CSS

css supports

@supports (display: grid) {
  div {
    display: grid;
  }
}
@supports not (display: grid) {
  div {
    float: right;
  }
}

@supports css

.primary-navigation {
  background: hsl(var(--clr-dark) / 0.95);
}
/* if backdrop-filter is supported by browser */
@supports (backdrop-filter: blur(1rem)) {
  .primary-navigation {
    background: hsl(var(--clr-white) / 0.05);
    backdrop-filter: blur(1.5rem);
  }
}