css3实现手机菜单展开收起动画

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
<title>Examples</title>
<meta name="description" content="">
<meta name="keywords" content="">
<link href="" rel="stylesheet">
<script type="text/javascript" src="jquery.js"></script>
</head>
<style type="text/css">
.test {
        margin: 500px auto;
        text-align: center;
        width: 100px;
        height: 100px;
}
.test button {
        height: 100px;
        background: none;
        outline: none;
        cursor: pointer;
        border: none;

}
.test span { 
        width: 100px;
        height: 10px;
        background: red;
        position: relative;
        display: block;
        border-radius: 10px;
        transition: background .3s .2s ;
        /*激活之后 ,前面的秒数是动画消耗的时间,后面的秒数是推迟开始的时间*/
}
.test span:before {
        content: "";
        display: block;
        top: -30px;
        left: 0;
        width: 100px;
        height: 10px;
        background: red;
        position: absolute;
        border-radius: 10px;
        transition: top .3s .2s ease, -webkit-transform .3s ease;
}
.test span:after {
        content: "";
        background: red;
        display: block;
        width: 100px;
        height: 10px;
        top: 30px;
        position: absolute;
        left: 0;
        border-radius: 10px;
        transition: top .3s .2s ease, -webkit-transform .3s ease;
}
.test button.active span {
        background: transparent;
        border-radius: 10px;
        -webkit-transform-origin: 50% 50%;
    transition:  background .2s .1s ease;
    /*激活之前 ,前面的秒数是动画消耗的时间,后面的秒数是推迟开始的时间*/
}
.test button.active span:before {
        transform: rotate(45deg);
        top: 0;
        transition: top .3s ease, -webkit-transform .3s .2s ease;
}
.test button.active span:after {
        transform: rotate(-45deg);
        top: 0;
        transition: top .3s ease, -webkit-transform .3s .2s ease;

}
</style>
<body>
    <div class="test">
        <button>
        <span></span>
        </button>
    </div>
</body>
</html>
<script type="text/javascript">
    //自定义开关
    var _a = true;
    $("button").click(function(){
            if(_a == true){
            $(this).addClass("active");
            _a= false;
        }else{
                $(this).removeClass("active");
            _a= true;
        }
    })
</script>