Neat puzzle game, it was fun watching the humans ragdoll when they were hit. The limitation is really baked into the gameplay as well.

 I think the game would have benefitted greatly from use of audio. Also, on the level where you swap between the blue block on top and the red block on the bottom, I found that it was too easy to clear the walls then go hurdling out of bounds and die because you could not see far enough past the wall.