Sonic the Hedgehog 2 is a side-scrolling platform game and the sequel to the original Sonic the Hedgehog. Players control Sonic as he traverses larger, faster-paced levels across West Side Island, collecting rings, defeating robot enemies, and pursuing Doctor Robotnik. The game introduces Sonic's sidekick Miles "Tails" Prower, a two-tailed fox who can be controlled by a second player. It also adds the spin dash move, a competitive split-screen multiplayer mode, and pseudo-3D special stages in which players collect rings to earn Chaos Emeralds.