.hairline(@direction, @color) {
  position: relative;

  &::after {
    position: absolute;
    top: -50%;
    right: -50%;
    bottom: -50%;
    left: -50%;
    pointer-events: none;
    content: ' ';
    border-@{direction}: 1px solid @color;
    transform: scale(0.5);
  }
}