It's a nice game, but the picking up and dropping of crates doesn't work well; it is really annoying. I have to press E multiple times before it works (both for picking up and dropping). There is also no feedback when I'm close enough/too far away. Add to that that these massive blue blocks get pushed around by these small crates and the frustration meter is maxed out.
The whole gravity thing is pretty nice though. I stopped at the level with the yellow hexagon thingy.