Good, but not great....
You get a 8/10 from me, not bad, but here ive got a few suggestions just to make your game a bit better.
Upgrades: We want more! Once you buy everything, your done, there, easy. Grenades should have to be bought, not just regenrate.
Enemies:HEADSHOT! A headshot to most enemies kills them, and while there was much variation, the only really different one was the headless one,
otherwise a headshot would destroy any of em. So what you should do, is make zombies stronger every level, make different ones, like legless, armless, headless(you have) maybe even other creatures.
Field of play: Chlosterphobic personas, beware! Theres not a ton of space in this game, and once you have the barbed wire, you dont have any time to waste before they get to it, so your forced to shoot if you dont want to pay for repairs, but you do have tons of money, so... yeah.
Defences: The more space the... better?! The defences were fine, but they were spread out, FAR out, disreguarding the wooden planks. The barbed wire was far out there, and the mines were behind it? Thats doesnt make much sense... cant you place the mines outside of the walls? Ide say just squeeze em in, and have the mines on the outside.
Weapons: Yaknow what, not bad! The weapons, or rather weapon, of this game was fun. You dont really need to change that. But the upgrades were too cheap for the amount of income you got. You could buy all the waepon upgrades and no defences after about 3 rounds.
Difficulty: 1 shot to rule them all... Really, i found this game to be very easy, and it doesnt get much harder after time. You must make it harder! Stronger enemies, faster ones, and anything really, just make it harder.
Graphics:You need a graphics change button. most of the graphics are pretty crummy, i mean, i dont want 3D xbox 360 stuff, just not so pixely in certain areas, like the defences and the enemies. A graphics change button with 3 settings would also be much appreciated.
Rating 8/10 Very Good! I can see that this could be better, but with just a little more effort, this could be great!