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 Gems Collection
Sonic Gems Collection is a 2005 compilation of Sega video games, primarily those in the "Sonic the Hedgehog" series. The emulated games span multiple genres and consoles—from the Sega Genesis to the Sega Saturn—and retain the features and errors of their initial releases with minimal edits. Player progress is rewarded with demos of other "Sonic" games, videos, and promotional artwork spanning the history of the "Sonic" franchise. While its 2002 predecessor, "Sonic Mega Collection", comprised the more popular "Sonic" games, "Gems Collection" focuses on more obscure games, such as "Sonic CD" and "Sonic the Fighters". Other non-"Sonic" games are included, but some, such as the "Streets of Rage" trilogy, are omitted in the North American localization.