The collision detection isnt workin very well, maybe the bullets are going very fast. Also the barrils could also interact maybe if they explode. I liked the models, they can be better but its ok.

What I see so far looks promising. I kind of like the movement pattern of the enemies. Feels a bit unfinished, but for a 3 day game jam the result is pretty solid in my opinion.

"The bullets interacts with the zombies by decreasing its health; the zombies interacts with the player by decreasing its health; and the score interacts with the zombies' spawn rate and speed." - Fair enough.

The projectiles are so fast that they can fly right through enemies without hitting them. If you need them to be this fast, they should use a raycast to make sure they don't fly past anything.

Overall good job! Hope you enjoyed the jam. :)

Let me start off by saying that it isn't very clear that the green boxes are the zombies. For me the main problem with the game is the shooting. I think you register a hit if you click on a zombie and the actually bullet is just an effect. However it is extremely hard to click multiple times on the same zombie when you're running across the level trying to avoid them.

I didn't really see anyway that the objects interact with each other. Perhaps you can make the bullets actual GameObjects, so that they can bounce of the walls. You can also make the barrels explode and zombies bounce from wall to wall.

Sebastian Lague has a good tutorial on how to make a shooter game, if you want to improve the shooting. Whenever I make a game in a new genre, I start with a tutorial to understand how the basics work and then I build on top of that.