You nailed the Old FPS feeling and it felt good :)
+ Speedy run & gun DOOM-like gameplay, complete with hidden items/areas
+ Enemy was extremely fun to kill
+ Very polished UI and sounds
- Shooting enemies on hills was a challenge.
- Using the die as both health and ammo felt unintuitive
Rolling a die to get an ammo count was extremely clever. I would keep playing this game. Nice job!