Well Done Bro... This game is awesome. I have a few suggestions though.
I never found a way to regain health. I get frustrated when you start a run and you get hit twice in the first wave, then you have 1 health for the rest of the run. I think you should reward the player with at least 1 health after every round. Have a repair center in the shop maybe. I think it will give the player something to fight toward other than random power-ups.
You should allow users to be able to change the crosshair color and the mouse sensitivity. Enemies are sometimes the same color as your crosshair so I lose my crosshair in the chaos. Also, you should allow mouse and keyboard users to adjust the mouse sensitivity. I would have enjoyed the game much more if I could have increased the mouse sensitivity more than it currently is in the game.