Kinda stupid.
Listen... When zombies get faster then you, there's nothing you can do. If one gets behind your nozzle, in about maybe two more hits, you're dead. May as well put a lives system instead of a health system.
I didn't enjoy this game, for the most part. You do the SAME thing EVERY level. There is little motivation to progress at all, even the background repeats and stays the same. There are only like five types of zombies, no boss, or anything.
And, why can't you aim higher or lower than a centimeter? This caused a lot of problems for me. MAYBE, if I could raise my damn arm and shoot higher, I could get through the levels without dying a ridiculous death.
Now, on to the good things.
Despite some things being annoying and taking away from the fun of the game, it's pretty addicting. And, when you get good weapons LATER IN THE GAME, and you don't die after every try, it gets even more addicting, and what I thought fun.
That fun part was really short lived though. I got it at around level 25, and once I had two levels of fun with the chain saw and laser gun, that was it.
An impatient person will flat out quit this game around level 15, where the player actually starts dying... It doesn't really hook the player in, since it's so repetetive.