css教程使用纯CSS画一个圆环（代码示例）

<div class="container">
    <span class="ring-style"></span>
</div>

.container {
    position: relative;
    top: 0;
    left: 0;
    width: 300px;
    height: 300px;
    background-color: lightgrey;
}
.ring-style {
    display: inline-block;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: blue;
    width: 260px;
    height: 260px;
    border-radius: 260px;
}
.ring-style::before {
    content: ' ';
    display: inline-block;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: white;
    width: 200px;
    height: 200px;
    border-radius: 200px;
}