案例-两面翻转的盒子（CSS3）

<!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>案例-两面翻转的盒子</title>
    <style>
        body {
            perspective: 400px;
        }

        .box {
            position: relative;
            width: 300px;
            height: 300px;
            margin: 100px auto;


            transition: all 0.5s;
            /* 让背面紫色盒子保留立体空间  给父级添加的*/
            transform-style: preserve-3d;
        }

        .front,
        .back {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            border-radius: 50%;
            font-size: 30px;
            color: #fff;
            text-align: center;
            line-height: 300px;
        }

        .box:hover {
            transform: rotateY(180deg);
        }


        .front {
            background-color: skyblue;
            z-index: 1;
            /* 加权重 */
        }

        .back {
            background-color: purple;
            transform: rotateY(180deg);
        }
    </style>
</head>

<body>
    <div class="box">
        <div class="front">1</div>

        <div class="back">2</div>
    </div>

</body>

</html>