<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
div{
max-width: 500px;
min-width: 200px;
width: 200px;
height: 200px;
margin: 10px;
margin: 10px 20px;
margin: 10px 15px 25px;
margin: 10px 15px 25px 30px;
padding: 10px;
background-color: red;
border-radius: 50%;
border-radius: 5px 15px 25px 5px/25px 20px 15px 5px;
}
</style>
</head>
<body>
<div>我是一个div</div>
</body>
</html>