Super Mario World/Donut Secret House

Donut Secret House is one of two ghost houses in Donut Plains.

Walkthrough

 * The Big Boo can be a bit difficult to pass. Lure him to move a bit up then quickly run under him, or if you want, you can spin jump off of him, although this is slightly riskier. The best option is to jump on the P-Switch block and jump facing left, so that the Big Boo goes up and you can safely go under him.
 * If you were curious about that turn block at the bottom right, you will end up there if you go through the trap by taking the mid-air door in the next section. It contains a 1-up mushroom.
 * Go through the door at the end to get to the second area.


 * You will end up on the right side of the room. The ? block in front of you contains a flower.
 * There are two doors you can see. The one at the very end leads back to the beginning. The other door you can see is hovering in mid-air. By grabbing the P-Switch above the door at the very end, carrying it over and stepping on it, you can make hidden ? blocks appear that serve as ground for entering this door. Unfortunately, if you were to do this, you would notice it just leads to a trap that takes you back to the beginning as well.
 * To find the real way out, inspect the coin formation after the mid-air door. If you carry the P-Switch there, a hidden door will pop up, however the coins will turn into brown blocks as well. Collect all coins beforehand and you will be able to easily reach the hidden door. It leads to the goal tape and allows you to complete this level.

Secret Exit
The secret exit is well-hidden in this level. In the second area, take the P-Switch to the mid-air door and step on it. As the ? blocks appear, go to the door, but don't enter it. Instead, jump at the turn block right above the door to make a vine appear. Climb it up and run to the right to see a hidden door. Quickly enter it before the P-Switch expires. If you're Cape Mario, you can take the P-Switch and fly up to that corridor, making this quite a bit easier.

Mini-boss: Big Boo


Unfortunately, it's not that easy to just unlock the secret exit. You will end up in a mini-boss battle against the Big Boo, who is guarded by two lesser Boos. To defeat him, you must take the blue blocks below you and throw them at the Big Boo while he is visible. You don't have infinite tries though - eventually the floor will open up and you'll be in trouble if you have nothing to stand on. As well, the two Boos in here can cause big trouble if you don't watch out. Hit the Big Boo three times and he will faint, completing the level. This endeavor is well-rewarded: the secret exit unlocks the first Star Road in the game, leading to Star World 1.