1. <!DOCTYPE html>
    2. <html lang="en">
    3. <head>
    4.     <meta charset="UTF-8">
    5.     <meta http-equiv="X-UA-Compatible" content="IE=edge">
    6.     <meta name="viewport" content="width=device-width, initial-scale=1.0">
    7.     <title>Document</title>
    9.     <style>
    10.         /* 圆角 */
    11.         div{
    12.             width: 400px;
    13.             height: 400px;
    14.             background-color: blueviolet;
    15.             border-radius: 20px;
    16.             margin: 0 auto;
    18.             /* 阴影 */
    19.             box-shadow: 0,10px,40px,rgba(10, 10, 10, 0.5);
    20.         }
    22.     </style>
    23. </head>
    24. <body>
    26.     <div ></div>
    27. </body>
    28. </html>
    <!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>
        /* 动画效果 */
        div{
            width: 200px;
            height: 200px;
            background-color: red;
            animation: myAnim 3s linear 0s infinite;
        }
        div:hover{
            animation-play-state: paused;
        }

        @keyframes myAnim{
           0%{
               background-color: red;
           } 
           50%{
               background-color: green;
           }
           100%{
               background-color: red;
           }
        }
    </style>

</head>
<body>
    <div></div>
</body>
</html>

    <!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>
        /* 呼吸灯效果 */
        .box{
            width: 300px;
            height: 300px;
            margin: 40px auto;
            background-color: aquamarine;
            border-radius: 5px;
            box-shadow: 0 1px 2px rgba(0, 0, 0, .5);
            animation: breathe 3s ease-in-out infinite alternate;
        }

        @keyframes breathe {
            0%{
                opacity: 0.2;
                box-shadow: 0 1px 2px rgba(rgb(83, 58, 58), green, blue, 0.1) ;
            }
            50%{
                opacity: 0.5;
                box-shadow: 0 1px 2px rgba(rgb(104, 151, 145), green, blue, 0.76);
            }
            100%{
                opacity: 1;
                box-shadow: 0 1px 2px rgba(rgb(158, 203, 46), green, blue, 1);
            }
        }
    </style>

</head>
<body>
    <div class="box"></div>
</body>
</html>