Sonic the Hedgehog
Due to the success of "Sonic" games on the Sega Genesis, the series was introduced to the Master System and the Game Gear. Sega began by releasing "Sonic the Hedgehog", a 2D platform game, in 1991. The game featured Sonic's ability to run and to jump at high speeds like its Mega Drive/Genesis counterpart but with notably different level design and music. Sega later released "Sonic the Hedgehog 2" another 2D platform game, in 1992. The game differed from its Genesis counterpart with different levels and music and by not including a "spin dash" maneuver. It also featured a different storyline in which Doctor Robotnik kidnaps Tails, who is non-playable in the Master System/Game Gear version. "Sonic Chaos"/"Sonic and Tails" (Japan), released in 1993, was similar to the earlier two Sega Master System/Game Gear "Sonic" games, but featured Tails as a playable character. A sequel, "Sonic Triple Trouble"/"Sonic and Tails 2" (Japan), a 2D platform game, was released in 1994 for the Game Gear and introduced a new character, Nack the Weasel, who, along with Knuckles and Doctor Robotnik, raced to collect the Chaos Emeralds. One of the last games for the Sega Game Gear, "Sonic Blast", was released in 1996 and featured prerendered sprites.
Sonic the Hedgehog (8-bit video game)
Porting the original game to the 8-bit hardware was impossible, so Ancient built their "Sonic" from scratch. The team decided to make their version completely different from its Genesis counterpart. According to Koshiro, the game had three phases of development. In the first phase, Ancient developed the game with the Genesis version in mind. The second and third phases were largely Ancient's own ideas, with Sega supervising their work. Koshiro thought reinventing "Sonic" for 8-bit hardware was challenging, as he did not work at Sega and had never developed a game before. However, Sega had faith in him because of his relationship to the company. Koshiro composed the soundtrack and sought to retain the feel of the Genesis version. He converted Masato Nakamura's 16-bit "Sonic" score to the 8-bit programmable sound generator to start, but ended up using only three of those tracks; the remainder of the music is Koshiro's work.