Bowser's Star Reactor: The Fiery Stronghold

Watch out for the spinning fire blades as you work your way up the colored ramp to the thwomp.

Run under the Thwomp when he rises off the ground, but watch out for the flamethrower just before. Now step on the green platform just beyond and ride it to the ceiling.

As the Luma puts it, the gravity's "all out of whack" here. The arrows along the wall point to which way the gravity is pulling; so if you enter that portion get ready to be pulled in that direction.

Start off by heading right and jumping at the coins to be pulled to the ceiling. Now leap over the spinning flames and jump at the next set of coins only when a platform stops below, as you'll be pulled to it. Now ride the platform until it comes to a stop again and leap through the coins to the ceiling.

Now quickly leap over the flames on the right and run under the Thwomp as soon as you can (otherwise the spinning flames will nail you). Now step on the nearby yellow platform to ride it to the next section.

Position Mario between the spinning flames and follow them slowly to the top side.

1-Up: After riding the yellow platform to the spinning flames, carefully jump around this circular platform clockwise for a 1-Up.

Run under the Thwomp and quickly dash past the three flamethrowers as soon as the fire subsides. Now ride the platform beyond up a level and carefully run past more spinning flames to a checkerboard floor, where you'll meet with Bowser.

Bowser will spit balls of fire at the walkway, destroying it. Quickly dash along it before it collapses, but make sure to grab the power-up Mushroom in the crystal at the first bend. When all is said and done, you'll have to take Bowser on Mano-a-Mario.

Boss: Bowser

This battle takes place on a giant sphere, and features what is some of the coolest music in the game, so enjoy it while it lasts.

Bower can't be attacked directly, well, not at first. So focus on avoiding his three main attacks: Fireballs, energy waves, and jump attacks. Every time Bowser lands from a jump, a least one energy wave will emit from him and continue around the entire globe. Try to jump over these while running at them, to insure you clear it completely.

Speaking of which, you'll have to use Bowser's ground pound attack against him to deal damage. Whenever Bowser spins in the air, that indicates he's going to try and land on you with a ground-pound. Quickly run to any of the several blue domes on the planet and watch for Bowser's shadow to appear over it; now quickly get out of the way while Bowser lands right on it, catching his tail on fire. This is his weakpoint.

When Bowser's tail on fire, he'll run around the globe in desperation trying to fan it out. Now here's the thing; Bowser's fast, so you won't be able to chase him down from behind. Instead, turn around and charge at him head-on. As soon as Bowser sees you, he'll turn around and run in the opposite direction - this is your chance to attack. As soon as Bowser's tail turns toward you, damage it with a spin attack to force him on his back, stunning him.

With Bowser stunned on his back, simply run up to him and perform a spin attack for the first hit. This is really easy the first time, as he stays in one place. However, for the 2nd and 3rd hits, he'll actually slide around the arena on his back - run around the globe in the opposite direction to intercept him.

After three hits, Bowser will admit defeat.