Not sure what you are meant to do in the game. I had fun jumping around and I reached the pole which I thought was going to be the finish flag but nothing happened :P
The spawn rate of the zombies is quite insane, I would wreck my mouse trying to kill them all :D
Well done on your first game !
Finetuning the rate of zombie spawning, adding some music and sounds and having a goal in the game would be good ways to expand on what you already have.