/*
 * Assume `default feature`
 * if only a number
 * $single-pixel-value: 500px;
 * $single-em-value: 30em;
 */
@media (min-width: 500px) {
  .foo {
    content: '$single-pixel-value';
    content: '@media (min-width: 500px)';
  }
}
@media (min-width: 30em) {
  .foo {
    content: '$single-em-value';
    content: '@media (min-width: 30em)';
  }
}
@media (min-width: 500px) {
  .foo {
    content: '$single-pixel-value';
    content: '@media (min-width: 500px)';
  }
}
@media (min-width: 30em) {
  .foo {
    content: '$single-em-value';
    content: '@media (min-width: 30em)';
  }
}
@media (min-width: 500px) {
  .foo {
    content: '$single-pixel-value';
    content: '@media (min-width: 500px)';
  }
}
@media (min-width: 30em) {
  .foo {
    content: '$single-em-value';
    content: '@media (min-width: 30em)';
  }
}