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.
Sega CD
The Sega CD supports a library of over 200 games created both by Sega and an array of third-party publishers. Included in this library are six games which, while receiving individual Sega CD releases, also received separate versions that utilized both the Sega CD and 32X add-ons. Among the games released for the add-on were a number of FMV games, including "Sewer Shark" and "Fahrenheit". Well-regarded games include "Sonic CD", "" and "", "Popful Mail", and "Snatcher", as well as the controversial "Night Trap". Although Sega created "Streets of Rage" for the Genesis to compete against the SNES port of the arcade hit "Final Fight", the Sega CD received an enhanced version of the latter game that has been praised for its greater faithfulness to the arcade original. "" was noted for its impressive use of the system's hardware as well as its violent content. In particular, "Sonic CD" garnered critical acclaim for its graphics and new time travel elements, which improved upon the traditional "Sonic" formula. The Sega CD also received enhanced ports of games from the Genesis, such as "Batman Returns" and "Ecco the Dolphin".