- 关键点：
padding，margin百分比是父级宽度
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
* {
margin: 0;
padding: 0;
}
.container {
display: flex;
flex-wrap: wrap;
justify-content: space-around;
list-style: none;
}
.container li {
padding-top: 30%;
margin-top: 3%;
background-color: orange;
width: 30%;
}
</style>
</head>
<body>
<ul class="container">
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
<li></li>
</ul>
</body>
</html>
