@media (max-width: 600px) {
  .iframe {
    display: block;
    justify-content: center;
    margin: 0 auto;
    width: 350px;
    height: 350px;
  }
}

@media (width > 600px) {
  .iframe {

    display: block;
    margin: 0 auto;
    width: 600px;
    height: 600px;
  }

}