CSS3-------弹簧特效

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>CSS3弹簧特效</title>
    <style>
        * {
            margin: 0;
            padding: 0
        }
        html,body{
            width: 100%;
            height: 100%;
            display: flex;
        }
        body{
            perspective: 800px;
        }

        .wrap{
            width: 400px;
            height: 400px;
            margin: auto;
            transform: rotateX(60deg);
            position: relative;
            transform-style: preserve-3d;
        }
        .wrap div{
            position: absolute;
            border: 15px solid #ccd7d9;
            border-color: #ccd7d9 #d2dbde #d7e0e2 #d2dbde;
            border-radius: 50%;
            box-shadow: 0 1px 0 #fff, 0 10px 0 #abbdc1 inset, 0 10px 0 #abbdc1;
            transform: translateZ(-50px);
        }
        .wrap div:nth-child(1){
            left: calc( 400px/2 - 340px/2 - 15px );
            top: calc( 400px/2 - 340px/2  - 15px );
            width: 340px;
            height: 340px;

            animation: play1 2s 2400ms ease-in-out infinite alternate;
        }
        .wrap div:nth-child(2){
            left: calc( 400px/2 - 280px/2 - 15px );
            top: calc( 400px/2 - 280px/2  - 15px );
            width: 280px;
            height: 280px;
            animation: play1 2s 2000ms ease-in-out infinite alternate;
        }
        .wrap div:nth-child(3){
            left: calc( 400px/2 - 220px/2 - 15px );
            top: calc( 400px/2 - 220px/2  - 15px );
            width: 220px;
            height: 220px;
            animation: play1 2s 1600ms ease-in-out infinite alternate;
        }
        .wrap div:nth-child(4){
            left: calc( 400px/2 - 160px/2 - 15px );
            top: calc( 400px/2 - 160px/2  - 15px );
            width: 160px;
            height: 160px;
            animation: play1 2s 1200ms ease-in-out infinite alternate;
        }
        .wrap div:nth-child(5){
            left: calc( 400px/2 - 100px/2 - 15px );
            top: calc( 400px/2 - 100px/2  - 15px );
            width: 100px;
            height: 100px;
            animation: play1 2s 800ms ease-in-out infinite alternate;
        }
        .wrap div:nth-child(6){
            left: calc( 400px/2 - 40px/2 - 15px );
            top: calc( 400px/2 - 40px/2  - 15px );
            width: 40px;
            height: 40px;
            animation: play1 2s 400ms ease-in-out infinite alternate;
        }
        @keyframes play1 {
            from{
                transform: translateZ(-50px);
            }
            to{
                transform: translateZ(100px);
            }
        }
    </style>
</head>
<body>
    <div class="wrap">
        <div></div>
        <div></div>
        <div></div>
        <div></div>
        <div></div>
        <div></div>
    </div>
</body>
</html>