New Super Luigi U: Acorn Plains- Fort -- Flame-Gear Tower

This fort features gears and jet engines. Go over the first gear, avoiding the engines, then when the flames coming down on the right side stop, jump for the first Star Coin, then wall jump to safety. There are flames below the Star Coin. Just above it are a cluster of four engines spewing flames to the left. The second Star Coin is in the flames, so time your jump to get it. Keep climbing up and you'll see a Dry Bones on the right side. There are two engines above it. Between them are two levels of invisible blocks. This will allow you to reach the third Star Coin between the flames. At the top, there are a lot of Dry Bones by the boss door. Going through the boss door will give you 100 extra seconds so you can defeat the boss. Boom Boom is the boss again. Stomp him three times to win. After you win, you can save the game. The path ahead splits to Acorn Plains-3 and -4.