Updated game structure

src/audio/Audio.h

@@ -0,0 +1,60 @@
+// Audio.h - MP3 playlist playback (Windows Media Foundation backend) + SDL3 stream
+#pragma once
+#include <SDL3/SDL.h>
+#include <vector>
+#include <string>
+#include <random>
+#include <cstdint>
+#include <thread>
+#include <mutex>
+#include <atomic>
+
+struct AudioTrack {
+    std::string path;
+    std::vector<int16_t> pcm;
+    int channels = 2;
+    int rate = 44100;
+    size_t cursor = 0;
+    bool ok = false;
+};
+
+class Audio {
+public:
+    static Audio& instance();
+    bool init();                  // initialize backend (MF on Windows)
+    void addTrack(const std::string& path); // decode MP3 -> PCM16 stereo 44100
+    void addTrackAsync(const std::string& path); // add track for background loading
+    void startBackgroundLoading(); // start background thread for loading
+    void waitForLoadingComplete(); // wait for all tracks to finish loading
+    bool isLoadingComplete() const; // check if background loading is done
+    int getLoadedTrackCount() const; // get number of tracks loaded so far
+    void shuffle();               // randomize order
+    void start();                 // begin playback
+    void toggleMute();
+    // Queue a sound effect to mix over the music (pcm can be mono/stereo, any rate; will be converted)
+    void playSfx(const std::vector<int16_t>& pcm, int channels, int rate, float volume);
+    void shutdown();
+private:
+    Audio()=default; ~Audio()=default; Audio(const Audio&)=delete; Audio& operator=(const Audio&)=delete;
+    static void SDLCALL streamCallback(void* userdata, SDL_AudioStream* stream, int additional, int total);
+    void feed(Uint32 bytesWanted, SDL_AudioStream* stream);
+    void nextTrack();
+    bool ensureStream();
+    void backgroundLoadingThread(); // background thread function
+    
+    std::vector<AudioTrack> tracks; int current=-1; bool playing=false; bool muted=false; std::mt19937 rng{std::random_device{}()};
+    SDL_AudioStream* audioStream=nullptr; SDL_AudioSpec outSpec{}; int outChannels=2; int outRate=44100; bool mfStarted=false;
+    
+    // Threading support
+    std::vector<std::string> pendingTracks;
+    std::thread loadingThread;
+    std::mutex tracksMutex;
+    std::mutex pendingTracksMutex;
+    std::atomic<bool> loadingComplete{false};
+    std::atomic<int> loadedCount{0};
+
+    // SFX mixing support
+    struct SfxPlay { std::vector<int16_t> pcm; size_t cursor=0; };
+    std::vector<SfxPlay> activeSfx;
+    std::mutex sfxMutex;
+};