Virtual reality
Around the same time, Douglas Engelbart used computer screens both as input and output devices. In 1968, Ivan Sutherland, with the help of many students including Bob Sproull, created what was widely considered to be the first head-mounted display (HMD) system for use in immersive simulation applications. It was primitive both in terms of user interface and realism, and the HMD to be worn by the user was so heavy that it had to be suspended from the ceiling. The graphics comprising the virtual environment were simple wire-frame model rooms. The formidable appearance of the device inspired its name, The Sword of Damocles.
HTC Vive
Prototypes of a Valve-produced virtual reality system were demonstrated during 2014. On 23 February 2015, Valve announced SteamVR and that it would demonstrate a "SteamVR hardware system" at the 2015 Game Developers Conference. HTC officially unveiled its device, Vive, during its Mobile World Congress keynote on 1 March 2015. Preorders started on 29 February 2016 at 10:00 a.m. EST. Valve and HTC have since announced that the headset will be free for selected developers.