Google Cardboard VR Viewer uses your mobile phone to show side by side virtual reality. While Oculus Rift and Gear VR use software to modify the original files to let you look around in 360 degrees, Google Cardboard needs the files to be pre-distorted or pre-undistorted as the case may be. Google is also developing their own smart software but that might defeat the purpose. Stay tuned as the VR headset wars continue. Girl VR.