.breakdance .box-corner{.breakdance .box-corner::after{content:"";position:absolute;right:0;bottom:0;width:100px;height:50px;border-right:5px solid red;border-bottom:5px solid red}.breakdance .box-corner::before{content:"";position:absolute;left:0;top:0;width:100px;height:50px;border-left:5px solid red;border-top:5px solid red}}