@mixin add-aspect($ratio...) {
  $ratio: unpack($ratio);
  $important: null;
  @if has-important($ratio) {
    $ratio: nth($ratio, 1);
    $important: "!important";
  }

  @if map-has-key($project-aspect-ratios, $ratio) {
    box-sizing: border-box #{$important};
    height: 0 #{$important};
    overflow: hidden #{$important};
    padding: 0 0 map-get($project-aspect-ratios, $ratio) #{$important};
  } @else {
    @error '`#{$ratio}` is not a valid key in $project-aspect-ratios. Valid values: #{map-keys($project-aspect-ratios)}';
  }
}