Edit: The game is impossible. I got to the end of level 4, and you can't win. You get to the chamber where the princess or toads or what the fuck ever, and there's a dude standing there as your character moves automatically into him, and gets killed. There is no way to avoid it, at all.
Oh, that's level 2. Yeah. In the box on the far left is a mushroom. let the enemy touch that mushroom, and it will grow very large and fall through the floor, smashing boxes as it goes. You have to get a little lucky, and time it so that it smashes boxes in such a way that will allow you to jump up at the other end.