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.
Game Gear
Over 300 games were released for the Game Gear, although at the time of the console's launch, there were only six software games available. Prices for game cartridges initially ranged from $24.99 to $29.99 each. The casings were molded black plastic with a rounded front to aid in removal. Games for the system included "Sonic the Hedgehog", "The GG Shinobi", "Space Harrier", and "Land of Illusion Starring Mickey Mouse", which was considered the best game for the system by GamesRadar. Later games took advantage of the success of the Genesis, Sega's 16-bit video game console, with games released from franchises originally released on the Genesis. A large part of the Game Gear's library consists of Master System ports. Because of the landscape orientation of the Game Gear's screen and the similarities in hardware between the handheld console and the Master System, it was easy for developers to port Master System games to the Game Gear.