From the Super Mario Wiki
Retrieved from "https://www.mariowiki.com/index.php?title=Level_x-3&oldid=2526570"
The player first has to ride a platform across a pool of lava to the left, while avoiding Lava Bubbles. From the lone block, the player can perform a Handstand Jump to get over the ledge ahead. Next, the player needs to jump across moving platforms while avoiding spikes below and Kurasshās above. To the far left is the Key, which the player needs to bring back to the start, avoiding all the obstacles again. Once back at the start, the player has to toss the Key up onto the above platform and then perform a Handstand Double Jump or a Backflip to reach the locked door.