Very nice atmosphere in the game. Love the whole cowboy and mine vibes. The enemies come at you fast, maybe a bit too fast. I really like the UI a lot, with the life bar, lantern and revolver reload UI. Like everyone else, I think you can do away with the hold to draw weapon mechanic and just have the shoot button always work. The player is a bit slidey on the floor as well, not sure if that is on purpose but it seems to go against the aesthetic of the mine. Also, it would be nice to use a pixel font for the default font.
Overall it's a very solid development though! I only played the beginning so far; can't get past the first "boss" with the shotgun.