lovecoding
/
W250913


			
				
					
						
						
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							<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            width: 200px;
            height: 200px;
            border: 2px dashed black;
        }
        .align0{
            text-align: center;
            line-height: 200px;
        }
        .box1{
            width: 100px;
            height: 100px;
            background-color: blue;
        }
        .align1{
            position: relative;
        }
        .box1{
            position: absolute;
            top: 50%;
            left: 50%;
            margin-top: -50px;
            margin-left: -50px;
        }
        .align2{
            position: relative;
        }
        .box2{
            width: 80px;
            background-color: blue;
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%,-50%);
        }

        .align3{
            display: flex;
            align-items: center;
            justify-content: center;
        }
        .box3{
            width: 80px;
            background-color: blue;
        }
    </style>
</head>
<body>
    <!-- 单行文本 -->
     <div class="box align0">
        hello
     </div>
     <!-- 块元素 已知大小 -->
    <div class="box align1">
        <div class="box1"></div>
    </div>

    <!-- 未知大小 -->
     <div class="box align2">
        <div class="box2">
            hello
        </div>
     </div>
     <div class="box align3">
        <div class="box3">
            hello
        </div>
     </div>
</body>
</html>