The puzzles were really fun! I like how you managed to keep the entire game confined to a small area, but still have a good variety of puzzles, backtracking, and atmosphere. However I was disappointed that there wasn't any actual threat throughout the game. The ending was also very disappointing, being a simple wall of text describing your final moments.
The bullet collection mechanic honestly felt like an afterthought. It was way to easy and had no meaningful reward for being perceptive. Here's my personal opinion on how I think you should of done the mechanic. Perhaps you could of made it a trial and error resource mechanic where there's multiple ways to solve a puzzle, but you have to fine the most efficient way to solve each one. Again, those are just my thoughts on how I see the mechanic working.
Overall I enjoyed my time playing through this game. It ran well with very minimal bugs. I most definitely look for forward to your future projects.