I have to say, for a first game...
This is pretty darn solid. I'm going to use the bulk of the review on things that could be improved, not because it's bad, but because there's a lot of stuff you could do to make this shine far beyond a solid base.
The good:
-Solid, decent controls.
-Solid, decent guns.
-Pixely graphics get across what they need to, and they aren't bad.
Improvements I'd suggest:
-A better soundtrack. While it's appropriate, a simple bass/drums combo is a bit... plain. Granted, the game itself is plain, and not complex, but it could definitely be improved upon.
-Better ammo system. It's really, really annoying when I have an uzi, an AK47, and a M16, I'm trying to use the bullets sparingly, and I STILL run out of ammo before the day ends. You pretty much have to learn to click the mouse really fast and be precise in bullet use. (4 for small zombie, 8 for middle, I think 16+ for the big one) Perhaps ammo drops would fix this, it could also cost per bullet at the store to make up for it. That would make it more realistic as well. Also, a weak melee weapon with knockback (or strong melee weapon without knockback) would really help. By the time you can use it, you'll have taken damage.
-Bigger area/more zombies/more weapons. This is a large section, which I think would make the game a lot cooler. Granted, it could also revamp the game completely, but... First of all, in a shop that sells an infinite amount of bullets, has the world's best doctor, and an entire arsenal of guns, why wouldn't it have grenades, bear traps, and some kind of 'armor'? Not to mention different kinds of guns, wood for blockades, and barbed wire. I'm sure you can see how these would be used (bear traps only outside, kills one zombie on the ground before being disabled, blockades can be placed, costing a certain amount of wood/cash, and barbed wire can be placed on a blockade to harm zombies destroying it). The house could have more floors, and the lawn could be wider. This would make it more interesting. I would recommend having a front lawn screen, first floor screen, second floor, and third floor. Zombies could eventually come in through the roof, they could come in through the back door, and through the window. You could shoot the floating zombies from the second floor and the front lawn to kill them, once they come in they're a normal zombie. An enemy with a ranged attack would be good as well.
Though this is a bit messy, hopefully it has some good ideas that could be implemented in another update or other game.
As I said, this game is a wonderful base. I just don't think it's a full game quite yet, more a mini-game that's for killing 10-15 minutes. I feel like it should be in a larger game rather than being on its own as it is. But as I said, it could take off and go quite far if done right.
Good luck!
(-4 because I need to leave room for its potential, +1 because I'm pretty impressed with the quality of it already, since it's your first game)
-Swint of the Review Request Club-