Sonic the Hedgehog
The Sega Genesis had "add-on" systems that incorporated "Sonic" games. "Sonic CD", released for the Sega CD, was a 2D platform game released in 1993. The game introduced the characters Amy Rose and Metal Sonic and featured levels that differed depending upon whether Sonic was in the past, present, or future time frames. "Knuckles' Chaotix", a spin-off released in 1995 for the Sega 32X, featured Knuckles and a new group named Chaotix fighting against Dr. Robotnik. The game featured a two-player cooperative system in which the on-screen characters were connected by magic rings. There was also "Sonic Eraser", a puzzle game released exclusively on Sega Game Toshokan in 1991.
Sonic the Hedgehog (8-bit video game)
In 1990, Sega released the Game Gear, an 8-bit handheld game console designed to compete with Nintendo's Game Boy. Around the same time, Sonic Team worked on "Sonic the Hedgehog" for the 16-bit Genesis and Sega wanted to increase consumer awareness of the Game Gear by producing a version of "Sonic" for the system. 22-year old composer Yuzo Koshiro had recently started working with Sega, having been asked to compose the soundtrack for the Genesis version of "The Revenge of Shinobi" (1989). After, he told a section chief he could develop games himself. As a result, a general manager, whom Koshiro met while working on "The Revenge of Shinobi", asked him to start developing a Game Gear version of "Sonic". Koshiro founded Ancient to develop the game because Sega could not make contracts with individuals. His sister Ayano Koshiro served as director and his mother Tomo Koshiro had a "behind the scenes" role, while the first programmer he hired was Shinobu Hayashi. The 8-bit "Sonic" was created specifically for the Game Gear, but Sega also had Ancient develop a version for the Master System, which was selling well and had similar hardware.