I like the core loop that you created with this one, and with a bit of polish this could be a really great incremental-upgrade type of FPS!
I'm not sure if my game bugged out, but once I interacted with the door using the key, the only thing that happened is that the time started counting down in larger chunks until it stopped completely.
There were also some movement issues, like gaining tonnes of speed if you ran diagonally, and each incline felt like I was running on the most slippery ice ever.
All in all, I had fun with the game! Great job :)