The main planet consists of many parts. The first area of this planet where Mario starts off in is a beach with the Toad Brigade relaxing. A few Crabbers roam the cove with 1 giving a 1-Up. A cannon has been installed so Mario can reach the planetoids. In the mission, Bubble Blastoff, the area has been taken over by an Undergrunt Gunner who must be defeated to gain access to the Fire Flower that opens the next area.
The two planets that are accessible are fairly small and simple. The first planetoid is covered with Octoguys but, it also has access to a Rainbow Star and a Fire Flower. A sling star on top will take Mario to the scaled down planetoid. It resembles the main planet from Gateway Galaxy. By spinning off the golden screw, the planet will shrink revealing a ring of coins before Mario falls back to the surface of the main planet.
Through the gate, Mario can access the underground lake. This underground lake is deep with lots of enemies and Guppy. Mario can also access a passageway that leads to an underground cave with a Pirate Ship. Mario fights Kamella on this ship. In Bubble Blastoff, the mission has Mario scale the walls using the Ice Flower and bubbles.
The Secret Star is located in the Boo Room Planet. It is a checkered box with tubes containing a Boo and an Urchin with the objective being to bring the Boo into the live to get the Power Star.