arrow.less

  &:before {
    content: "";
    position: absolute;
    bottom: -20px;
    left: 40px;
    border-width: 20px 20px 0;
    border-style: solid;
    border-color: #000 transparent;
    display: block;
    width: 0;
  }

  &:after {
    content: "";
    position: absolute;
    bottom: -16px;
    left: 44px;
    border-width: 16px 16px 0;
    border-style: solid;
    border-color: #fff transparent;
    display: block;
    width: 0;
  }