.stg{width:36px;height:20px;background:#ccc;border-radius:20px;cursor:pointer;position:relative;margin-left:8px}
.stg::after{content:"";position:absolute;top:2px;left:2px;width:16px;height:16px;background:#fff;border-radius:50%;transition:.2s}
.stg.on{background:var(--focus-color)}
.stg.on::after{left:18px}