"Sonic Jam" is a compilation which contains the four main "Sonic the Hedgehog" games released on the Sega Genesis: "Sonic the Hedgehog" (1991), "Sonic the Hedgehog 2" (1992), "Sonic the Hedgehog 3" (1994)"," and "Sonic & Knuckles" (1994). Unlike later "Sonic" collections, "Sonic Jam" does not use a Genesis emulator; the games are true ports, and all are nearly identical to the original 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, with altered levels and the choice to play as Tails in "Sonic and Knuckles" and Knuckles the Echidna in "Sonic the Hedgehog 2".