Sonic CD is a classic side-scrolling platformer about the blue hedgehog Sonic. Sonic the Hedgehog and Amy Rose travel to Never Lake and discover the legendary Little Planet, chained and covered in metal. Dr. Eggman uses the planet's resources to manipulate the structure of time. He created Sonic's evil counterpart, Metal Sonic, who kidnaps Amy and disappears. Now the brave hedgehog must go on a dangerous journey across the Minor Planet, collect seven gems that can change the course of time, free Amy and defeat Metal Sonic along with his master.