emulator: Sonic 3 A.I.R. type: standalone core_classification: game_engine source: "https://github.com/Eukaryot/sonic3air" upstream: "https://github.com/Eukaryot/sonic3air" source_commit: "de0fd6a7c07b399c9a612cb7cb8d61b54cb339d1" profiled_date: "2026-10-04" display_name: "Sonic 3 - Angel Island Revisited" cores: [] systems: [sonic3-air] notes: | Sonic 3 - Angel Island Revisited by Eukaryot. The Oxygen Engine runs the decompiled game logic (lemon scripts) against the original Genesis ROM loaded at runtime; the ROM is not shipped with the engine. ROM search order (ResourcesCache::loadRom): 1. GameAppData/ 2. Last known ROM path (settings.json RomPath) 3. Configured RomPath (config.json) 4. SteamRomName in the install directory 5. Steam library .../Sega Classics/uncompressed ROMs/ 6. User-picked file via native file dialog (filter *.bin) ref: Oxygen/oxygenengine/source/oxygen/resources/ResourcesCache.cpp:19-115, Oxygen/oxygenengine/source/oxygen/application/GameLoader.cpp:60-94, Oxygen/oxygenengine/source/oxygen/platform/PlatformFunctions.cpp:379-408 ROM validation (ResourcesCache::loadRomFile + checkRomContent): 1. Read file into memory. 2. applyRomModifications: XOR optional diff file, blank regions, then byte overwrites from the active RomInfo. The default S3K_Steam entry sets offset 0x2001f0 = 0x4a (patches the ROM header checksum field so the Steam dump matches the authoritative hash). 3. Size check: must equal 0x400000 (4 MiB). 4. Content check: Murmur2_64 of the full post-modification ROM must equal 0x344983ffcfeff8cb. ref: Oxygen/oxygenengine/source/oxygen/resources/ResourcesCache.cpp:152-282, Oxygen/sonic3air/source/sonic3air/ConfigurationImpl.cpp:33-47, Oxygen/sonic3air/oxygenproject.json:9-20 The engine ships four data packages built from Oxygen/sonic3air/data/ (enginedata.bin, gamedata.bin, audiodata.bin, audioremaster.bin). Three are required and part of the release; audioremaster.bin is optional and downloaded on demand from https://sonic3air.org/download/audioremaster.bin when the user enables the remastered soundtrack. ref: Oxygen/sonic3air/oxygenproject.json:32-38, Oxygen/sonic3air/source/sonic3air/EngineDelegate.cpp:115-118, Oxygen/sonic3air/source/sonic3air/audio/RemasteredMusicDownload.cpp:48-62 Each package is opened from the game data directory, data/ under the install directory, then from data/ under the app-data directory, where the downloader saves audioremaster.bin. Package paths below are written under sonic3-air/, which stands for either root. ref: Oxygen/oxygenengine/source/oxygen/engine/EngineMain.cpp:643-651, Oxygen/oxygenengine/source/oxygen/application/Configuration.cpp:288-289 Only one RomInfo is declared (S3K_Steam). The engine does not support on-the-fly Sonic 3 + Sonic & Knuckles lock-on concatenation at run time; the user must supply the 4 MiB combined ROM (as distributed with Sega Mega Drive & Genesis Classics / Sonic Origins). files: - name: "Sonic_Knuckles_wSonic3.bin" category: game_data system: sonic3-air required: true size: 4194304 validation: [size] source_ref: "Oxygen/sonic3air/source/sonic3air/ConfigurationImpl.cpp:39-46 (fillDefaultGameProfile), Oxygen/oxygenengine/source/oxygen/resources/ResourcesCache.cpp:262-277 (checkRomContent)" note: | Sonic 3 & Knuckles combined ROM as shipped on Steam (Sega Mega Drive and Genesis Classics / Sonic Origins). Expected size 0x400000 bytes. After the engine overwrites offset 0x2001f0 with 0x4a, Murmur2_64 of the whole buffer must equal 0x344983ffcfeff8cb (not CRC32; the hash is computed with rmx::getMurmur2_64 over mRom). The engine also accepts a user-picked .bin via the native file-selection dialog that satisfies the same post-modification check. - name: "enginedata.bin" path: "sonic3-air/data/enginedata.bin" category: game_data system: sonic3-air required: true bundled: true source_ref: "Oxygen/sonic3air/source/sonic3air/EngineDelegate.cpp:115, Oxygen/oxygenengine/source/oxygen/engine/EngineMain.cpp:603-617, Oxygen/oxygenengine/source/oxygen/engine/EngineMain.cpp:643-651" note: | Oxygen Engine data package. A required package that cannot be opened closes the application, unless the data is present unpacked (data/images/icon.png exists). The engine then checks for oxygen_icon.png in the engine data and stops when it is absent (EngineMain.cpp:584-593). - name: "gamedata.bin" path: "sonic3-air/data/gamedata.bin" category: game_data system: sonic3-air required: true bundled: true source_ref: "Oxygen/sonic3air/source/sonic3air/EngineDelegate.cpp:116, Oxygen/oxygenengine/source/oxygen/engine/EngineMain.cpp:603-617, Oxygen/oxygenengine/source/oxygen/engine/EngineMain.cpp:643-651" note: | Game data package. A required package that cannot be opened closes the application, unless the data is present unpacked (data/images/icon.png exists). - name: "audiodata.bin" path: "sonic3-air/data/audiodata.bin" category: game_data system: sonic3-air required: true bundled: true source_ref: "Oxygen/sonic3air/source/sonic3air/EngineDelegate.cpp:117, Oxygen/oxygenengine/source/oxygen/engine/EngineMain.cpp:603-617, Oxygen/oxygenengine/source/oxygen/engine/EngineMain.cpp:643-651" note: | Audio data package. A required package that cannot be opened closes the application, unless the data is present unpacked (data/images/icon.png exists). - name: "audioremaster.bin" path: "sonic3-air/data/audioremaster.bin" category: game_data system: sonic3-air required: false source_ref: "Oxygen/sonic3air/source/sonic3air/EngineDelegate.cpp:118 (mDataPackages, Required=false), Oxygen/sonic3air/source/sonic3air/audio/RemasteredMusicDownload.cpp:45-62" note: | Remastered soundtrack package (131677405 bytes). Downloaded on demand from https://sonic3air.org/download/audioremaster.bin, saved as data/audioremaster.bin under the app-data directory and reloaded via EngineMain::reloadFilePackage. Absent at first launch; the engine falls back to the emulated FM soundtrack.