New Super Mario Bros. U: Acorn Plains- Fort -- Crushing Cogs Tower

This fort is filled with spinning cogs to help you reach new heights, as well as possibly crush you. Climb up the first set of cogs and get the Ice Flower from the item block. There are Dry Bones in here, so use the Ice Flower to get rid of them. Wall jump up the right side of the fort to reach the first Star Coin. There's a moving stone above it that will block your access to the Star Coin, but it won't hurt you. Take the platform up, climb past some cogs, and go left for the second Star Coin. There's a Red Coin Ring over a cog. Soon after, you'll reach the midpoint. There's a set of three cogs above, which can crush you. The one on the right will crush you, so jump off it immediately. Jump from the cog to the left over to a ledge on the right wall. Jump up from there for an invisible area to the right, with a pipe cannon that takes you to the third Star Coin. You'll soon reach the boss door. The boss of this fort is Boom Boom. He runs around flailing his arms and bounces off the walls. Stomp him three times for victory. Mario kicks him out of the fort and the path to Acorn Plains-3 opens up. We can now save our game.