Sonic must defeat doctor Robotnik yet again!
This time, Robotnik wants the Master Emerald, the biggest and most powerful of all the Chaos Emeralds. With this emerald, the Death Egg, Robotnik's ultimate weapon will have limitless power and nothing can stop him from taking over the world. It's up to Sonic to stop Robotnik's plans, but he's not the only one. Knuckles, guardian of the Floating Island and the Chaos Emeralds tries to stop him as well.
Play as both Sonic and Knuckles in 8 new zones in two different adventures. Get as many rings as you can, get all the emeralds and defeat enemies. The original cartridge could be combined with Sonic 3 to play the game as it was meant to be played. When combined with Sonic 2, you were able to play it with Knuckles for a new game experience.