Sonic the Perfect Existence

Introduction: Sonic the Perfect Existence is an older Sonic the Hedgehog 2 ROM hack for the Sega Genesis / Mega Drive. It is notable for replacing Sonic with Shadow the Hedgehog and using Mizu as Shadow's companion while introducing new level content and music.

Gameplay & Mechanics: The project remains based on Sonic 2 rather than Sonic 3 & Knuckles. Shadow takes Sonic's role through modified stages, with Mizu accompanying him. Surviving versions are imperfect and some of Shadow's sprite work was never fully completed.

Key Features:

• Shadow the Hedgehog replaces Sonic as the main playable character.
• Mizu appears as Shadow's sidekick.
• New levels and music distinguish the hack from the original Sonic 2 presentation.

The project is best treated as an older Sonic 2 character-and-level hack rather than a polished Sonic 3 & Knuckles conversion with modern abilities such as the Drop Dash.