About
Open Sonic is a free, open-source 2D platformer Sonic fan game written in C using the Allegro library, started in 2009 by Brazilian developer Alexandre Martins. Its distinctive feature was cooperative play, letting the player control Sonic, Tails, and Knuckles simultaneously to solve puzzles.
The Open Sonic phase ended with version 0.1.4 in September 2010, after which the project was discontinued and reborn as the original-IP engine Open Surge, which remains actively maintained. It is notable as the origin of the Open Surge retro game engine and game-creation system.
Identity
Launch
- Binary
- opensonic
- Needs files
- none beyond the binary
Runtime
- Runs as
- Native Linux
- Proton
- not needed
⚙ Setup notes
Overview: A free, open-source (GPLv2) Sonic fan game; final release 0.1.4 (Sept 2010). Native Linux, no Proton, no DRM.
Native: type = 'native'. The official Linux package opensnc-linux-0.1.4.tar.gz is portable — extract it and run the bundled ELF opensonic; no installation step. Built on the Allegro 4 library.
IMPORTANT (32-bit): the 0.1.4 Linux binary is x86 (32-bit) only. The Steam Deck is x86-64, so the 32-bit Allegro 4 runtime / multilib must be present for the bundled opensonic to launch. Add it as a non-Steam game and verify it starts from a terminal first.
Sound fix: older builds can fail or hang on audio under PulseAudio/PipeWire. The known workaround is to wrap the launch with ALSA-OSS emulation — set launch_options to aoss %command% (or padsp %command%) if audio breaks the game on startup.
Alternative path: if the aging 32-bit 0.1.4 build won't run cleanly, the engine's actively maintained original-IP successor Open Surge (Flatpak org.opensurge2d.OpenSurge on Flathub) installs and runs natively on Deck — but it is a *different game* (the "Surge the Rabbit" project), not Open Sonic, so it's a separate recipe rather than a drop-in for these assets.
Controller: the Allegro 4 build has limited native joystick support; a Steam Input layout (keyboard/gamepad mapping) is the reliable way to drive it on Deck.
Note: project is discontinued/unfinished but what's there is playable.
The one thing to know
License: Free, open-source GPLv2 fan game (not SEGA), never sold on Steam — no DRM. Get it from the creator's official SourceForge page.
Native + portable: Native Linux (type = 'native'), no Proton. The opensnc-linux-0.1.4.tar.gz package is portable — extract and run the bundled opensonic ELF directly. Built on Allegro 4.
32-bit gotcha: the 0.1.4 Linux binary is x86 (32-bit) only; the Deck is x86-64, so the 32-bit Allegro 4 / multilib runtime must be available or it won't launch. Test from a terminal before adding it.
Sound fix: if audio breaks the game on PulseAudio/PipeWire, wrap the launch with aoss %command% (or padsp %command%).
Alternative: the actively maintained successor Open Surge (Flatpak org.opensurge2d.OpenSurge) runs natively on Deck, but it is a *different game*, not Open Sonic.
Controller: Steam Input layout recommended (Allegro 4 joystick support is limited).
Note: incomplete/discontinued but playable.
Community guides
Write-ups and threads from people who got this (or a similar) game running. deckport links to them — it doesn't reproduce them.
Get the artwork
deckport never hosts game images. Open this game on SteamGridDB, pick
the cover / hero / logo / icon you like, and drop them into the
game folder under .deckport-art/ before you push it to the
Deck. The importer files them under the right names automatically.
Run it on your Deck
Two files: the one-time importer (deckport.py) in your
Deck's home folder, and this game's install helper. Copy the game
into ~/Games and run the helper with Steam closed — it
writes the recipe (binary, launch options)
and registers the shortcut with artwork.