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.
1993 congressional hearings on video games
During this period, two key players were Nintendo and Sega. Nintendo had been instrumental in helping to recover the North American market after the crash with the introduction of the Nintendo Entertainment System; in 1990, with its release of the Super Nintendo Entertainment System (SNES), Nintendo sales accounted for 90% of the US market. However, to avoid repeating one of the issues that caused the crash, Nintendo took care to limit and review what third-party games could be made for its platforms to avoid a glut of poor games. Sega, which had already released its Mega Drive in Japan, found their sales to be lagging behind Nintendo. In a aggressive campaign aimed at the United States market, the Mega Drive was renamed the Sega Genesis, and heavily pushed the game "Sonic the Hedgehog", with its titular character aimed to become Sega's mascot and rival that of Nintendo's Mario. Sega was less selective about what titles it wanted for the platform, allowing many more third-party games onto the system to increase its library in contrast to Nintendo's. Further, Sega used marketing language purposely aimed at Nintendo, such as "Sega does what Nintendon't". By 1992, Sega had obtained 65% of the US gaming market, overtaking Nintendo's dominant position. Subsequently a strong rivalry between Nintendo and Sega was formed, referred as the "Console Wars", which continued through the next decade and into the fifth generation of consoles, after which Sega dropped out of the hardware market and became principally a game developer and publisher, and at times working collaborative with Nintendo.