fix(engine): resolve input coordination bugs in selection/pause/keyboard

- SelectionPlugin: add clear_selection_on_state_change system so undo/move/reject
  never leave a stale selection pointing at the wrong card
- SelectionPlugin: expose SelectionKeySet system set for cross-plugin ordering
- PausePlugin: skip Escape→pause when a card is keyboard-selected; toggle_pause
  now runs before SelectionKeySet so it reads SelectionState before it is cleared
- InputPlugin: guard Space→DrawRequestEvent when SelectionState has an active pile
  so Space executes a card move instead of also drawing from stock
- window: enforce 800×600 minimum via WindowResizeConstraints
- game_state: add precondition doc to next_auto_complete_move (waste exclusion)
- card_plugin: 12 unit tests for constants, face_colour, label_visibility, label_for
- pause_plugin: add paused_resource_default and draw_mode_label exhaustiveness tests

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

solitaire_app/src/main.rs

@@ -22,6 +22,11 @@ fn main() {
                 primary_window: Some(Window {
                     title: "Solitaire Quest".into(),
                     resolution: (1280u32, 800u32).into(),
+                    resize_constraints: bevy::window::WindowResizeConstraints {
+                        min_width: 800.0,
+                        min_height: 600.0,
+                        ..default()
+                    },
                     ..default()
                 }),
                 ..default()

solitaire_core/src/game_state.rs

@@ -361,6 +361,15 @@ impl GameState {
     /// Scans tableau piles 0–6 in order, returning the first top card that
     /// can be placed on any foundation pile. The scan order ensures Aces are
     /// resolved before higher ranks that depend on them.
+    ///
+    /// # Precondition
+    ///
+    /// This function is only called when `is_auto_completable` is `true`.
+    /// Auto-completability requires the waste pile to be empty, as enforced by
+    /// [`check_auto_complete`](Self::check_auto_complete) — it returns `false`
+    /// whenever `piles[Waste]` is non-empty. Therefore, skipping the waste pile
+    /// in this scan is intentional and correct: by the time this function is
+    /// reached, there are guaranteed to be no cards there to move.
     pub fn next_auto_complete_move(&self) -> Option<(PileType, PileType)> {
         if !self.is_auto_completable || self.is_won {
             return None;

solitaire_engine/src/card_plugin.rs

@@ -1322,6 +1322,129 @@ mod tests {
         );
     }
 
+    // -----------------------------------------------------------------------
+    // Constant sanity bounds (pure)
+    // -----------------------------------------------------------------------
+
+    #[test]
+    fn tableau_fan_frac_is_in_unit_interval() {
+        assert!(
+            TABLEAU_FAN_FRAC > 0.0 && TABLEAU_FAN_FRAC < 1.0,
+            "TABLEAU_FAN_FRAC must be in (0, 1), got {TABLEAU_FAN_FRAC}"
+        );
+    }
+
+    #[test]
+    fn flip_half_secs_is_positive() {
+        assert!(
+            FLIP_HALF_SECS > 0.0,
+            "FLIP_HALF_SECS must be positive, got {FLIP_HALF_SECS}"
+        );
+    }
+
+    #[test]
+    fn font_size_frac_is_positive_and_reasonable() {
+        assert!(
+            FONT_SIZE_FRAC > 0.0 && FONT_SIZE_FRAC <= 1.0,
+            "FONT_SIZE_FRAC should be in (0, 1], got {FONT_SIZE_FRAC}"
+        );
+    }
+
+    // -----------------------------------------------------------------------
+    // face_colour (pure) — color-blind mode
+    // -----------------------------------------------------------------------
+
+    #[test]
+    fn face_colour_normal_mode_returns_card_face_colour_for_red_suit() {
+        let card = Card { id: 0, suit: Suit::Hearts, rank: Rank::King, face_up: true };
+        assert_eq!(face_colour(&card, false), CARD_FACE_COLOUR);
+    }
+
+    #[test]
+    fn face_colour_normal_mode_returns_card_face_colour_for_black_suit() {
+        let card = Card { id: 0, suit: Suit::Spades, rank: Rank::King, face_up: true };
+        assert_eq!(face_colour(&card, false), CARD_FACE_COLOUR);
+    }
+
+    #[test]
+    fn face_colour_color_blind_mode_gives_red_suits_a_different_tint() {
+        let red_card = Card { id: 0, suit: Suit::Diamonds, rank: Rank::Queen, face_up: true };
+        let cbm_colour = face_colour(&red_card, true);
+        assert_ne!(
+            cbm_colour, CARD_FACE_COLOUR,
+            "color-blind mode must tint red-suit cards differently from the standard face colour"
+        );
+    }
+
+    #[test]
+    fn face_colour_color_blind_mode_does_not_change_black_suits() {
+        let black_card = Card { id: 0, suit: Suit::Clubs, rank: Rank::Jack, face_up: true };
+        assert_eq!(
+            face_colour(&black_card, true),
+            CARD_FACE_COLOUR,
+            "color-blind mode must not alter black-suit card face colour"
+        );
+    }
+
+    // -----------------------------------------------------------------------
+    // label_visibility (pure)
+    // -----------------------------------------------------------------------
+
+    #[test]
+    fn label_visibility_face_up_is_inherited() {
+        let card = Card { id: 0, suit: Suit::Clubs, rank: Rank::Ace, face_up: true };
+        assert_eq!(label_visibility(&card), Visibility::Inherited);
+    }
+
+    #[test]
+    fn label_visibility_face_down_is_hidden() {
+        let card = Card { id: 0, suit: Suit::Clubs, rank: Rank::Ace, face_up: false };
+        assert_eq!(label_visibility(&card), Visibility::Hidden);
+    }
+
+    // -----------------------------------------------------------------------
+    // label_for — remaining ranks not yet covered
+    // -----------------------------------------------------------------------
+
+    #[test]
+    fn label_for_all_ranks_contain_suit_letter() {
+        let suits = [Suit::Clubs, Suit::Diamonds, Suit::Hearts, Suit::Spades];
+        let letters = ["C", "D", "H", "S"];
+        for (suit, letter) in suits.iter().zip(letters.iter()) {
+            let card = Card { id: 0, suit: *suit, rank: Rank::King, face_up: true };
+            assert!(
+                label_for(&card).ends_with(letter),
+                "label for {suit:?} must end with '{letter}'"
+            );
+        }
+    }
+
+    #[test]
+    fn label_for_face_cards_use_letter_prefix() {
+        let make = |rank| Card { id: 0, suit: Suit::Spades, rank, face_up: true };
+        assert!(label_for(&make(Rank::Jack)).starts_with('J'));
+        assert!(label_for(&make(Rank::Queen)).starts_with('Q'));
+        assert!(label_for(&make(Rank::King)).starts_with('K'));
+    }
+
+    #[test]
+    fn label_for_numeric_ranks_two_through_nine() {
+        let make = |rank| Card { id: 0, suit: Suit::Clubs, rank, face_up: true };
+        let expected = [
+            (Rank::Two,   "2C"),
+            (Rank::Three, "3C"),
+            (Rank::Four,  "4C"),
+            (Rank::Five,  "5C"),
+            (Rank::Six,   "6C"),
+            (Rank::Seven, "7C"),
+            (Rank::Eight, "8C"),
+            (Rank::Nine,  "9C"),
+        ];
+        for (rank, label) in expected {
+            assert_eq!(label_for(&make(rank)), label, "rank {rank:?}");
+        }
+    }
+
     #[test]
     fn facedown_cards_use_tighter_fan_than_uniform_faceup_fan() {
         let g = GameState::new(42, solitaire_core::game_state::DrawMode::DrawOne);

solitaire_engine/src/input_plugin.rs

@@ -43,6 +43,7 @@ use crate::pause_plugin::PausedResource;
 use crate::progress_plugin::ProgressResource;
 use crate::layout::{Layout, LayoutResource};
 use crate::resources::{DragState, GameStateResource, HintCycleIndex};
+use crate::selection_plugin::SelectionState;
 use crate::time_attack_plugin::TimeAttackResource;
 
 /// Z-depth used for cards while being dragged — above all resting cards.
@@ -144,6 +145,7 @@ fn handle_keyboard_core(
     mut confirm: ResMut<KeyboardConfirmState>,
     mut ev: CoreKeyboardMessages<'_>,
     mut time_attack: Option<ResMut<TimeAttackResource>>,
+    selection: Option<Res<SelectionState>>,
 ) {
     if paused.is_some_and(|p| p.0) {
         return;
@@ -224,7 +226,11 @@ fn handle_keyboard_core(
         }
     }
 
-    if keys.just_pressed(KeyCode::KeyD) || keys.just_pressed(KeyCode::Space) {
+    // Space draws only when no card is keyboard-selected; when a card IS selected,
+    // SelectionPlugin handles Space to execute the move.
+    let space_draws = keys.just_pressed(KeyCode::Space)
+        && selection.as_ref().is_none_or(|s| s.selected_pile.is_none());
+    if keys.just_pressed(KeyCode::KeyD) || space_draws {
         // Cancel any pending forfeit when the player takes another action.
         confirm.forfeit_countdown = 0.0;
         ev.draw.write(DrawRequestEvent);

solitaire_engine/src/pause_plugin.rs

@@ -23,6 +23,7 @@ use crate::events::StateChangedEvent;
 use crate::game_plugin::{GameOverScreen, GameStatePath};
 use crate::progress_plugin::ProgressResource;
 use crate::resources::{DragState, GameStateResource};
+use crate::selection_plugin::{SelectionKeySet, SelectionState};
 use crate::settings_plugin::{SettingsChangedEvent, SettingsResource, SettingsStoragePath};
 use crate::stats_plugin::StatsResource;
 
@@ -58,7 +59,15 @@ impl Plugin for PausePlugin {
         app.add_message::<SettingsChangedEvent>()
             .add_message::<StateChangedEvent>()
             .init_resource::<PausedResource>()
-            .add_systems(Update, (toggle_pause, handle_pause_draw_toggle));
+            .add_systems(
+                Update,
+                (
+                    // toggle_pause must see SelectionState *before* handle_selection_keys
+                    // clears it, so it can skip Escape when a card is selected.
+                    toggle_pause.before(SelectionKeySet),
+                    handle_pause_draw_toggle,
+                ),
+            );
     }
 }
 
@@ -76,10 +85,16 @@ fn toggle_pause(
     settings: Option<Res<SettingsResource>>,
     mut drag: Option<ResMut<DragState>>,
     mut changed: MessageWriter<StateChangedEvent>,
+    selection: Option<Res<SelectionState>>,
 ) {
     if !keys.just_pressed(KeyCode::Escape) {
         return;
     }
+    // If a card is currently selected, let SelectionPlugin handle this Escape
+    // (it will clear the selection). Pause must not also open in the same frame.
+    if selection.is_some_and(|s| s.selected_pile.is_some()) {
+        return;
+    }
     // If the game-over overlay is visible, let handle_game_over_input consume
     // the Escape key (to start a new game). Do not open the pause overlay.
     if !game_over_screens.is_empty() {
@@ -415,6 +430,16 @@ mod tests {
         );
     }
 
+    // -----------------------------------------------------------------------
+    // PausedResource default (pure)
+    // -----------------------------------------------------------------------
+
+    #[test]
+    fn paused_resource_default_is_unpaused() {
+        let p = PausedResource::default();
+        assert!(!p.0, "game must start unpaused");
+    }
+
     // -----------------------------------------------------------------------
     // draw_mode_label (pure function) — Task #64
     // -----------------------------------------------------------------------
@@ -429,6 +454,17 @@ mod tests {
         assert_eq!(draw_mode_label(DrawMode::DrawThree), "Draw 3");
     }
 
+    /// Both variants are covered so the match is exhaustive — this test would
+    /// fail to compile if a new DrawMode variant were added without updating
+    /// `draw_mode_label`.
+    #[test]
+    fn draw_mode_label_covers_all_variants() {
+        for mode in [DrawMode::DrawOne, DrawMode::DrawThree] {
+            let label = draw_mode_label(mode);
+            assert!(!label.is_empty(), "draw_mode_label must never return an empty string");
+        }
+    }
+
     // -----------------------------------------------------------------------
     // pause_draw_toggle_flips_draw_mode — Task #64
     // -----------------------------------------------------------------------

solitaire_engine/src/selection_plugin.rs

@@ -22,7 +22,7 @@ use solitaire_core::card::Suit;
 use solitaire_core::pile::PileType;
 
 use crate::card_plugin::CardEntity;
-use crate::events::{InfoToastEvent, MoveRequestEvent};
+use crate::events::{InfoToastEvent, MoveRequestEvent, StateChangedEvent};
 use crate::game_plugin::GameMutation;
 use crate::input_plugin::{best_destination, best_tableau_destination_for_stack};
 use crate::layout::LayoutResource;
@@ -42,6 +42,13 @@ pub struct SelectionState {
     pub selected_pile: Option<PileType>,
 }
 
+/// System set label for the key-handling system.
+///
+/// `PausePlugin` registers `toggle_pause` before this set so it can read
+/// [`SelectionState`] before `handle_selection_keys` clears it on Escape.
+#[derive(SystemSet, Debug, Clone, PartialEq, Eq, Hash)]
+pub struct SelectionKeySet;
+
 /// Marker component placed on the outline sprite used as the keyboard-selection
 /// highlight.
 ///
@@ -59,7 +66,10 @@ impl Plugin for SelectionPlugin {
             .add_systems(
                 Update,
                 (
-                    handle_selection_keys.before(GameMutation),
+                    handle_selection_keys
+                        .in_set(SelectionKeySet)
+                        .before(GameMutation),
+                    clear_selection_on_state_change.after(GameMutation),
                     update_selection_highlight.after(GameMutation),
                 ),
             );
@@ -329,6 +339,20 @@ fn try_foundation_dest(
     None
 }
 
+/// Clears the selection whenever the game state changes.
+///
+/// Without this, an undo or a rejected move could leave `selected_pile`
+/// pointing at a pile whose top card changed, causing the highlight to
+/// trail a different card than the player expects.
+fn clear_selection_on_state_change(
+    mut state_events: MessageReader<StateChangedEvent>,
+    mut selection: ResMut<SelectionState>,
+) {
+    if state_events.read().next().is_some() {
+        selection.selected_pile = None;
+    }
+}
+
 /// Maintains the `SelectionHighlight` outline sprite.
 ///
 /// When a pile is selected, a cyan sprite is placed at the selected card's