Bowser's Star Reactor is the second boss galaxy in Super Mario Galaxy and the first galaxy where Bowser is fought. It is located in the Fountain. This galaxy is unlocked by collecting 15 Power Stars. Before reaching Bowser, Mario must travel through a short level that is similar to one of the Bowser levels in Super Mario 64. The music is also a remix from those levels in Super Mario 64. There are several inaccessible Airships floating over the galaxy, which can only be reached by hacking the game. By doing so, it reveals that the Airships are solid. At the end, there is a green and white staircase which Mario must climb. However, Bowser starts breathing Meteors at the stairs, which cause them to break. Mario must quickly climb the collapsing stairs to reach Bowser safely, otherwise he will fall in Space along with the destroyed stairs and lose a life. At the top, Bowser roars and changes the gravity, which lifts the two onto a metallic planet above the staircase. Mario battles Bowser on this planet. After defeating Bowser, Bowser claims he has not been defeated yet before teleporting away. He leaves a Grand Star for Mario to collect.
Starting PlanetThis planet has many Firebars and a 1-Up Mushroom. Once the player advances here, they will come across a loop. This planet also has a Thwomp and a Fire Shooter, as well as a platform that will take Mario to the Gravity Planet.
Gravity PlanetHere, Mario must be careful and make sure he does not fall off the platforms, for there are several Black Holes at the bottom of this planet. The gravity changes back and forth here. More Firebars are here as well as another Thwomp. At the end of this area, there is a platform leading to the Stairs.
StairsIn this area, there are stairs leading to the platform where Mario fights Bowser. Here, there are more Firebars, Fire Shooters and Thwomps that make getting to the top much more difficult. After the Firebars, Bowser appears and starts shooting Meteors from his mouth at the Stairs, causing them to break. Mario must quickly climb the stairs to reach the top. Bowser then uses gravity to take himself and Mario to the Star Reactor.
Star ReactorThis is the planet where Mario fights Bowser. When Bowser Ground Pounds the blue glass, Lava will erupt and burn his tail. The green plates here can be used to block the shockwaves that Bowser creates. When Bowser is defeated, Mario will receive a Grand Star, unlocking the Kitchen.
The Fiery StrongholdMario begins this level flying past Bowser's fleet of inaccessible Airships and landing on the Starting Planet. After moving forward, Mario will come across an Item Crystal with a 1-Up Mushroom (which can be freed by simply Spinning it and collecting the Mushroom inside). There's also a main platform here which has two Firebars, a Fire Shooter and a Thwomp. Afterwards there is a rotating green platform which takes Mario to the Gravity Planet. After this area, the player must jump onto a yellow platform, and then a gray platform (the Stairs) with four Firebars on it which rotate counterclockwise. There is a Thwomp after this, along with three Fire Shooters, a moving platform, and three groups of Firebars. After all these obstacles, Bowser appears and shoots Meteors at the Stairs, causing them to collapse. Mario must quickly run up the Stairs to avoid falling into Space below. At the top, Bowser uses gravity to lift him and Mario to the Star Reactor where the battle begins. Bowser's first attack is a stomp that creates shockwaves, which can simply be jumped over. Next, Bowser will try to Ground Pound Mario. When Bowser attempts to do this, Mario can lead him to one of the blue glass orbs on the planet so that Bowser Ground Pounds and breaks the orbs. This causes Lava to erupt and burn Bowser's tail, causing it to turn red. Bowser will run around the planet in pain. Mario can use this time to Spin Bowser. This will send Bowser spinning around the planet on his shell. Mario can then Spin Bowser again to damage him. Mario must do this two more times to defeat Bowser, however, Bowser will begin to breathe Fireballs at Mario in attempt to damage him. Once Bowser is defeated, he tells Mario that he's not finished yet before disappearing and leaving the Grand Star behind. Once Mario collects the Grand Star, he will now have access to the Kitchen on the Comet Observatory.
- Starting Planet
- Gravity Planet
- Star Reactor