Balloon Platform Defense is a game combining the Single-Screen Platformer with the Tower-Defense genre. The enemies in Balloon Platform Defense are all made of physics-based balloons, allowing you to attack them by any method that applies enough pressure to them - jumping on them, pushing them against a wall or a ceiling, or between two players.
Lovely windmill isn't it? Some levels have more stationary enemies, but there is always the risk that pieces can fly off into the exits when you try to jump on them.