This really seems like a great game, the interface is a little clunky but other then that I really like it. One suggestion in the future you might consider not using the same hotkeys for lots of different actions. It's confusing.
I'd probably rate this game a 3/5 if it weren't for the fact that you actually have to massage the speed button to break up the waves to win. That is total crap. It isn't a tower defense game, it's a speed button pushing game. WTH?
This game has a lot of potential. However a level select screen is a must as is some type of display for tower stats and pop ups for what the rewards actually mean.
The key is to focus on getting henchmen I ended the game with about 6 of level 1 and 2 and 22 of level 3 and about 12 level 4 henchmen. Also, kill the birds to get a free gun. Don't buy new guns or upgrade your old guns it's a waste of money.
The game is WAY too hard especially the first level which is supposed to be easy in a game like this. The towers are not balanced AT ALL. Moreover, there seems to be only one way to beat each level instead of a multitude of different strategies in most games like this... It has good graphics and great potential, however, it needs achievements, and the ability to upgrade your base abilities by replaying previous levels. 1/5 when it should have been 5/5...
You only need 3 blocks to beat the game with ease. Slow or eye block at the first square. Then at the last row, you put two piercing blocks facing forward and stack booster blocks on top of them. The digestive blocks are ok for easy boss kills as well.