I can hardly call that a game.

good concept, i hope it becomes a full game with different levels and weapons

It's a nice simple game. Two things I would do
1. Keep the score in the players view at all times
2. Make a quit button.
Found a bug where if you just spam the shoot button the zombies automatically die... need to be in view of course.

I did not enjoy, it seemed to be the same thing over and over. There was no flavor in my opinion, it lacked continuity