Was going so well until level 19... 18 was hard too but after that it feels like you pretty much need to go fast to get through the level at all. No room or time for precision. Crazy jump in difficulty if you weren't already playing that way.
I think I'll come back to these later on, frustration levels = waaay too high right now. Otherwise love the dynamics; the idea; the everything about this.
Seems like one of those games you can replay over and over too, and just get better the more you do. After completion there's still the times to refine.
Update 12/21: Finally came back to this and got 'em all! :D What a killer level 19 was, unproportionately difficult, but it is possible after all. Good sense of accomplishment when you finally get through it.
-cd-