feat(starfield): capa parallax al fons del playfield amb tint blanc-cyan

source/core/defaults.hpp

@@ -26,6 +26,7 @@
 #include "core/defaults/playfield.hpp"
 #include "core/defaults/rendering.hpp"
 #include "core/defaults/ship.hpp"
+#include "core/defaults/starfield_parallax.hpp"
 #include "core/defaults/title.hpp"
 #include "core/defaults/trail.hpp"
 #include "core/defaults/window.hpp"

source/core/defaults/starfield_parallax.hpp

@@ -0,0 +1,36 @@
+// starfield_parallax.hpp - Capa de fons del playfield: estrelles 2D amb parallax
+// © 2026 JailDesigner
+//
+// 3 capes de profunditat. Cada capa té estrelles amb brillantor, mida i
+// factor parallax propis. Les més properes són més brillants i grans i es
+// mouen més ràpid quan el món es desplaça; les més llunyanes són tènues i
+// petites i amb prou feines es mouen.
+
+#pragma once
+
+namespace Defaults::StarfieldParallax {
+
+    namespace Far {
+        constexpr int COUNT = 60;
+        constexpr float BRIGHTNESS = 0.15F;
+        constexpr float PARALLAX_FACTOR = 0.15F;  // multiplicador sobre world_velocity
+        constexpr int SIZE_PX = 1;                // 1 px (punt)
+    }  // namespace Far
+
+    namespace Mid {
+        constexpr int COUNT = 50;
+        constexpr float BRIGHTNESS = 0.30F;
+        constexpr float PARALLAX_FACTOR = 0.35F;
+        constexpr int SIZE_PX = 2;  // creu de 3x3 (extensió ±1)
+    }  // namespace Mid
+
+    namespace Near {
+        constexpr int COUNT = 40;
+        constexpr float BRIGHTNESS = 0.55F;
+        constexpr float PARALLAX_FACTOR = 0.70F;
+        constexpr int SIZE_PX = 3;  // creu de 5x5 (extensió ±2)
+    }  // namespace Near
+
+    constexpr int TOTAL_COUNT = Far::COUNT + Mid::COUNT + Near::COUNT;
+
+}  // namespace Defaults::StarfieldParallax

source/core/graphics/starfield_parallax.cpp

@@ -0,0 +1,145 @@
+// starfield_parallax.cpp - Implementació del starfield 2D amb parallax
+// © 2026 JailDesigner
+
+#include "core/graphics/starfield_parallax.hpp"
+
+#include <cstdlib>
+
+#include "core/defaults.hpp"
+#include "core/rendering/line_renderer.hpp"
+
+namespace Graphics {
+
+    namespace {
+
+        auto randUniform(float min_v, float max_v) -> float {
+            const float NORM = static_cast<float>(std::rand()) / static_cast<float>(RAND_MAX);
+            return min_v + (NORM * (max_v - min_v));
+        }
+
+    }  // namespace
+
+    StarfieldParallax::StarfieldParallax(Rendering::Renderer* renderer)
+        : renderer_(renderer) {
+        buildStars();
+    }
+
+    void StarfieldParallax::buildStars() {
+        const SDL_FRect& zona = Defaults::Zones::PLAYAREA;
+        const float MIN_X = zona.x;
+        const float MAX_X = zona.x + zona.w;
+        const float MIN_Y = zona.y;
+        const float MAX_Y = zona.y + zona.h;
+
+        // Tint aleatori entre blanc (255,255,255) i cyan (0,255,255) per estrella.
+        // T ∈ [0,1]: 0 → blanc; 1 → cyan. R = 255·(1-T), G=B=255.
+        const auto FILL_LAYER = [&](int layer, int count, int& idx) {
+            for (int i = 0; i < count; i++) {
+                const float T = randUniform(0.0F, 1.0F);
+                stars_[idx++] = Star{
+                    .x = randUniform(MIN_X, MAX_X),
+                    .y = randUniform(MIN_Y, MAX_Y),
+                    .layer = layer,
+                    .color = SDL_Color{
+                        .r = static_cast<Uint8>(255.0F * (1.0F - T)),
+                        .g = 255,
+                        .b = 255,
+                        .a = 255}};
+            }
+        };
+
+        int idx = 0;
+        FILL_LAYER(0, Defaults::StarfieldParallax::Far::COUNT, idx);
+        FILL_LAYER(1, Defaults::StarfieldParallax::Mid::COUNT, idx);
+        FILL_LAYER(2, Defaults::StarfieldParallax::Near::COUNT, idx);
+    }
+
+    auto StarfieldParallax::layerBrightness(int layer) -> float {
+        switch (layer) {
+            case 0:
+                return Defaults::StarfieldParallax::Far::BRIGHTNESS;
+            case 1:
+                return Defaults::StarfieldParallax::Mid::BRIGHTNESS;
+            case 2:
+                return Defaults::StarfieldParallax::Near::BRIGHTNESS;
+            default:
+                return 0.0F;
+        }
+    }
+
+    auto StarfieldParallax::layerParallax(int layer) -> float {
+        switch (layer) {
+            case 0:
+                return Defaults::StarfieldParallax::Far::PARALLAX_FACTOR;
+            case 1:
+                return Defaults::StarfieldParallax::Mid::PARALLAX_FACTOR;
+            case 2:
+                return Defaults::StarfieldParallax::Near::PARALLAX_FACTOR;
+            default:
+                return 0.0F;
+        }
+    }
+
+    auto StarfieldParallax::layerSize(int layer) -> int {
+        switch (layer) {
+            case 0:
+                return Defaults::StarfieldParallax::Far::SIZE_PX;
+            case 1:
+                return Defaults::StarfieldParallax::Mid::SIZE_PX;
+            case 2:
+                return Defaults::StarfieldParallax::Near::SIZE_PX;
+            default:
+                return 1;
+        }
+    }
+
+    void StarfieldParallax::update(float delta_time, Vec2 world_velocity) {
+        const SDL_FRect& zona = Defaults::Zones::PLAYAREA;
+        const float MIN_X = zona.x;
+        const float MAX_X = zona.x + zona.w;
+        const float MIN_Y = zona.y;
+        const float MAX_Y = zona.y + zona.h;
+        const float W = zona.w;
+        const float H = zona.h;
+
+        for (auto& star : stars_) {
+            const float FACTOR = layerParallax(star.layer);
+            star.x += world_velocity.x * FACTOR * delta_time;
+            star.y += world_velocity.y * FACTOR * delta_time;
+
+            // Wraparound (PLAYAREA torica).
+            while (star.x < MIN_X) {
+                star.x += W;
+            }
+            while (star.x > MAX_X) {
+                star.x -= W;
+            }
+            while (star.y < MIN_Y) {
+                star.y += H;
+            }
+            while (star.y > MAX_Y) {
+                star.y -= H;
+            }
+        }
+    }
+
+    void StarfieldParallax::draw() const {
+        for (const auto& star : stars_) {
+            const float B = layerBrightness(star.layer);
+            const int SIZE = layerSize(star.layer);
+            const int X = static_cast<int>(star.x);
+            const int Y = static_cast<int>(star.y);
+
+            if (SIZE <= 1) {
+                // Punt d'1 px: línia degenerada horitzontal de 1 px.
+                Rendering::linea(renderer_, X, Y, X + 1, Y, B, 0.0F, star.color);
+            } else {
+                // Creu "+" amb extensió HALF des del centre en cada direcció.
+                const int HALF = SIZE - 1;  // SIZE=2 → ±1 (creu 3x3); SIZE=3 → ±2 (creu 5x5)
+                Rendering::linea(renderer_, X - HALF, Y, X + HALF + 1, Y, B, 0.0F, star.color);
+                Rendering::linea(renderer_, X, Y - HALF, X, Y + HALF + 1, B, 0.0F, star.color);
+            }
+        }
+    }
+
+}  // namespace Graphics

source/core/graphics/starfield_parallax.hpp

@@ -0,0 +1,51 @@
+// starfield_parallax.hpp - Capa més profunda del fons: estrelles 2D amb parallax
+// © 2026 JailDesigner
+//
+// Estrelles 2D distribuïdes en 3 capes de profunditat. Cada capa té el seu
+// factor parallax: el "món" es desplaça amb world_velocity i les estrelles
+// d'una capa es mouen amb world_velocity * parallax_factor. Les més
+// properes es mouen més (factor alt) → sensació de profunditat.
+// Quan una estrella surt de PLAYAREA, reapareix per la banda oposada
+// (wraparound).
+
+#pragma once
+
+#include <SDL3/SDL.h>
+
+#include <array>
+
+#include "core/defaults/starfield_parallax.hpp"
+#include "core/rendering/render_context.hpp"
+#include "core/types.hpp"
+
+namespace Graphics {
+
+    class StarfieldParallax {
+       public:
+        explicit StarfieldParallax(Rendering::Renderer* renderer);
+
+        // Avança el desplaçament de les estrelles segons world_velocity (vector
+        // del moviment del món en px/s; típicament = -ship_velocity).
+        // world_velocity == {0, 0} → estrelles quietes.
+        void update(float delta_time, Vec2 world_velocity);
+
+        void draw() const;
+
+       private:
+        struct Star {
+            float x{0.0F};
+            float y{0.0F};
+            int layer{0};       // 0=Far, 1=Mid, 2=Near
+            SDL_Color color{};  // tint precomputat entre blanc i cyan
+        };
+
+        void buildStars();
+        static auto layerBrightness(int layer) -> float;
+        static auto layerParallax(int layer) -> float;
+        static auto layerSize(int layer) -> int;
+
+        Rendering::Renderer* renderer_;
+        std::array<Star, Defaults::StarfieldParallax::TOTAL_COUNT> stars_{};
+    };
+
+}  // namespace Graphics

source/game/scenes/game_scene.cpp

@@ -30,6 +30,7 @@ GameScene::GameScene(SDLManager& sdl, SceneContext& context)
       floating_score_manager_(sdl.getRenderer()),
       trail_manager_(sdl.getRenderer()),
       text_(sdl.getRenderer()),
+      starfield_parallax_(sdl.getRenderer()),
       playfield_(sdl.getRenderer()),
       border_(sdl.getRenderer()) {
     // Recuperar configuración de match des del context
@@ -213,6 +214,9 @@ void GameScene::stepPhysics(float delta_time) {
         bullet.postUpdate(delta_time);
     }
     trail_manager_.update(delta_time, ships_);
+    // De moment world_velocity = {0, 0} → estrelles quietes; al ser-hi l'estat
+    // del wraparound es resol normalment quan activem el moviment.
+    starfield_parallax_.update(delta_time, Vec2{.x = 0.0F, .y = 0.0F});
     playfield_.update(delta_time);
     border_.update(delta_time);
 
@@ -569,6 +573,7 @@ void GameScene::drawActiveShipsAlive() const {
 }
 
 void GameScene::drawContinueState() {
+    starfield_parallax_.draw();
     border_.draw();
     drawEnemies();
     drawBullets();
@@ -580,6 +585,7 @@ void GameScene::drawContinueState() {
 }
 
 void GameScene::drawGameOverState() {
+    starfield_parallax_.draw();
     border_.draw();
     drawEnemies();
     drawBullets();
@@ -625,6 +631,8 @@ void GameScene::drawInitHudState() {
         Defaults::Game::INIT_HUD_SHIP2_RATIO_INIT,
         Defaults::Game::INIT_HUD_SHIP2_RATIO_END);
 
+    // Capa de fons més profunda: estrelles 2D (apareixen senceres des del frame 0).
+    starfield_parallax_.draw();
     // Graella de fons al darrere (timer intern propi, cobreix tot l'INIT_HUD).
     playfield_.draw();
 
@@ -650,6 +658,7 @@ void GameScene::drawInitHudState() {
 }
 
 void GameScene::drawLevelStartState() {
+    starfield_parallax_.draw();
     playfield_.draw();
     border_.draw();
     trail_manager_.draw();
@@ -663,6 +672,7 @@ void GameScene::drawLevelStartState() {
 }
 
 void GameScene::drawPlayingState() {
+    starfield_parallax_.draw();
     playfield_.draw();
     border_.draw();
     trail_manager_.draw();
@@ -676,6 +686,7 @@ void GameScene::drawPlayingState() {
 }
 
 void GameScene::drawLevelCompletedState() {
+    starfield_parallax_.draw();
     playfield_.draw();
     border_.draw();
     trail_manager_.draw();

source/game/scenes/game_scene.hpp

@@ -10,6 +10,7 @@
 
 #include "core/graphics/border.hpp"
 #include "core/graphics/playfield.hpp"
+#include "core/graphics/starfield_parallax.hpp"
 #include "core/graphics/vector_text.hpp"
 #include "core/physics/physics_world.hpp"
 #include "core/rendering/sdl_manager.hpp"
@@ -82,6 +83,9 @@ class GameScene final : public Scene {
     // Text vectorial
     Graphics::VectorText text_;
 
+    // Capa més profunda del fons: estrelles 2D amb parallax (estàtiques de moment).
+    Graphics::StarfieldParallax starfield_parallax_;
+
     // Fons del playfield (graella + futures capes)
     Graphics::Playfield playfield_;