Stoneslide Tower, or Layer-Cake Desert-Tower, is the second tower in New Super Mario Bros. U. It features stone platforms that are movable by spinning on wooden screws. After completing this level for the first time, Magikoopa flies around Peach's Castle and a tornado starts to form around it. This level is unlocked by completing either Perilous Pokey Cave or Fire Snake Cavern, and completing this level unlocks a labyrinth of connected Stone-Eyes on the overworld map that serve as the location for both Goomba and Fire Bro enemy courses. Navigating the enemy courses unlocks Spike's Spouting Sands and Dry Desert Mushrooms.
The level begins with large Screwtop Platforms that can be moved by spinning on a wooden screw, allowing the player to reach a Warp Pipe that leads to the next section. Another screw controls a platform, allowing a ? Block containing a power-up and the platform above to be reached. Two Spike Top are found on a portion of the ground. A screw controls a pair of smaller Screwtop Platforms, along with another platform that crushes a group of Dry Bones blocking the path. More Dry Bones are found, along with a screw that controls two Screwtop Platforms. Three more Spike Tops are found. Another screw is used to control three Screwtop Platforms. On the left wall, there is a Hidden Block that contains a 1-Up Mushroom. The other one on the right contains a coin. These Screwtop Platforms allow access to a Warp Pipe that leads to the Checkpoint Flag. Another screw controls a group of Screwtop Platforms, one of which having a Big Dry Bones on it. A yellow Warp Pipe on the right takes the player to a room with a Roulette Block. A Dry Bones is found, along with Spike Tops on Screwtop Platforms. Following more Screwtop Platforms and Dry Bones, a group of Pipe Cannons is found. The player must use a screw to move Screwtop Platforms out of the way, allowing the Pipe Cannons to be used to reach the boss door. Two Big Dry Bones are found, as well as a Hidden Block containing a Fire Flower on the left.
Through the boss door, there is a boss battle with a Boom Boom. Magikoopa appears before the battle, giving Boom Boom the ability to attack using spin jumps. He is defeated after being jumped on three times.
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