laoshi kanakn

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>2-9</title>
    <style type="text/css">
        div {
            font-family: Arial;
            font-size: 72px;
            font-weight: bold;
            position: fixed;
            right: 0;
            left: 0;
            bottom:40px;
            width: 30px;
            height: 30px;
            margin: auto;
            transform: rotate(90deg);
            /*此处写代码*/
            animation:down 1s ease-in-out 0.5s infinite normal forwards running;
        }
        
        @keyframes down {
            from {bottom:40px;}
            to   {bottom:15px;}
            from {bottom:15px;}
            to   {bottom:20px;}
            from {bottom:20px;}
            to   {bottom:15px;}
        }
    </style>
</head>
<body>
    <div>&gt;</div>
</body>
</html>

RahodJoe 2019-09-25

源自：CSS3动画 2-28 编程练习