docs: function easing (time, start, distance, duration, settings) {
      switch (settings.easing) {
      case 'linear':
        return distance * time / duration + start;
        break;
  
      case 'easeInOutQuad':
        time = time / (duration / 2);
        if (time < 1) {
          return distance / 2 * time * time + start;
        } else {
          time--;
          return -distance / 2 * (time * (time - 2) - 1) + start;
        }
        break;
  
      case 'easeInOutCubic':
        time = time / (duration / 2);
        if (time < 1) {
          return distance / 2 * time * time * time + start;
        } else {
          time -= 2;
          return distance / 2 * (time * time * time + 2) + start;
        }
        break;
      }
    }