Cool game, here's some feedback
1. Mouse sensitivity was way too high; it felt impossible to aim
2: Gun mechanics: there could've been some shooting effects or subtle weapon animations - it felt like just tapping the center of the screen
3: A home menu or exit menu - there was no way to exit the game or anything like that
4: Post-processing, adding a skybox, or even simply adding anti-aliasing could've really enhanced the visuals
That said, I liked the concept of having to find moving props around the scene. Good game, especially if you are a beginner to Unity!