How to clear #4 Ludwig's Castle in Super Mario World for the Super Nintendo Entertainment System and Game Boy Advance.

How to Clear Ludwig's Castle
Go to the right and you will encounter a Bony Beetle, followed by a Ball 'N' Chain. You can stand in the path of the chain without getting hurt.
Jump up to the top, then go right and there will be another Bony Beetle, followed by five Ball 'N' Chains.
If you need a Super Mushroom, you can go to the right, but you should ignore the door. Instead, go to the left until you're underneath a square brick in the ceiling. It's fake, so jump up through it. Then go to the right and go down the pipe to reach a 1-Up Chamber.
After the 1-Up Chamber, you arrive in the right side of a long hallway. The spiked ceiling will slowly fall, so you need to quickly go to the left. Jump underneath the Lava Bubbles when they jump up out of the lava pits, then go to the right and hit the ON/OFF switch to make the ceiling go back up. However, it will start to fall again when it reaches the top, so you need to run to the left, jump over the Bony Beetles, Gray Blocks, and lava pits with Lava Bubbles that jump up. After the fourth lava pit, just keep running to the left. If you went quickly enough, you will get past the spikes before they can crush you. Go through the door at the end.
Jump up and climb on the fence and stay on the right side. When you reach the hallway to the right, go through it to find a Prize Block that contains a Cape Feather.
Then go back to the fence and climb up. You will need to stomp or punch the red Koopa Troopa and green Koopa Troopa above the spikes. Then jump to the next section of fence, where there is another red Koopa Troopa and green Koopa Troopa. The next section is partly over some spikes. If you go to the right, you reach some small squares of fence that have coins between them.
Keep making your way up this room, getting past red Koopa Troopas and green Koopa Troopas and avoiding falling on spikes, to reach the boss door at the top.
Ludwig von Koopa
Go to the right to find Ludwig. He will spit fireballs at you, then he will go into his shell and start sliding toward you. You can't stomp the shell, but you and Spin Jump off of it. After a while, his shell will stop, then Ludwig will jump in an arc, then he will land and start spitting fireballs again. If he lands beyond the right side of the screen, you just have to wait for him to stop spitting fireballs and start sliding to the left again, so make sure to lure Ludwig toward the left whenever he is sliding around in his shell. Stomp him or hit him with fireballs until he is defeated.
After the Level
The path to the east unlocks, and you can go to Forest of Illusion 1.