纯css实现的导航按钮图标样式切换效果，图标样式是css画出来的，再辅以css3动画效果。

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>css3效果切换的导航按钮</title>
<style type="text/css">
  *{ 
    margin: 0; 
    padding: 0;
  }
  body {
    background: #3B9DFF;
  }
  .menuCtrl {
    display: block;
    position: relative;
    border: 5px solid #fff;
    border-radius: 50%;
    width: 30px;
    height: 40px;
    padding: 20px 25px;
    margin: 150px auto;
    transition: all 0.25s ease-in-out;
  }
  .menuCtrl .line {
    width: 35px;
    height: 0;
    border-bottom: 5px solid #fff;
    position: relative;
    margin-left: -2px;
    transition: all 0.25s ease-in-out;
  }
  .menuCtrl .line:nth-child(1) {
    top: 10px;
  }
  .menuCtrl .line:nth-child(2) {
    top: 13px;
  }
  .menuCtrl .line:nth-child(3) {
    top: 16px;
  }
  .menuCtrl:hover {
    padding: 25px 30px;
  }
  .menuCtrl:hover .line:nth-child(1) {
    width: 20px;
    transform: rotateZ(-45deg) translateX(-3px) translateY(0px);
  }
  .menuCtrl:hover .line:nth-child(2) {
    width: 40px;
  }
  .menuCtrl:hover .line:nth-child(3) {
    width: 20px;
    transform: rotateZ(45deg) translateX(-3px) translateY(0px);
  }
</style>
</head>
<body>
  <a href="javascript:;" class="menuCtrl">
    <div class="line"></div>
    <div class="line"></div>
    <div class="line"></div>
  </a>
</body>
</html>