Actually, its more funny than I thought. Reminding me of old Doom or Wolfenstein games.
I feel like this game can be done on two ways, one, by going slowly, eliminating every enemies, or trying to rush it as fast as possible.
The first way is boring, while the second is fun. You should make something that will push the player to a need to beat the level quickly, such as respawning opponents or simply the time limit.
Anyway, Good Job!
My gameplay