Codex Gamicus

Sonic Crackers, also known by the name in the ROM header, Sonic Studium, is an early Sonic the Hedgehog prototype game for the Sega Mega Drive/Genesis. It is believed to have been an engine test, containing essentially multiple different game engines, swapped out in realtime using code written into RAM. The concepts, engine and various other materials in the prototype was subsequently implemented in the Sega 32X game Knuckles' Chaotix.