Exercise : what just happened? What is the main advantage of that kind of interaction? What kind of interface can you build with that? Which ones can't you? Where did you see it used before in the exercises and demos?
Alt: http://output.jsbin.com/kaxara/ make sure to use it in VR, as you always should! Nod and shake your head and see what happens.
Take a minute to think about UX and culture though, in which countries would this alternative mode of interaction be a problem?
Done? Go back to learn more.