World 3-Tower (New Super Mario Bros. 2)
World 3-Tower is an autoscrolling underwater tower level in World 3 of New Super Mario Bros. 2. It is the only level in the entire game to feature Skewers. This level can be unlocked by completing either World 3-3 or World 3-A. This level has two exits - the first one unlocks World 3-4 and the second one unlocks World 3- and a Green Toad House. Mario has 500 seconds to complete the level.
Mario begins on a blue platform above the water with a single Fishbone. A ? Block containing a Fire Flower can first be found, followed by a Warp Pipe in the water leading to the next area, which will begin autoscrolling upwards upon entering. Two Fishbones can first be found, followed by brown moving walls, which will move after a set period of time. Some of these walls are spiked. More Fishbones will then appear. After the moving walls, Mario will approach spike pillars coming from both sides of the wall. Above the checkpoint enclosed in a safety zone, there is a ? Block containing a Fire Flower and a Brick Block that can be turned into a Gold Block. After passing by another Fishbone, the walls close an area with a Red Ring surrounded by 4 current-producing pipes. Seconds later, the top walls will open. More Fishbones and spiked pillars will then appear, followed by a green pipe. Warping through will lead Mario to a small area with a ? Block containing a Fire Flower and the boss door. Here the player needs to defeat four Reznors on a single wheel with four rectangular ? Blocks to clear the level.
Mini Mario is required to access this secret exit. Located before the checkpoint and the area with the spiked pillars, there are two brown blocks which will move away to make way for Mario to pass through. Following the block on the right will bring Mario to a mini Warp Pipe. After warping, the level will autoscroll upwards once again. This area has more moving walls, Fishbones and spiked pillars. Along the way, there are several moving walls that close the area. Mario can collect coins in bubbles while avoiding them. When the walls open, Mario needs to swim to the top avoiding spiked pillars. Upon reaching the top, Mario can get two 1-Up Mushrooms in Brick Blocks. A red pipe will lead Mario to the flagpole.
This exit unlocks a Green Toad House and World 3-Warp Cannon.