:root::before {
  aspect-ratio: 1;
  background:
    radial-gradient(farthest-side circle, #0000 80%, #fff 0) 0 0,
    conic-gradient(from 180deg, #000 75%, #0000 0) 0 0 no-repeat,
    conic-gradient(from 270deg, #000 75%, #0000 0) 100% 0 no-repeat,
    conic-gradient(from 90deg, #000 75%, #0000 0) 0 100% no-repeat,
    conic-gradient(from 0deg, #000 75%, #0000 0) 100% 100% no-repeat;
  background-size: 50% 50%;
  content: "";
  left: 50%;
  margin: 0;
  position: absolute;
  width: 60vmin;
  top: 50%;
  translate: -50% -50%;
  
  /* hack to remove background line */
  mask: conic-gradient(#000 0 0) 50% 50% / 99% 99% no-repeat;
}