Very clean UI! Nicely done there!
Feedback on enemies when they took damage would be great - sometimes I felt like it took only 1 shot to kill (not just when using the super shot) and other times it felt like 3 and I wasn't sure why. Also disappointed the flames on the first map didn't hurt me - where's my realism??? (Jokes).
It also took me a bit to realize I needed to kill X amount of mobs before I could move on to the next level, especially since there was more than that many mobs on a level (e.g., I need to kill 15, but there's 20 on the map and then I get transferred).
A couple of other things of note if you decide to keep development! The voice line "One dice left" would play seemingly at random. I would get it no matter what amount of dice I had left. Also, besides adding screen shake when firing, I think turning your cross hairs red when you're over an enemy would help aiming a lot! Also adding a least a little bit of vertical aim to your game would be good. I know you were going to match Doom, but if I remember correctly, their maps were mostly flat, so there was no need to aim up or down. Yours had bumps, which added to the realism of the map, but made it much harder to aim. I would also turn down the bloom, the game felt very bright. Food for thought!
Overall, considering this was a solo project - very well done! It's impressive you were able to get in as much as you did!