Cardboard as a device is a simple cardboard enclosure that I'm bands a pair of 40 mm focal distance lens and employees and open source software development kit to turn your phone into an expensive virtual reality headset. To make it work the phone must be an optimal distance away from the lens point with cardboard compatible apps the lens create 3D effect when held up to your eyes. The image respond according to the position of your head when you move it announce just as they would blown expensive VR headset.