feat(engine): reduce-transparency + high-contrast support for glass chrome

New Settings::reduce_transparency_mode (serde-default, Accessibility
toggle row) swaps every GlassSurface's gradients for a flat opaque
BG_ELEVATED fill; high-contrast mode now also boosts the glass fill
opacity and rim luminance to BORDER_SUBTLE_HC levels. Both applied by
settings_plugin::update_glass_surfaces, which retargets the gradients
in place on toggle or on newly spawned glass.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

solitaire_engine/src/settings_plugin/input.rs

@@ -353,6 +353,14 @@ pub(super) fn handle_settings_buttons(
                     **t = on_off_label(settings.0.reduce_motion_mode);
                 }
             }
+            SettingsButton::ToggleReduceTransparency => {
+                settings.0.reduce_transparency_mode = !settings.0.reduce_transparency_mode;
+                persist(&path, &settings.0);
+                changed.write(SettingsChangedEvent(settings.0.clone()));
+                // Text refreshed by `update_reduce_transparency_text`; the
+                // glass chrome itself follows via `update_glass_surfaces`
+                // next frame.
+            }
             SettingsButton::ToggleTouchInputMode => {
                 use solitaire_data::settings::TouchInputMode;
                 settings.0.touch_input_mode = match settings.0.touch_input_mode {

solitaire_engine/src/settings_plugin/mod.rs

@@ -135,6 +135,10 @@ struct HighContrastText;
 #[derive(Component, Debug)]
 struct ReduceMotionText;
 
+/// Marks the `Text` node showing the current reduce-transparency state.
+#[derive(Component, Debug)]
+struct ReduceTransparencyText;
+
 /// Marks the `Text` node showing the current touch input mode state.
 #[derive(Component, Debug)]
 struct TouchInputModeText;
@@ -277,6 +281,10 @@ enum SettingsButton {
     /// non-essential motion (card-slide animations become instant
     /// snaps) per `design-system.md` §Accessibility (#3).
     ToggleReduceMotion,
+    /// Toggle the [`Settings::reduce_transparency_mode`] flag — swaps
+    /// translucent glass chrome (the floating touch tab bar) for opaque
+    /// fills so table content never bleeds through UI text.
+    ToggleReduceTransparency,
     /// Toggle [`Settings::touch_input_mode`] between `OneTap`
     /// (auto-move on tap, default) and `TapToSelect` (first tap selects
     /// a card/stack, second tap on a target pile moves it).
@@ -361,8 +369,9 @@ impl SettingsButton {
             // run before continuing to the picker rows.
             SettingsButton::ToggleHighContrast => 61,
             SettingsButton::ToggleReduceMotion => 62,
-            SettingsButton::ToggleTouchInputMode => 63,
-            SettingsButton::CycleUiScale => 64,
+            SettingsButton::ToggleReduceTransparency => 63,
+            SettingsButton::ToggleTouchInputMode => 64,
+            SettingsButton::CycleUiScale => 65,
             // Picker rows — every swatch in a row shares the row's
             // priority so entity-index tiebreaking yields left → right.
             SettingsButton::SelectCardBack(_) => 70,
@@ -514,6 +523,16 @@ impl Plugin for SettingsPlugin {
                     update_smart_default_size_text,
                 ),
             );
+            app.add_systems(
+                Update,
+                (
+                    update_reduce_transparency_text,
+                    // Guards internally on settings-change / newly added
+                    // glass — `Added<GlassSurface>` can't be expressed as
+                    // a resource run condition.
+                    update_glass_surfaces,
+                ),
+            );
             app.add_systems(
                 Update,
                 (

solitaire_engine/src/settings_plugin/ui.rs

@@ -317,6 +317,15 @@ fn spawn_accessibility_tab(
         "Skips card-slide animations and other non-essential motion. Cards snap instantly to their target.",
         font_res,
     );
+    toggle_row(
+        body,
+        "Reduce Transparency",
+        ReduceTransparencyText,
+        on_off_label(settings.reduce_transparency_mode),
+        SettingsButton::ToggleReduceTransparency,
+        "Replaces the see-through glass toolbar with a solid panel so cards behind it never reduce readability.",
+        font_res,
+    );
     toggle_row(
         body,
         "Touch Input Mode",

solitaire_engine/src/settings_plugin/updates.rs

@@ -9,8 +9,10 @@ use crate::font_plugin::FontResource;
 use crate::progress_plugin::ProgressResource;
 use crate::resources::{SettingsScrollPos, SyncStatus, SyncStatusResource};
 use crate::theme::ThemeThumbnailCache;
+use crate::ui_glass::{GlassSurface, glass_decorations};
 use crate::ui_modal::ModalScrim;
 use crate::ui_theme::{BORDER_SUBTLE_HC, HighContrastBackground, HighContrastBorder};
+use bevy::ui::{BackgroundGradient, BorderGradient};
 
 /// Spawns the Settings panel when `SettingsScreen` becomes `true`;
 /// despawns it when it becomes `false`.
@@ -330,6 +332,41 @@ pub(super) fn update_reduce_motion_text(
     }
 }
 
+pub(super) fn update_reduce_transparency_text(
+    settings: Res<SettingsResource>,
+    mut text_nodes: Query<&mut Text, With<ReduceTransparencyText>>,
+) {
+    if !settings.is_changed() {
+        return;
+    }
+    for mut text in &mut text_nodes {
+        **text = on_off_label(settings.0.reduce_transparency_mode);
+    }
+}
+
+/// Retargets every [`GlassSurface`]'s sheen + rim gradients when the
+/// reduce-transparency or high-contrast toggles change. Runs on
+/// `SettingsResource` change and on newly added surfaces (so glass
+/// spawned after startup picks up an already-active toggle). Parallel to
+/// [`update_high_contrast_borders`]: same trigger, different components.
+pub(super) fn update_glass_surfaces(
+    settings: Res<SettingsResource>,
+    mut surfaces: Query<(&mut BackgroundGradient, &mut BorderGradient), With<GlassSurface>>,
+    added: Query<(), Added<GlassSurface>>,
+) {
+    if !settings.is_changed() && added.is_empty() {
+        return;
+    }
+    let (sheen, rim) = glass_decorations(
+        settings.0.reduce_transparency_mode,
+        settings.0.high_contrast_mode,
+    );
+    for (mut s, mut r) in &mut surfaces {
+        *s = sheen.clone();
+        *r = rim.clone();
+    }
+}
+
 pub(super) fn update_touch_input_mode_text(
     settings: Res<SettingsResource>,
     mut text_nodes: Query<&mut Text, With<TouchInputModeText>>,