Ooooh, I hope that this evolves beyond a concept demo...
Once the game is longer, I think you should add a "run" feature. If the slow walking is for creepiness or suspense, consider having some parts where walk speed/direction is fixed and others where movement is free and faster. At the current movement speed, I found myself wasting bullets out of pure boredom.
I also think it didn't make much sense when the snow blocked the entrance, but there was still light inside of the bunker. Maybe give the mysterious protagonist a flashlight and have him/her navigate in the pitch dark with only one beam of light (until the lights are turned on, anyway.)