Sonic the Hedgehog is a 1991 side-scrolling platform game and companion to the 16-bit Sega Genesis game of the same name for the 8-bit Game Gear and Master System consoles. Ancient—a studio founded by composer Yuzo Koshiro for the project—developed the game and Sega published it to promote the handheld Game Gear. The 8-bit Sonic is similar in style to its Genesis predecessor, but reduced in complexity to fit the 8-bit systems. (wikipedia.org)