Zombie Outbreak All but perfect!
The only two criticisms I can really give you is that the area becomes somewhat stagnant; running around in essentially a circle for however long your alive. So perhaps in the future you could make one that scrolls with the character so you can go throughout the entire city? Maybe one where you're attacked in different parts of the city and you have a map in-between waves showing your movement towards a potential safehaven?
The only other criticism isn't that bad at all; the overhead of the trees got in the way at some points. Nothing wrong with that, and it makes for a more diverse gameplay, but it also feels a little cheap when you're taking damage from a direction you can't see.
Other than that you obviously know what you're doing! Graphics were great and the sounds were decent! Can't wait to see a sequel!