It's a pretty cool shooter. 3D, several stages, multiple power-ups and a boss battle. And one of the most epic Credits sequences I have ever seen.

Although considering it's the core of the gameplay, I'd expect to enjoy the shooting more… but it's fairly bland. I can barely tell I successfully shot someone. The torso very briefly blinks red if you hit it, but I'm not sure if any other body part does the same… or if there's a difference in damage between shooting other body parts.
But mainly I’d try looking for ways to improve the main feel; gunplay (for inspiration – https://youtu.be/SWf9pNdivpo) and add impacts to affected body parts, temporary stun animation or some better visual indication (for inspiration – https://gamedevacademy.org/game-feel-tutorial/).
Otherwise, it's always such a surprise when you click a few times to seemingly no effect and then the enemy drops dead.

Other notes
– Default Unity buttons in the Menu; they're pretty recognizable for bad reasons – they don't look too good on purpose so people would be more inclined to replace them
– You can hide Quit button in WebGL games, it's pointless as it just freezes the game forever until you refresh the page
– I'm not sure what the menu background is supposed to be (blurry texture, overlapping models, different grass texture scale); but it certainly isn't very representative of the actual game (it should ideally make players excited to play it; for example you could show some enemies posing with their weapons)
– You start without a gun in the tutorial and before you even have time to look around and learn the controls, enemies already shoot at you.
– Half of the fence in the tutorial area doesn't have a collision
– I love the audience members with their creepy smiles; a pretty good choice to include them there watching you all kill each other
– If your FPS avatar is a capsule, disable its shadow (no one needs to see that)
– There are different weapons, but they don't feel that different; only by sound (related to the gunplay feel mentioned above)
– “green gun” plays audio only “from the right” when using headphones which is somewhat distracting
– after teleporting, your weapon changes
– I wasn't really sure who the boss was, no one seemed to look too different or be tougher
– I ended with a boss count of -3

Still, it's an impressive game with a lot of content, but it feels like a prototype rather than a game I'd love to return to and recommend to others.
Hope the tips above will help you if you'd like to continue with this project or when you start your next one. Good luck!