feat(demo): transició per fosa a/desde negre en el salt títol→demo

source/game/scenes/game_scene.cpp

@@ -55,7 +55,8 @@ GameScene::GameScene(SDLManager& sdl, SceneContext& context)
       text_(sdl.getRenderer()),
       starfield_parallax_(sdl.getRenderer()),
       playfield_(sdl.getRenderer()),
-      border_(sdl.getRenderer()) {
+      border_(sdl.getRenderer()),
+      fade_(sdl.getRenderer()) {
     // Recuperar configuración de match des del context
     match_config_ = context_.getMatchConfig();
 
@@ -170,6 +171,8 @@ GameScene::GameScene(SDLManager& sdl, SceneContext& context)
         Audio::get()->enableSound(false);
         // El fons (graella) ha d'aparèixer ja muntat: la demo és una partida en marxa.
         playfield_.completeBuild();
+        // Fosa des de negre sobre el joc ja en marxa (transició suau des del títol).
+        fade_.start(1.0F, 0.0F, Defaults::Game::Fade::DEMO_IN_DURATION);
     } else {
         stage_manager_->init();
     }
@@ -363,6 +366,8 @@ void GameScene::updateShipsControl(float delta_time) {
 }
 
 auto GameScene::stepDemo(float delta_time) -> bool {
+    fade_.update(delta_time);  // fosa d'entrada des de negre
+
     // Qualsevol input trenca la demo i torna al títol (música intacta).
     if (Input::get()->checkAnyPlayerAction(DEMO_EXIT_ACTIONS)) {
         context_.setNextScene(SceneType::TITLE, Option::JUMP_TO_TITLE_MAIN);
@@ -708,6 +713,10 @@ void GameScene::draw() {
             drawLevelCompletedState();
             break;
     }
+
+    // Fosa d'entrada de la demo: per damunt de tot. No-op fora del mode DEMO
+    // (fade_ mai s'arrenca) i quan ja ha acabat (alpha 0).
+    fade_.draw();
 }
 
 void GameScene::drawEnemies() const {

source/game/scenes/game_scene.hpp

@@ -10,6 +10,7 @@
 
 #include "core/graphics/border.hpp"
 #include "core/graphics/playfield.hpp"
+#include "core/graphics/screen_fade.hpp"
 #include "core/graphics/starfield_parallax.hpp"
 #include "core/graphics/vector_text.hpp"
 #include "core/physics/physics_world.hpp"
@@ -95,6 +96,9 @@ class GameScene final : public Scene {
     // Border del playfield (4 línies amb desplaçaments i flash per impactes)
     Graphics::Border border_;
 
+    // Fosa des de negre en entrar a la demo (només mode DEMO; inactiu en partida normal).
+    Graphics::ScreenFade fade_;
+
     // [NEW] Stage system
     std::unique_ptr<StageSystem::StageSystemConfig> stage_config_;
     std::unique_ptr<StageSystem::StageManager> stage_manager_;

source/game/scenes/title_scene.cpp

@@ -37,7 +37,8 @@ namespace {
 TitleScene::TitleScene(SDLManager& sdl, SceneContext& context)
     : sdl_(sdl),
       context_(context),
-      text_(sdl.getRenderer()) {
+      text_(sdl.getRenderer()),
+      fade_(sdl.getRenderer()) {
     std::cout << "SceneType Titol: Inicialitzant...\n";
 
     match_config_.player1_active = false;
@@ -333,6 +334,9 @@ void TitleScene::update(float delta_time) {
         case TitleState::BLACK_SCREEN:
             updateBlackScreenState(delta_time);
             break;
+        case TitleState::DEMO_FADE_OUT:
+            updateDemoFadeOutState(delta_time);
+            break;
     }
 
     // Les animacions segueixen pero els inputs es bloquegen mentre el menu
@@ -368,7 +372,12 @@ void TitleScene::update(float delta_time) {
             demo_cfg.player2_active = (SC.players >= 2);
             demo_cfg.mode = GameConfig::Mode::DEMO;
             context_.setMatchConfig(demo_cfg);
-            context_.setNextScene(SceneType::GAME);
+            // No saltem en sec: fosa a negre i, en acabar, canvi a GAME (el salt
+            // real el fa updateDemoFadeOutState). L'estat deixa de ser MAIN, així
+            // que ni es re-dispara la demo ni s'accepta START durant la fosa.
+            current_state_ = TitleState::DEMO_FADE_OUT;
+            fade_.start(0.0F, 1.0F, Defaults::Game::Fade::DEMO_OUT_DURATION);
+            temps_acumulat_ = 0.0F;
         }
     }
 }
@@ -473,6 +482,13 @@ void TitleScene::updateBlackScreenState(float delta_time) {
     }
 }
 
+void TitleScene::updateDemoFadeOutState(float delta_time) {
+    fade_.update(delta_time);
+    if (fade_.isDone()) {
+        context_.setNextScene(SceneType::GAME);
+    }
+}
+
 void TitleScene::handleSkipInput() {
     if (current_state_ != TitleState::STARFIELD_FADE_IN && current_state_ != TitleState::STARFIELD) {
         return;
@@ -577,7 +593,8 @@ void TitleScene::draw() {
         (current_state_ == TitleState::STARFIELD_FADE_IN ||
             current_state_ == TitleState::STARFIELD ||
             current_state_ == TitleState::MAIN ||
-            current_state_ == TitleState::PLAYER_JOIN_PHASE)) {
+            current_state_ == TitleState::PLAYER_JOIN_PHASE ||
+            current_state_ == TitleState::DEMO_FADE_OUT)) {
         ship_animator_->draw();
     }
     drawFlashes();
@@ -586,7 +603,12 @@ void TitleScene::draw() {
         return;
     }
 
-    if (current_state_ != TitleState::MAIN && current_state_ != TitleState::PLAYER_JOIN_PHASE) {
+    // DEMO_FADE_OUT es pinta com MAIN (logo + text) perquè el títol segueixi
+    // visible sota la fosa a negre.
+    if (current_state_ != TitleState::MAIN &&
+        current_state_ != TitleState::PLAYER_JOIN_PHASE &&
+        current_state_ != TitleState::DEMO_FADE_OUT) {
+        fade_.draw();  // BLACK_SCREEN i altres: només la fosa (si activa)
         return;
     }
 
@@ -657,6 +679,9 @@ void TitleScene::draw() {
     }
 
     dibuixarPeuTitol(SPACING);
+
+    // Fosa a negre (attract): per damunt de tot. No-op si no està activa.
+    fade_.draw();
 }
 
 auto TitleScene::checkSkipButtonPressed() -> bool {

source/game/scenes/title_scene.hpp

@@ -18,6 +18,7 @@
 #include <vector>
 
 #include "core/graphics/camera3d.hpp"
+#include "core/graphics/screen_fade.hpp"
 #include "core/graphics/shape.hpp"
 #include "core/graphics/starfield.hpp"
 #include "core/graphics/vector_text.hpp"
@@ -46,6 +47,7 @@ class TitleScene final : public Scene {
         MAIN,
         PLAYER_JOIN_PHASE,
         BLACK_SCREEN,
+        DEMO_FADE_OUT,  // Attract: fosa a negre abans de saltar a la demo
     };
 
     struct LogoLetter {
@@ -60,6 +62,7 @@ class TitleScene final : public Scene {
     SceneManager::SceneContext& context_;
     GameConfig::MatchConfig match_config_;
     Graphics::VectorText text_;
+    Graphics::ScreenFade fade_;  // Fosa a negre en saltar a la demo (attract)
     std::unique_ptr<Graphics::Camera3D> camera_;
     std::unique_ptr<Graphics::Starfield> starfield_;
     std::unique_ptr<Title::ShipAnimator> ship_animator_;
@@ -143,6 +146,7 @@ class TitleScene final : public Scene {
     void updateMainState(float delta_time);
     void updatePlayerJoinPhaseState(float delta_time);
     void updateBlackScreenState(float delta_time);
+    void updateDemoFadeOutState(float delta_time);
     void handleSkipInput();
     void handleStartInput();
     void triggerExitForJoinedPlayers(bool p1_was_active, bool p2_was_active, const char* log_prefix);