.frame {
  background: #fff;
  height: 0;
    padding-top: 70%; /* aspect ratio */
    position: relative;
    width: 100%;
}


iframe {
    border: 0;
    bottom: 0;
    height: 100%;
    left: 0;
    margin: 0;
    padding: 0;
    position: absolute;
    right: 0;
    top: 0;
    width: 100%;
}