Just like Jinairen said, the game has pretty solid mechanics, although I doubt he played it till the end. The room with the large chest is missing the second switch (which should be to the right) to lower the row of bars. The fact that you can't finish this game is a real game breaker.
I've posted an update to the game that should fix this.
Pretty solid game with a steep difficulty curve. One missed shot usually means not having enough ammo and having to restart from the last checkpoint, but those are frequent enough that it's not so bad. All in all, it felt like an old NES game, which isn't a bad thing. It even allows players to save and pick it back up later if you're short on time.