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
"Sonic Colors", released in November 2010, expanded further on the "Rush" series gameplay with the addition of the use of "Wisps", which gave Sonic various new power-ups and gimmicks. "Sonic Free Riders" was released in November 2010 as a follow-up to the "Sonic Riders" series, and was developed exclusively for Xbox 360's Kinect system. Later on, "Sega Superstars Tennis" for the Wii, Xbox 360, PlayStation 3, PlayStation 2 and Nintendo DS was released in 2008 and "Sonic & Sega All-Stars Racing" for the Wii, Xbox 360, PlayStation 3, Nintendo DS and PC and iOS was released in 2010, followed by a sequel in 2012.