Very enjoyable, great graphics, way too easy
First play through of the game is great because you expect it to get harder and are worried that bad choices will screw you over. Then it doesn't and you win, and wonder why you were afraid; the answer of course is that it has excellent atmosphere and visuals, really creates a mood and does a decent job maintaining it. But it's just too easy.
To prove this, I played it through a second time without repairing the wall once, and I didn't even really try that hard... ended up surviving with 15% left. That means that the wall repair is a completely useless feature because it doesn't actually protect you from anything, since the enemies never really do much damage to it anyway.
My suggestion to the creator: a climactic final level would be a plus. By the time you have the last gun everything dies in less than one hit -- I've killed four zombies with one bullet before. So... add something hideously powerful to the last level that really makes the player afraid, and which might require a couple retries to beat. That's seriously all this game is missing. Good work.