Awesome game.
I liked the achievements (Although Kongregate ones are nice), got bored a bit quickly but it would be better with things like - Combos, Perks and push-back (even on 1 in 10 shots). Example of Combos = After ??? kills damage/speed/firerate increases by ???%. Example of Perks = Laser sight which puts laser on-screen and increases acurracy by ???%. Example of Pushback = Zombies get pushed back a bit on 1/10 shots.
All in all a good game 4/5.
Regards, Tricky.