I must have been doing something wrong, because nothing worked. I went and followed the instructions and once I put my towers up, nothing happened. They didn't fire at the enemy or anything. I tried clicking on them and nothing happened again. I guess I have to give you credit for having some pretty cool music and sound effects. The enemies themselves are fairly unique.
I just wish I knew how to play this game! At least other people seem to have a lot more fun with this. I just wish the instructions would tell you a lot more. Everything's done in a fairly organized matter. It's a bit out of the ordinary for its kind.