Entertaining concept, but my computer can not do anything with this on.

I had to do some good thinking for the last ones with gravity. The visuals are actually pretty neat aside from the menu/end. The simple look allows you to focus on the achieving the goals. Also it would be good to fix up some of the mouse placement, as you can cheese your way in a few levels by spawning the physics box very close to the goal. (perhaps a radius check around the goal could work?)
Being able to place blocks with no constraint allows some interesting quick moves when you want to, for example, adjust the direction of the physics block or catch it right into the goal. I thought that was neat and perhaps you could explore more dynamic objects. Good work!

really fun and has an interesting concept