title: What's the difference between Google cardboard sdk and google vr for unity sdk?
body: <p>I've seen several tutorials for creating a mobile VR app with Unity. </p>
  
  <p>Some of them are using the Cardboard SDK and others are using the Google VR SDK. </p>
  
  <p>What's the main difference and is there a recommendation to use one over the other?</p>