few bugs: 1) After last level, Next takes you back to level 1 (what, no end game screen? :)). 2) Even if you kill the last zombie with your last shot, it says "ran out of missiles" and you have to retry. 3) Need to wait longer for last missile to resolve. It said I had to retry even though the missile hadn't exploded yet and was on target.
It is obvious that some GREAT work went into this. The computer may take a bit longer than the noobs who can't build games would like, but all-in-all wonderful achievement. You certainly know your stuff! :)