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 CD
The 1991 release of "Sonic the Hedgehog", the first game in the "Sonic" series, was a major commercial success and positioned Sega as Nintendo's main rival in the console market. Lead programmer Yuji Naka, dissatisfied with Sega of Japan's rigid corporate policies, moved with several members of Sonic Team to the United States to develop "Sonic the Hedgehog 2" with Sega Technical Institute (STI). Meanwhile, Sega planned to release the Sega CD add-on for its Genesis, and wanted a "Sonic" sequel that would demonstrate its more advanced features. Sonic's character designer Naoto Ohshima was "Sonic CD"s director; the remainder of the team comprised Sega staff who had developed "The Revenge of Shinobi", "Golden Axe 2", and "Streets of Rage".