.hot{
width: 100px;
height: 100px;
border: 1px solid red;
position:relative;
justify-content: ;
}
.hot:after{
content:‘‘;
height:12px;
background-color:red;
bottom:0;
width:100%;
position:absolute;
left: 0;
}
原文：https://www.cnblogs.com/xiedashi/p/15196208.html