feat: Add intro splash screen with transition effects and rendering support

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

packages/wolf_3d_dart/lib/src/engine/wolf_3d_engine_base.dart

@@ -295,6 +295,9 @@ class WolfEngine {
     }
 
     switch (menuManager.activeMenu) {
+      case WolfMenuScreen.introSplash:
+        menuManager.updateIntroSplash(input);
+        break;
       case WolfMenuScreen.mainMenu:
         _tickMainMenu(input);
         break;
@@ -370,7 +373,7 @@ class WolfEngine {
       _currentEpisodeIndex = 0;
       onEpisodeSelected?.call(null);
       menuManager.clearEpisodeSelection();
-      menuManager.startTransition(WolfMenuScreen.mainMenu);
+      menuManager.beginIntroSplash();
     }
   }
 

packages/wolf_3d_dart/lib/src/menu/menu_manager.dart

@@ -1,7 +1,15 @@
 import 'package:wolf_3d_dart/wolf_3d_data_types.dart';
 import 'package:wolf_3d_dart/wolf_3d_engine.dart';
 
-enum WolfMenuScreen { mainMenu, gameSelect, episodeSelect, difficultySelect }
+enum WolfMenuScreen {
+  introSplash,
+  mainMenu,
+  gameSelect,
+  episodeSelect,
+  difficultySelect,
+}
+
+enum _WolfIntroPhase { fadeIn, hold, fadeOut }
 
 enum WolfMenuMainAction {
   newGame,
@@ -52,11 +60,20 @@ bool _isWiredMainMenuAction(WolfMenuMainAction action) {
 /// Handles menu-only input state such as selection movement and edge triggers.
 class MenuManager {
   static const int transitionDurationMs = 280;
+  static const int introFadeDurationMs = 280;
+  static const int _introSlideCount = 2;
+  static const int _introPg13BackgroundRgb = 0x33A2E8;
+  static const int _introTitleBackgroundRgb = 0x000000;
 
   WolfMenuScreen _activeMenu = WolfMenuScreen.difficultySelect;
   WolfMenuScreen? _transitionTarget;
   int _transitionElapsedMs = 0;
   bool _transitionSwappedMenu = false;
+  WolfMenuScreen _introLandingMenu = WolfMenuScreen.mainMenu;
+  int _introSlideIndex = 0;
+  int _introElapsedMs = 0;
+  _WolfIntroPhase _introPhase = _WolfIntroPhase.fadeIn;
+  bool _introAdvanceRequested = false;
 
   int _selectedMainIndex = 0;
   int _selectedGameIndex = 0;
@@ -74,6 +91,27 @@ class MenuManager {
 
   bool get isTransitioning => _transitionTarget != null;
 
+  bool get isIntroSplashActive => _activeMenu == WolfMenuScreen.introSplash;
+
+  bool get isIntroPg13Slide => _introSlideIndex == 0;
+
+  int get introBackgroundRgb =>
+      isIntroPg13Slide ? _introPg13BackgroundRgb : _introTitleBackgroundRgb;
+
+  double get introOverlayAlpha {
+    if (!isIntroSplashActive) {
+      return 0.0;
+    }
+    switch (_introPhase) {
+      case _WolfIntroPhase.fadeIn:
+        return (1.0 - (_introElapsedMs / introFadeDurationMs)).clamp(0.0, 1.0);
+      case _WolfIntroPhase.hold:
+        return 0.0;
+      case _WolfIntroPhase.fadeOut:
+        return (_introElapsedMs / introFadeDurationMs).clamp(0.0, 1.0);
+    }
+  }
+
   /// Returns the fade alpha during transitions (0.0..1.0).
   double get transitionAlpha {
     if (!isTransitioning) {
@@ -162,15 +200,33 @@ class MenuManager {
         : Difficulty.values
               .indexOf(initialDifficulty)
               .clamp(0, Difficulty.values.length - 1);
-    _activeMenu = gameCount > 1
-        ? WolfMenuScreen.gameSelect
-        : WolfMenuScreen.mainMenu;
+    _introLandingMenu = WolfMenuScreen.mainMenu;
+    if (gameCount > 1) {
+      _activeMenu = WolfMenuScreen.gameSelect;
+      _introElapsedMs = 0;
+      _introPhase = _WolfIntroPhase.fadeIn;
+      _introSlideIndex = 0;
+    } else {
+      _startIntroSequence();
+    }
     _transitionTarget = null;
     _transitionElapsedMs = 0;
     _transitionSwappedMenu = false;
     _resetEdgeState();
   }
 
+  /// Starts the intro splash sequence and lands on [landingMenu] when done.
+  void beginIntroSplash({
+    WolfMenuScreen landingMenu = WolfMenuScreen.mainMenu,
+  }) {
+    _introLandingMenu = landingMenu;
+    _transitionTarget = null;
+    _transitionElapsedMs = 0;
+    _transitionSwappedMenu = false;
+    _startIntroSequence();
+    _resetEdgeState();
+  }
+
   /// Resets menu navigation state for a new difficulty selection flow.
   void beginDifficultySelection({Difficulty? initialDifficulty}) {
     beginSelectionFlow(
@@ -194,6 +250,7 @@ class MenuManager {
     _transitionTarget = null;
     _transitionElapsedMs = 0;
     _transitionSwappedMenu = false;
+    _introElapsedMs = 0;
     _resetEdgeState();
   }
 
@@ -213,6 +270,11 @@ class MenuManager {
 
   /// Advances transition timers and swaps menu at midpoint.
   void tickTransition(int deltaMs) {
+    if (isIntroSplashActive) {
+      _tickIntro(deltaMs);
+      return;
+    }
+
     if (!isTransitioning) {
       return;
     }
@@ -229,6 +291,85 @@ class MenuManager {
     }
   }
 
+  void updateIntroSplash(EngineInput input) {
+    if (!isIntroSplashActive) {
+      return;
+    }
+
+    final bool confirmNow = input.isInteracting;
+    if (confirmNow && !_prevConfirm) {
+      if (_introPhase == _WolfIntroPhase.fadeOut) {
+        // Ignore repeat confirms while already transitioning out.
+      } else if (_introPhase == _WolfIntroPhase.hold) {
+        _introPhase = _WolfIntroPhase.fadeOut;
+        _introElapsedMs = 0;
+      } else {
+        // Queue advance while fade-in is still in progress.
+        _introAdvanceRequested = true;
+      }
+    }
+
+    _consumeEdgeState(input);
+  }
+
+  void _startIntroSequence() {
+    _activeMenu = WolfMenuScreen.introSplash;
+    _introSlideIndex = 0;
+    _introElapsedMs = 0;
+    _introPhase = _WolfIntroPhase.fadeIn;
+    _introAdvanceRequested = false;
+  }
+
+  void _tickIntro(int deltaMs) {
+    if (!isIntroSplashActive) {
+      return;
+    }
+
+    _introElapsedMs += deltaMs;
+
+    switch (_introPhase) {
+      case _WolfIntroPhase.fadeIn:
+        if (_introElapsedMs >= introFadeDurationMs) {
+          _introElapsedMs = 0;
+          if (_introAdvanceRequested) {
+            _introPhase = _WolfIntroPhase.fadeOut;
+            _introAdvanceRequested = false;
+          } else {
+            _introPhase = _WolfIntroPhase.hold;
+          }
+        }
+        break;
+      case _WolfIntroPhase.hold:
+        // Hold indefinitely until the user confirms.
+        _introElapsedMs = 0;
+        if (_introAdvanceRequested) {
+          _introPhase = _WolfIntroPhase.fadeOut;
+          _introAdvanceRequested = false;
+        }
+        break;
+      case _WolfIntroPhase.fadeOut:
+        if (_introElapsedMs >= introFadeDurationMs) {
+          _advanceIntroSlide();
+        }
+        break;
+    }
+  }
+
+  void _advanceIntroSlide() {
+    if (_introSlideIndex < _introSlideCount - 1) {
+      _introSlideIndex += 1;
+      _introElapsedMs = 0;
+      _introPhase = _WolfIntroPhase.fadeIn;
+      _introAdvanceRequested = false;
+      return;
+    }
+
+    _activeMenu = _introLandingMenu;
+    _introElapsedMs = 0;
+    _introPhase = _WolfIntroPhase.fadeIn;
+    _introAdvanceRequested = false;
+  }
+
   void clearEpisodeSelection() {
     _selectedEpisodeIndex = 0;
   }

packages/wolf_3d_dart/lib/src/rendering/ascii_renderer.dart

@@ -419,6 +419,11 @@ class AsciiRenderer extends CliRendererBackend<dynamic> {
 
     final art = WolfClassicMenuArt(engine.data);
 
+    if (engine.menuManager.activeMenu == WolfMenuScreen.introSplash) {
+      _drawIntroSplash(engine, art);
+      return;
+    }
+
     if (engine.menuManager.activeMenu == WolfMenuScreen.mainMenu) {
       _fillRect320(68, 52, 178, 136, panelColor);
 
@@ -703,6 +708,59 @@ class AsciiRenderer extends CliRendererBackend<dynamic> {
     }
   }
 
+  void _drawIntroSplash(WolfEngine engine, WolfClassicMenuArt art) {
+    final image = engine.menuManager.isIntroPg13Slide
+        ? art.mappedPic(WolfMenuPic.pg13)
+        : art.mappedPic(WolfMenuPic.title);
+
+    int splashBg = _rgbToPaletteColor(engine.menuManager.introBackgroundRgb);
+    if (engine.menuManager.isIntroPg13Slide &&
+        image != null &&
+        image.pixels.isNotEmpty) {
+      splashBg = ColorPalette.vga32Bit[_dominantPaletteIndex(image)];
+    }
+
+    if (_usesTerminalLayout) {
+      _fillTerminalRect(0, 0, width, _terminalPixelHeight, splashBg);
+    } else {
+      _fillRect(0, 0, width, height, activeTheme.solid, splashBg);
+    }
+
+    if (image != null) {
+      final int x = engine.menuManager.isIntroPg13Slide
+          ? (320 - image.width).clamp(0, 319)
+          : ((320 - image.width) ~/ 2).clamp(0, 319);
+      final int y = engine.menuManager.isIntroPg13Slide
+          ? (200 - image.height).clamp(0, 199)
+          : ((200 - image.height) ~/ 2).clamp(0, 199);
+      _blitVgaImageAscii(image, x, y);
+    }
+
+    _applyMenuFade(
+      engine.menuManager.introOverlayAlpha,
+      _rgbToPaletteColor(0x000000),
+    );
+  }
+
+  int _dominantPaletteIndex(VgaImage image) {
+    final List<int> histogram = List<int>.filled(256, 0);
+    for (final int colorIndex in image.pixels) {
+      if (colorIndex >= 0 && colorIndex < histogram.length) {
+        histogram[colorIndex]++;
+      }
+    }
+
+    int bestIndex = 0;
+    int bestCount = -1;
+    for (int i = 0; i < histogram.length; i++) {
+      if (histogram[i] > bestCount) {
+        bestCount = histogram[i];
+        bestIndex = i;
+      }
+    }
+    return bestIndex;
+  }
+
   void _applyMenuFade(double alpha, int fadeColor) {
     if (alpha <= 0.0) {
       return;

packages/wolf_3d_dart/lib/src/rendering/sixel_renderer.dart

@@ -372,6 +372,11 @@ class SixelRenderer extends CliRendererBackend<String> {
     // Draw footer first so menu panels can clip overlap in the center.
     _drawMenuFooterArt(art);
 
+    if (engine.menuManager.activeMenu == WolfMenuScreen.introSplash) {
+      _drawIntroSplash(engine, art);
+      return;
+    }
+
     if (engine.menuManager.activeMenu == WolfMenuScreen.mainMenu) {
       _fillRect320(68, 52, 178, 136, panelColor);
 
@@ -555,6 +560,57 @@ class SixelRenderer extends CliRendererBackend<String> {
     }
   }
 
+  void _drawIntroSplash(WolfEngine engine, WolfClassicMenuArt art) {
+    final image = engine.menuManager.isIntroPg13Slide
+        ? art.mappedPic(WolfMenuPic.pg13)
+        : art.mappedPic(WolfMenuPic.title);
+
+    int splashBg = _rgbToPaletteIndex(engine.menuManager.introBackgroundRgb);
+    if (engine.menuManager.isIntroPg13Slide &&
+        image != null &&
+        image.pixels.isNotEmpty) {
+      splashBg = _dominantPaletteIndex(image);
+    }
+
+    for (int i = 0; i < _screen.length; i++) {
+      _screen[i] = splashBg;
+    }
+
+    if (image != null) {
+      final int x = engine.menuManager.isIntroPg13Slide
+          ? (320 - image.width).clamp(0, 319)
+          : ((320 - image.width) ~/ 2).clamp(0, 319);
+      final int y = engine.menuManager.isIntroPg13Slide
+          ? (200 - image.height).clamp(0, 199)
+          : ((200 - image.height) ~/ 2).clamp(0, 199);
+      _blitVgaImage(image, x, y);
+    }
+
+    _applyMenuFade(
+      engine.menuManager.introOverlayAlpha,
+      _rgbToPaletteIndex(0x000000),
+    );
+  }
+
+  int _dominantPaletteIndex(VgaImage image) {
+    final List<int> histogram = List<int>.filled(256, 0);
+    for (final int colorIndex in image.pixels) {
+      if (colorIndex >= 0 && colorIndex < histogram.length) {
+        histogram[colorIndex]++;
+      }
+    }
+
+    int bestIndex = 0;
+    int bestCount = -1;
+    for (int i = 0; i < histogram.length; i++) {
+      if (histogram[i] > bestCount) {
+        bestCount = histogram[i];
+        bestIndex = i;
+      }
+    }
+    return bestIndex;
+  }
+
   void _applyMenuFade(double alpha, int bgColor) {
     if (alpha <= 0.0) {
       return;

packages/wolf_3d_dart/lib/src/rendering/software_renderer.dart

@@ -159,6 +159,9 @@ class SoftwareRenderer extends RendererBackend<FrameBuffer> {
     _drawCenteredMenuFooter(art);
 
     switch (engine.menuManager.activeMenu) {
+      case WolfMenuScreen.introSplash:
+        _drawIntroSplash(engine, art);
+        break;
       case WolfMenuScreen.mainMenu:
         _drawMainMenu(
           engine,
@@ -205,6 +208,99 @@ class SoftwareRenderer extends RendererBackend<FrameBuffer> {
     _applyMenuFade(engine.menuManager.transitionAlpha, bgColor);
   }
 
+  void _drawIntroSplash(WolfEngine engine, WolfClassicMenuArt art) {
+    final image = engine.menuManager.isIntroPg13Slide
+        ? art.mappedPic(WolfMenuPic.pg13)
+        : art.mappedPic(WolfMenuPic.title);
+
+    int splashBgColor = _rgbToFrameColor(engine.menuManager.introBackgroundRgb);
+    int? matteIndex;
+    if (engine.menuManager.isIntroPg13Slide &&
+        image != null &&
+        image.pixels.isNotEmpty) {
+      matteIndex = _dominantPaletteIndex(image);
+      splashBgColor =
+          ColorPalette.vga32Bit[_pg13BackgroundPaletteIndex(image, matteIndex)];
+    }
+
+    for (int i = 0; i < _buffer.pixels.length; i++) {
+      _buffer.pixels[i] = splashBgColor;
+    }
+
+    if (image != null) {
+      final int x = engine.menuManager.isIntroPg13Slide
+          ? (320 - image.width).clamp(0, 319)
+          : ((320 - image.width) ~/ 2).clamp(0, 319);
+      final int y = engine.menuManager.isIntroPg13Slide
+          ? (200 - image.height).clamp(0, 199)
+          : ((200 - image.height) ~/ 2).clamp(0, 199);
+      if (engine.menuManager.isIntroPg13Slide && matteIndex != null) {
+        _blitVgaImage(image, x, y, transparentIndex: matteIndex);
+      } else {
+        _blitVgaImage(image, x, y);
+      }
+    }
+
+    _applyMenuFade(
+      engine.menuManager.introOverlayAlpha,
+      _rgbToFrameColor(0x000000),
+    );
+  }
+
+  int _dominantPaletteIndex(VgaImage image) {
+    final List<int> histogram = List<int>.filled(256, 0);
+    for (final int colorIndex in image.pixels) {
+      if (colorIndex >= 0 && colorIndex < histogram.length) {
+        histogram[colorIndex]++;
+      }
+    }
+
+    int bestIndex = 0;
+    int bestCount = -1;
+    for (int i = 0; i < histogram.length; i++) {
+      if (histogram[i] > bestCount) {
+        bestCount = histogram[i];
+        bestIndex = i;
+      }
+    }
+    return bestIndex;
+  }
+
+  int _pg13BackgroundPaletteIndex(VgaImage image, int matteIndex) {
+    final List<(int x, int y)> probes = <(int x, int y)>[
+      (0, 0),
+      (image.width - 1, 0),
+      (0, image.height - 1),
+      (image.width - 1, image.height - 1),
+      (image.width - 8, image.height - 8),
+      (image.width - 16, image.height - 16),
+    ];
+    final Map<int, int> counts = <int, int>{};
+    for (final probe in probes) {
+      final int x = probe.$1.clamp(0, image.width - 1);
+      final int y = probe.$2.clamp(0, image.height - 1);
+      final int idx = image.decodePixel(x, y);
+      if (idx == matteIndex) {
+        continue;
+      }
+      counts[idx] = (counts[idx] ?? 0) + 1;
+    }
+
+    if (counts.isEmpty) {
+      return matteIndex;
+    }
+
+    int bestIndex = counts.keys.first;
+    int bestCount = counts[bestIndex] ?? 0;
+    for (final MapEntry<int, int> entry in counts.entries) {
+      if (entry.value > bestCount) {
+        bestCount = entry.value;
+        bestIndex = entry.key;
+      }
+    }
+    return bestIndex;
+  }
+
   void _drawMainMenu(
     WolfEngine engine,
     WolfClassicMenuArt art,
@@ -663,7 +759,12 @@ class SoftwareRenderer extends RendererBackend<FrameBuffer> {
   ///
   /// UI coordinates are expressed in canonical 320x200 space and scaled to the
   /// current framebuffer so higher-resolution render targets preserve layout.
-  void _blitVgaImage(VgaImage image, int startX, int startY) {
+  void _blitVgaImage(
+    VgaImage image,
+    int startX,
+    int startY, {
+    int? transparentIndex,
+  }) {
     final int destStartX = (startX * _uiScaleX).floor();
     final int destStartY = (startY * _uiScaleY).floor();
     final int destWidth = math.max(1, (image.width * _uiScaleX).ceil());
@@ -678,7 +779,7 @@ class SoftwareRenderer extends RendererBackend<FrameBuffer> {
           final int srcX = (dx / _uiScaleX).toInt().clamp(0, image.width - 1);
           final int srcY = (dy / _uiScaleY).toInt().clamp(0, image.height - 1);
           final int colorByte = image.decodePixel(srcX, srcY);
-          if (colorByte != 255) {
+          if (colorByte != 255 && colorByte != transparentIndex) {
             _buffer.pixels[drawY * width + drawX] =
                 ColorPalette.vga32Bit[colorByte];
           }

packages/wolf_3d_renderer/lib/wolf_3d_glsl_renderer.dart

@@ -53,9 +53,7 @@ class _WolfGlslRendererState extends BaseWolfRendererState<WolfGlslRenderer> {
   }
 
   @override
-  Color get scaffoldColor => widget.engine.difficulty == null
-      ? _colorFromRgb(widget.engine.menuBackgroundRgb)
-      : const Color.fromARGB(255, 4, 64, 64);
+  Color get scaffoldColor => Colors.black;
 
   @override
   void dispose() {
@@ -149,10 +147,6 @@ class _WolfGlslRendererState extends BaseWolfRendererState<WolfGlslRenderer> {
       widget.onUnavailable?.call();
     }
   }
-
-  Color _colorFromRgb(int rgb) {
-    return Color(0xFF000000 | (rgb & 0x00FFFFFF));
-  }
 }
 
 class _GlslFramePainter extends CustomPainter {