ytube{
  position: relative;
  margin-left: auto;
  margin-right: auto;
  padding-top: 56.25%;
  width: 100%;
   iframe {
      position: absolute;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
    }
    a{
      /* lityを動かすためにirameを覆う */
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
    }
}