Another ROM hack of Sonic the Hedgehog for the Sega Genesis, this version by D.A.Garden introduces Westside Island as a significant alteration. This likely involves new level design, potentially entirely new zones or significant alterations to existing ones.  The original gameplay mechanics are likely maintained, with the focus of the hack being on expanding or changing the game's world and progression.   The impact would be a noticeably extended or altered experience from the original game. The game remains a fan-made project, showcasing the dedication of the modding community.

Sonic the Hedgehog (USA, Europe) [Hack by D.A.Garden v1.0] (~Sonic the Hedgehog - Westside Island)

Sonic the hedgehog (Speed Battle)