Can't believe how much time I wasted on such a bad game.
Too many levels that are too long. It gets repetitive.
Also: there should be more of a visual change for upgrading monsters, or at least the catipiller thing.
There is one major problem! When you try to fit blocks together on the side, the block usually stops before making it all the way it, leaving a gap and making towers unstable. You should have a .5, to .25 sec delay from when the block touches to when you lose control of it. That would be nice.