Sonic Extreme was a prototype video game created by Vision Scape Interactive in May 2003. Proposed as a spin-off to Sega's Sonic the Hedgehog series, Sonic Extreme featured Sonic and Shadow riding hoverboards in a Green Hill Zone-themed open world, with gameplay likened to Tony Hawk's Pro Skater. It featured three gameplay modes, which included searching for keys and Chaos Emeralds and fighting or racing another player. Vision Scape created the prototype while it made cutscenes for Sonic Heroes (2003); it was developed on the Xbox with intent to port it to the GameCube and PlayStation 2. The prototype was assembled using the RenderWare game engine and assets from prior Vision Scape and Sonic games.