Grandmaster Galaxy

Grandmaster Galaxy is the final galaxy that appears in Super Mario Galaxy 2. The galaxy is located in World S. This galaxy is unlocked when the player gets all 240 stars and is an obstacle course with puzzles, enemies and Power Stars at the end. This galaxy contains two extra Stars: one for completing the level and another one for doing it again, but with only one hit point. In the last case the player gets the star from Rosalina.

Flower Grapple Planet
The first planet is where Mario must use Yoshi to swing on the flower grapples to reach the Launch Star. There are several obstacles along the way, such as Mines and Bullet Bills.

Flipswitch Planet
After using the Launch Star from the first planet, Mario and Yoshi lands on a planet with Flipswitches, with a backdrop showing moving sprites of items from Super Mario Bros.. The player must touch all the Flipswitches (while avoiding laser-firing robots) to reveal the Launch Star.

Electric Maze Planet
After landing, Mario/Luigi will find a Cloud Flower and a fan making an upward gust. Mario/Luigi must use the cloud flower to make it to the Launch Star at the end of the maze. More flowers are supplied along the way. In The Perfect Run, Mario/Luigi is stuck with this status for the rest of the level.

Platform Planet
A planet that has many platforms that have electric walls moving through them, making it tedious. From there, monsters who fire lasers at you, and shrinking platforms. Then you get Red/Blue tiles, where you reach the pull star.

Hammer Bro Planet
This planet is highly infested with Hammer Bros., and Mario has to get past them to reach the other side. Flimps are also present in this area.

The end area has three Boomerang Bros. that Mario must take out. Defeating them reveals a Power Star (or a Launch Star in the Daredevil run).

The Comet Medal for this galaxy is on the far right side of this planet, next to some platforms.

The Gate Planet
This planet is only accessed during the Daredevil run. It's basically a small planet with a small house built on it. Mario also meets Rosalina on this planet, which strongly resembles the Gate in its prequel, Super Mario Galaxy.

The Ultimate Test
The first level of the Grandmaster Galaxy. You have to traverse a couple of planets, the first being a small, 2D style area in which you must use Yoshi to navigate. There are some enemies, and electric balls that stand in your way, and you must use yoshi's tounge to grab onto circular objects to move around. At the end, there is a bullet bill, and a star launcher. From there, you will have to navigate a challenge in which there is an electric wall, and wind pushes you into it. You must use Cloud Mario and do jumps, and collect more clouds. There is another planet where you have to turn on many blue switches while avoiding lasers. (Add more planet descriptions)

Music The following themes play in this galaxy from first to last. "Yoshi Star Galaxy, Sky Station 2 Theme, Final Bowser Level, Comet Observatory 3".

The Perfect Run
The Prankster Comet for this galaxy is unlocked when the player finds this galaxy's Comet Medal, and gives Banktoad 9999 Star Bits.

Basically, the player redos the "The Ultimate Test" star, but under the Daredevil conditions. There are no checkpoint flags, and some of the Paragoombas are replaced with Choppahs.

If the player survives all the obstacles, he/she will run into Rosalina, who will thank the player.

Music from the original Super Mario Galaxy is played as well. The music that's played is from Gusty Garden Galaxy, Good Egg Galaxy, Bowser's Galaxy Reactor, and Comet Observatory, in that exact order.

Trivia

 * This is the only galaxy in Super Mario Galaxy 2 to not encounter the green stars. This is primarily because the player had to collect all the green stars to unlock this galaxy.
 * This is the only galaxy in Super Mario Galaxy 2 that requires the player to collect Star Bits in addition to collecting the Comet Medal for a prankster comet to appear.
 * The galaxy uses the themes "Yoshi Star Galaxy, Sky Station Galaxy, Bowser's Galaxy Generator, Comet Observatory 3" for the first mission, and "Good Egg Galaxy, Gusty Garden Galaxy, Bowser's Galaxy Reactor, Comet Observatory 3" for the second mission.