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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/<SteamRomName>
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/<SteamRomName>
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 (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
The packages are written by the game binary itself when run with -pack
from Oxygen/sonic3air/ (PackageBuilder::performPacking), which the
mastering scripts call before copying the results to the release image.
gamedata.bin data/ without data/audio/ and data/metadata.json
audiodata.bin data/audio/original/
audioremaster.bin data/audio/remastered/
enginedata.bin ../oxygenengine/data/
Each package is a flat container: "OPCK", format version 3, content
version BUILD_NUMBER, then one entry per file keyed by its path relative
to the base directory, in std::map order. Packing reads the data
directories only; the ROM is not involved.
ref: Oxygen/sonic3air/source/sonic3air/main.cpp:92-97,
Oxygen/sonic3air/source/sonic3air/helper/PackageBuilder.cpp:16-63,
Oxygen/oxygenengine/source/oxygen/file/FilePackage.cpp:44-151,
Oxygen/oxygenengine/source/oxygen/file/FilePackage.h:28-30,
Oxygen/sonic3air/source/sonic3air/version.inc:1,
Oxygen/sonic3air/___internal/mastering/mastering_linux.sh:48-52
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
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, Oxygen/sonic3air/source/sonic3air/helper/PackageBuilder.cpp:57-62"
note: |
Oxygen Engine data package, packed from Oxygen/oxygenengine/data/
(fonts, images, shaders, sprites, oxygen_icon.png). 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
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, Oxygen/sonic3air/source/sonic3air/helper/PackageBuilder.cpp:36-41"
note: |
Game data package, packed from Oxygen/sonic3air/data/ without the
audio directory and metadata.json (binary tables, fonts, images,
rawdata, sprites). 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
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, Oxygen/sonic3air/source/sonic3air/helper/PackageBuilder.cpp:43-48"
note: |
Audio data package, packed from Oxygen/sonic3air/data/audio/original/
(emulated soundtrack definitions and prototype SMPS tracks). 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.