I think this game had some pretty interesting mechanics and I enjoyed playing it. The visuals were simple but pretty good and made the levels feel like actual places. I like levels two and three, though I'm a little confused about what I was supposed to do for level one and it sort of feels out of place with the rest of the game. The bullets were sort of slow for bullet standards, but I kind of liked this as it sometimes required me to think ahead and aim at where the NPC was moving, rather than at the NPC itself. I do like how the progression from level two to three introduced new NPCs, though admittedly they are pretty easy to outsmart, but it was still pretty fun to fight them. I do think there could've been some more player feedback when killing enemies, but it was fine enough.

I really liked that each level had its own objective and feel. It was like playing 3 mini games in 1. The progress bars on the enemies were a nice touch. The first time playing through Level One I noticed there were no health or progress bars visible on my screen when I opened it. I died but did not know how close I was to death or reaching the objective when playing. I liked that the guns turned green to indicate success. 

Here's a revised version of your critique:

"It's a funny little mini-game. I like the art style for the first level.

Critique:

Level 1 - I was a bit confused because there was no direction on what to do. Knowing the objective of grabbing the gun would be helpful.

Levels 2 & 3 - I noticed that when enemies get near the player, it's challenging to shoot them; you have to create some distance to hit them. Regarding the gun, knowing where the bullets shoot would be very helpful, and increasing the bullet speed would be great. It's really difficult when the bullets are very slow, and the crosshair disappears."

I like how your game has three distinct feels for the three levels. You have clear goals and the UI provides you with all the information you need. The cars in the second level would sometimes get caught in the walls around the level but would eventually fix themselves. The first level I understood that the pick ups were guns but why turn them green instead of destroying them? That is more of a nitpicky critique than anything. The shooting was responsive and the AI was responsive for the enemies as well. The game itself was very simple but also clear and well designed. Good Job!

I love how each level has their own objective! Only feedback I got is making it so the player can hold down the left click to shoot.

Very fun little game! Love the art style you went with the nice fps controls.

 Some constructive critique: 

Level 1 - Its not very clear what objects the player is supposed to collect and how many. Some sort of tracker or indicator would be helpful.

Level 2 & 3 - I like the addition of the healthbar for the enemies but I would personally have it always rotated to the players perspective (it currently rotates with the enemy). Also the projectiles seem to deactivate early sometimes when pressing the fire button quickly. Could be related to the object pool (if used).

I love the camera rotation and movement. I am not sure why but it feels a lot smoother than anything I've played in unity before. I enjoy the style of the game but the lack of sound and player feedback make it a bit hard to immerse myself in the game. The first level seems a bit out of theme, I was a little shocked going from level one to level two but that may just be me. The enemy reactions seem a bit slow and too close range, I would recommend having them start shooting at you when you shoot them as well as the bullets going a bit faster as having no crosshair and a very slow bullet made it very challenging to consistently hit the enemy.

Just a bug probably but the cars in level two receive the same particle effect as the enemy's when shot.(I doubt you meant for the cars to bleed but maybe they're weird in this universe)