Some minor issues :)
When I hug the wall, I can see through the Unity's default skybox. Which itself is not a very bad thing, but it's just nicer if the players don't see that.
Though I understand the surprise element in the game, it feels like it is still not a complete game yet because it doesn't come with a goals and challenges other than running around and shooting zombies. Maybe putting a little challenge for a single level may make the game feel more complete.
But overall, it's a good submission for a game jam! Also, nice job with the controls of the game! It is the first submission with first-person camera that doesn't make me feel dizzy. .. :)