The game is split into six principal zones, followed by a short 'Final Zone.' Each main zone has its own visual style, and while some enemies appear throughout, each zone has unique enemies and obstacles. Each main zone is split into three acts, all of which must be completed. At the end of each main zone's third act, the player confronts Dr. Robotnik for a boss fight. For most of the fights, Robotnik's vehicle is fitted with different weapons. After completing the sixth zone, the player continues directly to the single-level "Final Zone" for a last encounter with Robotnik inside a large machine environment. Destroying Robotnik's machine ends the game. A brief animation shows Sonic's return to the first zone, with animals liberated from Dr. Robotnik.