Sonic The Hedgehog Open Source Project 0.05, like its predecessor 0.04A, is a ROM hack for the Sega Genesis, built upon Sonic the Hedgehog. The version number indicates a subsequent release, suggesting improvements, additions, and bug fixes. As an open-source project, community contributions are central to its evolution, allowing for collective enhancements and creative expansion on the original game.  The community collaboration is independent of any official Sega support.

Sonic The Hedgehog Open Source Project 0.05

Sonic The Hedgehog Megamix January 7, 2007 Build (S1 Hack)