What was the FIRST Valve game to have VR?

Explanation

Valve Corporation released its first virtual reality game called 'The Lab' for HTC Vive on April 2nd, 2016. It was a free standalone title that included five different experimental levels designed to showcase the capabilities of VR technology. The game also served as a teaser for the company's upcoming flagship VR game, 'HTC Vive VR titles'.