New Super Mario Bros./World 4-Ghost

A moldy old shack in the middle of the jungle isn't a very welcoming place. This ghost house contains its fair share of Boos and their odd tricks, but it comes with some unique features of its own. Swiveling platforms create one-way passages through walls, while enormous Balloon Boos pursue trespassers with a burst of air. Keep them deflated as you try to find your way out.

Level walkthrough
The starting section is pretty generic for a ghost house, consisting of just several platforms arranged randomly while a few Boos hover around. This is also the only part of the stage with a bottomless pit, so be careful not to miss your jumps. Get to the right and you'll be faced with a choice, a door or a swivel platform. Since doors are notorious for being a tool for trickery in ghost houses, you might be prompted to take the swivel platform instead. This isn't a bad choice, as you're taken to some more rooms that make use of swivel platforms as exits, as well as encounter the first Balloon Boo. These special Boos puff up into huge sizes, but will deflate to the size of a normal Boo when you have your backs turned to them. Unlike most Boos, Balloon Boos can't chase you and won't react to you across walls, making their danger more confined.

After the first room with a Balloon Boo, you will be taken to another area with one, and no apparent exit. You must go right and hit a P-Switch, then jump to the previously blocked off entrance of the warp pipe in the top left. Go through it to be carried to the room above. A Star Coin can be seen behind a wall, but you can't reach it if you chose the path as described by the walkthrough previously. Instead, you should have went through the first door. This takes you to a small room with a single switch. Hit the switch to make some question mark blocks drop down, although their contents are not what makes them interesting. Stand on a block and wait for the timer to expire, which causes the blocks to go back up, taking you with them. You will emerge on the room above the first Balloon Boo, and can get the Star Coin simply by running left.

Get on the swivel platform to return to the point where the two paths converge. Go to the right and head up to encounter another Balloon Boo. The door is suspended in midair, so you can't head in it until you create some solid ground below. Go left and hit the red switch to make some blocks appear, including ones below the door from before. Go through the door to end up right next to another Balloon Boo. Go left and you can see another red switch. Hit it, then wall jump up the two columns of red blocks to the ceiling. The Star Coin will be right above you.

Go left and fall down. Hit the red switch again and run right. There will be some red blocks next to a warp pipe. Head through it to be transported to the room above, where the final Boo resides. Go left and jump the platforms. Ignore the first door you see, as it simply takes you back to the area below. Instead, get to the top and go right to another door. Head through it to exit the mansion. Jump around at the flagpole area to reveal some hidden blocks, which you can use to help you reach the top of the flag.

Star Coins

 * 1) Go in the first door you see and hit the switch. Stand on one of the blocks that fall down, and wait for them to go back up to be transported to another area. Go right to get the coin.
 * 2) After heading through the one way door, go left and hit the red switch, then wall jump up the two columns of blocks to the ceiling. The coin is easily within reach here.
 * 3) You'll need to be in Mini form for this. In the same area as the second Star Coin, hit the red switch and use the blocks that form to get on top of the entrance to the warp pipe. Wall jump off the pipe and on to a platform on the right. Keep going up with wall jumps, ignoring the door, until you can get the coin.

Alternate exit
You'll need a Mini Mushroom to get to this secret exit. After hitting the second red switch, head on to the pipe with red blocks beside its exit. Instead of heading through and progressing as normal, hop on the top of the warp pipe. Wall jump off the pipe and to the right, where there is a ledge that is otherwise inaccessible without the floaty jumps of Mini Mario/Luigi. Jump up and into the gap above. You will emerge in another room. Ignore the door first and keep using Mini Mario's wall jumps to get the last Star Coin. Fall back down and go through the door to be taken to the red flag.

This hidden exit leads to the World 4 Cannon, which blast you far above the canopy and into the cloudy World 7. The usual warning about difficulty applies here as well. Note that this cannon is actually more useful than the others when playing for total completion, since it is easier to unlock World 7 with the cannon than with the normal method.