老师，麻烦看一下有哪里需要改进

相关代码：

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title></title>
    <style>
     /* 在此处补充代码*/
     *{
     	padding:0;
     	margin:0;
     }
     li{
     	list-style:none;
     }
     input{
     	background:orange;
     	border:1px solid orange;
     	border-radius:5px;
     	color:white;
     	font-size:18px;
     }
     header{
     	width:100%;
     	display:flex;
     	justify-content:space-around;
        align-items:center;
     	color:white;
     	background:black;
     	font-size:20px;
     }
     .logo{
     	flex-grow:1;
     }
     .nav{
     	display:flex;
     	flex-grow:2;
     	align-items:center;
     }
     .nav li{flex:1;}
     .login{
     	display:inline-flex;
     	justify-content:space-around;
     	flex-grow:1;
     }
     section{
     	width:100%;
     	margin-top:20px;
     	display:flex;
     	flex-wrap:wrap;
        justify-content:space-around;

     }
     .section{
     	width:40%;
     	margin-bottom:30px;
     	background:pink;
     	border:1px solid pink;
     	border-radius:10px;
     	display:flex;
     	justify-content:space-around;
     	align-items:center;
     }
     .box{
     	height:120px;
     	display:flex;
     	flex-direction:column;
     	justify-content: space-around;
     }
     .btn{
     	width:100px;
     	height:30px;
     	background:orange;
     	border:1px solid orange;
     	border-radius:5px;
     	color:white;
     	display:flex;
     	justify-content:center;
     	align-items:center;
     }
    </style>
</head>
<body>
<!-- 头部 -->
   <header>
     <div class="logo">
       <img src="http://img1.sycdn.imooc.com/climg//59197ab000014f1503000100.jpg" alt="">
     </div>
       <ul class="nav">
         <li>课程</li>
         <li>路径</li>
         <li>猿问</li>
         <li>手记</li>
       </ul>     
     <div class="login">
       <input type="button" value="登录">
       <input type="button" value="注册">
     </div>
   </header>
<!-- 主体内容 -->
   <section>
    <div class="section">
      <div class="box">
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      </div>
      <div class="shopping">
        <div class="btn">加入购物车</div>
      </div>
    </div>
    <div class="section">
      <div class="box">
        <p>《HTML5月CSS3实现动态网页》</p>
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      </div>
      <div class="shopping">
        <div class="btn">加入购物车</div>
      </div>
    </div>
    <div class="section">
      <div class="box">
        <p>《HTML5月CSS3实现动态网页》</p>
        <div>适用人群：有html和css基础的童鞋</div>
        <div>费用：￥599</div>
      </div>
      <div class="shopping">
        <div class="btn">加入购物车</div>
      </div>
    </div>
    <div class="section">
      <div class="box">
        <p>《HTML5月CSS3实现动态网页》</p>
        <div>适用人群：有html和css基础的童鞋</div>
        <div>费用：￥599</div>
      </div>
      <div class="shopping">
        <div class="btn">加入购物车</div>
      </div>
    </div>
    </section>  
</body>
</html>