@import "normalize.css";
@custom-media --narrow-viewport all and (min-width:300px);
:root {
  --color: green;
  --width: 100px;
}
@media (--narrow-viewport) {
  .example {
    /* simple variable */
    color: var(--color);
    /* variable with fallback */
    outline: var(--outline, 1px solid red);
    /* calc */
    width: calc(var(--width) * 2);
  }
}

/* …inlined normalize.css source code… */
@media all and (min-width:300px) {
  .example {
    /* simple variable */
    color: green;
    /* variable with fallback */
    outline: 1px solid red;
    /* calc */
    width: 200px;
  }
}