Open Sonic

Open Sonic is an open-source game based on the "Sonic the Hedgehog" universe. It introduces a different style of gameplay called cooperative play, in which it's possible to control 3 characters simultaneously. Unlike most similar games, Open Sonic provides a greater level of interaction between the player and the levels. It's more than just a jump'n'run; the user must come up with some strategy in order to get through the levels.

Open Sonic is available for Windows and Linux. The latest release is 0.1.4 (September 19th, 2010). Main features:

It's portable! No installation is required!
Sonic-style physics (360° movement engine)
Available in 9 languages: English, Portuguese, French, Polish, German, Czech, Dutch, Indonesian, Italian
2 levels + innovative items + extras
You can create your own levels using the built-in level editor
You can make your own custom items, enemies and bosses using our object scripting system
MODdable capabilities
Good performance even on old computers*