Bad Graphics But Nice Gameplay Makes Up for It
It's a really good game, I liked it. I see this game is good because of its great game play, and not because of its graphics. Pokemon for gameboy was a hit not because of its great graphics (Pokemon had the worst graphics), but because of its really nice game play like this game. Two things though:
1. It was kind of hard to see the zombies after a while.
2. It's possible to become relatively invincible.
I will elaborate on point two with simple algorithm:
Power-up Overkill + Weapon Desert Eagle + Moderate Aim Skill = Massive Experience
Massive Experience = Infinity Health
and
Massive Experience = Infinity Base Armor
Infinity Health + Infinity Base Armor = Boring
Algorithm's End
That should help. Good job though.