lovecoding
/
VIP20


			
				
					
						
						
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							<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    *{
      margin: 0;
      padding: 0;
    }
    html{
      font-size: 50px;
    }
    #div1{
      height: 200px;
      width: 3rem;
      background: red;
      font-size: 100px;
    }
    /* rem  相对于根元素html的字体大小 */
    /* em   相对于父元素的字体大小 */
    #div2{
      /* width: 2em;
      height: 100px; */
      background: yellow;
      /* width: 50vw;
      height: 50vw; */
      width: 50%;
      height: 50%;
    }
    #div3{
      width: 100%;
      height: calc(100vh - 100px);
      background: blue;
    }
    /* vw vh 相对于设备 或者  视口 */
  </style>
</head>
<body>
  <div id="div1">
    <div id="div2"></div>
  </div>
  <div id="div3"></div>
</body>
</html>