Rolling Coaster Galaxy

The Rolling Coaster Galaxy is one of the many galaxies found in Super Mario Galaxy 2. As its name implies, this galaxy is similar to a roller coaster and, similar to Rolling Masterpiece Galaxy, Mario (or Luigi) must roll a Star Ball to the end. Also, many Starshrooms appear along the way. It appears to be a reference to the Rainbow Road courses in the Mario Kart series. The name of the first mission, "The Rainbow Road Roll", in this galaxy confirms this. The music speeds up as the Star Ball rolls faster, and slows down as the Star Ball rolls slower. This galaxy is also similar to Rolling Green Galaxy and Rolling Gizmo Galaxy from the first game.

Partway through the level, the path splits in two. One of the Toads says that the right path is for experts, while the other is assumed to be for beginners. In the "Purple Coins on the Rainbow Road" mission, the path for experts is the only path present. The Comet Medal is also on this path. The only enemies found in this galaxy are Bob-ombs and Mini Goombas.

Planets/Areas
NOTE: Unless otherwise noted, all names are unofficial.

Rainbow Road
Rather than being separate planets, this galaxy is connected by chutes which allow the player to access the different paths and platforms.

Starting Platform
Mario starts on a simple orange and red platform. There is nothing of significance here besides the Star Ball, some coins, and a chute that takes Mario to the next area.

Rainbow Road Path 1
This is a simple path that consists of colored tiles. There are no hazards on this path. It eventually drops the player off at an area where two roads diverge in different directions. Bob-ombs are found at the end of the pathway.

Beginner Path
When Mario takes the left path, it leads him here. Possibly dubbed "Beginner Path", by the Toads, it is covered in beige tiles and is covered with light-colored Mini Goombas and Bob-ombs. The edges of the path are concave, meaning that Mario cannot fall off the edge unless blasted off by a Bob-omb. This pathway is also wider than adjacent one and has more undulations. At the end of the path, Mario is dropped off at Rainbow Road Path 2.

Expert Path
Taking the right path at the junction takes Mario to this area. Dubbed "Expert Path", by the Toads, it is a narrow, rainbow-tiled pathway. There are numerous beams found on the edges of the path, which bounces Mario off course if he is to come in contact with it. There are a few Bob-ombs here and a Comet Medal is also found here. At the end of the path, Mario is dropped off at Rainbow Road Path 2.

Rainbow Road Path 2
This pathway is much like the first rainbow road pathway, except that it is more inclined and it sometimes gets narrow during certain times. Mario is dropped off at several pink and purple platforms where there is a chute that takes him to the final path.

Rainbow Road Path 3
This pathway is more inclined than the others. The path also gets narrower as Mario travels towards the end. He is dropped off at a grassy platform where there is a chute that connects to the final platform.

Ending Planet
There is nothing of importance on this planet except for the hole which the Star Ball goes into. During the Purple Coin mission, there is a Gearmo present, which takes away Mario/Luigi's life if he does not have enough Purple Coins (if he does not have any lives to lose, he gets a Game Over).

Enemies

 * Bob-ombs
 * Mini Goombas

Green Star 1
The first Green Star is located near the beginning of the level. The player should take the Beginner Path instead of the Expert Path. They need to stay in the middle and to avoid Bob-ombs and Mini Goombas, up a bumpy slope. Just before the player drops off the end of the slope, they must use the momentum of the Star Ball and jump into the air, directly into the star.

Green Star 2
The last Green Star is near the end of the final rainbow road path, just before the Ending Planet. It is positioned at the right side of the course, hovering in the air. For the player to reach it, they must either carefully use the momentum of the course to land on the star or jump before reaching the edge. If done correctly, the player should easily grab the star instead of falling off the course.

Prima Official Game Guide description

 * "The Rolling Coaster Galaxy is modeled after one of Mario's favorite karting tracks. However, there are no wheels to be found here. Instead, you must roll through this colorful cosmic challenge on a sphere. The Power Star you seek is actually right under your toes."

Trivia

 * The two missions in this galaxy are the only times in this game that the player can see all five of the Toad Brigade's Starshroom spacecraft at once; however, the Purple Coin mission of the Sea Slide Galaxy in Super Mario Galaxy features all five ships as well.
 * This galaxy uses a cover version of the music that plays in The Princess's Secret Slide, Tick Tock Clock and Rainbow Ride levels in Super Mario 64, which is also the song that plays when sliding down the large slide in the Tall Trunk Galaxy.

Achterbahn-Galaxie