Sonic X-treme was a cancelled platform video game in the Sonic the Hedgehog series. Developed by Sega Technical Institute (STI), X-treme was designed to capitalize on the success of Sega's mascot character by being the first fully 3D Sonic game and the first original Sonic title developed for the Sega Saturn. During the course of development, several different styles of gameplay were tried and the plot of the game changed several times.