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: After the Sequel
"After the Sequel" is a 2D platformer in the style of the "Sonic" games for the Sega Genesis. As such, it lets the player control either the blue hedgehog Sonic or his orange fox friend Tails. Both characters can move left and right with the arrow keys and jump with the "Z" key; Tails can also fly to reach areas Sonic cannot. The game takes place in seven levels, known as zones, each divided into three acts followed by a boss fight with Doctor Eggman. These zones are designed for fast-paced gameplay, featuring typical "Sonic" obstacles such as bottomless pits and vertical loops. The zones are based on various themes, including haunted houses, cities, magma caverns, winter theme parks, and sugar processing plants.