html使用定位实现同心圆

方法1：div有层级关系

<!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>
        .lx {
            top: 30px;
            left: 450px;
            position: absolute;
        }
        .yangshi {
            border-radius: 50%;
            position: relative;
        }
        .yi {
            width: 500px;
            height: 500px;
            border: 20px solid brown;
            top: 30px;
            left: 30px;
            position: absolute;
        }
        .er {
            width: 300px;
            height: 300px;
            border: 20px solid aqua;
            top: 80px;
            left: 80px;
            position: absolute;
        }
        .sang {
            width: 200px;
            height: 200px;
            border: 20px solid chocolate;
            top: 30px;
            left: 30px;
            position: absolute;
        }
        .si {
            width: 100px;
            height: 100px;
            border: 20px solid darkmagenta;
            top: 30px;
            left: 30px;
            position: absolute;
        }
    </style>
</head>
<body>
    <div class="lx">
        <div class="yangshi yi">
            <div class="yangshi er">
                <div class="yangshi sang">
                    <div class="yangshi si">
                    </div>
                </div>
            </div>
        </div>
    </div>
</body>
</html>

方法2：没有层级关系


<!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>
        body {
            margin: 0px;
        }
        .item {
            height: 100px;
            width: 100px;
            border-radius: 50%;
            box-sizing: border-box;
            position: absolute;
        }
        .circle1 {
            border: 7px solid blue;
            left: 300px;
            top: 300px;
            height: 100px;
            width: 100px;
        }
        .circle2 {
            border: 7px solid black;
            left: 250px;
            top: 250px;
            height: 200px;
            width: 200px;
        }
        .circle3 {
            border: 7px solid red;
            left: 200px;
            top: 200px;
            height: 300px;
            width: 300px;
        }
        .circle4 {
            border: 7px solid yellow;
            left: 150px;
            top: 150px;
            height: 400px;
            width: 400px;
        }
        .circle5 {
            border: 7px solid green;
            left: 100px;
            top: 100px;
            height: 500px;
            width: 500px;
        }
    </style>
</head>
<body>
    <div class="item circle1"></div>
    <div class="item circle2"></div>
    <div class="item circle3"></div>
    <div class="item circle4"></div>
    <div class="item circle5"></div>
</body>
</html>

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