Replace Game::initialize() with factory method

src/app.cppm

@@ -15,8 +15,8 @@ export
 {
     class App
     {
-        std::unique_ptr<core::Engine> engine_ = nullptr;
-        std::unique_ptr<game::Game> game_ = nullptr;
+        std::unique_ptr<core::Engine> engine_{nullptr};
+        std::unique_ptr<game::Game> game_{nullptr};
 
         public:
             App() = default;
@@ -36,10 +36,9 @@ export
                     // Initialize SDL subsystems
                     sdl::Init(sdl::InitFlags::Video | sdl::InitFlags::Events);
 
+                    // Create engine (includes window and renderer) and game state
                     engine_ = core::Engine::create();
-
-                    game_ = std::make_unique<game::Game>(*engine_);
-                    game_->initialize();
+                    game_ = game::Game::create(*engine_);
                 }
                 catch (const std::runtime_error& e) {
                     std::cerr << "Unhandled exception during initialization: " << e.what() << '\n';

src/core/engine.cppm

@@ -59,12 +59,12 @@ export namespace core
                     0
                 );
 
-                return std::unique_ptr<Engine>(
+                return std::unique_ptr<Engine>{
                     new Engine{
                         std::move(sdl_window),
                         Renderer{std::move(sdl_renderer)}
                     }
-                );
+                };
             }
 
             bool keep_running() const

src/game/game.cppm

@@ -1,5 +1,6 @@
 module;
 
+#include <cassert>
 #include <memory>
 #include <SDL3/SDL.h>
 
@@ -15,27 +16,18 @@ export namespace game
 {
     class Game
     {
+        // Whether this class is currently instantiated (to prevent multiple instances)
+        static bool instantiated_;
+
+        // Reference to the engine
         core::Engine& engine_;
 
         // Sprite for testing
-        std::unique_ptr<Sprite> sprite_ = nullptr;
-
-        public:
-            Game() = delete;
+        std::unique_ptr<Sprite> sprite_{nullptr};
 
+        // Private constructor
         explicit Game(core::Engine& engine)
             : engine_(engine)
-            {}
-
-            // No copy or move operations because we have a reference to the engine
-            Game(const Game&) = delete;
-            Game& operator=(const Game&) = delete;
-            Game(Game&&) = delete;
-            Game& operator=(Game&&) = delete;
-
-            ~Game() = default;
-
-            void initialize()
         {
             // TODO: Texture should be a reference/pointer to an object managed by a ResourceManager or similar.
             auto texture = sdl_image::LoadTexture(
@@ -46,6 +38,29 @@ export namespace game
             sprite_ = std::make_unique<Sprite>(std::move(texture), 100, 100);
         }
 
+        public:
+            Game() = delete;
+
+            // No copy or move operations because we have a reference to the engine
+            Game(const Game&) = delete;
+            Game& operator=(const Game&) = delete;
+            Game(Game&&) = delete;
+            Game& operator=(Game&&) = delete;
+
+            ~Game()
+            {
+                instantiated_ = false;
+            }
+
+            static std::unique_ptr<Game> create(core::Engine& engine)
+            {
+                // Prevent the class from being instantiated multiple times
+                assert(!instantiated_);
+                return std::unique_ptr<Game>{
+                    new Game(engine)
+                };
+            }
+
             // Handles an SDL event. Returns true if the event has been handled.
             bool handle_event(const sdl::Event* event) const
             {
@@ -75,4 +90,6 @@ export namespace game
             {
             }
     };
+
+    bool Game::instantiated_ = false;
 }

src/game/sprite.cppm

@@ -29,16 +29,6 @@ export namespace game
                 dest_rect_.h = static_cast<float>(height);
             }
 
-            // Don't allow copy operations
-            Sprite(const Sprite&) = delete;
-            Sprite& operator=(const Sprite&) = delete;
-
-            // Default move operations
-            Sprite(Sprite&& other) = default;
-            Sprite& operator=(Sprite&& other) = default;
-
-            ~Sprite() = default;
-
             void move(const float x, const float y)
             {
                 dest_rect_.x = x;

src/wrappers/sdl/render.cppm

@@ -21,10 +21,10 @@ export namespace sdl
         std::unique_ptr<
             SDL_Texture,
             utils::FuncDeleter<SDL_DestroyTexture>
-        > raw_texture_ = nullptr;
+        > raw_texture_;
 
         public:
-            Texture() = default;
+            Texture() = delete;
 
             explicit Texture(SDL_Texture* raw_texture)
                 : raw_texture_{raw_texture}
@@ -45,10 +45,10 @@ export namespace sdl
         std::unique_ptr<
             SDL_Renderer,
             utils::FuncDeleter<SDL_DestroyRenderer>
-        > raw_renderer_ = nullptr;
+        > raw_renderer_;
 
         public:
-            Renderer() = default;
+            Renderer() = delete;
 
             explicit Renderer(SDL_Renderer* raw_renderer)
                 : raw_renderer_{raw_renderer}

src/wrappers/sdl/video.cppm

@@ -18,10 +18,10 @@ export namespace sdl
         std::unique_ptr<
             SDL_Window,
             utils::FuncDeleter<SDL_DestroyWindow>
-        > raw_window_ = nullptr;
+        > raw_window_;
 
         public:
-            Window() = default;
+            Window() = delete;
 
             explicit Window(SDL_Window* raw_window)
                 : raw_window_{raw_window}