Sonic 1 Definitive is another ROM hack of the original Sonic the Hedgehog for Sega Genesis, aiming for an enhanced experience. While specifics vary depending on the version, it generally involves graphical updates, possible gameplay tweaks, and potentially new levels or level sections.  The original Sonic the Hedgehog was developed by Sonic Team and published by Sega. This hack, however, is a fan-made project and its details depend on the specific developer.

Sonic 1 Definitive

Sonic 1 Classic Edition (SHC 2023)