Sonic the Hedgehog: Proto-Mix is a ROM modification for the 2013 mobile/RSDK version of Sonic the Hedgehog. The hack is defined by its objective to "mix" the high-speed gameplay of the final 1991 release with rare, scrapped elements found in early prototype builds and magazine scans.
Sonic 2 Addendum it aims to create an enhanced, definitive version of the original game by restoring and reimagining content from unused beta versions and prototypes, alongside adding modern quality-of-life improvements.
The project reimagines the original West Side Island adventure with a narrative focused on Dr. Robotnik’s "terraformation scheme," which has transformed classic zones into surreal, expanded environments filled with new secrets and branching paths.
Sonic 3 Ultimate is a hack of Sonic 3 & Knuckles that aims to give an upgrade to the game. Graphics have been updated and multiple bugs have been fixed.