Interesting
It's an interesting principle, and it makes for some fun gameplay. I do have a few gripes though... it's a little tricky figuring out what direction/velocity yields the best results and though that's part of the core gameplay, it might be nice to see some sort of indication of what your previous move(s) was/where so you can more easily offset your next one taking into account the results of your previous attempt. Also I found that the air/surface friction of the cubes and the projectiles are pretty strong. I've seen some constructions that held on that would've been impossible in any accurate physics simulation.
In any case, keep up the good work!