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 Genesis
Designed by an R&D team supervised by Hideki Sato and Masami Ishikawa, the hardware was adapted from Sega's System 16 arcade board, centered on a Motorola 68000 processor as the CPU, a Zilog Z80 as a sound controller, and a video system supporting hardware sprites, tiles, and scrolling. The system plays a library of more than 900 games created by Sega and a wide array of third-party publishers and delivered on ROM-based cartridges. The Genesis has benefited from several add-ons, including a Power Base Converter to play Master System games, as well as multiple first and third party licensed variations of the console. Sega created two network services to support the Genesis: Sega Meganet and Sega Channel.