World 7-Tower (New Super Mario Bros.)
This level primarily consists of moving platforms and walls covered in spikes, though there are no enemies found within the level apart from the boss. The player must be careful when moving through this level to avoid taking damage from the spikes or being crushed by the moving walls.
In the first room, the player must jump onto the top floor of the room while avoiding a moving wall and ceiling covered in spikes. There is a row of six blocks here, one of which contains a Fire Flower. In the second room, there are multiple moving spiked platforms which will try to crush the player if they are not fast enough. There is a dangerous section of spiked platforms packed closely together, forcing the player to jump while ducking at the same time to avoid taking damage. Afterwards, there is a "staircase" of sorts made up of more moving spiked platforms, which take the player to a door. In the room behind the door is the level's midway point, along with a row of eight blocks; one contains an additional Fire Flower.
In the next section of the level, the player must dodge spiked platforms which come poking out of the ground and come down from above. After this, there is a section containing more tightly-packed spiked platforms, which will crush the player if they are too slow; they must use these platforms to advance upwards into the last area. Here, there is a multitude of moving platforms, which all converge onto the boss door and will crush the player if they stand still.
Bowser Jr. awaits the player yet again beyond the boss door. He is fought on top of a moving platform, and cannot be jumped on; he will only take damage from shells or fireballs from Fire Mario. After being hit by three shells or ten fireballs, he will be defeated, and the player will be able to advance to World 7-4.