource;
+
+/// Duration of a card slide (move) animation in seconds.
+pub const SLIDE_SECS: f32 = 0.15;
+
+const WIN_TOAST_SECS: f32 = 4.0;
+const ACHIEVEMENT_TOAST_SECS: f32 = 3.0;
+const CASCADE_STAGGER: f32 = 0.05;
+const CASCADE_DURATION: f32 = 0.5;
+
+/// Linear-lerp slide animation.
+///
+/// After `delay` seconds the card moves from `start` to `target` over
+/// `duration` seconds. The component removes itself when the slide completes.
+#[derive(Component, Debug, Clone)]
+pub struct CardAnim {
+    pub start: Vec3,
+    pub target: Vec3,
+    pub elapsed: f32,
+    pub duration: f32,
+    /// Additional wait before the slide begins.
+    pub delay: f32,
+}
+
+/// Marker on a toast overlay UI node.
+#[derive(Component, Debug)]
+pub struct ToastOverlay;
+
+/// Auto-dismiss countdown (seconds remaining). Attached to toast entities.
+#[derive(Component, Debug)]
+pub struct ToastTimer(pub f32);
+
+pub struct AnimationPlugin;
+
+impl Plugin for AnimationPlugin {
+    fn build(&self, app: &mut App) {
+        // Register the events this plugin consumes so tests that don't include
+        // GamePlugin can still run AnimationPlugin in isolation. Double-registration
+        // is idempotent in Bevy.
+        app.add_event::<GameWonEvent>()
+            .add_event::<AchievementUnlockedEvent>()
+            .add_systems(
+                Update,
+                (
+                    advance_card_anims,
+                    handle_win_cascade,
+                    handle_achievement_toast,
+                    tick_toasts,
+                )
+                    .after(GameMutation),
+            );
+    }
+}
+
+fn advance_card_anims(
+    mut commands: Commands,
+    time: Res<Time>,
+    mut anims: Query<(Entity, &mut Transform, &mut CardAnim)>,
+) {
+    let dt = time.delta_secs();
+    for (entity, mut transform, mut anim) in &mut anims {
+        if anim.delay > 0.0 {
+            anim.delay = (anim.delay - dt).max(0.0);
+            continue;
+        }
+        anim.elapsed += dt;
+        let t = (anim.elapsed / anim.duration).min(1.0);
+        transform.translation = anim.start.lerp(anim.target, t);
+        if t >= 1.0 {
+            commands.entity(entity).remove::<CardAnim>();
+        }
+    }
+}
+
+fn handle_win_cascade(
+    mut commands: Commands,
+    mut events: EventReader<GameWonEvent>,
+    cards: Query<(Entity, &Transform), With<CardEntity>>,
+    layout: Option<Res<LayoutResource>>,
+) {
+    if events.read().next().is_none() {
+        return;
+    }
+
+    let margin = layout.as_ref().map_or(800.0, |l| l.0.card_size.x * 8.0);
+
+    // Eight off-screen destinations spread around the window edges.
+    let targets: [Vec3; 8] = [
+        Vec3::new(margin, margin, 300.0),
+        Vec3::new(-margin, margin, 300.0),
+        Vec3::new(margin, -margin, 300.0),
+        Vec3::new(-margin, -margin, 300.0),
+        Vec3::new(0.0, margin, 300.0),
+        Vec3::new(0.0, -margin, 300.0),
+        Vec3::new(margin, 0.0, 300.0),
+        Vec3::new(-margin, 0.0, 300.0),
+    ];
+
+    spawn_toast(&mut commands, "You Win!".to_string(), WIN_TOAST_SECS);
+
+    for (i, (entity, transform)) in cards.iter().enumerate() {
+        commands.entity(entity).insert(CardAnim {
+            start: transform.translation,
+            target: targets[i % 8],
+            elapsed: 0.0,
+            duration: CASCADE_DURATION,
+            delay: i as f32 * CASCADE_STAGGER,
+        });
+    }
+}
+
+fn handle_achievement_toast(
+    mut commands: Commands,
+    mut events: EventReader<AchievementUnlockedEvent>,
+) {
+    for ev in events.read() {
+        spawn_toast(
+            &mut commands,
+            format!("Achievement: {}", ev.0),
+            ACHIEVEMENT_TOAST_SECS,
+        );
+    }
+}
+
+fn tick_toasts(
+    mut commands: Commands,
+    time: Res<Time>,
+    mut toasts: Query<(Entity, &mut ToastTimer)>,
+) {
+    let dt = time.delta_secs();
+    for (entity, mut timer) in &mut toasts {
+        timer.0 -= dt;
+        if timer.0 <= 0.0 {
+            commands.entity(entity).despawn_recursive();
+        }
+    }
+}
+
+fn spawn_toast(commands: &mut Commands, message: String, duration_secs: f32) {
+    commands
+        .spawn((
+            ToastOverlay,
+            ToastTimer(duration_secs),
+            Node {
+                position_type: PositionType::Absolute,
+                left: Val::Percent(25.0),
+                top: Val::Percent(42.0),
+                width: Val::Percent(50.0),
+                padding: UiRect::axes(Val::Px(16.0), Val::Px(10.0)),
+                justify_content: JustifyContent::Center,
+                align_items: AlignItems::Center,
+                ..default()
+            },
+            BackgroundColor(Color::srgba(0.0, 0.0, 0.0, 0.72)),
+        ))
+        .with_children(|b| {
+            b.spawn((
+                Text::new(message),
+                TextFont {
+                    font_size: 32.0,
+                    ..default()
+                },
+                TextColor(Color::srgb(1.0, 0.87, 0.0)),
+            ));
+        });
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::card_plugin::CardPlugin;
+    use crate::game_plugin::GamePlugin;
+    use crate::table_plugin::TablePlugin;
+
+    fn app_with_anim() -> App {
+        let mut app = App::new();
+        app.add_plugins(MinimalPlugins)
+            .add_plugins(GamePlugin)
+            .add_plugins(TablePlugin)
+            .add_plugins(CardPlugin)
+            .add_plugins(AnimationPlugin);
+        app.update(); // PostStartup: spawns cards
+        app
+    }
+
+    #[test]
+    fn card_anim_at_half_elapsed_reaches_midpoint() {
+        let mut app = App::new();
+        app.add_plugins(MinimalPlugins).add_plugins(AnimationPlugin);
+
+        let start = Vec3::ZERO;
+        let target = Vec3::new(100.0, 0.0, 0.0);
+        // elapsed = 0.5, duration = 1.0 → t = 0.5 even when dt=0
+        let entity = app
+            .world_mut()
+            .spawn((
+                Transform::from_translation(start),
+                CardAnim { start, target, elapsed: 0.5, duration: 1.0, delay: 0.0 },
+            ))
+            .id();
+
+        app.update();
+
+        let pos = app.world().entity(entity).get::<Transform>().unwrap().translation;
+        assert!((pos.x - 50.0).abs() < 1e-3, "expected midpoint x=50, got {}", pos.x);
+        assert!(
+            app.world().entity(entity).get::<CardAnim>().is_some(),
+            "animation not yet complete"
+        );
+    }
+
+    #[test]
+    fn card_anim_removed_and_at_target_when_elapsed_equals_duration() {
+        let mut app = App::new();
+        app.add_plugins(MinimalPlugins).add_plugins(AnimationPlugin);
+
+        let target = Vec3::new(10.0, 0.0, 0.0);
+        let entity = app
+            .world_mut()
+            .spawn((
+                Transform::from_translation(Vec3::ZERO),
+                CardAnim { start: Vec3::ZERO, target, elapsed: 1.0, duration: 1.0, delay: 0.0 },
+            ))
+            .id();
+
+        app.update();
+
+        assert!(
+            app.world().entity(entity).get::<CardAnim>().is_none(),
+            "CardAnim should be removed when done"
+        );
+        let pos = app.world().entity(entity).get::<Transform>().unwrap().translation;
+        assert!((pos.x - 10.0).abs() < 1e-3);
+    }
+
+    #[test]
+    fn card_anim_does_not_move_during_delay() {
+        let mut app = App::new();
+        app.add_plugins(MinimalPlugins).add_plugins(AnimationPlugin);
+
+        let entity = app
+            .world_mut()
+            .spawn((
+                Transform::from_translation(Vec3::ZERO),
+                CardAnim {
+                    start: Vec3::ZERO,
+                    target: Vec3::new(100.0, 0.0, 0.0),
+                    elapsed: 0.0,
+                    duration: 0.15,
+                    delay: 100.0, // large delay — card must not move
+                },
+            ))
+            .id();
+
+        app.update();
+
+        let pos = app.world().entity(entity).get::<Transform>().unwrap().translation;
+        assert!(pos.x.abs() < 1e-3, "card must not move during delay period");
+    }
+
+    #[test]
+    fn win_cascade_adds_anim_to_all_52_cards() {
+        let mut app = app_with_anim();
+
+        let before = app
+            .world_mut()
+            .query::<&CardAnim>()
+            .iter(app.world())
+            .count();
+        assert_eq!(before, 0, "no animations before win");
+
+        app.world_mut()
+            .send_event(GameWonEvent { score: 500, time_seconds: 60 });
+        app.update();
+
+        let after = app
+            .world_mut()
+            .query::<&CardAnim>()
+            .iter(app.world())
+            .count();
+        assert_eq!(after, 52, "all 52 cards should have cascade animations");
+    }
+}
diff --git a/solitaire_engine/src/card_plugin.rs b/solitaire_engine/src/card_plugin.rs
index bfe3a70..c5dc90c 100644
--- a/solitaire_engine/src/card_plugin.rs
+++ b/solitaire_engine/src/card_plugin.rs
@@ -19,6 +19,7 @@ use solitaire_core::card::{Card, Rank, Suit};
 use solitaire_core::game_state::GameState;
 use solitaire_core::pile::PileType;
 
+use crate::animation_plugin::{CardAnim, SLIDE_SECS};
 use crate::events::StateChangedEvent;
 use crate::game_plugin::GameMutation;
 use crate::layout::{Layout, LayoutResource};
@@ -68,7 +69,7 @@ fn sync_cards_startup(
     commands: Commands,
     game: Res<GameStateResource>,
     layout: Option<Res<LayoutResource>>,
-    entities: Query<(Entity, &CardEntity)>,
+    entities: Query<(Entity, &CardEntity, &Transform)>,
 ) {
     if let Some(layout) = layout {
         sync_cards(commands, &game.0, &layout.0, &entities);
@@ -80,7 +81,7 @@ fn sync_cards_on_change(
     commands: Commands,
     game: Res<GameStateResource>,
     layout: Option<Res<LayoutResource>>,
-    entities: Query<(Entity, &CardEntity)>,
+    entities: Query<(Entity, &CardEntity, &Transform)>,
 ) {
     if events.read().next().is_none() {
         return;
@@ -94,20 +95,20 @@ fn sync_cards(
     mut commands: Commands,
     game: &GameState,
     layout: &Layout,
-    entities: &Query<(Entity, &CardEntity)>,
+    entities: &Query<(Entity, &CardEntity, &Transform)>,
 ) {
     let positions = card_positions(game, layout);
 
-    // Map card_id -> Entity for in-place updates.
-    let mut existing: HashMap<u32, Entity> = HashMap::new();
-    for (entity, marker) in entities.iter() {
-        existing.insert(marker.card_id, entity);
+    // Map card_id -> (Entity, current_translation) for in-place updates.
+    let mut existing: HashMap<u32, (Entity, Vec3)> = HashMap::new();
+    for (entity, marker, transform) in entities.iter() {
+        existing.insert(marker.card_id, (entity, transform.translation));
     }
 
     let live_ids: HashSet<u32> = positions.iter().map(|(c, _, _)| c.id).collect();
 
     // Despawn any entity whose card is no longer tracked.
-    for (card_id, entity) in &existing {
+    for (card_id, (entity, _)) in &existing {
         if !live_ids.contains(card_id) {
             commands.entity(*entity).despawn_recursive();
         }
@@ -116,7 +117,9 @@ fn sync_cards(
     // For each card in the current state: spawn or update its entity.
     for (card, position, z) in positions {
         match existing.get(&card.id) {
-            Some(&entity) => update_card_entity(&mut commands, entity, &card, position, z, layout),
+            Some(&(entity, cur)) => {
+                update_card_entity(&mut commands, entity, &card, position, z, layout, cur)
+            }
             None => spawn_card_entity(&mut commands, &card, position, z, layout),
         }
     }
@@ -206,6 +209,7 @@ fn update_card_entity(
     pos: Vec2,
     z: f32,
     layout: &Layout,
+    cur: Vec3,
 ) {
     let body_colour = if card.face_up {
         CARD_FACE_COLOUR
@@ -213,14 +217,34 @@ fn update_card_entity(
         CARD_BACK_COLOUR
     };
 
-    commands.entity(entity).insert((
-        Sprite {
-            color: body_colour,
-            custom_size: Some(layout.card_size),
-            ..default()
-        },
-        Transform::from_xyz(pos.x, pos.y, z),
-    ));
+    let target = Vec3::new(pos.x, pos.y, z);
+
+    // Always refresh the visual appearance.
+    commands.entity(entity).insert(Sprite {
+        color: body_colour,
+        custom_size: Some(layout.card_size),
+        ..default()
+    });
+
+    // Slide to the new position when it differs meaningfully; snap otherwise.
+    if (cur.truncate() - target.truncate()).length() > 1.0 {
+        let start = Vec3::new(cur.x, cur.y, z); // update Z immediately
+        commands
+            .entity(entity)
+            .insert(Transform::from_translation(start))
+            .insert(CardAnim {
+                start,
+                target,
+                elapsed: 0.0,
+                duration: SLIDE_SECS,
+                delay: 0.0,
+            });
+    } else {
+        commands
+            .entity(entity)
+            .remove::<CardAnim>()
+            .insert(Transform::from_xyz(pos.x, pos.y, z));
+    }
 
     // Despawn the old label child and respawn a fresh one, so rank/suit/
     // colour/visibility all stay in sync with the card's current state.
diff --git a/solitaire_engine/src/events.rs b/solitaire_engine/src/events.rs
index dacc35e..3226100 100644
--- a/solitaire_engine/src/events.rs
+++ b/solitaire_engine/src/events.rs
@@ -41,3 +41,9 @@ pub struct GameWonEvent {
 /// Fired when a card's face-up state changes during gameplay.
 #[derive(Event, Debug, Clone, Copy)]
 pub struct CardFlippedEvent(pub u32);
+
+/// Achievement unlocked notification — name of the achievement.
+///
+/// Uses `String` as a placeholder; replaced with `AchievementRecord` in Phase 5.
+#[derive(Event, Debug, Clone)]
+pub struct AchievementUnlockedEvent(pub String);
diff --git a/solitaire_engine/src/game_plugin.rs b/solitaire_engine/src/game_plugin.rs
index 11577f7..c9c9d1c 100644
--- a/solitaire_engine/src/game_plugin.rs
+++ b/solitaire_engine/src/game_plugin.rs
@@ -37,6 +37,7 @@ impl Plugin for GamePlugin {
             .add_event::<StateChangedEvent>()
             .add_event::<GameWonEvent>()
             .add_event::<crate::events::CardFlippedEvent>()
+            .add_event::<crate::events::AchievementUnlockedEvent>()
             .add_systems(
                 Update,
                 (
diff --git a/solitaire_engine/src/input_plugin.rs b/solitaire_engine/src/input_plugin.rs
index ed7b482..9e8e3c9 100644
--- a/solitaire_engine/src/input_plugin.rs
+++ b/solitaire_engine/src/input_plugin.rs
@@ -511,8 +511,12 @@ mod tests {
         });
 
         let layout = compute_layout(Vec2::new(1280.0, 800.0));
-        // Click the middle card (Queen at stack index 1).
-        let pos = card_position(&game, &layout, PileType::Tableau(0), 1);
+        // The Queen's geometric center (index 1) is inside the Jack's bounding box
+        // (Jack fans 0.5h below base; its box spans [base-h, base]).  To hit the
+        // Queen we click in her visible strip: the 0.25h band above the Jack's top
+        // edge (base.y to base.y+0.25h).  Midpoint = queen_center + 0.375*card_h.
+        let queen_center = card_position(&game, &layout, PileType::Tableau(0), 1);
+        let pos = queen_center + Vec2::new(0.0, layout.card_size.y * 0.375);
         let (pile, start, ids) = find_draggable_at(pos, &game, &layout).expect("hit");
         assert_eq!(pile, PileType::Tableau(0));
         assert_eq!(start, 1);
diff --git a/solitaire_engine/src/lib.rs b/solitaire_engine/src/lib.rs
index 453b39f..92a0c46 100644
--- a/solitaire_engine/src/lib.rs
+++ b/solitaire_engine/src/lib.rs
@@ -1,9 +1,6 @@
 //! Bevy integration layer for Solitaire Quest.
-//!
-//! Currently exposes `GamePlugin` plus the resources and events it owns.
-//! Additional plugins (`TablePlugin`, `CardPlugin`, `InputPlugin`,
-//! `AnimationPlugin`, etc.) land in later sub-phases of Phase 3.
 
+pub mod animation_plugin;
 pub mod card_plugin;
 pub mod events;
 pub mod game_plugin;
@@ -12,10 +9,11 @@ pub mod layout;
 pub mod resources;
 pub mod table_plugin;
 
+pub use animation_plugin::{AnimationPlugin, CardAnim};
 pub use card_plugin::{CardEntity, CardLabel, CardPlugin};
 pub use events::{
-    CardFlippedEvent, DrawRequestEvent, GameWonEvent, MoveRequestEvent, NewGameRequestEvent,
-    StateChangedEvent, UndoRequestEvent,
+    AchievementUnlockedEvent, CardFlippedEvent, DrawRequestEvent, GameWonEvent, MoveRequestEvent,
+    NewGameRequestEvent, StateChangedEvent, UndoRequestEvent,
 };
 pub use game_plugin::{GameMutation, GamePlugin};
 pub use input_plugin::InputPlugin;