img.portrait {
  width: 200px;
}

img.portrait.float {
  margin-left: 20px;
  margin-bottom: 20px;
  float: right;
}

img.portrait.below {
  display: none;
  width: 100%;
  max-width: 300px;
  margin: 20px auto;
}

@media (max-width: 500px) {
  img.portrait.float {
    display: none;
  }
  img.portrait.below {
    display: block;
  }
}