First FPS I've seen on this jam and it's great. Especially the music choice, though I can't give it to you because it's a free asset. Here's a few things I'd suggest:
- If you were going for the retro DOOM style, the walls, doors and the gun are way too polished, flat and clean. Maybe at least making those textures pixelated just like the enemies would add to the aesthetic.
- I think it would be better if you either gave the player the choice of what color to shoot next or made an indication of what color was coming next as the current system is rather confusing, especially considering that it's never stated clearly that the color changes automatically.
- The enemies die before they can even try defending themselves. You can enter a room filled with enemies and by the time you kill them all they'll only shoot 2-3 times, which is very easy to dodge and doesn't do much damage anyway. I'd suggest either making them move more and avoid the player so they're harder to hit, making them shoot more with more accuracy so they can do more in their short lifespan or making them have more than 1 HP so they live more.
- I think occasional random obstacles would make the gameplay more diverse,