<!doctype html>
[code=html,html 代码,true]<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style>
*{
margin: 0;
padding: 0;
list-style: none;
}
.box{
margin: 100px;
}
li{
position: relative;
float: left;
width: 50px;
height: 50px;
margin-right: 100px;
}
span{
width: 100px;
height: 100px;
margin: 12px;
display: block;
border-radius: 50%;
background: -webkit-linear-gradient(red, blue);
transition:1s all ease;
}
li:hover span{
transform:rotateZ(360deg);
}
@keyframes warn {
0% {
transform: scale(1);
opacity: 0.8;
}
20% {
transform: scale(1);
opacity: 0.6;
}
40% {
transform: scale(1.2);
opacity: 0.4;
}
60% {
transform: scale(1.4);
opacity: 0.2;
}
80% {
transform: scale(1.6);
opacity: 0.1;
}
100% {
transform: scale(1.8);
opacity: 0.0;
}
}
a:before{
border: 12px solid #A8E957;
content:‘‘;
position: absolute;
width: 100px;
height: 100px;
border-radius: 62px;
opacity: 0;
}
li:hover a:before{animation: warn 1s ease-out infinite;}
</style>
</head>
<body>
<div class="box">
<ul>
<li>
<a href="#">
<span></span>
</a>
</li>
<li>
<a href="#">
<span></span>
</a>
</li>
<li>
<a href="#">
<span></span>
</a>
</li>
<li>
<a href="#">
<span></span>
</a>
</li>
</ul>
</div>
</body>
</html>原文：http://www.cnblogs.com/wwjm/p/7105051.html