A guide to completing the second World 5 Fortress in Super Mario Bros 3 for the Nintendo Entertainment System.
How to Clear the Second Fortress of World 5
Carefully jump to the brick on the right, and from there to the pipe. (You can make a running jump directly to the pipe, but it's more difficult.) Go down the pipe.
There are many Podoboos (flames) that go up and down in your path. There are some flames that come down from the ceiling and then go back up. Make your way slowly so you can see where the flames are before you try to go past. Keep in mind that the flames aren't always in the gaps between bridges. They can come up from beneath bridges or above them as well.
While avoiding the flames, make your way to the right, jumping from bridge to bridge. You will reach a larger platform that has some ? Blocks above it. There is a Dry Bones coming from the right of the platform. The rightmost ? Block contains a Starman.
Go to the right and jump on the two small platforms in the path, then make a running jump to reach the slightly larger platform after that. There aren't any flames for a short distance, and then there is a Boo Ghost. After the Boo Ghost, the flames start again.
Go to the right on a series of four small platforms, which is followed by a larger platform that has two ? Blocks above it. The leftmost ? Block contains a Super Mushroom or Super Leaf.
Make a running jump to the next platform, where there is a Boo Ghost, followed by a Dry Bones, and a pipe. Go up the pipe.
Go to the right, and you eventually reach the fortress boss.
Boom Boom
Boom Boom will move left and right, and sometimes he will crouch and slide. Whenever he crouches, his spiky shell is not safe to stomp on. Try to stomp on him when he is running around. You can also hit him with fireballs. After you stomp him the first time, he will start flying in the air, going left and right, then he sometimes stops and swoops down, then lands on the ground and crouches, showing his spiky shell. Try to stomp him just after he starts flying again. After you stomp on him a second time, he will very quickly run left and right, so jump carefully to avoid letting him bump into you.
After you stomp him a third time, he is defeated, and drops a Magic Ball. Collect it and you will complete the level.
After the Level
You can optionally visit the Spade House for a chance to get 1UPs.
Otherwise, continue on to World 5-8.