Very much self-explanatory! It was very addicting building up a zombie army.
On the first level, I was a little bored once I understood the mechanics. And I actually thought "It needs someone shooting back or something.." and lo and behold, level 2 was exactly that, and level 3 built on it further. Each level was more fun than the last.
The music was fine, but it was a little monotonous after a while. I think there needed to be additional sound effects, like the sound of humans being eaten, etc.
It was a very smart decision to have the camera zoom out based on horde size. I really appreciate that design decision.
Overall, very cool.