World 2 - Level 9
This level requires a lot of switching between Stinky and Loof to get prisms around corners and away from walls. First, get a prism to the conveyor belt and push it into the Kaboom! marked with the yellow circle. This requires good timing, both the Kaboom! and the prism must be destroyed in this operation. Now you can retrieve two addtional prisms along the yellow arrows. Place the three prisms (carefully timing the cannon) at the three "X"s - make sure to place the middle position last.