interesting, i guess
it's all right
but
could use some updated visuals (it honestly looks like it's from the early 2000's)
maybe centre the text and icons on the main menu buttons
maybe give some more fitting music (the weird pop song in the background doesn't really fit with the whole gameplay stuff of killing zombies)
make zombies not just pop in (or at least give some indicator of where they'll appear a tiny bit beforehand? i've had like 5 zombies spawn on me in the first round)
more guns?
in conclusion, i rate it a 3.5/10 but 4 for encouragement