CSS3弹力球

如下代码实现方块在限定区域内不停弹跳。

<!DOCTYPE html>
<html>
<head>
<style>
div
{
width:100px;
height:100px;
background:red;
position:relative;
animation:myfirst 5s linear 2s infinite alternate;
/* Firefox: */
-moz-animation:myfirst 5s linear 2s infinite alternate;
/* Safari and Chrome: */
-webkit-animation:myfirst 5s linear 2s infinite alternate;
/* Opera: */
-o-animation:myfirst 5s linear 2s infinite alternate;
}

@keyframes myfirst
{
0%   {background:red; left:0px; top:0px;}
25%  {background:yellow; left:200px; top:0px;}
50%  {background:blue; left:200px; top:200px;}
75%  {background:green; left:0px; top:200px;}
100% {background:red; left:0px; top:0px;}
}

@-moz-keyframes myfirst /* Firefox */
{
0%   {background:red; left:0px; top:0px;}
25%  {background:yellow; left:200px; top:0px;}
50%  {background:blue; left:200px; top:200px;}
75%  {background:green; left:0px; top:200px;}
100% {background:red; left:0px; top:0px;}
}

@-webkit-keyframes myfirst /* Safari and Chrome */
{
0%   {background:red; left:0px; top:0px;}
25%  {background:yellow; left:200px; top:0px;}
50%  {background:blue; left:200px; top:200px;}
75%  {background:green; left:0px; top:200px;}
100% {background:red; left:0px; top:0px;}
}

@-o-keyframes myfirst /* Opera */
{
0%   {background:red; left:0px; top:0px;}
25%  {background:yellow; left:200px; top:0px;}
50%  {background:blue; left:200px; top:200px;}
75%  {background:green; left:0px; top:200px;}
100% {background:red; left:0px; top:0px;}
}
</style>
</head>
<body>

<p><b>注意:</b> 该实例在 Internet Explorer 9 及更早 IE 版本是无效的。</p>

<div></div>

</body>
</html>