Great first game!
For your first game, this is pretty good. As for the game itself, its good. Decent graphics, nice variety of weapons though it be cool to get some explosives like grenades to break up those mobs.
Only real problem with the game is that its a bit too easy, especially near the end. Because once you get all the weapons and have a full crew of survivors you can take your time because even if the zombies do heavy damage to the barricade, you can use all your hours to repair it. Maybe a bit more fast zombies would of made it a bit more harder.
But still, for a first game its pretty good. A sequel to this be cool, or more games from you...so I hope you make more!