文本是闲暇之余练习svg的运用的产物，记录以备有需。
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 500 500" width="500px" height="500px"><path d="M150,100 A50,50 0 1,1 150,99.999" stroke="#fff" stroke-width="16" fill="none" /><path d="M150,100 A50,50 0 1,1 150,99.999" stroke="#bbb" stroke-width="14" fill="none" /><path d="M130,100 A50,50 0 1,0 130,99.999" stroke="#fff" stroke-width="16" fill="none" /><path d="M130,100 A50,50 0 1,0 130,99.999" stroke="#bbb" stroke-width="14" fill="none" /><path d="M310,100 A50,50 0 1,1 310,99.999" stroke="#fff" stroke-width="16" fill="none" /><path d="M310,100 A50,50 0 1,1 310,99.999" stroke="#bbb" stroke-width="14" fill="none" /><path d="M390,100 A50,50 0 1,1 390,99.999" stroke="#fff" stroke-width="16" fill="none" /><path d="M390,100 A50,50 0 1,1 390,99.999" stroke="#bbb" stroke-width="14" fill="none" />
</svg>
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 500 500" width="500px" height="500px"><path d="M150,150 A50,50 0 1,1 150,80" stroke="#999" stroke-width="30" stroke-linecap="square" fill="none" /><path d="M150,150 A50,50 0 1,1 150,80" stroke="#f00" stroke-width="30" stroke-linecap="butt" fill="none" />
</svg>
