Great Game!
This is a great game all around, way to go! I only have a few suggestions for you.
1. It’s very hard to get EXP, so I would recommend having some of the zombies (maybe the faster ones or the zombies that are farther away) be worth more that others.
2. I almost want to say that the reloading was too hard, but in reality it doesn’t take that long. However, it would have been nice if while one gun is reloading, you could switch to another instead of having to wait.
3. Giving an option at the beginning of the game for the level of difficulty someone wants to play at (easy, medium, hard, impossible) is always a nice feature.
Other than the first two things, it was a fantastic game!