A Near Perfect Tower Defense Game
First I will start out by saying that this is one of the best games on Newgrounds by far. In fact, it is one of the better games that I have ever played. Amazing gameplay that only gets better the more you experience it. Additionally, great sound, graphics, and everything else was nearly flawless (no gem pun intended.)
I have no real suggestions for you but the only minor thing that I would change is adding more hotkey/quick use functionality in order to speed up the gameplay.
I am looking forward to your next game and please, please, keep up the amazing contributions to Newgrounds!