:root {
  --x: 15vmin;
  --y: calc(var(--x) / 4);
  background: repeating-conic-gradient(#fff 0 25%, #000 0 50%) 0 0 / var(--x) var(--y);
}

:root::before {
  aspect-ratio: 1;
  background: inherit;
  border-radius: 50%;
  content: "";
  left: 50%;
  position: absolute;
  rotate: 90deg;
  top: 50%;
  translate: -50% -50%;
  width: calc(var(--x) * 3);
}