The total game consists of seven worlds - Oasis, Diva, Earth, Shelltarl, Cosmo Heaven, Fo9, and Millitar. With the exception of Shelltarl, which is a single long level, each world is divided into three main stages, followed by a boss. Oasis is the only world unlocked at first. You also have access to Cosmo Heaven, but only as a hub at first. After beating Oasis, you unlock Diva and Shelltarl. After beating those, Earth and Fo9 are unlocked. Beating these unlocks Millitar. Upon completing Millitar, Cosmo Heaven is invaded by the Zooligans, turning it into the final world of the game.