It's very hard. Maybe add Player-HP (3 hit = dead)
EDIT: ok, I never used the gun xD
EDIT: Cant beat lvl 3...
Thanks for the feedback! I'll consider adding extra lives. The last level is possible...the strategy is meant to be to rush the first several zombies so that the spawner at the end doesn't have the time to create a whole army.
yoooooooo theres a gun?