Progress: Just beat Level 6.
There's one thing that bothered me in Level 6, though. In the bottom right room of the top-right 3X3 section of the map (the room where octoroks appear in the closed off corners of the room, there's a horizontal line of pits that drop you to the room where you find the wand item room, and conveyor belts that try to push you into the pits. The room comes after a room with a key), a chest appears after you take out all the enemies. However, I can't open the chest because of the conveyor belts going in the direction away from the chest.
What's inside that chest? Heart Piece? Rupees?