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 2
Reviewers praised the large levels, colorful graphics and backgrounds, increased characters, enemies, and music. GameSpot stated that "time may have eroded Sega's prominence, but it hasn't done much to diminish how sweet "Sonic the Hedgehog 2" is," and, along with other reviewers, commented on how it is still a fun game to play. "Electronic Gaming Monthly" named it the best Genesis game of 1992. In 2000, "Game Informer" ranked "Sonic 2" number 61 on its "Top 100 Games of All Time" list, calling it "the most challenging and finely polished "Sonic the Hedgehog" title." "Mega" placed the game at #36 in their "Top Sega Mega Drive Games of All Time" list. Critics also enjoyed the faster gameplay in comparison to its predecessor, as well as its new features. Lucas Thomas of IGN praised the new "spin dash" ability.