This is a Garry's Mod gamemode I began developing a few months ago. It started out as an experiment to see how much of a horror atmosphere I could introduce to an existing level using dynamically generated audio & visual effects.
Everyone loved how it turned out and asked me to add more of a "game" to it; which I eventually did. There are several puzzle-quests the players are put through (yes its multiplayer), but I didn't spend any time in the video demonstrating them. Maybe I'll show them in another video (if anyone is interested)