World 4-Ghost House (New Super Mario Bros. 2)

Mario begins in front of three moving ? Blocks. A Boo follows. Further down are two ? Blocks, one of them containing a Fire Flower. To the right is a fake door. Going up the stairs leads to the real door, taking Mario to a room where the walls are 'driven' by several Boos. Moving forward are some stairs and another fake door. There will then be several platforms on the floor which rises or lowers when Mario stands on them. This is followed by two ? Blocks, one of them containing a Super Leaf. The Boos will then 'drive' the walls in the reverse direction for a short moment. Following the ? Blocks is a Red Ring. Mario then has to climb several platforms and drop down a small shaftbefore getting crushed by the walls. Mario will then come across two ? Blocks containing coins. Following that is a P-Switch, which makes blue coins appear. After that there is a structure which Mario has to climb before getting crushed by the walls. At the top is the door leading outside. A Boo and a Springboard can be found, followed by the flagpole.

Star Coins

 * Star Coin 1: Early in the second area, there are several platforms which rises and lowers. Mario needs to stand on the last one which rises and wait till he reaches a high ledge on the left, where the Boos will then 'drive' the walls in the reverse direction. Alternatively, Mario can do a running jump from the nearby ? Blocks to reach the hidden aclove or wall kick from the right wall when the Boos begin to go backwards. The Star Coin can be found there.
 * Star Coin 2: After the Red Ring, Mario will then drop down a wall and find two ? Blocks. Mario needs to climb on these two blocks and when the blocks are about in the middle of the two walls, quickly wall jump of the walls starting with the right wall, to find the Star Coin up above.
 * Star Coin 3: Near the end of the level, Mario will find a P-Switch. Ignoring it, Mario will need to quickly climb up the structure after that and look for the Star Coin on the left wall of the structure before getting obscured by the Boo-driven wall.

Secret Exit
After the area with the platforms that rises and lowers early in the level, there are two ? Blocks, of which one of them has a Super Leaf. After the Boos reverse and return to their normal direction, climb above these blocks and when they are about to go offscreen, quickly wall kick between the two Boo-driven walls to find a secret door. Quickly enter the door and continue on to find the flagpole.

This exit unlocks World 4-B.