.chess {
  position: relative;
  width: 20px;
  height: 20px;
  overflow: hidden;
  border: 1px solid black;
}

.chess:before {
  position: absolute;
  content: '';
  display: block;
  top: -4px;
  left: 0;
  width: 4px;
  height: 4px;
  box-shadow: 
    0px 4px, 
    0px 12px,
    0px 20px,
    4px 8px, 
    4px 16px,
    4px 24px,
    8px 4px, 
    8px 12px,
    8px 20px,
    12px 8px, 
    12px 16px,
    12px 24px,
    16px 4px, 
    16px 12px,
    16px 20px;
}