Last Box Standing May Go On

Try yourself on a handful of levels in a grid-based puzzle game; no large commitments required. Once you push them, these box creatures won't stop moving until they hit either a wall or another box. Be careful where you send them, or you won't get them back out! Equal boxes block each other, but the bigger ones eat the smaller ones. Once only one box remains, the goal door will open. You made sure you could reach it from where you stand, right?