Sonic Megamix 1.0 is a ROM hack of Sonic the Hedgehog for the Sega Genesis. It's not a direct sequel but rather a significant overhaul of the original game, adding new levels, zones, and features while retaining the core gameplay of the classic title.  The hack was created by a group of dedicated fans, showcasing the community's commitment to expanding and improving upon the original Sonic experience. The gameplay remains largely true to the original Sonic, emphasizing fast-paced platforming, speed, and collecting rings.  The original Sonic the Hedgehog was developed and published by Sega in 1991, and this ROM hack is an example of fan-made content built upon that foundation.

Sonic Megamix 1.0 

Sonic Mega Fusion