"I have no mouth and i must scream..."
Why do zombies and humans(?) look exactly the same? You could at least paint the zombies green. ;) The fact that neither of them has a mouth actually is fine with me.
You could also put a little twist in so that sometimes a zombie wins. (Maybe even with 2 counters, longest streak etc...)
And a mute-button! I can always switch out my speakers, but a button in your flash would be more convenient.