diff --git a/solitaire_core/src/card.rs b/solitaire_core/src/card.rs
deleted file mode 100644
index fe6e753..0000000
--- a/solitaire_core/src/card.rs
+++ /dev/null
@@ -1,23 +0,0 @@
-pub use card_game::{Card, Deck, Rank, Suit};
-
-/// Maps a [`Card`] to a stable `0..=51` numeric identity, independent of the
-/// upstream `card_game::Card` bit-packing.
-///
-/// Encoding: `suit_index * 13 + (rank as u32 - 1)`, where `suit_index` is
-/// Clubs=0, Diamonds=1, Hearts=2, Spades=3 and `rank` is 1 (Ace) ..= 13 (King).
-/// The deck id is intentionally ignored so the id depends only on the visible
-/// face.
-///
-/// This is the single source of truth shared by `CardEntity` numeric tracking,
-/// deterministic per-card animation jitter, and the WASM replay layer — those
-/// must agree byte-for-byte so replay snapshots are identical across the
-/// desktop and browser builds.
-pub fn card_to_id(card: &Card) -> u32 {
-    let suit_index: u32 = match card.suit() {
-        Suit::Clubs => 0,
-        Suit::Diamonds => 1,
-        Suit::Hearts => 2,
-        Suit::Spades => 3,
-    };
-    suit_index * 13 + (card.rank() as u32 - 1)
-}
diff --git a/solitaire_core/src/lib.rs b/solitaire_core/src/lib.rs
index 702f431..8655f83 100644
--- a/solitaire_core/src/lib.rs
+++ b/solitaire_core/src/lib.rs
@@ -1,5 +1,4 @@
 pub mod achievement;
-pub mod card;
 pub mod error;
 pub mod game_state;
 pub mod klondike_adapter;
@@ -12,7 +11,7 @@ pub mod klondike_adapter;
 // re-exported — they are only used internally (in `klondike_adapter.rs` and
 // when decoding instructions to piles in `instruction_to_piles`) and do not
 // appear in any public method signature.
-pub use card_game::{Card, Session, SolveError};
+pub use card_game::{Card, Deck, Rank, Session, SolveError, Suit};
 pub use klondike::{DrawStockConfig, Foundation, Klondike, KlondikeInstruction, KlondikePile, Tableau};
 
 // Solvability check API (delegates to `card_game::Session::solve`); replaces the
diff --git a/solitaire_engine/src/assets/card_face_svg.rs b/solitaire_engine/src/assets/card_face_svg.rs
index c45a955..5fd7223 100644
--- a/solitaire_engine/src/assets/card_face_svg.rs
+++ b/solitaire_engine/src/assets/card_face_svg.rs
@@ -22,7 +22,7 @@
 //! red/black colour split.
 
 use bevy::math::UVec2;
-use solitaire_core::card::{Rank, Suit};
+use solitaire_core::{Rank, Suit};
 
 /// Target rasterisation size in pixels (2:3 aspect, half the default
 /// `SvgLoaderSettings` resolution).
diff --git a/solitaire_engine/src/auto_complete_plugin.rs b/solitaire_engine/src/auto_complete_plugin.rs
index 55fae1b..68df902 100644
--- a/solitaire_engine/src/auto_complete_plugin.rs
+++ b/solitaire_engine/src/auto_complete_plugin.rs
@@ -168,7 +168,7 @@ mod tests {
     use crate::game_plugin::GamePlugin;
     use crate::table_plugin::TablePlugin;
     use solitaire_core::{Foundation, KlondikePile, Tableau};
-    use solitaire_core::card::{Deck, Rank, Suit};
+    use solitaire_core::{Deck, Rank, Suit};
     use solitaire_core::{DrawStockConfig, game_state::GameState};
 
     fn headless_app() -> App {
@@ -207,7 +207,7 @@ mod tests {
         }
         g.set_test_tableau_cards(
             Tableau::Tableau1,
-            vec![solitaire_core::card::Card::new(Deck::Deck1, Suit::Clubs, Rank::Ace)],
+            vec![solitaire_core::Card::new(Deck::Deck1, Suit::Clubs, Rank::Ace)],
         );
         g.set_test_auto_completable(true);
         let expected = (
diff --git a/solitaire_engine/src/card_animation/interaction.rs b/solitaire_engine/src/card_animation/interaction.rs
index b9bc4a8..7e18936 100644
--- a/solitaire_engine/src/card_animation/interaction.rs
+++ b/solitaire_engine/src/card_animation/interaction.rs
@@ -33,7 +33,7 @@ use std::collections::VecDeque;
 
 use bevy::prelude::*;
 use bevy::window::PrimaryWindow;
-use solitaire_core::card::Card;
+use solitaire_core::Card;
 
 use super::animation::CardAnimation;
 use super::tuning::AnimationTuning;
diff --git a/solitaire_engine/src/card_plugin.rs b/solitaire_engine/src/card_plugin.rs
index b5caf43..ab89cfd 100644
--- a/solitaire_engine/src/card_plugin.rs
+++ b/solitaire_engine/src/card_plugin.rs
@@ -17,7 +17,7 @@ use bevy::prelude::*;
 use bevy::sprite::Anchor;
 use bevy::window::WindowResized;
 use solitaire_core::{Foundation, KlondikePile, Tableau};
-use solitaire_core::card::{Card, Rank, Suit};
+use solitaire_core::{Card, Rank, Suit};
 use solitaire_core::{DrawStockConfig, game_state::GameState};
 
 use crate::animation_plugin::{CARD_ANIM_Z_LIFT, CardAnim, EffectiveSlideDuration};
@@ -2472,7 +2472,7 @@ mod tests {
     use super::*;
     use crate::game_plugin::GamePlugin;
     use crate::table_plugin::TablePlugin;
-    use solitaire_core::card::Deck;
+    use solitaire_core::Deck;
 
     /// Convenience constructor — all unit tests use Deck1.
     fn make_card(suit: Suit, rank: Rank) -> Card {
diff --git a/solitaire_engine/src/cursor_plugin.rs b/solitaire_engine/src/cursor_plugin.rs
index 0726979..8bd4987 100644
--- a/solitaire_engine/src/cursor_plugin.rs
+++ b/solitaire_engine/src/cursor_plugin.rs
@@ -34,7 +34,7 @@
 
 use bevy::prelude::*;
 use bevy::window::{CursorIcon, PrimaryWindow, SystemCursorIcon};
-use solitaire_core::card::Card;
+use solitaire_core::Card;
 use solitaire_core::{Foundation, KlondikePile, Tableau};
 use solitaire_core::{DrawStockConfig, game_state::GameState};
 
@@ -580,7 +580,7 @@ mod tests {
     // -----------------------------------------------------------------------
 
     use crate::layout::compute_layout;
-    use solitaire_core::card::{Card, Deck, Rank, Suit};
+    use solitaire_core::{Card, Deck, Rank, Suit};
     use solitaire_core::{DrawStockConfig, game_state::{GameMode, GameState}};
 
     /// Builds an `App` with `MinimalPlugins` and the overlay system
diff --git a/solitaire_engine/src/events.rs b/solitaire_engine/src/events.rs
index 3bcd8bb..e8c7ada 100644
--- a/solitaire_engine/src/events.rs
+++ b/solitaire_engine/src/events.rs
@@ -2,7 +2,7 @@
 
 use bevy::prelude::Message;
 use solitaire_core::KlondikePile;
-use solitaire_core::card::{Card, Suit};
+use solitaire_core::{Card, Suit};
 use solitaire_core::game_state::GameMode;
 use solitaire_data::AchievementRecord;
 use solitaire_sync::SyncResponse;
diff --git a/solitaire_engine/src/feedback_anim_plugin.rs b/solitaire_engine/src/feedback_anim_plugin.rs
index 3e832dc..5ef2689 100644
--- a/solitaire_engine/src/feedback_anim_plugin.rs
+++ b/solitaire_engine/src/feedback_anim_plugin.rs
@@ -43,7 +43,7 @@ use std::hash::{Hash, Hasher};
 
 use bevy::prelude::*;
 use bevy::window::RequestRedraw;
-use solitaire_core::card::Card;
+use solitaire_core::Card;
 use solitaire_core::KlondikePile;
 use solitaire_core::klondike_adapter::foundation_from_slot;
 use solitaire_data::AnimSpeed;
@@ -189,10 +189,6 @@ pub fn deal_stagger_jitter(card_id: u32) -> f32 {
     (jitter_norm - 0.5) * 0.2 // ±0.1 == ±10 %
 }
 
-// Per-card jitter keys off the shared stable card id so it matches the
-// numeric identity used elsewhere (and on the WASM replay side).
-use solitaire_core::card::card_to_id;
-
 // ---------------------------------------------------------------------------
 // Plugin
 // ---------------------------------------------------------------------------
@@ -413,10 +409,14 @@ fn start_deal_anim(
 
     for (index, (entity, card_marker, transform)) in card_entities.iter().enumerate() {
         let final_pos = transform.translation;
-        // ±10 % jitter, deterministic per card id, so the deal feels organic
-        // without losing reproducibility (a given seed still produces the
-        // same per-card stagger pattern across runs).
-        let per_card_stagger = stagger_secs * (1.0 + deal_stagger_jitter(card_to_id(&card_marker.card)));
+        // ±10 % jitter, deterministic per card, so the deal feels organic
+        // without losing reproducibility (a given deal produces the same
+        // per-card stagger pattern across runs). The seed is a hash of the
+        // card's own identity — no separate numeric id needed.
+        let mut card_hasher = DefaultHasher::new();
+        card_marker.card.hash(&mut card_hasher);
+        let per_card_stagger =
+            stagger_secs * (1.0 + deal_stagger_jitter(card_hasher.finish() as u32));
         commands.entity(entity).insert((
             Transform::from_translation(stock_start.with_z(final_pos.z)),
             CardAnim {
@@ -639,7 +639,7 @@ fn lerp_color(from: Color, to: Color, t: f32) -> Color {
 fn pile_cards(
     game: &solitaire_core::game_state::GameState,
     pile: &KlondikePile,
-) -> Vec<(solitaire_core::card::Card, bool)> {
+) -> Vec<(solitaire_core::Card, bool)> {
     match pile {
         KlondikePile::Stock => game.waste_cards(),
         _ => game.pile(*pile),
@@ -917,7 +917,7 @@ mod tests {
             .resource_mut::<Messages<FoundationCompletedEvent>>()
             .write(FoundationCompletedEvent {
                 slot: 0,
-                suit: solitaire_core::card::Suit::Spades,
+                suit: solitaire_core::Suit::Spades,
             });
         app.update();
 
diff --git a/solitaire_engine/src/game_plugin.rs b/solitaire_engine/src/game_plugin.rs
index d75cc7d..e822129 100644
--- a/solitaire_engine/src/game_plugin.rs
+++ b/solitaire_engine/src/game_plugin.rs
@@ -824,7 +824,7 @@ fn handle_draw(
         // so we can fire flip events after they land face-up in the waste.
         // Only relevant when stock is non-empty; a recycle moves waste back to
         // stock face-down, so no flip events are needed in that case.
-        let drawn_cards: Vec<solitaire_core::card::Card> = {
+        let drawn_cards: Vec<solitaire_core::Card> = {
             let stock = game.0.stock_cards();
             if stock.is_empty() {
                 Vec::new()
@@ -1013,7 +1013,7 @@ pub fn record_replay_on_win(
     }
 }
 
-fn pile_cards(game: &GameState, pile: &KlondikePile) -> Vec<(solitaire_core::card::Card, bool)> {
+fn pile_cards(game: &GameState, pile: &KlondikePile) -> Vec<(solitaire_core::Card, bool)> {
     match pile {
         KlondikePile::Stock => game.waste_cards(),
         _ => game.pile(*pile),
@@ -1391,7 +1391,7 @@ mod tests {
     #[test]
     fn new_game_request_reseeds() {
         let mut app = test_app(1);
-        let before: Vec<solitaire_core::card::Card> = app
+        let before: Vec<solitaire_core::Card> = app
             .world()
             .resource::<GameStateResource>()
             .0
@@ -1407,7 +1407,7 @@ mod tests {
         });
         app.update();
 
-        let after: Vec<solitaire_core::card::Card> = app
+        let after: Vec<solitaire_core::Card> = app
             .world()
             .resource::<GameStateResource>()
             .0
@@ -1649,7 +1649,7 @@ mod tests {
 
     #[test]
     fn moving_cards_off_face_up_card_does_not_fire_card_flipped_event() {
-        use solitaire_core::card::{Card, Deck, Rank, Suit};
+        use solitaire_core::{Card, Deck, Rank, Suit};
         let mut app = test_app(1);
         // Build a tableau with two face-up cards.
         {
@@ -1706,7 +1706,7 @@ mod tests {
         // Klondike (unlimited recycles), even if the drawn card cannot be
         // immediately placed. The game is only stuck when both stock AND waste
         // are exhausted and no visible card can be moved.
-        use solitaire_core::card::{Card, Deck, Rank, Suit};
+        use solitaire_core::{Card, Deck, Rank, Suit};
         let mut game = GameState::new(1, DrawStockConfig::DrawOne);
         for foundation in [
             Foundation::Foundation1,
@@ -1742,7 +1742,7 @@ mod tests {
 
     #[test]
     fn has_legal_moves_returns_true_when_ace_can_go_to_foundation() {
-        use solitaire_core::card::{Card, Deck, Rank, Suit};
+        use solitaire_core::{Card, Deck, Rank, Suit};
         let mut game = GameState::new(1, DrawStockConfig::DrawOne);
 
         // Empty stock and waste so draw is NOT available.
@@ -1786,7 +1786,7 @@ mod tests {
         // If the only legal move involves a face-up card that is NOT the top
         // card of its column the previous code would return false (softlock)
         // even though the player can still move that run.
-        use solitaire_core::card::{Card, Deck, Rank, Suit};
+        use solitaire_core::{Card, Deck, Rank, Suit};
         let mut game = GameState::new(1, DrawStockConfig::DrawOne);
 
         game.set_test_stock_cards(Vec::new());
@@ -1976,7 +1976,7 @@ mod tests {
     /// to have been a King.
     #[test]
     fn foundation_completed_event_does_not_fire_for_non_foundation_moves() {
-        use solitaire_core::card::{Card, Deck, Rank, Suit};
+        use solitaire_core::{Card, Deck, Rank, Suit};
 
         let mut app = test_app(1);
         // Reset the world: clear stock + waste so a draw isn't possible,
diff --git a/solitaire_engine/src/hud_plugin.rs b/solitaire_engine/src/hud_plugin.rs
index 631d511..c52c88f 100644
--- a/solitaire_engine/src/hud_plugin.rs
+++ b/solitaire_engine/src/hud_plugin.rs
@@ -9,7 +9,7 @@
 use bevy::prelude::*;
 use bevy::window::WindowResized;
 use solitaire_core::{Foundation, KlondikePile, Tableau};
-use solitaire_core::card::Suit;
+use solitaire_core::Suit;
 use solitaire_core::{DrawStockConfig, game_state::GameMode};
 
 use crate::auto_complete_plugin::AutoCompleteState;
diff --git a/solitaire_engine/src/input_plugin.rs b/solitaire_engine/src/input_plugin.rs
index 3874dfe..f2ea1d9 100644
--- a/solitaire_engine/src/input_plugin.rs
+++ b/solitaire_engine/src/input_plugin.rs
@@ -27,7 +27,7 @@ use bevy::window::PrimaryWindow;
 #[cfg(not(target_os = "android"))]
 use bevy::window::{MonitorSelection, WindowMode};
 use solitaire_core::{Foundation, KlondikeInstruction, KlondikePile, Tableau};
-use solitaire_core::card::{Card, Suit};
+use solitaire_core::{Card, Suit};
 use solitaire_core::game_state::GameState;
 
 use crate::auto_complete_plugin::AutoCompleteState;
@@ -1953,8 +1953,8 @@ mod tests {
     fn find_draggable_returns_run_when_picking_mid_stack() {
         // Manually construct a tableau with three face-up cards all stacked.
         let mut game = GameState::new(1, DrawStockConfig::DrawOne);
-        use solitaire_core::card::Deck as D;
-        use solitaire_core::card::{Card, Rank, Suit};
+        use solitaire_core::Deck as D;
+        use solitaire_core::{Card, Rank, Suit};
         let king = Card::new(D::Deck1, Suit::Spades, Rank::King);
         let queen = Card::new(D::Deck1, Suit::Hearts, Rank::Queen);
         let jack = Card::new(D::Deck1, Suit::Clubs, Rank::Jack);
@@ -1980,8 +1980,8 @@ mod tests {
     #[test]
     fn find_draggable_skips_non_top_waste_card() {
         let mut game = GameState::new(1, DrawStockConfig::DrawOne);
-        use solitaire_core::card::Deck as D;
-        use solitaire_core::card::{Card, Rank, Suit};
+        use solitaire_core::Deck as D;
+        use solitaire_core::{Card, Rank, Suit};
         let two_spades = Card::new(D::Deck1, Suit::Spades, Rank::Two);
         let three_hearts = Card::new(D::Deck1, Suit::Hearts, Rank::Three);
         game.set_test_waste_cards(vec![two_spades, three_hearts.clone()]);
@@ -2044,8 +2044,8 @@ mod tests {
 
     #[test]
     fn find_draggable_draw_three_waste_top_card_hit_at_fanned_position() {
-        use solitaire_core::card::Deck as D;
-        use solitaire_core::card::{Card, Rank, Suit};
+        use solitaire_core::Deck as D;
+        use solitaire_core::{Card, Rank, Suit};
         use solitaire_core::{DrawStockConfig, game_state::GameMode};
         let mut game = GameState::new_with_mode(1, DrawStockConfig::DrawThree, GameMode::Classic);
         // Three waste cards; top (four_clubs) is rightmost in the fan.
@@ -2103,8 +2103,8 @@ mod tests {
 
     #[test]
     fn best_destination_returns_none_when_no_legal_move() {
-        use solitaire_core::card::Deck as D;
-        use solitaire_core::card::{Card, Rank, Suit};
+        use solitaire_core::Deck as D;
+        use solitaire_core::{Card, Rank, Suit};
         let mut game = GameState::new(1, DrawStockConfig::DrawOne);
 
         // Clear everything except one card that has nowhere to go.
@@ -2121,8 +2121,8 @@ mod tests {
 
     #[test]
     fn best_tableau_destination_for_stack_skips_source_pile() {
-        use solitaire_core::card::Deck as D;
-        use solitaire_core::card::{Card, Rank, Suit};
+        use solitaire_core::Deck as D;
+        use solitaire_core::{Card, Rank, Suit};
         let mut game = GameState::new(1, DrawStockConfig::DrawOne);
 
         clear_test_piles(&mut game);
@@ -2147,8 +2147,8 @@ mod tests {
 
     #[test]
     fn best_tableau_destination_for_stack_returns_none_when_no_legal_move() {
-        use solitaire_core::card::Deck as D;
-        use solitaire_core::card::{Card, Rank, Suit};
+        use solitaire_core::Deck as D;
+        use solitaire_core::{Card, Rank, Suit};
         let mut game = GameState::new(1, DrawStockConfig::DrawOne);
 
         clear_test_piles(&mut game);
@@ -2176,8 +2176,8 @@ mod tests {
 
     #[test]
     fn find_hint_finds_ace_to_foundation() {
-        use solitaire_core::card::Deck as D;
-        use solitaire_core::card::{Card, Rank, Suit};
+        use solitaire_core::Deck as D;
+        use solitaire_core::{Card, Rank, Suit};
         let mut game = GameState::new(1, DrawStockConfig::DrawOne);
 
         // Place Ace of Clubs on top of tableau 0.
@@ -2220,8 +2220,8 @@ mod tests {
     /// are no other moves and the stock is non-empty.
     #[test]
     fn all_hints_suggests_draw_when_no_moves_and_stock_nonempty() {
-        use solitaire_core::card::Deck as D;
-        use solitaire_core::card::{Card, Rank, Suit};
+        use solitaire_core::Deck as D;
+        use solitaire_core::{Card, Rank, Suit};
         let mut game = GameState::new(1, DrawStockConfig::DrawOne);
 
         // Remove all foundation, tableau, and waste cards so no pile-to-pile
@@ -2273,8 +2273,8 @@ mod tests {
     /// gets a CardAnimation" — same coverage, new component.
     #[test]
     fn rejected_drag_inserts_card_animation_on_each_dragged_card() {
-        use solitaire_core::card::Deck as D;
-        use solitaire_core::card::{Card, Rank, Suit};
+        use solitaire_core::Deck as D;
+        use solitaire_core::{Card, Rank, Suit};
         // Simulate a stack drag of two cards.
         let dragged_cards: Vec<Card> = vec![
             Card::new(D::Deck1, Suit::Hearts, Rank::King),
diff --git a/solitaire_engine/src/pending_hint.rs b/solitaire_engine/src/pending_hint.rs
index 9e6fae5..3e7c9bf 100644
--- a/solitaire_engine/src/pending_hint.rs
+++ b/solitaire_engine/src/pending_hint.rs
@@ -179,7 +179,7 @@ mod tests {
     use crate::events::HintVisualEvent;
     use crate::input_plugin::HintSolverConfig;
     use solitaire_core::{Foundation, KlondikePile, Tableau};
-    use solitaire_core::card::{Card, Deck, Rank, Suit};
+    use solitaire_core::{Card, Deck, Rank, Suit};
     use solitaire_core::{DrawStockConfig, game_state::GameState};
 
     /// Build a minimal Bevy app exercising only the polling system
diff --git a/solitaire_engine/src/radial_menu.rs b/solitaire_engine/src/radial_menu.rs
index 31faf3f..fb72dea 100644
--- a/solitaire_engine/src/radial_menu.rs
+++ b/solitaire_engine/src/radial_menu.rs
@@ -48,7 +48,7 @@ use bevy::math::Vec2;
 use bevy::prelude::*;
 use bevy::window::PrimaryWindow;
 use solitaire_core::{Foundation, KlondikePile, Tableau};
-use solitaire_core::card::Card;
+use solitaire_core::Card;
 use solitaire_core::game_state::GameState;
 
 use crate::card_plugin::TABLEAU_FACEDOWN_FAN_FRAC;
@@ -113,9 +113,9 @@ pub enum RightClickRadialState {
         /// radial is built around single-card foundation/tableau
         /// shortcuts and that matches the right-click highlight set).
         count: usize,
-        /// Card ids that would be moved (bottom-to-top order). Length
+        /// Cards that would be moved (bottom-to-top order). Length
         /// always equals `count`. Currently always one element.
-        cards: Vec<u32>,
+        cards: Vec<Card>,
         /// Pre-computed `(destination, icon_anchor_world_pos)` pairs.
         ///
         /// Anchors are evenly spaced around a ring of radius
@@ -359,7 +359,6 @@ fn pile_cards(game: &GameState, pile: &KlondikePile) -> Vec<(Card, bool)> {
     }
 }
 
-use solitaire_core::card::card_to_id;
 
 const fn foundations() -> [Foundation; 4] {
     [
@@ -500,7 +499,7 @@ fn radial_open_on_right_click(
     *state = RightClickRadialState::Active {
         source_pile,
         count: 1,
-        cards: vec![card_to_id(&card)],
+        cards: vec![card.clone()],
         legal_destinations,
         centre: world,
         hovered_index: None,
@@ -573,7 +572,7 @@ fn radial_open_on_long_press(
     *state = RightClickRadialState::Active {
         source_pile,
         count: 1,
-        cards: vec![card_to_id(&card)],
+        cards: vec![card.clone()],
         legal_destinations,
         centre: world,
         hovered_index: None,
@@ -796,7 +795,7 @@ mod tests {
     use super::*;
     use crate::layout::compute_layout;
     use bevy::ecs::message::Messages;
-    use solitaire_core::card::{Card as CoreCard, Deck, Rank, Suit};
+    use solitaire_core::{Card as CoreCard, Deck, Rank, Suit};
     use solitaire_core::{DrawStockConfig, game_state::GameState};
 
     /// Build a minimal Bevy app wired with `RadialMenuPlugin` and the
diff --git a/solitaire_engine/src/replay_overlay/format.rs b/solitaire_engine/src/replay_overlay/format.rs
index 22ed3ee..d3e141b 100644
--- a/solitaire_engine/src/replay_overlay/format.rs
+++ b/solitaire_engine/src/replay_overlay/format.rs
@@ -1,7 +1,7 @@
 use super::ReplayPlaybackState;
 use chrono::Datelike;
 use solitaire_core::{Foundation, KlondikePile, Tableau};
-use solitaire_core::card::{Card, Rank, Suit};
+use solitaire_core::{Card, Rank, Suit};
 use solitaire_core::game_state::GameState;
 use solitaire_core::klondike_adapter::SavedKlondikePile;
 use solitaire_data::ReplayMove;
diff --git a/solitaire_engine/src/replay_overlay/tests.rs b/solitaire_engine/src/replay_overlay/tests.rs
index e22e845..32155ec 100644
--- a/solitaire_engine/src/replay_overlay/tests.rs
+++ b/solitaire_engine/src/replay_overlay/tests.rs
@@ -1,7 +1,7 @@
 use super::*;
 use chrono::NaiveDate;
 use solitaire_core::{Foundation, KlondikePile, Tableau};
-use solitaire_core::card::{Rank, Suit};
+use solitaire_core::{Rank, Suit};
 use solitaire_core::{DrawStockConfig, game_state::GameMode};
 use solitaire_core::klondike_adapter::{SavedKlondikePile, SavedTableau};
 use solitaire_data::{Replay, ReplayMove};
diff --git a/solitaire_engine/src/resources.rs b/solitaire_engine/src/resources.rs
index 109bebb..473aa38 100644
--- a/solitaire_engine/src/resources.rs
+++ b/solitaire_engine/src/resources.rs
@@ -7,7 +7,7 @@ use bevy::math::Vec2;
 use bevy::prelude::Resource;
 use chrono::{DateTime, Utc};
 use solitaire_core::KlondikePile;
-use solitaire_core::card::Card;
+use solitaire_core::Card;
 use solitaire_core::game_state::GameState;
 
 /// Wraps the currently active `GameState`. Single source of truth for the in-progress game.
diff --git a/solitaire_engine/src/selection_plugin.rs b/solitaire_engine/src/selection_plugin.rs
index 6eb31ee..c87fdfe 100644
--- a/solitaire_engine/src/selection_plugin.rs
+++ b/solitaire_engine/src/selection_plugin.rs
@@ -38,7 +38,7 @@
 use bevy::input::ButtonInput;
 use bevy::prelude::*;
 use solitaire_core::{Foundation, KlondikePile, Tableau};
-use solitaire_core::card::Card;
+use solitaire_core::Card;
 use solitaire_core::game_state::GameState;
 
 use crate::card_plugin::CardEntityIndex;
@@ -534,7 +534,7 @@ fn handle_selection_keys(
 /// destination after a lift. Players who want a different column simply
 /// press the right-arrow key once or twice.
 pub(crate) fn legal_destinations_for(
-    _bottom: &solitaire_core::card::Card,
+    _bottom: &solitaire_core::Card,
     source: &KlondikePile,
     game: &GameState,
     stack_count: usize,
@@ -579,7 +579,7 @@ pub(crate) fn legal_destinations_for(
 /// Walks backwards from the last element and stops at the first face-down card
 /// (or when the slice is exhausted). Returns at least `1` when the top card is
 /// face-up; returns `0` for an empty slice or when the top card is face-down.
-fn face_up_run_len(cards: &[(solitaire_core::card::Card, bool)]) -> usize {
+fn face_up_run_len(cards: &[(solitaire_core::Card, bool)]) -> usize {
     let mut count = 0;
     for (_, face_up) in cards.iter().rev() {
         if *face_up {
@@ -598,7 +598,7 @@ fn face_up_run_len(cards: &[(solitaire_core::card::Card, bool)]) -> usize {
 /// handler can attempt a foundation move first and fall through to a
 /// multi-card stack move rather than accepting a single-card tableau move.
 fn try_foundation_dest(
-    card: &solitaire_core::card::Card,
+    card: &solitaire_core::Card,
     game: &solitaire_core::game_state::GameState,
 ) -> Option<KlondikePile> {
     let source = game.pile_containing_card(card.clone())?;
@@ -886,7 +886,7 @@ mod tests {
 
     #[test]
     fn face_up_run_len_all_face_up() {
-        use solitaire_core::card::{Card, Deck, Rank, Suit};
+        use solitaire_core::{Card, Deck, Rank, Suit};
         let cards = vec![
             (Card::new(Deck::Deck1, Suit::Clubs, Rank::King), true),
             (Card::new(Deck::Deck1, Suit::Hearts, Rank::Queen), true),
@@ -897,7 +897,7 @@ mod tests {
 
     #[test]
     fn face_up_run_len_mixed_stops_at_face_down() {
-        use solitaire_core::card::{Card, Deck, Rank, Suit};
+        use solitaire_core::{Card, Deck, Rank, Suit};
         let cards = vec![
             (Card::new(Deck::Deck1, Suit::Clubs, Rank::King), false),
             (Card::new(Deck::Deck1, Suit::Hearts, Rank::Queen), false),
@@ -910,7 +910,7 @@ mod tests {
 
     #[test]
     fn face_up_run_len_top_card_face_down_is_zero() {
-        use solitaire_core::card::{Card, Deck, Rank, Suit};
+        use solitaire_core::{Card, Deck, Rank, Suit};
         let cards = vec![
             (Card::new(Deck::Deck1, Suit::Clubs, Rank::King), true),
             (Card::new(Deck::Deck1, Suit::Hearts, Rank::Queen), false),
@@ -920,7 +920,7 @@ mod tests {
 
     #[test]
     fn face_up_run_len_single_face_up_card() {
-        use solitaire_core::card::{Card, Deck, Rank, Suit};
+        use solitaire_core::{Card, Deck, Rank, Suit};
         let cards = vec![(Card::new(Deck::Deck1, Suit::Hearts, Rank::Ace), true)];
         assert_eq!(face_up_run_len(&cards), 1);
     }
@@ -934,7 +934,7 @@ mod tests {
     // -----------------------------------------------------------------------
 
     use bevy::ecs::message::Messages;
-    use solitaire_core::card::{Card, Deck, Rank, Suit};
+    use solitaire_core::{Card, Deck, Rank, Suit};
     use solitaire_core::{DrawStockConfig, game_state::GameState};
 
     /// Build a minimal app with `SelectionPlugin` only — no GamePlugin, no
diff --git a/solitaire_engine/src/table_plugin.rs b/solitaire_engine/src/table_plugin.rs
index b8c6f90..8aa375b 100644
--- a/solitaire_engine/src/table_plugin.rs
+++ b/solitaire_engine/src/table_plugin.rs
@@ -7,7 +7,7 @@
 use bevy::prelude::*;
 use bevy::window::WindowResized;
 use solitaire_core::{Foundation, KlondikePile, Tableau};
-use solitaire_core::card::Suit;
+use solitaire_core::Suit;
 
 use crate::events::{HintVisualEvent, StateChangedEvent};
 use crate::hud_plugin::HudVisibility;
@@ -520,7 +520,7 @@ fn sync_pile_marker_visibility(
 fn pile_cards(
     game: &solitaire_core::game_state::GameState,
     pile: &KlondikePile,
-) -> Vec<(solitaire_core::card::Card, bool)> {
+) -> Vec<(solitaire_core::Card, bool)> {
     match pile {
         KlondikePile::Stock => {
             let stock = game.stock_cards();
diff --git a/solitaire_engine/src/theme/mod.rs b/solitaire_engine/src/theme/mod.rs
index 86fde60..2e6d751 100644
--- a/solitaire_engine/src/theme/mod.rs
+++ b/solitaire_engine/src/theme/mod.rs
@@ -27,7 +27,7 @@ use bevy::reflect::TypePath;
 use serde::{Deserialize, Serialize};
 use thiserror::Error;
 
-use solitaire_core::card::{Rank, Suit};
+use solitaire_core::{Rank, Suit};
 
 #[cfg(not(target_arch = "wasm32"))]
 pub use importer::{ImportError, ThemeId, import_theme, import_theme_into};
diff --git a/solitaire_engine/src/theme/plugin.rs b/solitaire_engine/src/theme/plugin.rs
index 6ffe8dc..f72e015 100644
--- a/solitaire_engine/src/theme/plugin.rs
+++ b/solitaire_engine/src/theme/plugin.rs
@@ -12,7 +12,7 @@ use bevy::asset::AssetEvent;
 use bevy::ecs::message::MessageReader;
 use bevy::math::UVec2;
 use bevy::prelude::*;
-use solitaire_core::card::{Rank, Suit};
+use solitaire_core::{Rank, Suit};
 
 use crate::assets::{
     bundled_theme_url, classic_theme_svg_bytes, dark_theme_svg_bytes, rasterize_svg, user_theme_dir,
diff --git a/solitaire_engine/src/touch_selection_plugin.rs b/solitaire_engine/src/touch_selection_plugin.rs
index f26e854..d976f61 100644
--- a/solitaire_engine/src/touch_selection_plugin.rs
+++ b/solitaire_engine/src/touch_selection_plugin.rs
@@ -29,7 +29,7 @@
 use bevy::ecs::message::MessageReader;
 use bevy::prelude::*;
 use solitaire_core::KlondikePile;
-use solitaire_core::card::Card;
+use solitaire_core::Card;
 
 use crate::card_plugin::CardEntity;
 use crate::events::StateChangedEvent;
@@ -194,7 +194,7 @@ fn spawn_touch_highlight(
 mod tests {
     use super::*;
     use solitaire_core::Tableau;
-    use solitaire_core::card::{Card, Deck, Rank, Suit};
+    use solitaire_core::{Card, Deck, Rank, Suit};
 
     /// Three distinct test cards, used in place of the old `vec![1, 2, 3]`
     /// numeric ids. Identity is now the `Card` value.
diff --git a/solitaire_wasm/src/lib.rs b/solitaire_wasm/src/lib.rs
index 05775b7..e85819f 100644
--- a/solitaire_wasm/src/lib.rs
+++ b/solitaire_wasm/src/lib.rs
@@ -21,7 +21,7 @@
 use chrono::NaiveDate;
 use solitaire_core::{Foundation, KlondikePile, Tableau};
 use serde::{Deserialize, Serialize};
-use solitaire_core::card::Suit;
+use solitaire_core::{Card, Deck, Rank, Suit};
 use solitaire_core::error::MoveError;
 use solitaire_core::{DrawStockConfig, game_state::{GameMode, GameState}};
 use solitaire_core::klondike_adapter::{
@@ -77,9 +77,11 @@ pub struct StateSnapshot {
 /// means the card back is drawn; in that case `suit` and `rank` are
 /// still set (so the renderer doesn't need separate "unknown" data),
 /// just hidden visually.
-#[derive(Debug, Clone, Copy, Serialize, PartialEq, Eq)]
+#[derive(Debug, Clone, Serialize, PartialEq, Eq)]
 pub struct CardSnapshot {
-    pub id: u32,
+    /// Stable per-card identity for the JS renderer (an opaque key). Serialises
+    /// as the upstream `Card`'s transparent integer value.
+    pub id: Card,
     /// `"clubs" | "diamonds" | "hearts" | "spades"`.
     pub suit: &'static str,
     /// 1-13, where 1 is Ace and 13 is King.
@@ -87,14 +89,10 @@ pub struct CardSnapshot {
     pub face_up: bool,
 }
 
-// Stable 0..=51 card identity, shared with the desktop engine via
-// solitaire_core so replay snapshots are identical across platforms.
-use solitaire_core::card::card_to_id;
-
-impl From<&(solitaire_core::card::Card, bool)> for CardSnapshot {
-    fn from((card, face_up): &(solitaire_core::card::Card, bool)) -> Self {
+impl From<&(Card, bool)> for CardSnapshot {
+    fn from((card, face_up): &(Card, bool)) -> Self {
         Self {
-            id: card_to_id(card),
+            id: card.clone(),
             suit: match card.suit() {
                 Suit::Clubs => "clubs",
                 Suit::Diamonds => "diamonds",
@@ -318,9 +316,10 @@ pub enum DebugMove {
 pub struct DebugInvariantReport {
     pub state_ok: bool,
     pub total_cards_seen: usize,
-    pub duplicate_card_ids: Vec<u32>,
-    pub missing_card_ids: Vec<u32>,
-    pub out_of_range_card_ids: Vec<u32>,
+    /// Cards that appeared more than once across all piles.
+    pub duplicate_cards: Vec<Card>,
+    /// Cards from the full single-deck set that are absent from the board.
+    pub missing_cards: Vec<Card>,
     pub stock_has_face_up_cards: bool,
     pub waste_has_face_down_cards: bool,
     pub foundation_has_face_down_cards: bool,
@@ -389,24 +388,15 @@ fn invariant_report_for_game(game: &GameState, legal_moves: &[DebugMove]) -> Deb
         game.pile(KlondikePile::Tableau(Tableau::Tableau7)),
     ];
 
-    let mut seen = [false; 52];
-    let mut duplicate_card_ids = Vec::new();
-    let mut out_of_range_card_ids = Vec::new();
+    let mut seen: std::collections::HashSet<Card> = std::collections::HashSet::new();
+    let mut duplicate_cards = Vec::new();
     let mut total_cards_seen = 0_usize;
 
-    let mut feed = |cards: &[(solitaire_core::card::Card, bool)]| {
+    let mut feed = |cards: &[(Card, bool)]| {
         for (card, _) in cards {
             total_cards_seen += 1;
-            let id = card_to_id(card);
-            if id >= 52 {
-                out_of_range_card_ids.push(id);
-                continue;
-            }
-            let idx = id as usize;
-            if seen[idx] {
-                duplicate_card_ids.push(id);
-            } else {
-                seen[idx] = true;
+            if !seen.insert(card.clone()) {
+                duplicate_cards.push(card.clone());
             }
         }
     };
@@ -420,9 +410,22 @@ fn invariant_report_for_game(game: &GameState, legal_moves: &[DebugMove]) -> Deb
         feed(pile);
     }
 
-    let missing_card_ids = (0_u32..52_u32)
-        .filter(|id| !seen[*id as usize])
-        .collect::<Vec<_>>();
+    // Reference set: the full 52-card single deck, using whichever deck id the
+    // dealt cards carry. Any of those 52 not on the board is missing.
+    let deck = seen
+        .iter()
+        .next()
+        .map(|c| c.deck())
+        .unwrap_or_else(|| Deck::new(0).expect("deck id 0 is valid"));
+    let mut missing_cards = Vec::new();
+    for suit in Suit::SUITS {
+        for rank in Rank::RANKS {
+            let card = Card::new(deck, suit, rank);
+            if !seen.contains(&card) {
+                missing_cards.push(card);
+            }
+        }
+    }
 
     let stock_has_face_up_cards = stock.iter().any(|(_, face_up)| *face_up);
     let waste_has_face_down_cards = waste.iter().any(|(_, face_up)| !*face_up);
@@ -444,9 +447,8 @@ fn invariant_report_for_game(game: &GameState, legal_moves: &[DebugMove]) -> Deb
 
     let soft_lock = !game.is_won() && stock.is_empty() && waste.is_empty() && legal_moves.is_empty();
 
-    let state_ok = duplicate_card_ids.is_empty()
-        && missing_card_ids.is_empty()
-        && out_of_range_card_ids.is_empty()
+    let state_ok = duplicate_cards.is_empty()
+        && missing_cards.is_empty()
         && !stock_has_face_up_cards
         && !waste_has_face_down_cards
         && !foundation_has_face_down_cards
@@ -455,9 +457,8 @@ fn invariant_report_for_game(game: &GameState, legal_moves: &[DebugMove]) -> Deb
     DebugInvariantReport {
         state_ok,
         total_cards_seen,
-        duplicate_card_ids,
-        missing_card_ids,
-        out_of_range_card_ids,
+        duplicate_cards,
+        missing_cards,
         stock_has_face_up_cards,
         waste_has_face_down_cards,
         foundation_has_face_down_cards,
@@ -893,6 +894,25 @@ mod tests {
     use std::collections::HashSet;
     use std::fmt::Write;
 
+    /// The JS card renderer reads `card.id` as an opaque identity key. After the
+    /// `card_to_id` removal, `CardSnapshot.id` is a `card_game::Card`, which is
+    /// `#[serde(transparent)]` over `NonZeroU8` — so it must still serialise as a
+    /// plain JSON number (the same `Serialize` impl `serde_wasm_bindgen` uses).
+    #[test]
+    fn card_snapshot_id_serialises_as_a_plain_number() {
+        let card = Card::new(Deck::new(0).unwrap(), Suit::Hearts, Rank::RANKS[0]);
+        let snap = CardSnapshot::from(&(card, true));
+        let json = serde_json::to_value(&snap).expect("serialise CardSnapshot");
+        assert!(
+            json["id"].is_number(),
+            "card.id must serialise as a JSON number for the JS opaque key, got {:?}",
+            json["id"]
+        );
+        assert_eq!(json["suit"], "hearts");
+        assert_eq!(json["rank"], 1);
+        assert_eq!(json["face_up"], true);
+    }
+
     fn pick_move_index(moves: &[DebugMove]) -> Option<usize> {
         if moves.is_empty() {
             return None;
@@ -933,7 +953,7 @@ mod tests {
             for card in cards {
                 let _ = write!(
                     key,
-                    "{}:{}:{},",
+                    "{:?}:{}:{},",
                     card.id,
                     card.rank,
                     if card.face_up { 1 } else { 0 }