OpenSA2 0.1.0-alpha.6.1

Note

Updated November 1, 2026: a new look for the Android app. The Android download now has a redesigned app, laid out like Android's own settings. Play and Chao World come first, with a Tweaks card on the home screen. Game settings opens to an overview of Display, Touch controls, Controller, Sound, Saves and Debug, each showing its current value, and each opens as its own page. The Tweaks screen lists its groups with how many tweaks are on, has a search, and has a Suggest a tweak link to a short form on GitHub. The game itself is unchanged: the APK's game, player and installer libraries are the same files as before. Install the new APK over the old one; your imported game, saves and settings stay. The Windows and Linux downloads are unchanged.

OpenSA2 0.1.0-alpha.6.1 adds volume controls. The music, the characters' voices and the sound effects each get their own level, and the Android app gets sliders for them. It is otherwise alpha.6.

You must supply your own unmodified PC game installation: the version Steam sells and installs today. These downloads include recompiled game logic and the port's runtime. They contain no original game executable or assets.

What's new

Volume levels. The PC version mixes its music loud, and the game has no volume settings. On Android, Game settings has a new Sound page with Music, Voices and Sound effects sliders, from 0 to 100% of the game's own level. Moving a slider turns on the Volume levels tweak (Tweaks, Audio); turn it off there and every sound goes back to the game's own level, with your slider positions kept. On Windows and Linux, add volume-levels to SA2_TWEAKS in game.env, and set the levels with lines such as SA2_MUSIC_VOLUME=40, SA2_VOICE_VOLUME=100 and SA2_SFX_VOLUME=80. With none set, the music plays at 60% and the rest at 100%.

The short music cues (1-up, speed shoes, invincibility, goal ring, boss cues) keep the game's level, because the game sets their volume another way.

Building from source. The setup guide now says how to make the pinned unpacked executable the source build needs, and why the same tool on Microsoft .NET gives a different file. It also explains why OpenSA2 rebuilds fixes from PC mods as tweaks instead of loading the mods themselves.

Downloads

Platform	Asset	Start here
Windows x86-64	OpenSA2-v0.1.0-alpha.6.1-windows-x86_64.zip	Extract the entire ZIP and run OpenSA2.cmd.
Android arm64	OpenSA2-v0.1.0-alpha.6.1-android-arm64.apk	Install the APK over the earlier one; your imported game, saves and settings stay.
Linux x86-64	OpenSA2-v0.1.0-alpha.6.1-linux-x86_64.deb	Install with sudo apt install './OpenSA2-v0.1.0-alpha.6.1-linux-x86_64.deb', then launch OpenSA2.

Setup instructions and requirements

Windows requires Windows 10 or later and a Vulkan or Direct3D 12 graphics driver. Android requires Android 10 or later, a 64-bit ARM device, and a Vulkan 1.1 or later driver. The Linux package requires Ubuntu 24.04, Debian 13, or a compatible newer distribution with Vulkan graphics.

Known problems

alpha.6's known problems still apply:

• The tweaks that patch the game's code (no music, no voices, faster spin dash, every stage in Stage Select, and powerups on the victory screen) are on Linux and Android only for now.
• Heavy stages such as Dry Lagoon can still run below 60 fps on phones. Video cutscenes can drop in frame rate and break up the audio on some phones (#26).
• Broad stage, boss, story-event and game-mode coverage is unfinished. Widescreen menus and overlays still need work.

Tested scope

The game binaries are alpha.6's with one tweak added. Each level was measured in real City Escape runs of the Linux build with the audio recorded: at 20%, the music, the voice lines and the sound effects each came out 14 dB quieter, and the other sounds did not change. The Android build was installed on a Galaxy S25, where the sliders were checked by ear. With every tweak off, the Linux build and the Windows build under Wine match the boot recording frame for frame. The Windows ZIP, Linux DEB and Android APK passed their package checks. These checks cover the exercised paths only.

The updated Android app was checked on a Galaxy S25: the home screen, Game settings and its pages, the Tweaks screen and its groups and search, a settings dialog and the touch layout editor. Its game libraries are byte-identical to the first alpha.6.1 APK's.

Thanks

Thanks to ManyMilesLongAway for asking for this, and to @crocchetto for reporting the missing unpacked-executable recipe (#41). The levels follow the idea of the SA2 Volume Controls mod by Shaddatic; OpenSA2 does not use its code.

Source, licenses, and checksums

SHA256SUMS records the downloadable files. The project source for all three packages is at this release tag, except the updated Android app's, which is at commit a54942f on main. The public source-build bootstrap remains incomplete and still needs locally generated game inputs.

Original project code is GPL-3.0-only. Packages preserve the licenses and notices for their bundled components. Original game rights remain with their respective holders. OpenSA2 is independent of SEGA and Sonic Team.

Report a problem. On Android, use the app's Report on GitHub button. Keep game files and recordings containing game data out of reports.