beyond-css-course-material/challenges/05-partials/01/abstracts/_mixins.scss

@mixin decorative-corner($color: #333) {
  position: relative;
  &::before {
    content: "";
    position: absolute;
    left: -4rem;
    top: -4rem;
    width: 100px;
    aspect-ratio: 1;
    border-left: 3px solid $color;
    border-top: 3px solid $color;
  }
}