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 (1991 video game)
"Sonic the Hedgehog" was well received by critics, who praised its visuals, audio, and gameplay. It was also commercially successful, establishing the Genesis as a key player in the 16-bit era and allowing it to compete with Nintendo and their Super Nintendo Entertainment System console. The game has been ported a number of times, and inspired several clones, a successful franchise, and adaptations into other media. It is often cited as one of the greatest video games of all time.