The Boomsday Machine is a castle-like boss that appears in the game Super Mario Galaxy 2. It has three Firebars circling around it and the top section has a a spinning-like mechanism. It is fought in the level Bowser Jr.'s Boom Bunker. The music heard during this battle is the same as in the Bowser Jr.'s Airship Armada battle.
There are ample Cloud Flowers around the area to grab. Mario must use his Cloud Mario ability to ascend the battlefield and get to the top of the Boomsday Machine. For the first round, Cloud Mario must run for one of the updrafts and spin to create a cloud and ride it upwards. From here, he can traverse across the various clouds scattered throughout the battlefield, using his cloud-making ability to assist him. Once Cloud Mario reaches the top of the tower, he must damage the machine by Ground Pounding the glass.
The second round is much like the first, but now the tower will attempt to vacuum the area, pulling the clouds out from under Cloud Mario's feet. Cloud Mario should still be able to just long jump to the top of the tower in the same manner, he should just be ready to make a backup platform if he gets sucked up. Cloud Mario also needs to watch out for an electric shield that covers Bowser Jr.'s dome periodically when he is sucking up Clouds. He may have to use a cloud platform to wait this out before making his second attack.
In the final round, the tower goes mobile. This will makes Cloud Mario's climb to the top more difficult, since Bowser Jr.'s dome is much higher up, but the moving tank doesn't present that much more of a threat. He still needs to watch out for yellow projectiles, the spinning fire wheel and the vacuum attack, but Cloud Mario should really focus on climbing. The fire on the Boomsday Machine will also destroy Mario's clouds.
Once Cloud Mario reaches the top of an updraft, he needs to use the Cloud Flower refill to get to an even higher cloud tier. He should use long jumps to get to the distant cloud and he can score another refill. From here he can reach the brittle dome with his cloud platform recharge. Once Mario reaches the top of the machine for a third time, he must Ground Pound the glass dome a third time to finally take Bowser Jr. out.
Mario faces this boss twice, with the second match being under a Daredevil Comet's conditions.
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