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.