.collapse_span {
    position: absolute;
    bottom: 1px;
    left: 50%;
    width: 60px;
    height: 12px;
    cursor: pointer;
}
.collapse_span:before {
        content: "";
  position: absolute;
  top: 0; 
  right: 0; 
  bottom: 0; 
  left: 0;
  border: 1px solid rgba(12,131,242,0.5);
        transform: perspective(1em) rotateX(15deg);
    }
.collapse_span:after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  border-left: 10px solid transparent;
  border-bottom: 6px solid #409EFF;
  border-top: 10px solid transparent;
  border-right: 10px solid transparent;
}