.auto-resizable-iframe {
  max-width: 640px;
  margin: 0px auto;
}

.auto-resizable-iframe > div {
  position: relative;
  padding-bottom: 60%;
  height: 0px;
}

.auto-resizable-iframe iframe {
  position: absolute;
  top: 0px;
  left: 0px;
  width: 100%;
  height: 100%;
}