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 Blast
The game was developed by Aspect Co. and published by Sega for the Game Gear. It was the final "Sonic the Hedgehog" game for the system, and has been rereleased on the Master System (1997), through two "Sonic"-themed compilations (2003 and 2004), and the Nintendo 3DS's Virtual Console (2012). Despite their similar titles and coinciding releases, "Sonic Blast" and "Sonic 3D Blast" have little in common. Retrospective reviewers generally had little praise for "Sonic Blast" and have deemed it one of the series' worst games. Although some considered its graphics impressive when considering the technological restrictions of the Game Gear, most found its animations and colors mediocre. The level designs and slow gameplay were also criticized.