GVS or galvanic vestibular stimulation is a technology that directly affects a user's vestibular system by altering their sense of balance and direction. It works through electrical stimulation via electrodes placed on the mastoid bones behind each ear. In standing users, GVS evokes a prolonged "galvanic body sway." In walking users, it affects balance and causes users to stagger in the anodal direction. However, in walking users, with their head pitched forward, it causes them to turn smoothly from their planned trajectory in the anodal direction. Dark Room is a cooperative asymmetrical "escape the room" style game played by a VR and a PC user, inspired by the single-player mobile game Dark Echo. The PC user controls the walking direction of the VR user to guide them around virtual or physical obstacles. The VR player uses echolocation to detect obstacles. Video and paper available here: http://web.media.mit.edu/~sra/gvs.html