World 4-Tower (New Super Mario Bros. 2)

 is an autoscrolling level. Mario begins on an ice platform which constantly moves up. He will first meet with a Bone Goomba. Many Bone Piranha Plants can be seen from pipes on the walls of the level. More Bone Goombas follow. A Bone Piranha Plant will then join the ride upwards. A Buzzy Beetle can then be found, followed by two Coin Roulette Blocks. Several rectangular Donut Lifts can be found. This is followed by two Bone Piranha Plants and the first Star Coin. More Donut Lifts can then be found, followed by a Buzzy Beetle. After that is the door leading to the next area, where the checkpoint and several rectangular ? Blocks can be found, one of which has a Fire Flower. The next area will feature another moving ice platform (this time moving faster), where another ? Block with a Fire Flower can be found. Two black pipes which convert fireballs into coins can be found. Exhausting the left pipe releases three 1-Up Mushrooms while exhausting the right one releases a Star. Another Buzzy Beetle can be found, followed by more Bone Piranha Plants and a Big Bone Piranha Plant. At the top is a door to the next area. Here, two rectangular ? Blocks can be found, one with a Fire Flower, and also a Cannon Pipe. On the way up are several pipes with Bone Piranha Plants and at the very top is the boss door. Here, there will be two wheels with four rectangular ? Blocks on each wheel with two Reznors on each wheel. Mario will then have to defeat all four Reznors to complete the level.

Star Coins

 * Star Coin 1: The first Star Coin can be found easily halfway through the first room between two Bone Piranha Plants.
 * Star Coin 2: Mini Mario is required to obtain this Star Coin. Mario should already be Mini Mario before entering the level. After the second Buzzy Beetle is the door to the next area. Mario should not jump up to the platform with the door as he needs to enter a mini Warp Pipe on the right wall of the lower platform and thus he won't be able to get down later, even if he uses the Donut Lifts. Entering the pipe takes Mario to a small room with the Star Coin.
 * Star Coin 3: The third Star Coin is above the Big Bone Piranha Plant in the third area. Mario will need to use the platforms to the left or right of it before the Piranha Plant blocks it.

Secret Exit
This is easy. In the third room, where another ice platform can be found, Mario needs to enter a blue pipe infested with a Bone Piranha Plant which is differently coloured from the other green pipes to the left of the Big Bone Piranha Plant. To make it easier, Fire Mario can exhaust the black pipe on the right wall earlier in the level to release a Star. Entering the pipe takes Mario to a small room with coins, Donut Lifts and another blue Warp Pipe on the ceiling. Entering that pipe takes Mario to the roof of the fortress, where several Donut Lifts and rectangular ones can be found, followed by the flagpole.

This exit unlocks a yellow Toad House and World 4-C.

Enemies

 * Bone Goombas
 * Bone Piranha Plants
 * Big Bone Piranha Plants
 * Buzzy Beetles
 * Reznors (Boss)