I finally finished all 36 levels! Very nice puzzle. Cute, intuitive (once you get your head around it), and tricky. Stairway to Heaven took me the longest.

I did discover a few physics bugs. They all seemed to be when two blocks in C shapes were supporting each other, and one of them was supported by a solid wall as well: they'd both drop off the screen, through each other. Something like this (where # is wall and 1-2 are blobs of putty):

___11__
####122
___1112
_____22

It doesn't happen without the bottom-left square of 2, which I think is confusing the game into thinking 2 is supporting 1 rather than hanging onto it.