(function() {

  'use strict';

  var scene = document.querySelector('a-scene'),
      tapTimer = null,
      tapSpeed = 500;

  document.addEventListener('touchstart', onCardboardTouch, false);

  function onCardboardTouch() {
    if (!tapTimer) {
      tapTimer = setTimeout(function() {
        tapTimer = null;
      }, tapSpeed);
    }
    else {
      clearTimeout(tapTimer);
      tapTimer = null;
      scene.enterVR();
    }
  }

})();