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 Spinball
The game has been rereleased on 11 different platforms. The Genesis version of the game has been rereleased on the "Sonic Mega Collection" compilation for the Nintendo GameCube, PlayStation 2, Xbox and PCs, "Sonic's Ultimate Genesis Collection" for the Xbox 360 and PlayStation 3, and multiple iterations of the "Sega Smash Pack" series of compilations. The Game Gear version appears as an unlockable game in "" for the GameCube and PC, as well as "Sonic Gems Collection" for the GameCube and PlayStation 2. The game was intended to be included in the "Sonic Classic Collection" for the Nintendo DS, but was cut for unspecified reasons. The Genesis version was released on the Wii's Virtual Console on March 12, 2007 in North America and April 5, 2007 in Europe. An emulated form of the game was also made available for iOS devices via Apple's App Store in 2010, but was later removed along with other Sega titles in 2015. On September 13, 2010, it was released on Steam.