New Super Mario Bros./World 3-Tower

Bowser Jr.'s World 3 tower is taller and more convoluted than ever, especially now that he has installed climbable fences. Use your attacks to switch sides on the fences and to knock enemies off. Bowser Jr.'s castle layout is designed to confound and confuse, so don't get lost within this labyrinth of fences. If you lose a life, you must start over from the bottom!

Level walkthrough
At the bottom of the tower are three cannon pipes. Two of them lead to nowhere, so your only choice is to take the middle pipe, which will launch you high into the air. While you do pass some fences on your way up, you want to fall back down and grab on to the first fence you passed with. Move to the left and jump up to the next fence, where there are Koopas climbing around the fence. To defeat them, you can either drop from the fence and hit them from above, or just punch them while they're on the opposite side of the fence. Red Koopas are faster than green ones at fence scaling. After you climb to the top, make a jump to get the first Star Coin.

Fall back down and launch yourself with the cannon pipe again, this time grabbing the closer fence to you at the peak of your ascent. Jump up some more fences to reach a large fence with a flappable center. Your way forward is blocked by some Amps, immobile obstacles immune to most forms of attack. To cross to the left, you must punch the middle part of the fence to switch to the other side, the back of the fence. Switching sides on the fence is not some minor quirk, as some coins can only be collected on a certain side. For now, you should move around the border of the fence after switching sides, passing the Amps on your side, then flip again back to the front.

Continue your climb up the tower. There are three rooms here. You can knock the roaming red Koopa and use its shell to break a block leading to the room at the left, which contains a power-up block. From there, you can jump to the fence and break the block in the ceiling to reach the next level, which has a fence with a Star Coin at the front. You must have switched sides two times to be able to collect it, which you should have done if you followed the walkthrough so far. You can jump through another gap in the ceiling from here and eventually reach a door. However, for completion's sake, it is recommended that you backtrack and return to the room above the Amp fence. Go straight up, breaking any blocks in your way, to get to the next flappable fence. You can alternatively use this fence to get to the previous Star Coin. More importantly, above this fence is a door that leads to an alternate section of the tower.

If you went straight up after collecting the Star Coin, you will reach a section of the tower with more fences, plenty of Koopas on the fences and some spikes. Upon entering the room, jump to the right door and go through it to get to an isolated part of the previous area, where you can collect some more coins. Return through the door and start scaling the fences. There are plenty of coins here, none of them in front of or behind fences, so there are no concerns about switching sides. However, there are many, many Koopas on these fences, so you must take your time evading or defeating each one. In the end, you should reach the door at the top without any trouble if you take it slow.

If you go into the alternative section through the door above the Amp fence, you will be taken to a taller, less packed area of the tower. You must have quick fingers for this section, however, as it must be scaled with the help of a red switch. The only one in this room is found at the bottom of the area, near the door. Pressing it causes blocks to appear temporarily, which are necessary to climb this area. Start scaling the moment you hit the switch, ignoring any coins and deftly dodging enemies while you do. If you make a mistake and fall, you likely won't get to the top in time, and will have to try over. Make it to the top, and you'll be awarded with a Star Coin, as well as the door to the final area of the tower.

Whichever door you went through, you will arrive at the room with the double doors to Bowser Jr. There are some more Koopas you have to contend with, as well as a block with a power-up to buff yourself up for the inevitable boss fight. Go through the double doors to initiate your third battle against the bratty Koopa kid.

Boss: Bowser Jr.
Bowser Jr. is your challenger as always, and he still isn't mixing up his attack pattern. As usual, Bowser Jr. will blindly charge at you. Stomping him causes him to stay in his shell, during which hitting him will injure you. Stomp him three times or throw enough fireballs at him to defeat Bowser Jr. For this fight, Bowser Jr.'s arena is set above a pool of water. Like the quicksand from the last world, falling into the water makes it difficult to return to the platform without getting hit.

Star Coins

 * 1) From the first cannon pipe, fall to the lowest fence and climb to the left. Climb up the next fence to get to where the Star Coin is.
 * 2) After switching sides on the fence for the first time, move around the Amps to the left and switch again. Go up, left a room and up a room to reach the Star Coin in front of a fence.
 * 3) In the first section, you want to take the rightmost door. In the area it leads to, press the red switch and quickly move up to get to the door. The Star Coin is right next to it.