css 打钩

.active::before {
  width: 8px;
  height: 4px;
  display: inline-block;
  border: 2px solid #ffffff;
  border-width: 0 0 1px 1px;
  transform: rotate(-45deg);
  -ms-transform: rotate(-45deg);
  -moz-transform: rotate(-45deg);
  -webkit-transform: rotate(-45deg);
  -o-transform: rotate(-45deg);
  vertical-align: baseline;
}