<!docType html>
<html>
    <head>
        <title>svg demo</title>
        <style>
            .circle {
                fill: rgb(0, 255, 0);
                fill-opacity: 0.7;
                stroke-width: 2px;
                stroke: rgb(100, 100, 100)
            }
        </style>
    </head>
    <body>
        <svg xmlns="http://www.w3.org/2000/svg" version="1.1">
            <!-- 
                圆形
                cx,cy:圆心坐标
                r:半径
             -->
            <circle cx="100" cy="50" r="20" class="circle"></circle>>
        </svg> 
    </body>
</html>