麻烦老师看一下，还有哪里需要优化的。

<!DOCTYPE html>
<html>

<head>
    <meta charset="UTF-8">
    <title></title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        body {
            display: flex;
            flex-direction: column;
        }

        header {
            width: 100%;
            background-color: #000;
            font-size: 20px;
            display: flex;
            justify-content: space-around;
            align-items: center;
        }

        header .logo img {
            vertical-align: top;
        }

        header .nav {
            width: 35%;
            color: white;
            list-style: none;
            display: flex;
            align-items: center;
            align-content: space-around;
        }

        header .nav li {
            flex: 1;
            display: flex;
            justify-content: center;
        }

        header .login {
            width: 8.5%;
            display: flex;
            justify-content: space-between;
        }

        header .login input {
            background-color: orange;
            font-size: 20px;
            border-radius: 5px;
            color: white;
            border: none;
            padding: 3px 5px;
        }

        section {
            height: 340px;
            width: 100%;
            display: flex;
            flex-wrap: wrap;
            align-content: space-around;
            justify-content: space-around;
        }

        section .section {
            width: 45%;
            height: 150px;
            border-radius: 10px;
            background-color: rgb(173, 216, 230);
            display: flex;
            justify-content: space-around;
            align-items: center;
        }

        section .section .box {
            height: 100%;
            display: flex;
            flex-direction: column;
            justify-content: space-around;
        }

        section .section .shopping {
            display: flex;
            align-items: center;
        }

        section .section .shopping .btn {
            color: white;
            font-size: 20px;
            padding: 2px 6px;
            background-color: orange;
            border-radius: 5px;
        }
    </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 class="shopping">
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            <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>《从H5网页开发到移动端响应式开发》</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>