Really creative game idea, which is executed well. However I could note a few flaws / bugs:
- If you cough, and it is mid-air and gonna inflect someone, but you die... You lose the game. Even though you technically didn't lose.
- I think you should think about using different controls. Using numpad is fine, nut if someone doesn't have a numpad it is a problem. Yeah, then they can play with QWEASDZXC... But in some keyboards (e.g. German, Hungarian) the Y and the Z is flipped, which make using this control scheme unpleasant.
Don't get me wrong. I really enjoyed this game, since you've done a great job balancing it. It didn't feel unfair once, since the enemies spawn at a correct rate. Overall, I liked the game, had fun playing it. :)