I'm not sure why...
I voted 4. Its not REALLY that great this game is such a clone of flash TD, but then again there are more games like it, or is that not the first one? Anyways, I've played lots of games like this, and this one doesn't seem really out of the norm.
Its pretty good I guess.... BUT nothing special. Im not quite fond of paths... I like mazing it out... So air could be a factor. Yeah.