Sonic Jam
"Sonic Jam" is a compilation which contains the four main "Sonic the Hedgehog" games released on the Sega Genesis: "Sonic the Hedgehog", "Sonic the Hedgehog 2", "Sonic the Hedgehog 3", and "Sonic & Knuckles". Unlike future "Sonic" collections, "Sonic Jam" does not use a Genesis emulator; the games are proper ports, and all are nearly identical to the original Sega Genesis releases, with the exception of minor bug fixes. "Sonic Jam" emulates "Sonic & Knuckles" "lock-on technology"—a special feature that allows the player to merge elements of "Sonic & Knuckles" into previous games, resulting in changes to the level design as well as the choice to play as Knuckles the Echidna in "Sonic the Hedgehog 2" and Tails in "Sonic & Knuckles".
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.