Fixed gameplay

src/app/BackgroundManager.h

@@ -0,0 +1,18 @@
+#pragma once
+#include <SDL3/SDL.h>
+
+class BackgroundManager {
+public:
+    BackgroundManager();
+    ~BackgroundManager();
+
+    bool queueLevelBackground(SDL_Renderer* renderer, int level);
+    void update(float frameMs);
+    void render(SDL_Renderer* renderer, int winW, int winH, float motionClockMs);
+    void reset();
+
+    struct Impl;
+
+private:
+    Impl* impl;
+};