Yay The zombies Can't hurt me

Well, it's good. A fine concept with appropriately chosen music and sound effects. I really like that there are multiple environments (grass, snow…) but I don't think there's a gameplay difference between them which is a pity. I like snow the most because it's the most well-lit area. In the other, the ground isn't even visible without your flashlight.

Let's get the bugs out of the way first:
– Enemies don't harm you AT ALL. Therefore it's impossible to lose and while writing this, I'm getting surrounded by a *horde* of enemies. To your credit, they push you all over the place, but not once did I fall out of the boundaries of the world, so the game still keeps going.
– Pause doesn't actually pause the game, it just shows the menu. Did you mean to set Time.timeScale to zero or something?

As for improvements:
– I think it's too dark. Nothing should be that much shrouded in darkness, everything should be lit at least to a certain amount. Especially the player character, not just the light cone in front of him.
– There should be some sort of visual response from killing a zombie – e.g. popping up. Now it seems it just stops – but when there are many zombies onscreen, you wouldn't even notice you shot a zombie if it wasn't for the increasing counter
– You probably should be able to reach the edge of the world "plane". There could be an environmental barrier just like it is in the middle between different areas.

Suggestions:
– Give us a reason to explore, such as items appearing somewhere on the map. E.g. temporary powerups (increased damage, wider shot), health replenishment.
– Different kinds of enemies appearing over time.

The zombies don't hurt you.