div#container {
  width: min(80vw, 700px);
  margin-top: 70px;
  margin-bottom: 50px;
  display: flex;
  flex-direction: column;

  left: 50%;
  transform: translateX(-50%);
  -webkit-transform: translateX(-50%);
  -moz-transform: translateX(-50%);
  -ms-transform: translateX(-50%);
  -o-transform: translateX(-50%);
}

div#container > img {
  max-width: 100%;
  min-height: 400px;
  height: auto;
}