message: Scrolled scenes individually instead of page
  This retains scene scroll position on navigating along crumb trail back
  to previous scenes
diff: <div key={url}
  style={{
  position: 'absolute',
  - opacity
  + opacity,
  + left: 0,
  + right: 0,
  + top: 0,
  + bottom: 0,
  + overflow: 'auto'
  }}>
  {scene}
  </div>
  