As most of the other people pointed out, the game is a little easy as it is. But it is well polished, the visuals are clear and go straight to the point.
My only gripe with it was that I felt everyone was a little too slow, both the character and the zombies. However it may be just an issue of lacking any proper environment other than a squared floor, which gives no context to compare the movement to.
I just found it a little weird that you need to aim before you can shoot, not really sure why that is there but it might make sense if you'd use melee when not aiming.