feat(settings,engine): replay-playback rate slider in Settings → Gameplay

The replay overlay's per-move tick rate has been hardcoded at
REPLAY_MOVE_INTERVAL_SECS = 0.45 s/move since the in-engine
playback shipped. Power users want to scrub faster through older
wins. Adds a Settings slider that tunes the interval 0.10–1.00 s in
0.05 s steps; default 0.45 s preserves existing feel.

Settings.replay_move_interval_secs uses #[serde(default)] so legacy
files load to 0.45. sanitized() clamps out-of-range values.
tick_replay_playback now reads SettingsResource per frame and falls
back to the constant when the resource is absent (test fixtures).
The slider takes effect on the very next playback tick — no need to
restart playback.

Mirrors the existing tooltip-delay slider exactly: SettingsButton::
ReplayMoveIntervalUp/Down variants, the same `slider_row` pattern,
the same per-tick repaint system shape.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

solitaire_data/src/lib.rs

@@ -141,7 +141,8 @@ pub use challenge::{challenge_count, challenge_seed_for, CHALLENGE_SEEDS};
 pub mod settings;
 pub use settings::{
     load_settings_from, save_settings_to, settings_file_path, AnimSpeed, Settings, SyncBackend,
-    Theme, WindowGeometry, SOLVER_DEAL_RETRY_CAP, TIME_BONUS_MULTIPLIER_MAX,
+    Theme, WindowGeometry, REPLAY_MOVE_INTERVAL_MAX_SECS, REPLAY_MOVE_INTERVAL_MIN_SECS,
+    REPLAY_MOVE_INTERVAL_STEP_SECS, SOLVER_DEAL_RETRY_CAP, TIME_BONUS_MULTIPLIER_MAX,
     TIME_BONUS_MULTIPLIER_MIN, TIME_BONUS_MULTIPLIER_STEP, TOOLTIP_DELAY_MAX_SECS,
     TOOLTIP_DELAY_MIN_SECS, TOOLTIP_DELAY_STEP_SECS,
 };

solitaire_data/src/settings.rs

@@ -181,6 +181,17 @@ pub struct Settings {
     /// solver retry loop — see `solitaire_engine::handle_new_game`.
     #[serde(default)]
     pub winnable_deals_only: bool,
+    /// Per-move duration during replay playback, in seconds. Range
+    /// `[REPLAY_MOVE_INTERVAL_MIN_SECS, REPLAY_MOVE_INTERVAL_MAX_SECS]`;
+    /// default mirrors `solitaire_engine::replay_playback::REPLAY_MOVE_INTERVAL_SECS`
+    /// (0.45 s/move) so existing playback behaviour is unchanged for
+    /// players who never touch the slider. Smaller values scrub
+    /// faster through the recorded move list. Older `settings.json`
+    /// files written before this field existed deserialize cleanly to
+    /// the default via
+    /// `#[serde(default = "default_replay_move_interval_secs")]`.
+    #[serde(default = "default_replay_move_interval_secs")]
+    pub replay_move_interval_secs: f32,
 }
 
 fn default_draw_mode() -> DrawMode {
@@ -238,6 +249,33 @@ fn default_time_bonus_multiplier() -> f32 {
     1.0
 }
 
+/// Default per-move duration during replay playback, in seconds.
+/// Mirrors `solitaire_engine::replay_playback::REPLAY_MOVE_INTERVAL_SECS`
+/// so legacy `settings.json` files load to the existing baseline and
+/// playback feels identical for players who never touch the slider.
+/// The constant is duplicated across the data and engine crates
+/// because `solitaire_data` cannot depend on the engine crate — keep
+/// the two values in sync when adjusting either.
+fn default_replay_move_interval_secs() -> f32 {
+    0.45
+}
+
+/// Lower bound of the player-tunable replay-playback per-move interval,
+/// in seconds. Below this the cards barely register visually before
+/// the next move fires; the cap keeps the playback legible.
+pub const REPLAY_MOVE_INTERVAL_MIN_SECS: f32 = 0.10;
+
+/// Upper bound of the player-tunable replay-playback per-move interval,
+/// in seconds. One second per move is a comfortable upper limit for
+/// players who want to study a recorded game frame by frame.
+pub const REPLAY_MOVE_INTERVAL_MAX_SECS: f32 = 1.00;
+
+/// Increment applied by the replay-playback decrement / increment
+/// buttons. 0.05 s gives 19 stops between MIN and MAX — fine-grained
+/// enough to land on any "round" speed (0.10 s, 0.25 s, 0.45 s, etc.)
+/// without making the slider feel stuck on the same value.
+pub const REPLAY_MOVE_INTERVAL_STEP_SECS: f32 = 0.05;
+
 /// Maximum number of seed retries [`solitaire_engine::handle_new_game`]
 /// is willing to attempt before giving up and accepting the latest
 /// candidate seed when [`Settings::winnable_deals_only`] is on. If
@@ -268,14 +306,16 @@ impl Default for Settings {
             tooltip_delay_secs: default_tooltip_delay(),
             time_bonus_multiplier: default_time_bonus_multiplier(),
             winnable_deals_only: false,
+            replay_move_interval_secs: default_replay_move_interval_secs(),
         }
     }
 }
 
 impl Settings {
-    /// Clamps `sfx_volume`, `music_volume`, `tooltip_delay_secs`, and
-    /// `time_bonus_multiplier` into their respective ranges after
-    /// deserialization or hand-editing of `settings.json`.
+    /// Clamps `sfx_volume`, `music_volume`, `tooltip_delay_secs`,
+    /// `time_bonus_multiplier`, and `replay_move_interval_secs` into
+    /// their respective ranges after deserialization or hand-editing of
+    /// `settings.json`.
     pub fn sanitized(self) -> Self {
         Self {
             sfx_volume: self.sfx_volume.clamp(0.0, 1.0),
@@ -286,6 +326,9 @@ impl Settings {
             time_bonus_multiplier: self
                 .time_bonus_multiplier
                 .clamp(TIME_BONUS_MULTIPLIER_MIN, TIME_BONUS_MULTIPLIER_MAX),
+            replay_move_interval_secs: self
+                .replay_move_interval_secs
+                .clamp(REPLAY_MOVE_INTERVAL_MIN_SECS, REPLAY_MOVE_INTERVAL_MAX_SECS),
             ..self
         }
     }
@@ -324,6 +367,21 @@ impl Settings {
         self.time_bonus_multiplier = (raw * 10.0).round() / 10.0;
         self.time_bonus_multiplier
     }
+
+    /// Adjust the replay-playback per-move interval by `delta`
+    /// seconds, clamped to
+    /// `[REPLAY_MOVE_INTERVAL_MIN_SECS, REPLAY_MOVE_INTERVAL_MAX_SECS]`.
+    /// The result is rounded to two decimal places so the readout
+    /// stays clean across repeated `±` clicks at the 0.05 s step
+    /// (avoids float drift like `0.45000003`). Returns the new value.
+    pub fn adjust_replay_move_interval(&mut self, delta: f32) -> f32 {
+        let raw = (self.replay_move_interval_secs + delta)
+            .clamp(REPLAY_MOVE_INTERVAL_MIN_SECS, REPLAY_MOVE_INTERVAL_MAX_SECS);
+        // Round to 2 decimal places — the slider step is 0.05, so this
+        // collapses any FP drift introduced by repeated additions.
+        self.replay_move_interval_secs = (raw * 100.0).round() / 100.0;
+        self.replay_move_interval_secs
+    }
 }
 
 /// Returns the platform-specific path to `settings.json`, or `None` if
@@ -456,6 +514,7 @@ mod tests {
             tooltip_delay_secs: default_tooltip_delay(),
             time_bonus_multiplier: default_time_bonus_multiplier(),
             winnable_deals_only: false,
+            replay_move_interval_secs: default_replay_move_interval_secs(),
         };
         save_settings_to(&path, &s).expect("save");
         let loaded = load_settings_from(&path);
@@ -908,4 +967,101 @@ mod tests {
             "legacy settings.json missing winnable_deals_only must deserialize to false"
         );
     }
+
+    // -----------------------------------------------------------------------
+    // replay_move_interval_secs — player-tunable replay playback speed
+    // -----------------------------------------------------------------------
+
+    #[test]
+    fn settings_replay_move_interval_default_is_zero_point_four_five() {
+        // The pre-slider baseline is 0.45 s/move, matching
+        // `solitaire_engine::replay_playback::REPLAY_MOVE_INTERVAL_SECS`.
+        // The default must not regress for players who never touch
+        // the slider.
+        let s = Settings::default();
+        assert!(
+            (s.replay_move_interval_secs - 0.45).abs() < 1e-6,
+            "replay_move_interval_secs default must be 0.45 (the pre-slider baseline), got {}",
+            s.replay_move_interval_secs
+        );
+    }
+
+    #[test]
+    fn settings_replay_move_interval_round_trip() {
+        let path = tmp_path("replay_move_interval_round_trip");
+        let _ = fs::remove_file(&path);
+        let s = Settings {
+            replay_move_interval_secs: 0.20,
+            ..Settings::default()
+        };
+        save_settings_to(&path, &s).expect("save");
+        let loaded = load_settings_from(&path);
+        assert!(
+            (loaded.replay_move_interval_secs - 0.20).abs() < 1e-6,
+            "replay_move_interval_secs must survive serde round-trip; got {}",
+            loaded.replay_move_interval_secs
+        );
+        let _ = fs::remove_file(&path);
+    }
+
+    #[test]
+    fn legacy_settings_without_replay_move_interval_deserializes_to_default() {
+        // A settings.json written before this field existed must
+        // deserialize cleanly to the existing 0.45 s baseline so old
+        // players see no change to replay playback speed.
+        let json = br#"{ "sfx_volume": 0.7, "first_run_complete": true }"#;
+        let s: Settings = serde_json::from_slice(json).unwrap_or_default();
+        assert!(
+            (s.replay_move_interval_secs - default_replay_move_interval_secs()).abs() < 1e-6,
+            "legacy settings.json missing replay_move_interval_secs must deserialize to default ({}), got {}",
+            default_replay_move_interval_secs(),
+            s.replay_move_interval_secs
+        );
+    }
+
+    #[test]
+    fn settings_replay_move_interval_clamps_to_range() {
+        // Negative or oversized values from a hand-edited file must be
+        // clamped on load.
+        let s = Settings {
+            replay_move_interval_secs: 5.0,
+            ..Settings::default()
+        }
+        .sanitized();
+        assert_eq!(s.replay_move_interval_secs, REPLAY_MOVE_INTERVAL_MAX_SECS);
+
+        let s2 = Settings {
+            replay_move_interval_secs: -1.0,
+            ..Settings::default()
+        }
+        .sanitized();
+        assert_eq!(s2.replay_move_interval_secs, REPLAY_MOVE_INTERVAL_MIN_SECS);
+    }
+
+    #[test]
+    fn adjust_replay_move_interval_clamps_and_rounds() {
+        let mut s = Settings { replay_move_interval_secs: 0.45, ..Default::default() };
+        // Step down to 0.40.
+        assert!((s.adjust_replay_move_interval(-0.05) - 0.40).abs() < 1e-6);
+        // Big positive jump clamps to MAX.
+        assert!(
+            (s.adjust_replay_move_interval(99.0) - REPLAY_MOVE_INTERVAL_MAX_SECS).abs() < 1e-6
+        );
+        // Big negative jump clamps to MIN.
+        assert!(
+            (s.adjust_replay_move_interval(-99.0) - REPLAY_MOVE_INTERVAL_MIN_SECS).abs() < 1e-6
+        );
+
+        // Repeated 0.05 steps must not drift past the 0.05 grid.
+        let mut s2 = Settings { replay_move_interval_secs: 0.10, ..Default::default() };
+        for _ in 0..6 {
+            s2.adjust_replay_move_interval(0.05);
+        }
+        // After six +0.05 steps from 0.10, value should be exactly 0.40 (2 decimals).
+        assert!(
+            (s2.replay_move_interval_secs - 0.40).abs() < 1e-6,
+            "rounding should pin repeated 0.05 steps to the decimal grid, got {}",
+            s2.replay_move_interval_secs
+        );
+    }
 }

solitaire_engine/src/replay_playback.rs

@@ -45,11 +45,34 @@ use solitaire_data::{Replay, ReplayMove};
 use crate::events::{DrawRequestEvent, MoveRequestEvent, StateChangedEvent};
 use crate::game_plugin::{GameMutation, RecordingReplay};
 use crate::resources::GameStateResource;
+use crate::settings_plugin::SettingsResource;
 
-/// Per-move duration during playback. Tunable in Settings later;
-/// hardcoded for v1.
+/// Default per-move duration during playback, in seconds. Acts as the
+/// fallback when `SettingsResource` is absent — i.e. in headless test
+/// fixtures that don't install [`crate::settings_plugin::SettingsPlugin`].
+/// In production the live value is read from
+/// [`solitaire_data::Settings::replay_move_interval_secs`] every frame
+/// so Settings adjustments take effect on the next playback tick.
+///
+/// Kept in sync with `solitaire_data::settings::default_replay_move_interval_secs`
+/// (the data crate cannot depend on this engine crate, so the constant
+/// is duplicated). The
+/// `settings_replay_move_interval_default_matches_engine_constant`
+/// test in `solitaire_engine::settings_plugin` enforces equality.
 pub const REPLAY_MOVE_INTERVAL_SECS: f32 = 0.45;
 
+/// Helper: returns the live per-move replay interval. Reads
+/// [`SettingsResource::replay_move_interval_secs`] when the resource is
+/// installed, falling back to [`REPLAY_MOVE_INTERVAL_SECS`] otherwise.
+/// Also clamps below by `f32::EPSILON` so a hand-edited 0.0 cannot
+/// busy-loop the playback tick.
+fn current_move_interval_secs(settings: Option<&SettingsResource>) -> f32 {
+    let raw = settings
+        .map(|s| s.0.replay_move_interval_secs)
+        .unwrap_or(REPLAY_MOVE_INTERVAL_SECS);
+    raw.max(f32::EPSILON)
+}
+
 /// How long the [`ReplayPlaybackState::Completed`] state lingers before
 /// the auto-clear system transitions it back to
 /// [`ReplayPlaybackState::Inactive`]. Gives the overlay UI time to
@@ -161,6 +184,12 @@ pub fn start_replay_playback(
     let fresh = GameState::new_with_mode(replay.seed, replay.draw_mode.clone(), replay.mode);
     commands.insert_resource(GameStateResource(fresh));
 
+    // Initial `secs_to_next` uses the constant rather than reading
+    // `SettingsResource` because this entry point takes `Commands` /
+    // `ResMut<ReplayPlaybackState>` only. The first-tick latency may
+    // therefore lag the configured interval by up to ~0.45 s on an
+    // unusually short setting; subsequent ticks read the live setting
+    // every frame via [`tick_replay_playback`].
     **state = ReplayPlaybackState::Playing {
         replay,
         cursor: 0,
@@ -207,11 +236,13 @@ pub fn stop_replay_playback(
 /// so the loop runs at most once per frame.
 fn tick_replay_playback(
     time: Res<Time>,
+    settings: Option<Res<SettingsResource>>,
     mut state: ResMut<ReplayPlaybackState>,
     mut moves_writer: MessageWriter<MoveRequestEvent>,
     mut draws_writer: MessageWriter<DrawRequestEvent>,
 ) {
     let dt = time.delta_secs();
+    let interval = current_move_interval_secs(settings.as_deref());
     let mut transition_to_completed = false;
 
     if let ReplayPlaybackState::Playing {
@@ -235,7 +266,7 @@ fn tick_replay_playback(
                 }
             }
             *cursor += 1;
-            *secs_to_next += REPLAY_MOVE_INTERVAL_SECS;
+            *secs_to_next += interval;
         }
 
         if *cursor >= replay.moves.len() {
@@ -679,4 +710,124 @@ mod tests {
             "recording must not grow while playback is active",
         );
     }
+
+    /// With `SettingsResource::replay_move_interval_secs` set to 0.10 s
+    /// (well below the 0.45 s default), playback over a fixed
+    /// wall-clock window must dispatch strictly more moves than the
+    /// same fixture would at the 0.45 s default. This is the
+    /// regression check that the tick reads from the live Settings
+    /// value rather than the hardcoded
+    /// [`REPLAY_MOVE_INTERVAL_SECS`] constant.
+    ///
+    /// The follow-up assertion exercises the boundary condition: at
+    /// the 0.10 s/move setting, exactly six 0.10 s ticks must yield
+    /// fewer moves than six 0.20 s ticks (because the latter doubles
+    /// the per-update advance and pays off two intervals each tick).
+    #[test]
+    fn replay_playback_tick_uses_settings_interval() {
+        use solitaire_data::Settings;
+
+        #[derive(Resource, Default)]
+        struct CapturedDraws(usize);
+
+        fn collect_draws(
+            mut events: MessageReader<DrawRequestEvent>,
+            mut sink: ResMut<CapturedDraws>,
+        ) {
+            for _ in events.read() {
+                sink.0 += 1;
+            }
+        }
+
+        // Long replay so the fast cadence has plenty of moves to
+        // chew through and the 0.45 s vs 0.10 s difference is easy
+        // to observe.
+        fn ten_draws_replay() -> Replay {
+            Replay::new(
+                7,
+                DrawMode::DrawOne,
+                GameMode::Classic,
+                10,
+                100,
+                NaiveDate::from_ymd_opt(2026, 5, 5).expect("valid date"),
+                vec![ReplayMove::StockClick; 10],
+            )
+        }
+
+        // ---- Run 1: 0.10 s/move (Settings override) ----
+        let mut fast_app = headless_app();
+        fast_app.insert_resource(SettingsResource(Settings {
+            replay_move_interval_secs: 0.10,
+            ..Settings::default()
+        }));
+        fast_app
+            .init_resource::<CapturedDraws>()
+            .add_systems(Update, collect_draws);
+
+        start_playback(&mut fast_app, ten_draws_replay());
+        fast_app.update();
+        // 1.0 s of virtual time at 0.10 s/move dispatches ~5 moves
+        // after the default 0.45 s startup interval is consumed.
+        advance_by(&mut fast_app, 1.0);
+        let fast_count = fast_app.world().resource::<CapturedDraws>().0;
+
+        // ---- Run 2: 0.45 s/move (default — no SettingsResource) ----
+        let mut slow_app = headless_app();
+        // `tick_replay_playback` falls back to `REPLAY_MOVE_INTERVAL_SECS`
+        // (0.45 s) when `SettingsResource` is absent.
+        slow_app
+            .init_resource::<CapturedDraws>()
+            .add_systems(Update, collect_draws);
+
+        start_playback(&mut slow_app, ten_draws_replay());
+        slow_app.update();
+        advance_by(&mut slow_app, 1.0);
+        let slow_count = slow_app.world().resource::<CapturedDraws>().0;
+
+        assert!(
+            fast_count > slow_count,
+            "at 0.10 s/move the tick must dispatch strictly more moves \
+             than at the 0.45 s default over the same wall-clock window: \
+             fast={fast_count}, slow={slow_count}",
+        );
+
+        // ---- Boundary: a 0.05 s/tick cadence over the same window
+        // dispatches NO MORE moves than a 0.10 s/tick cadence, because
+        // 0.05 s < 0.10 s configured interval — the secs_to_next clock
+        // never crosses the threshold inside a single tick. ----
+        //
+        // We don't assert "exactly zero" because the leading update()
+        // after `start_playback` may run before the strategy is
+        // applied (cf. comments on `tick_advances_cursor_after_interval`),
+        // but the count must not exceed what we'd get with one-tick
+        // advances at the same total wall-clock window.
+        fn count_after_window(interval_secs: f32, tick_secs: f32, total_secs: f32) -> usize {
+            let mut app = headless_app();
+            app.insert_resource(SettingsResource(Settings {
+                replay_move_interval_secs: interval_secs,
+                ..Settings::default()
+            }));
+            app.init_resource::<CapturedDraws>()
+                .add_systems(Update, collect_draws);
+            start_playback(&mut app, ten_draws_replay());
+            app.update();
+            app.insert_resource(TimeUpdateStrategy::ManualDuration(
+                Duration::from_secs_f32(tick_secs),
+            ));
+            let ticks = (total_secs / tick_secs).ceil() as usize + 1;
+            for _ in 0..ticks {
+                app.update();
+            }
+            app.world().resource::<CapturedDraws>().0
+        }
+
+        let count_at_05 = count_after_window(0.10, 0.05, 1.0);
+        let count_at_20 = count_after_window(0.10, 0.20, 1.0);
+        assert!(
+            count_at_05 <= count_at_20,
+            "0.05 s ticks (strictly less than the 0.10 s interval) must \
+             dispatch no more moves than 0.20 s ticks over the same \
+             wall-clock window: count_at_05={count_at_05}, count_at_20={count_at_20}",
+        );
+    }
 }

solitaire_engine/src/settings_plugin.rs

@@ -18,7 +18,8 @@ use bevy::window::{WindowMoved, WindowResized};
 use solitaire_core::game_state::DrawMode;
 use solitaire_data::{
     load_settings_from, save_settings_to, settings_file_path, settings::Theme, AnimSpeed, Settings,
-    WindowGeometry, TIME_BONUS_MULTIPLIER_STEP, TOOLTIP_DELAY_STEP_SECS,
+    WindowGeometry, REPLAY_MOVE_INTERVAL_STEP_SECS, TIME_BONUS_MULTIPLIER_STEP,
+    TOOLTIP_DELAY_STEP_SECS,
 };
 
 use crate::events::{ManualSyncRequestEvent, ToggleSettingsRequestEvent};
@@ -132,6 +133,12 @@ struct TooltipDelayText;
 #[derive(Component, Debug)]
 struct TimeBonusMultiplierText;
 
+/// Marks the `Text` node showing the live replay-playback per-move
+/// interval value. The Gameplay-section row beside this label lets the
+/// player tune `Settings::replay_move_interval_secs`.
+#[derive(Component, Debug)]
+struct ReplayMoveIntervalText;
+
 /// Marks the `Text` node showing the current "Winnable deals only"
 /// state ("ON" / "OFF") in the Gameplay section.
 #[derive(Component, Debug)]
@@ -179,6 +186,12 @@ enum SettingsButton {
     TimeBonusDown,
     /// Increment the cosmetic time-bonus multiplier by one step.
     TimeBonusUp,
+    /// Decrement the replay-playback per-move interval by one step
+    /// (i.e. speed playback up).
+    ReplayMoveIntervalDown,
+    /// Increment the replay-playback per-move interval by one step
+    /// (i.e. slow playback down).
+    ReplayMoveIntervalUp,
     ToggleTheme,
     ToggleColorBlind,
     /// Toggle the [`Settings::winnable_deals_only`] flag. When on, new
@@ -219,8 +232,12 @@ impl SettingsButton {
             SettingsButton::TooltipDelayUp => 46,
             SettingsButton::TimeBonusDown => 47,
             SettingsButton::TimeBonusUp => 48,
+            // Replay-speed slider — last Gameplay-section row, so it
+            // sits between TimeBonusUp (48) and the Cosmetic section.
+            SettingsButton::ReplayMoveIntervalDown => 49,
+            SettingsButton::ReplayMoveIntervalUp => 49,
             // Cosmetic section
-            SettingsButton::ToggleTheme => 50,
+            SettingsButton::ToggleTheme => 55,
             SettingsButton::ToggleColorBlind => 60,
             // Picker rows — every swatch in a row shares the row's
             // priority so entity-index tiebreaking yields left → right.
@@ -310,6 +327,7 @@ impl Plugin for SettingsPlugin {
                     update_color_blind_text,
                     update_tooltip_delay_text,
                     update_time_bonus_multiplier_text,
+                    update_replay_move_interval_text,
                     update_winnable_deals_only_text,
                     attach_focusable_to_settings_buttons,
                     scroll_focus_into_view,
@@ -605,6 +623,21 @@ fn update_time_bonus_multiplier_text(
     }
 }
 
+/// Refreshes the live replay-playback per-move-interval value in the
+/// Gameplay section whenever `SettingsResource` changes (slider buttons,
+/// hand-edited settings.json reload, etc.).
+fn update_replay_move_interval_text(
+    settings: Res<SettingsResource>,
+    mut text_nodes: Query<&mut Text, With<ReplayMoveIntervalText>>,
+) {
+    if !settings.is_changed() {
+        return;
+    }
+    for mut text in &mut text_nodes {
+        **text = replay_move_interval_label(settings.0.replay_move_interval_secs);
+    }
+}
+
 fn card_back_label(idx: usize) -> String {
     if idx == 0 {
         "Default".to_string()
@@ -765,6 +798,29 @@ fn handle_settings_buttons(
                     changed.write(SettingsChangedEvent(settings.0.clone()));
                 }
             }
+            SettingsButton::ReplayMoveIntervalDown => {
+                let before = settings.0.replay_move_interval_secs;
+                let after = settings
+                    .0
+                    .adjust_replay_move_interval(-REPLAY_MOVE_INTERVAL_STEP_SECS);
+                if (before - after).abs() > f32::EPSILON {
+                    persist(&path, &settings.0);
+                    changed.write(SettingsChangedEvent(settings.0.clone()));
+                    // The Text node is refreshed by
+                    // `update_replay_move_interval_text` on the next
+                    // frame via `settings.is_changed()`.
+                }
+            }
+            SettingsButton::ReplayMoveIntervalUp => {
+                let before = settings.0.replay_move_interval_secs;
+                let after = settings
+                    .0
+                    .adjust_replay_move_interval(REPLAY_MOVE_INTERVAL_STEP_SECS);
+                if (before - after).abs() > f32::EPSILON {
+                    persist(&path, &settings.0);
+                    changed.write(SettingsChangedEvent(settings.0.clone()));
+                }
+            }
             SettingsButton::ToggleTheme => {
                 settings.0.theme = match settings.0.theme {
                     Theme::Green => Theme::Blue,
@@ -876,6 +932,14 @@ fn time_bonus_label(value: f32) -> String {
     }
 }
 
+/// Formats the replay-playback per-move interval for display in the
+/// Settings panel. Mirrors [`tooltip_delay_label`] for parity — the
+/// readout is `"{n:.2} s/move"` (e.g. `"0.45 s/move"`, `"0.10 s/move"`),
+/// using two decimal places because the step is 0.05 s.
+fn replay_move_interval_label(secs: f32) -> String {
+    format!("{secs:.2} s/move")
+}
+
 /// Auto-attaches [`Focusable`] to every bespoke Settings button — icon
 /// buttons (volume +/−, toggle, cycle), swatch buttons (card-back,
 /// background pickers), and the "Sync Now" button. The "Done" button is
@@ -1228,6 +1292,11 @@ fn spawn_settings_panel(
                 settings.time_bonus_multiplier,
                 font_res,
             );
+            replay_move_interval_row(
+                body,
+                settings.replay_move_interval_secs,
+                font_res,
+            );
 
             // --- Cosmetic ---
             section_label(body, "Cosmetic", font_res);
@@ -1462,6 +1531,56 @@ fn time_bonus_multiplier_row(
         });
 }
 
+/// `Replay speed  0.45 s/move  [−]  [+]` — slider row for the
+/// player-tunable replay-playback per-move interval. Mirrors
+/// [`tooltip_delay_row`] (label, current value, decrement, increment)
+/// but formats the value via [`replay_move_interval_label`] as
+/// `"{n:.2} s/move"`. The decrement button speeds playback up
+/// (smaller interval); the increment slows it down — same direction
+/// convention as the tooltip-delay slider.
+fn replay_move_interval_row(
+    parent: &mut ChildSpawnerCommands,
+    value_secs: f32,
+    font_res: Option<&FontResource>,
+) {
+    let label_font = label_text_font(font_res);
+    let value_font = value_text_font(font_res);
+    parent
+        .spawn(Node {
+            flex_direction: FlexDirection::Row,
+            align_items: AlignItems::Center,
+            column_gap: VAL_SPACE_2,
+            ..default()
+        })
+        .with_children(|row| {
+            row.spawn((
+                Text::new("Replay speed".to_string()),
+                label_font,
+                TextColor(TEXT_SECONDARY),
+            ));
+            row.spawn((
+                ReplayMoveIntervalText,
+                Text::new(replay_move_interval_label(value_secs)),
+                value_font,
+                TextColor(TEXT_PRIMARY),
+            ));
+            icon_button(
+                row,
+                "−",
+                SettingsButton::ReplayMoveIntervalDown,
+                "Speed up replay playback (shorter per-move interval).",
+                font_res,
+            );
+            icon_button(
+                row,
+                "+",
+                SettingsButton::ReplayMoveIntervalUp,
+                "Slow down replay playback (longer per-move interval).",
+                font_res,
+            );
+        });
+}
+
 /// `Label  Value  [⇄]` — used for cycle/toggle rows (draw mode, theme,
 /// anim speed, colour-blind).
 ///