

Bowser reveals that he is creating a new galaxy from the Power Stars he stole, and intends to rule the entire universe from this galaxy with Peach at his side. After collecting enough Power Stars, Rosalina brings the observatory to the center of the universe, where Bowser is holding Peach captive. Mario travels throughout the universe, encountering allies (such as his brother Luigi and a brigade of Toads) and enemies (including Bowser and his army) as he searches for Power Stars. Rosalina gives Mario one of the Lumas, allowing him to travel through space, and he sets off to collect Power Stars to restore the Observatory.

Rosalina, a protector of the cosmos, has traveled across the universe in her Comet Observatory until it was attacked by Bowser, who robbed the Observatory of the Power Stars it used as a fuel source, rendering it powerless.

Mario awakens on a small planet, where he meets the Lumas, star-shaped aliens, and a woman named Rosalina whom they call their mother. Mario manages to reach the base of the castle before it is pulled into outer space, but he is blasted away by Kamek. "Inviting" Peach to the creation of his new galaxy, he summons a massive UFO to rip Peach's Castle from the ground. Shortly after he arrives, the festival is interrupted by Bowser, who attacks the Mushroom Kingdom in his armada of airships. Mario is invited by Princess Peach to the Star Festival, which is held once a century to celebrate the arrival of a comet. Luigi has slightly different controls than Mario: he has a higher maximum speed and jump height, but he has less traction and longer acceleration. As the name suggests, Mario is replaced with Luigi, and the player can collect all of the Power Stars again. "Super Luigi Galaxy" is a gameplay mode unlocked after collecting all 120 Power Stars and defeating Bowser a second time. In this mode, one player controls Mario, while the other uses the Wii Remote to control a second pointer on screen, allowing them to gather Star Bits and shoot them at enemies. "Co-Star Mode" is a form of limited co-op. This allows Mario to circumnavigate most of the planetoids he lands on, and jump from one planetoid to the next. The galaxies themselves consist of various planetoids for the player to explore, all of which have their own gravitational field. Taking control of Mario, the player travels to different galaxies in order to collect Power Stars. Super Mario Galaxy is a 3D platformer set in outer space.
