I like how this looks like and the zombie theme. It reminds me another game I played once, except yours has maps and is isometric. Also I like how it looks like Minecraft
EDIT: Ok just tried it now and awesome work so far. I like the achievements and online features. Difficulty seems pretty fine and while controls takes a bit to get used to (to aim in particular), they're pretty intuitive I think. The only loading issues I got was when selecting stuff in menus, where it sometimes took 3-4 seconds to load on my nexus, but frame rate during gameplay is fine.
As suggestion, though, you might want to make sure you won't run into copyright issues with the Minecraft graphics if you ever decide to sell the game, in case the new Minecraft authors and owners are like Notch when it comes to re-using his graphics.