SVG Shapes
1.矩形 <rect><rect x="50" y="20" width="150" height="150" style="fill:red;stroke:black;stroke-width:5;opacity:0.5"/>
<circle>
<circle cx="100" cy="50" r="40" stroke="black" stroke-width="2" fill="red"/>
<line>
<line x1="0" y1="0" x2="200" y2="200"
style="stroke:rgb(255,0,0);stroke-width:2"/>