Been done before but good effort and gameplay
i think you should put an Zombie Infection like you need to build to avoid INFECTIOn
I know the shit-ton of coding that is needed for making a game, I hope Flash doesn't need that much of coding, It's a pretty good effort, I like the smothness and the overall desing, simple but good. Event though this has been done many times in many styles. But I not saying this is not a good game, it is!
its ok but its not great its a very simplistic game style that has been done over and over but for what it is its ok.