@media screen and (min-height: 510px) and (min-width: 510px) {
  html,
  body,
  html > body > div,
  #login_block {
    height: 100%;
    overflow: hidden;
  }
  form {
    width: 300px;
    margin: auto;
    position: relative;
    top: 33%;
    transform: translateY(-50%);
  }
}