
实现这种效果
demo

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.father{
/* padding: 30px; */
display: flex;
}
.son{
width: 100px;
height: 100px;
box-shadow:2px 2px 3px #aaaaaa;
}
.son.active{
background-color: aqua;
position: relative;
}
.son.active::after{
content: "";
position: absolute;
width: 100px;
height: 20px;
background-color: blue;
bottom: 0;
}
</style>
</head>
<body>
<div class="father">
<div class="son"></div>
<div class="son active"></div>
<div class="son"></div>
</div>
</body>
</html>
来源:oschina
链接:https://my.oschina.net/u/4004801/blog/4315609