There were a few releases, with this being the most recent build that found its way into public hands and still ran on the Genesis, while newer versions run on the SegaCD and thus, unfortunately, can't be added to this Steam Workshop. This particular version of Sonic 1 Megamix, from 2007, is a full game modification for Sonic 1, featuring five playable characters with their own unique movesets, new level layouts, and a ton of imported music
