html {
  --s: 84px; /* control the size*/
  /* the colors */
  --c1: #f2f2f2;
  --c2: #cdcbcc;
  --c3: #999999;
  /* */
  
  --_g: 0 120deg,#0000 0;
  background:
    conic-gradient(from    0deg at calc(500%/6) calc(100%/3),var(--c3) var(--_g)),
    conic-gradient(from -120deg at calc(100%/6) calc(100%/3),var(--c2) var(--_g)),
    conic-gradient(from  120deg at calc(100%/3) calc(500%/6),var(--c1) var(--_g)),
    conic-gradient(from  120deg at calc(200%/3) calc(500%/6),var(--c1) var(--_g)),
    conic-gradient(from -180deg at calc(100%/3) 50%,var(--c2)  60deg,var(--c1) var(--_g)),
    conic-gradient(from   60deg at calc(200%/3) 50%,var(--c1)  60deg,var(--c3) var(--_g)),
    conic-gradient(from  -60deg at 50% calc(100%/3),var(--c1) 120deg,var(--c2) 0 240deg,var(--c3) 0);
  background-size: calc(var(--s)*1.732) var(--s);
  /* sqrt(3) = 1.732 */
}