Sonic 3 Complete is a hack of Sonic 3 & Knuckles which aims to provide a much improved variant of the original game, with many new options and features, without straying from the original levels or gameplay. The inclusion of separate modes for Sonic 3, Sonic & Knuckles and Blue Sphere also make this a close cousin of the PC compilation Sonic & Knuckles Collection.
More info: http://info.sonicretro.org/Sonic_3_Complete
Cartridge label design subject to change depending on availability.
Credit to the following people for their artwork on the box cover:
Hazard the Porgoyle