feat(engine): add Play-by-Seed dialog with solver preview

Adds a numeric-input modal (PlayBySeedPlugin) that lets the player type
a decimal seed and receive an instant solver-verified verdict before the
hand is dealt.  A new HomeMode::PlayBySeed card surfaces it in the home
overlay, matched by the StartPlayBySeedRequestEvent carrier.

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

solitaire_app/src/lib.rs

@@ -29,10 +29,11 @@ use solitaire_engine::{
     AudioPlugin, AutoCompletePlugin, CardAnimationPlugin, CardPlugin, ChallengePlugin,
     CursorPlugin, DailyChallengePlugin, DiagnosticsHudPlugin, FeedbackAnimPlugin, FontPlugin,
     GamePlugin, HelpPlugin, HomePlugin, HudPlugin, InputPlugin, LeaderboardPlugin,
-    OnboardingPlugin, PausePlugin, ProfilePlugin, ProgressPlugin, RadialMenuPlugin,
-    ReplayOverlayPlugin, ReplayPlaybackPlugin, SelectionPlugin, SettingsPlugin, SplashPlugin,
-    StatsPlugin, SyncPlugin, TablePlugin, ThemePlugin, ThemeRegistryPlugin, TimeAttackPlugin,
-    UiFocusPlugin, UiModalPlugin, UiTooltipPlugin, WeeklyGoalsPlugin, WinSummaryPlugin,
+    OnboardingPlugin, PausePlugin, PlayBySeedPlugin, ProfilePlugin, ProgressPlugin,
+    RadialMenuPlugin, ReplayOverlayPlugin, ReplayPlaybackPlugin, SelectionPlugin, SettingsPlugin,
+    SplashPlugin, StatsPlugin, SyncPlugin, TablePlugin, ThemePlugin, ThemeRegistryPlugin,
+    TimeAttackPlugin, UiFocusPlugin, UiModalPlugin, UiTooltipPlugin, WeeklyGoalsPlugin,
+    WinSummaryPlugin,
 };
 
 /// App entry point — builds and runs the Bevy app.
@@ -145,6 +146,13 @@ pub fn run() {
         .add_plugins(GamePlugin)
         .add_plugins(TablePlugin)
         .add_plugins(CardPlugin)
+        // Cursor-icon feedback is desktop-only; Android has no pointer cursor.
+        // The drop-target highlight systems (update_drop_highlights,
+        // update_drop_target_overlays) live in CursorPlugin but ARE useful
+        // on Android — they've been left running because their Bevy system
+        // params compile and function on Android; only the CursorIcon insert
+        // is inert. Gate the whole plugin if the cursor APIs ever cause
+        // Android linker issues; for now it's harmless to leave it registered.
         .add_plugins(CursorPlugin)
         .add_plugins(InputPlugin)
         .add_plugins(RadialMenuPlugin)
@@ -161,6 +169,7 @@ pub fn run() {
         .add_plugins(DailyChallengePlugin)
         .add_plugins(WeeklyGoalsPlugin)
         .add_plugins(ChallengePlugin)
+        .add_plugins(PlayBySeedPlugin)
         .add_plugins(TimeAttackPlugin)
         .add_plugins(HudPlugin)
         .add_plugins(HelpPlugin)

solitaire_engine/src/events.rs

@@ -172,6 +172,13 @@ pub struct StartTimeAttackRequestEvent;
 #[derive(Message, Debug, Clone, Copy, Default)]
 pub struct StartDailyChallengeRequestEvent;
 
+/// Request to open the Play-by-Seed dialog. Fired by the Home overlay
+/// "Play by Seed" mode card. The handler in `play_by_seed_plugin` spawns
+/// a numeric-input modal where the player types a decimal seed and
+/// optionally sees a solver-verified verdict before dealing.
+#[derive(Message, Debug, Clone, Copy, Default)]
+pub struct StartPlayBySeedRequestEvent;
+
 /// Request to toggle the Stats overlay. Fired by the HUD Menu-popover
 /// "Stats" row alongside the existing `S` accelerator.
 #[derive(Message, Debug, Clone, Copy, Default)]

solitaire_engine/src/home_plugin.rs

@@ -23,8 +23,8 @@ use crate::challenge_plugin::CHALLENGE_UNLOCK_LEVEL;
 use crate::daily_challenge_plugin::DailyChallengeResource;
 use crate::events::{
     InfoToastEvent, NewGameRequestEvent, StartChallengeRequestEvent,
-    StartDailyChallengeRequestEvent, StartTimeAttackRequestEvent, StartZenRequestEvent,
-    ToggleProfileRequestEvent,
+    StartDailyChallengeRequestEvent, StartPlayBySeedRequestEvent, StartTimeAttackRequestEvent,
+    StartZenRequestEvent, ToggleProfileRequestEvent,
 };
 use crate::font_plugin::FontResource;
 use crate::progress_plugin::ProgressResource;
@@ -96,6 +96,7 @@ enum HomeMode {
     Zen,
     Challenge,
     TimeAttack,
+    PlayBySeed,
 }
 
 impl HomeMode {
@@ -107,6 +108,7 @@ impl HomeMode {
             HomeMode::Zen => "Zen Mode",
             HomeMode::Challenge => "Challenge",
             HomeMode::TimeAttack => "Time Attack",
+            HomeMode::PlayBySeed => "Play by Seed",
         }
     }
 
@@ -118,6 +120,7 @@ impl HomeMode {
             HomeMode::Zen => "No timer, no score. Just the cards.",
             HomeMode::Challenge => "Hand-picked hard deals. No undo. Win to advance.",
             HomeMode::TimeAttack => "How many can you finish in ten minutes?",
+            HomeMode::PlayBySeed => "Enter any number to play a specific deal.",
         }
     }
 
@@ -150,6 +153,9 @@ impl HomeMode {
             // ships ▲ (up triangle) but evidently not the sideways
             // siblings.
             HomeMode::TimeAttack => "\u{2192}",
+            // Number sign — ASCII, universally available. Reads as
+            // "a specific number / seed ID".
+            HomeMode::PlayBySeed => "#",
         }
     }
 
@@ -162,6 +168,7 @@ impl HomeMode {
             HomeMode::Zen => "Z",
             HomeMode::Challenge => "X",
             HomeMode::TimeAttack => "T",
+            HomeMode::PlayBySeed => "6",
         }
     }
 
@@ -238,6 +245,7 @@ impl Plugin for HomePlugin {
             .add_message::<StartChallengeRequestEvent>()
             .add_message::<StartTimeAttackRequestEvent>()
             .add_message::<StartDailyChallengeRequestEvent>()
+            .add_message::<StartPlayBySeedRequestEvent>()
             .add_message::<InfoToastEvent>()
             .add_message::<ToggleProfileRequestEvent>()
             .add_message::<SettingsChangedEvent>()
@@ -423,6 +431,7 @@ fn handle_home_card_click(
     mut challenge: MessageWriter<StartChallengeRequestEvent>,
     mut time_attack: MessageWriter<StartTimeAttackRequestEvent>,
     mut daily: MessageWriter<StartDailyChallengeRequestEvent>,
+    mut play_by_seed: MessageWriter<StartPlayBySeedRequestEvent>,
     mut info_toast: MessageWriter<InfoToastEvent>,
 ) {
     let level = progress.as_ref().map_or(0, |p| p.0.level);
@@ -457,6 +466,9 @@ fn handle_home_card_click(
             HomeMode::TimeAttack => {
                 time_attack.write(StartTimeAttackRequestEvent);
             }
+            HomeMode::PlayBySeed => {
+                play_by_seed.write(StartPlayBySeedRequestEvent);
+            }
         }
 
         // Close the modal after dispatching the launch event.
@@ -619,6 +631,7 @@ fn digit_to_home_mode(key: KeyCode) -> Option<HomeMode> {
         KeyCode::Digit3 => Some(HomeMode::Zen),
         KeyCode::Digit4 => Some(HomeMode::Challenge),
         KeyCode::Digit5 => Some(HomeMode::TimeAttack),
+        KeyCode::Digit6 => Some(HomeMode::PlayBySeed),
         _ => None,
     }
 }
@@ -646,6 +659,7 @@ fn handle_home_digit_keys(
     mut challenge: MessageWriter<StartChallengeRequestEvent>,
     mut time_attack: MessageWriter<StartTimeAttackRequestEvent>,
     mut daily: MessageWriter<StartDailyChallengeRequestEvent>,
+    mut play_by_seed: MessageWriter<StartPlayBySeedRequestEvent>,
 ) {
     // Modal-scoped: do nothing when the Mode Launcher isn't open.
     if screens.is_empty() {
@@ -658,6 +672,7 @@ fn handle_home_digit_keys(
         KeyCode::Digit3,
         KeyCode::Digit4,
         KeyCode::Digit5,
+        KeyCode::Digit6,
     ]
     .into_iter()
     .find(|k| keys.just_pressed(*k))
@@ -687,6 +702,9 @@ fn handle_home_digit_keys(
         HomeMode::TimeAttack => {
             time_attack.write(StartTimeAttackRequestEvent);
         }
+        HomeMode::PlayBySeed => {
+            play_by_seed.write(StartPlayBySeedRequestEvent);
+        }
     }
 
     // Close the modal after dispatching the launch event — same shape as
@@ -784,6 +802,7 @@ fn spawn_home_screen(commands: &mut Commands, ctx: HomeContext<'_>) {
                     HomeMode::Zen,
                     HomeMode::Challenge,
                     HomeMode::TimeAttack,
+                    HomeMode::PlayBySeed,
                 ] {
                     spawn_mode_card(grid, mode, &ctx);
                 }
@@ -999,6 +1018,7 @@ fn home_mode_focus_order(mode: HomeMode) -> i32 {
         HomeMode::Zen => 2,
         HomeMode::Challenge => 3,
         HomeMode::TimeAttack => 4,
+        HomeMode::PlayBySeed => 5,
     }
 }
 
@@ -1402,13 +1422,14 @@ mod tests {
             HomeMode::Zen,
             HomeMode::Challenge,
             HomeMode::TimeAttack,
+            HomeMode::PlayBySeed,
         ] {
             assert!(
                 modes.contains(&expected),
                 "missing card for {expected:?}; found {modes:?}"
             );
         }
-        assert_eq!(modes.len(), 5, "exactly five cards expected");
+        assert_eq!(modes.len(), 6, "exactly six cards expected");
     }
 
     #[test]
@@ -1600,7 +1621,7 @@ mod tests {
             .map(|(c, f)| (c.0, *f))
             .collect();
 
-        assert_eq!(cards.len(), 5, "all five cards must carry a Focusable");
+        assert_eq!(cards.len(), 6, "all six cards must carry a Focusable");
         for (mode, focusable) in &cards {
             assert_eq!(
                 focusable.group,
@@ -1626,7 +1647,7 @@ mod tests {
 
         for (mode, disabled) in states {
             match mode {
-                HomeMode::Classic | HomeMode::Daily => assert!(
+                HomeMode::Classic | HomeMode::Daily | HomeMode::PlayBySeed => assert!(
                     !disabled,
                     "{mode:?} must not be Disabled at level 0 (it's never locked)"
                 ),

solitaire_engine/src/lib.rs

@@ -24,6 +24,7 @@ pub mod layout;
 pub mod onboarding_plugin;
 pub mod pause_plugin;
 pub mod pending_hint;
+pub mod play_by_seed_plugin;
 pub mod profile_plugin;
 pub mod radial_menu;
 pub mod replay_overlay;
@@ -92,11 +93,12 @@ pub use events::{
     ForfeitEvent, ForfeitRequestEvent, FoundationCompletedEvent, GameWonEvent, HelpRequestEvent,
     HintVisualEvent, InfoToastEvent, ManualSyncRequestEvent, MoveRejectedEvent, MoveRequestEvent,
     NewGameRequestEvent, PauseRequestEvent, StartChallengeRequestEvent,
-    StartDailyChallengeRequestEvent, StartTimeAttackRequestEvent, StartZenRequestEvent,
-    StateChangedEvent, SyncCompleteEvent, ToggleAchievementsRequestEvent,
+    StartDailyChallengeRequestEvent, StartPlayBySeedRequestEvent, StartTimeAttackRequestEvent,
+    StartZenRequestEvent, StateChangedEvent, SyncCompleteEvent, ToggleAchievementsRequestEvent,
     ToggleLeaderboardRequestEvent, ToggleProfileRequestEvent, ToggleSettingsRequestEvent,
     ToggleStatsRequestEvent, UndoRequestEvent, WinStreakMilestoneEvent, XpAwardedEvent,
 };
+pub use play_by_seed_plugin::{PlayBySeedPlugin, PlayBySeedScreen};
 pub use game_plugin::{
     ConfirmNewGameScreen, GameMutation, GameOverScreen, GamePlugin, GameStatePath, RecordingReplay,
     ReplayPath,

solitaire_engine/src/play_by_seed_plugin.rs

@@ -0,0 +1,663 @@
+//! Play-by-Seed dialog: lets the player type a decimal seed number and start
+//! a Classic game with that exact deal. A live solver-verification badge
+//! updates asynchronously after a short typing debounce so the player knows
+//! whether the deal is provably winnable before committing.
+//!
+//! # Flow
+//!
+//! 1. `HomePlugin` fires [`StartPlayBySeedRequestEvent`] when the "Play by
+//!    Seed" card is clicked (or `6` is pressed in the Mode Launcher).
+//! 2. `handle_open_dialog` reads the event and spawns the seed-input modal.
+//! 3. `handle_text_input` appends decimal digits / handles Backspace while
+//!    the modal is open, updating [`SeedInputBuffer`] each frame.
+//! 4. `tick_debounce_and_spawn_solver_task` waits for 12 frames (~200 ms at
+//!    60 Hz) of no input before spawning a [`try_solve`] task on
+//!    [`AsyncComputeTaskPool`]. Any fresh keypress drops the in-flight task
+//!    by resetting the resource.
+//! 5. `poll_solver_task` polls the in-flight task each frame and updates the
+//!    [`SolverVerdictBadge`] text node with the verdict.
+//! 6. `handle_confirm` fires [`NewGameRequestEvent`] with the parsed seed and
+//!    despawns the dialog on Play click or `Enter`.
+//! 7. `handle_cancel` despawns the dialog on Cancel click or `Escape`.
+
+use bevy::input::ButtonInput;
+use bevy::prelude::*;
+use bevy::tasks::{futures_lite::future, AsyncComputeTaskPool, Task};
+use solitaire_core::game_state::DrawMode;
+use solitaire_core::solver::{try_solve, SolverConfig, SolverResult};
+
+use crate::events::{NewGameRequestEvent, StartPlayBySeedRequestEvent};
+use crate::font_plugin::FontResource;
+use crate::game_plugin::GameMutation;
+use crate::settings_plugin::SettingsResource;
+use crate::ui_modal::{
+    spawn_modal, spawn_modal_actions, spawn_modal_body_text, spawn_modal_button, spawn_modal_header,
+    ButtonVariant, ScrimDismissible,
+};
+use crate::ui_theme::{
+    ACCENT_PRIMARY, BG_ELEVATED_PRESSED, BORDER_SUBTLE, HighContrastBorder, RADIUS_MD,
+    TEXT_DISABLED, TEXT_PRIMARY, TEXT_SECONDARY, TYPE_BODY_LG, VAL_SPACE_2, VAL_SPACE_3,
+    Z_MODAL_PANEL,
+};
+
+// ---------------------------------------------------------------------------
+// Components and resources
+// ---------------------------------------------------------------------------
+
+/// Marker on the seed-input modal scrim (the despawn root).
+#[derive(Component, Debug)]
+pub struct PlayBySeedScreen;
+
+/// Holds the decimal digit string the player is typing and a frame counter
+/// used to debounce solver task spawning.
+#[derive(Component, Debug, Default)]
+struct SeedInputBuffer {
+    /// Raw decimal digit string. Never longer than 20 chars (u64::MAX is 20
+    /// decimal digits). Empty means "no seed entered".
+    text: String,
+    /// Frames elapsed since the last keystroke. The solver task is spawned
+    /// once this crosses [`DEBOUNCE_FRAMES`] and the buffer is non-empty.
+    frames_since_change: u32,
+}
+
+/// Marker on the text node that renders the solver verdict caption.
+#[derive(Component, Debug)]
+struct SolverVerdictBadge;
+
+/// Marker on the Play (confirm) button so `handle_confirm` can find it.
+#[derive(Component, Debug)]
+struct PlayBySeedConfirmButton;
+
+/// Marker on the Cancel button.
+#[derive(Component, Debug)]
+struct PlayBySeedCancelButton;
+
+/// Marker on the input-field text node so `handle_text_input` can update
+/// it without a separate query for the buffer entity.
+#[derive(Component, Debug)]
+struct SeedInputDisplay;
+
+/// In-flight async solver verification task. At most one is live at a time —
+/// a fresh keypress resets this resource (dropping the previous `Task<_>`)
+/// before spawning the next one.
+#[derive(Resource, Default)]
+struct PendingVerification {
+    seed: Option<u64>,
+    handle: Option<Task<SolverResult>>,
+}
+
+// ---------------------------------------------------------------------------
+// Constants
+// ---------------------------------------------------------------------------
+
+/// Frames of no-keypress activity before the solver task is spawned.
+/// 12 frames ≈ 200 ms at 60 Hz — long enough to avoid thrashing on fast
+/// typists but short enough to feel responsive.
+const DEBOUNCE_FRAMES: u32 = 12;
+
+/// Maximum decimal digits accepted. 20 covers all of u64::MAX (18,446,744,073,709,551,615).
+const MAX_SEED_DIGITS: usize = 20;
+
+// ---------------------------------------------------------------------------
+// Plugin
+// ---------------------------------------------------------------------------
+
+/// Registers all play-by-seed systems and resources.
+pub struct PlayBySeedPlugin;
+
+impl Plugin for PlayBySeedPlugin {
+    fn build(&self, app: &mut App) {
+        app.init_resource::<PendingVerification>()
+            .add_message::<StartPlayBySeedRequestEvent>()
+            .add_message::<NewGameRequestEvent>()
+            .add_systems(
+                Update,
+                (
+                    handle_open_dialog,
+                    handle_text_input,
+                    tick_debounce_and_spawn_solver_task,
+                    poll_solver_task,
+                    handle_confirm,
+                    handle_cancel,
+                )
+                    .chain()
+                    // Fire before GameMutation so `handle_confirm`'s
+                    // NewGameRequestEvent is processed on the same frame.
+                    .before(GameMutation),
+            );
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Systems
+// ---------------------------------------------------------------------------
+
+/// Spawns the seed-input dialog when `StartPlayBySeedRequestEvent` fires.
+fn handle_open_dialog(
+    mut commands: Commands,
+    mut requests: MessageReader<StartPlayBySeedRequestEvent>,
+    font_res: Option<Res<FontResource>>,
+    existing: Query<(), With<PlayBySeedScreen>>,
+) {
+    if requests.read().count() == 0 {
+        return;
+    }
+    // Guard against double-spawn (e.g. two events in one frame).
+    if !existing.is_empty() {
+        return;
+    }
+    let font = font_res.as_deref();
+    let font_handle = font.map(|f| f.0.clone()).unwrap_or_default();
+
+    let scrim = spawn_modal(&mut commands, PlayBySeedScreen, Z_MODAL_PANEL, |card| {
+        spawn_modal_header(card, "Play by Seed", font);
+        spawn_modal_body_text(
+            card,
+            "Enter a number to play that specific deal.",
+            TEXT_SECONDARY,
+            font,
+        );
+
+        // Input field — a bordered box that shows the typed digits.
+        card.spawn((
+            Node {
+                width: Val::Percent(100.0),
+                padding: UiRect::axes(VAL_SPACE_3, VAL_SPACE_2),
+                border: UiRect::all(Val::Px(1.0)),
+                border_radius: BorderRadius::all(Val::Px(RADIUS_MD)),
+                ..default()
+            },
+            BackgroundColor(BG_ELEVATED_PRESSED),
+            BorderColor::all(BORDER_SUBTLE),
+            HighContrastBorder::with_default(BORDER_SUBTLE),
+            SeedInputBuffer::default(),
+        ))
+        .with_children(|field| {
+            field.spawn((
+                SeedInputDisplay,
+                Text::new(""),
+                TextFont {
+                    font: font_handle.clone(),
+                    font_size: TYPE_BODY_LG,
+                    ..default()
+                },
+                TextColor(TEXT_DISABLED),
+            ));
+        });
+
+        // Solver verdict badge — updates as solver runs.
+        card.spawn((
+            SolverVerdictBadge,
+            Text::new("Type a number"),
+            TextFont {
+                font: font_handle,
+                font_size: TYPE_BODY_LG,
+                ..default()
+            },
+            TextColor(TEXT_SECONDARY),
+        ));
+
+        spawn_modal_actions(card, |row| {
+            spawn_modal_button(
+                row,
+                PlayBySeedCancelButton,
+                "Cancel",
+                Some("Esc"),
+                ButtonVariant::Secondary,
+                font,
+            );
+            spawn_modal_button(
+                row,
+                PlayBySeedConfirmButton,
+                "Play",
+                Some("Enter"),
+                ButtonVariant::Primary,
+                font,
+            );
+        });
+    });
+
+    // Play-by-Seed is read-only input — opt into click-outside-to-dismiss.
+    commands.entity(scrim).insert(ScrimDismissible);
+}
+
+/// Appends decimal digits and handles Backspace while the dialog is open.
+fn handle_text_input(
+    keys: Res<ButtonInput<KeyCode>>,
+    screen: Query<(), With<PlayBySeedScreen>>,
+    mut buffers: Query<&mut SeedInputBuffer>,
+    mut displays: Query<(&mut Text, &mut TextColor), With<SeedInputDisplay>>,
+    mut pending: ResMut<PendingVerification>,
+) {
+    if screen.is_empty() {
+        return;
+    }
+    let Ok(mut buf) = buffers.single_mut() else {
+        return;
+    };
+
+    let digit_keys = [
+        (KeyCode::Digit0, '0'),
+        (KeyCode::Digit1, '1'),
+        (KeyCode::Digit2, '2'),
+        (KeyCode::Digit3, '3'),
+        (KeyCode::Digit4, '4'),
+        (KeyCode::Digit5, '5'),
+        (KeyCode::Digit6, '6'),
+        (KeyCode::Digit7, '7'),
+        (KeyCode::Digit8, '8'),
+        (KeyCode::Digit9, '9'),
+        (KeyCode::Numpad0, '0'),
+        (KeyCode::Numpad1, '1'),
+        (KeyCode::Numpad2, '2'),
+        (KeyCode::Numpad3, '3'),
+        (KeyCode::Numpad4, '4'),
+        (KeyCode::Numpad5, '5'),
+        (KeyCode::Numpad6, '6'),
+        (KeyCode::Numpad7, '7'),
+        (KeyCode::Numpad8, '8'),
+        (KeyCode::Numpad9, '9'),
+    ];
+
+    let mut changed = false;
+
+    for (key, ch) in digit_keys {
+        if keys.just_pressed(key) && buf.text.len() < MAX_SEED_DIGITS {
+            // Drop a leading zero unless the buffer is empty (prevents "007").
+            if ch == '0' && buf.text.is_empty() {
+                continue;
+            }
+            buf.text.push(ch);
+            changed = true;
+        }
+    }
+
+    if keys.just_pressed(KeyCode::Backspace) && !buf.text.is_empty() {
+        buf.text.pop();
+        changed = true;
+    }
+
+    if changed {
+        buf.frames_since_change = 0;
+        // Cancel any in-flight solver task — its seed is now stale.
+        *pending = PendingVerification::default();
+
+        // Update the display node.
+        if let Ok((mut text, mut color)) = displays.single_mut() {
+            if buf.text.is_empty() {
+                text.0 = String::new();
+                color.0 = TEXT_DISABLED;
+            } else {
+                text.0 = buf.text.clone();
+                color.0 = TEXT_PRIMARY;
+            }
+        }
+    }
+}
+
+/// Increments the debounce counter each frame and spawns the solver task
+/// once the counter passes [`DEBOUNCE_FRAMES`] and the buffer holds a
+/// valid u64.
+fn tick_debounce_and_spawn_solver_task(
+    screen: Query<(), With<PlayBySeedScreen>>,
+    mut buffers: Query<&mut SeedInputBuffer>,
+    mut pending: ResMut<PendingVerification>,
+    mut badges: Query<(&mut Text, &mut TextColor), With<SolverVerdictBadge>>,
+    settings: Option<Res<SettingsResource>>,
+) {
+    if screen.is_empty() {
+        return;
+    }
+    let Ok(mut buf) = buffers.single_mut() else {
+        return;
+    };
+
+    // Always update the badge when the buffer is empty.
+    if buf.text.is_empty() {
+        if let Ok((mut text, mut color)) = badges.single_mut() {
+            text.0 = "Type a number".to_string();
+            color.0 = TEXT_SECONDARY;
+        }
+        return;
+    }
+
+    // Don't spawn if a task is already running for this seed.
+    let parsed = buf.text.parse::<u64>().ok();
+    if pending.handle.is_some() && pending.seed == parsed {
+        return;
+    }
+
+    buf.frames_since_change = buf.frames_since_change.saturating_add(1);
+    if buf.frames_since_change < DEBOUNCE_FRAMES {
+        return;
+    }
+
+    let Some(seed) = parsed else {
+        return;
+    };
+
+    let draw_mode = settings
+        .as_ref()
+        .map_or(DrawMode::DrawOne, |s| s.0.draw_mode.clone());
+    let cfg = SolverConfig::default();
+    let task = AsyncComputeTaskPool::get()
+        .spawn(async move { try_solve(seed, draw_mode, &cfg) });
+
+    pending.seed = Some(seed);
+    pending.handle = Some(task);
+
+    if let Ok((mut text, mut color)) = badges.single_mut() {
+        text.0 = "Verifying\u{2026}".to_string();
+        color.0 = TEXT_SECONDARY;
+    }
+}
+
+/// Polls the in-flight solver task and updates the verdict badge on completion.
+fn poll_solver_task(
+    mut pending: ResMut<PendingVerification>,
+    mut badges: Query<(&mut Text, &mut TextColor), With<SolverVerdictBadge>>,
+) {
+    let Some(handle) = pending.handle.as_mut() else {
+        return;
+    };
+    let Some(result) = future::block_on(future::poll_once(handle)) else {
+        return;
+    };
+    pending.handle = None;
+
+    let Ok((mut text, mut color)) = badges.single_mut() else {
+        return;
+    };
+    match result {
+        SolverResult::Winnable => {
+            text.0 = "\u{2713} Provably winnable".to_string();
+            color.0 = ACCENT_PRIMARY;
+        }
+        SolverResult::Inconclusive => {
+            text.0 = "? Likely winnable (search timed out)".to_string();
+            color.0 = TEXT_SECONDARY;
+        }
+        SolverResult::Unwinnable => {
+            text.0 = "\u{2717} Provably unwinnable".to_string();
+            color.0 = TEXT_DISABLED;
+        }
+    }
+}
+
+/// Fires [`NewGameRequestEvent`] with the parsed seed when Play is clicked
+/// or `Enter` is pressed, then despawns the dialog. Does nothing when the
+/// buffer is empty.
+fn handle_confirm(
+    mut commands: Commands,
+    keys: Res<ButtonInput<KeyCode>>,
+    buttons: Query<&Interaction, (With<PlayBySeedConfirmButton>, Changed<Interaction>)>,
+    buffers: Query<&SeedInputBuffer>,
+    screen: Query<Entity, With<PlayBySeedScreen>>,
+    mut new_game: MessageWriter<NewGameRequestEvent>,
+) {
+    if screen.is_empty() {
+        return;
+    }
+
+    let click = buttons.iter().any(|i| *i == Interaction::Pressed);
+    let enter = keys.just_pressed(KeyCode::Enter) || keys.just_pressed(KeyCode::NumpadEnter);
+    if !click && !enter {
+        return;
+    }
+
+    let Ok(buf) = buffers.single() else { return };
+    let Ok(seed) = buf.text.parse::<u64>() else { return };
+
+    new_game.write(NewGameRequestEvent {
+        seed: Some(seed),
+        mode: None,
+        confirmed: false,
+    });
+
+    for entity in &screen {
+        commands.entity(entity).despawn();
+    }
+}
+
+/// Despawns the dialog on Cancel click or `Escape`.
+fn handle_cancel(
+    mut commands: Commands,
+    keys: Res<ButtonInput<KeyCode>>,
+    buttons: Query<&Interaction, (With<PlayBySeedCancelButton>, Changed<Interaction>)>,
+    screen: Query<Entity, With<PlayBySeedScreen>>,
+    other_scrims: Query<(), (With<crate::ui_modal::ModalScrim>, Without<PlayBySeedScreen>)>,
+) {
+    if screen.is_empty() {
+        return;
+    }
+
+    let click = buttons.iter().any(|i| *i == Interaction::Pressed);
+    // Esc only closes this dialog when it is the topmost modal.
+    let esc = keys.just_pressed(KeyCode::Escape) && other_scrims.is_empty();
+    if !click && !esc {
+        return;
+    }
+
+    for entity in &screen {
+        commands.entity(entity).despawn();
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::game_plugin::GamePlugin;
+    use crate::table_plugin::TablePlugin;
+
+    fn headless_app() -> App {
+        let mut app = App::new();
+        app.add_plugins(MinimalPlugins)
+            .add_plugins(GamePlugin)
+            .add_plugins(TablePlugin)
+            .add_plugins(PlayBySeedPlugin);
+        app.init_resource::<ButtonInput<KeyCode>>();
+        app.update();
+        app
+    }
+
+    fn open_dialog(app: &mut App) {
+        app.world_mut()
+            .write_message(StartPlayBySeedRequestEvent);
+        app.update();
+    }
+
+    fn press_key(app: &mut App, key: KeyCode) {
+        app.world_mut()
+            .resource_mut::<ButtonInput<KeyCode>>()
+            .press(key);
+        app.update();
+        // Simulate what Bevy's PreUpdate input system does: flush just_pressed /
+        // just_released so stale key state doesn't bleed into the next frame.
+        let mut input = app.world_mut().resource_mut::<ButtonInput<KeyCode>>();
+        input.release(key);
+        input.clear();
+    }
+
+    fn dialog_present(app: &mut App) -> bool {
+        app.world_mut()
+            .query::<&PlayBySeedScreen>()
+            .iter(app.world())
+            .next()
+            .is_some()
+    }
+
+    fn read_buffer_text(app: &mut App) -> String {
+        let mut q = app.world_mut().query::<&SeedInputBuffer>();
+        q.iter(app.world())
+            .next()
+            .map(|b| b.text.clone())
+            .unwrap_or_default()
+    }
+
+    #[test]
+    fn dialog_spawns_on_request() {
+        let mut app = headless_app();
+        assert!(!dialog_present(&mut app));
+        open_dialog(&mut app);
+        assert!(dialog_present(&mut app));
+    }
+
+    #[test]
+    fn digit_keys_append_to_buffer() {
+        let mut app = headless_app();
+        open_dialog(&mut app);
+
+        press_key(&mut app, KeyCode::Digit4);
+        press_key(&mut app, KeyCode::Digit2);
+
+        assert_eq!(read_buffer_text(&mut app), "42");
+    }
+
+    #[test]
+    fn backspace_removes_last_char() {
+        let mut app = headless_app();
+        open_dialog(&mut app);
+
+        press_key(&mut app, KeyCode::Digit4);
+        press_key(&mut app, KeyCode::Digit2);
+        press_key(&mut app, KeyCode::Backspace);
+
+        assert_eq!(read_buffer_text(&mut app), "4");
+    }
+
+    #[test]
+    fn confirm_does_nothing_when_buffer_is_empty() {
+        let mut app = headless_app();
+        open_dialog(&mut app);
+
+        // Simulate Enter with empty buffer.
+        app.world_mut()
+            .resource_mut::<ButtonInput<KeyCode>>()
+            .press(KeyCode::Enter);
+        app.update();
+
+        let msgs = app.world().resource::<Messages<NewGameRequestEvent>>();
+        let mut cursor = msgs.get_cursor();
+        assert!(cursor.read(msgs).next().is_none(), "no NewGameRequestEvent when buffer empty");
+        // Dialog should still be open.
+        assert!(dialog_present(&mut app));
+    }
+
+    #[test]
+    fn confirm_writes_new_game_request_with_parsed_seed() {
+        let mut app = headless_app();
+        open_dialog(&mut app);
+
+        press_key(&mut app, KeyCode::Digit4);
+        press_key(&mut app, KeyCode::Digit2);
+
+        app.world_mut()
+            .resource_mut::<ButtonInput<KeyCode>>()
+            .press(KeyCode::Enter);
+        app.update();
+
+        let msgs = app.world().resource::<Messages<NewGameRequestEvent>>();
+        let mut cursor = msgs.get_cursor();
+        let fired: Vec<_> = cursor.read(msgs).copied().collect();
+        assert_eq!(fired.len(), 1);
+        assert_eq!(fired[0].seed, Some(42));
+        assert_eq!(fired[0].mode, None);
+        assert!(!fired[0].confirmed);
+
+        // Dialog should be gone.
+        assert!(!dialog_present(&mut app));
+    }
+
+    #[test]
+    fn cancel_despawns_dialog_without_new_game_request() {
+        let mut app = headless_app();
+        open_dialog(&mut app);
+
+        press_key(&mut app, KeyCode::Escape);
+
+        assert!(!dialog_present(&mut app));
+
+        let msgs = app.world().resource::<Messages<NewGameRequestEvent>>();
+        let mut cursor = msgs.get_cursor();
+        assert!(cursor.read(msgs).next().is_none());
+    }
+
+    #[test]
+    fn solver_task_spawns_after_debounce_window() {
+        let mut app = headless_app();
+        open_dialog(&mut app);
+
+        press_key(&mut app, KeyCode::Digit4);
+        press_key(&mut app, KeyCode::Digit2);
+
+        // Debounce window — no task yet.
+        for _ in 0..DEBOUNCE_FRAMES {
+            app.update();
+        }
+
+        let pending = app.world().resource::<PendingVerification>();
+        assert!(pending.handle.is_some(), "solver task should have been spawned after debounce");
+        assert_eq!(pending.seed, Some(42));
+    }
+
+    #[test]
+    fn keypress_mid_flight_cancels_previous_solver_task() {
+        let mut app = headless_app();
+        open_dialog(&mut app);
+
+        press_key(&mut app, KeyCode::Digit4);
+        press_key(&mut app, KeyCode::Digit2);
+
+        // Let the debounce fire.
+        for _ in 0..DEBOUNCE_FRAMES {
+            app.update();
+        }
+        assert!(app.world().resource::<PendingVerification>().handle.is_some());
+
+        // New keypress should cancel the in-flight task.
+        press_key(&mut app, KeyCode::Digit3);
+        assert!(app.world().resource::<PendingVerification>().handle.is_none());
+        assert_eq!(app.world().resource::<PendingVerification>().seed, None);
+    }
+
+    #[test]
+    fn solver_task_completes_and_updates_badge() {
+        use std::time::Instant;
+
+        let mut app = headless_app();
+        open_dialog(&mut app);
+
+        // Seed 42 — solver will return some verdict.
+        press_key(&mut app, KeyCode::Digit4);
+        press_key(&mut app, KeyCode::Digit2);
+
+        // Wait for the debounce to spawn the task.
+        for _ in 0..DEBOUNCE_FRAMES {
+            app.update();
+        }
+
+        // Poll until the solver task resolves (cap at 15 s wall-clock).
+        let deadline = Instant::now() + std::time::Duration::from_secs(15);
+        while app.world().resource::<PendingVerification>().handle.is_some()
+            && Instant::now() < deadline
+        {
+            app.update();
+            std::thread::yield_now();
+        }
+
+        // Badge text should no longer read "Verifying…".
+        let badge_text = app
+            .world_mut()
+            .query::<(&Text, &SolverVerdictBadge)>()
+            .iter(app.world())
+            .next()
+            .map(|(t, _)| t.0.clone())
+            .unwrap_or_default();
+        assert_ne!(badge_text, "Verifying\u{2026}", "badge should have resolved to a verdict");
+        assert_ne!(badge_text, "Type a number", "badge should show verdict, not idle state");
+    }
+}