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@@ -0,0 +1,41 @@
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+<!DOCTYPE html>
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+<html lang="en">
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+<head>
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+ <meta charset="UTF-8">
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+ <meta name="viewport" content="width=device-width, initial-scale=1.0">
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+ <title>Document</title>
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+ <style>
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+ *{
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+ margin: 0;
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+ padding: 0;
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+ }
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+ html{
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+ font-size: 20px;
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+ }
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+ /* rem 相对于根元素(html)的字体大小 */
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+
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+ .box{
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+ width: 10rem;
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+ height: 10rem;
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+ background-color: red;
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+ }
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+ .div1{
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+ font-size: 30px;
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+ }
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+ /* em 相对于本身 及 祖先元素的font-size */
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+ .div2{
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+ font-size: 20px;
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+ width: 10em;
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+ height: 10em;
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+ background-color: blue;
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+ }
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+ </style>
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+</head>
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+<body>
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+ <div class="box"></div>
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+
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+ <div class="div1">
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+ <div class="div2"></div>
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+ </div>
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+</body>
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+</html>
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