less的运算操作

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title></title>
    <style type="text/less">
        /*
        less的运算操作
            我们可以在数值及颜色值上做一些基本的运算操作,注意,操作符左右最好是空格。如下
        */
        @span-width:100px;
        @color:#099999;
        span{
            height:50px;
            display: inline-block;
        }
        #left{
            width: @span-width;
            background-color: @color;
        }

        #right{
            width: @span-width * 2;
            background-color: @color - 100;
        }
    </style>
</head>
<body>

<span id="left">
hello1
</span>
<span id="right">
hello2
</span>

<script type="text/javascript" src="js/es5-shim.js"></script>
<script type="text/javascript" src="js/less.min.js"></script>
<script type="text/javascript">
    less.watch();
</script>
</body>
</html>