老师帮我检查下代码，还有什么需要改进的吗？

来源：5-6 编程练习

原来是晓琪_

2019-08-29 09:35:33

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>方法的调用</title>
<style type="text/css">
    #box{position: relative; width: 100px; height: 100px;
         background-color: red; margin: 10px auto;}
    #close{position: absolute; right: 0px; top: -4px; color: yellow;}
    #btn{display: block; width: 100px; margin: 0 auto;}
</style>
</head>
<body>
    <div id="box">
        <span id="close">X</span>
    </div>
    <button id="btn">关闭</button>
<script type="text/javascript">
    // 在此处补充代码
    var box = document.getElementById('box');
    var close = document.getElementById('close');
    var btn = document.getElementById('btn');
    btn.onclick = function(){
    box.style.display = 'none';
    }
    close.onclick = btn.onclick;
    box.onmouseover = function(){
    box.style.cursor = 'pointer';
    }
</script>
</body>
</html>