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 compilation of obscure video games published by Sega for various consoles, such as the Sega CD, Sega Saturn, and Game Gear. It primarily focuses on "Sonic the Hedgehog" games, such as "Sonic CD" (1993) and "Sonic the Fighters" (1996). It also includes six of the twelve "Sonic" games released for the Game Gear. These games encompass various genres, such as platforming, fighting, pinball, and puzzle. Additionally, players can unlock several Sega Genesis games unrelated to "Sonic", including the two "Vectorman" games (1995 and 1996). Four games in the international version, "Bonanza Bros." (1990) and the "Streets of Rage" trilogy (1991—1994), are not included in the North American version. Each game is mostly identical to its initial release, but some were changed; for example, "Sonic R" runs at a higher frame rate.