练习盒模型,边框，边框阴影
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style>
.box{
width: 200px;
height: 200px;
border: 1px solid #bbb;
padding: 2px;/*上右下左*/
margin:3px
}
button{
border: none;
border-radius: 5px;
box-shadow: 2px 2px 3px #000000;
}
</style>
</head>
<body>
<div class="box">111</div>
<button>按我</button>
</body>
</html>