Great game!
Doesn't even describe it.
Graphics: Sweetest stuff for a game...
Sound: Almost perfect firing sounds, and liked the death sounds.
Style: Original, zombie-defense game... Uberness...
Violence: Er....
Interactivity: Somehow, some of my bullet dont come out... Maybe the sandbags/survivors?
Humor: None...
You'll want to have a 'winning' stage, lvl 100?
Saving is VITAL...
More weapons, maybe grenades, missiles, RPGs, tanks, machine guns, etc.
The last sniper rifles should have one hit kills... (Ultimate sweetness)
Please have base expansion so you can hold more survivors.
New environments? (City, Village, Army Base, Pentagon, etc.)
Cutscenes? (Ultimate game if so...)
Maybe a story, like killing the person who made the zombies, or perhaps destroying the virus that makes people into zombies, etc.
Overall: Probably the best survival game/zombie game, but if you have these improvements... Ultimate sweetness...