css实现：不固定宽高，随内容宽度自动增长的圆形

<div class="circle"><span>1</span></div>


.circle {
  display: inline-block;
  border-radius: 50%;
  min-width: 20px;
  min-height: 20px;
  padding: 5px;
  background: red;
  color: white;
  text-align: center;
  line-height: 1;
  box-sizing: content-box;
  white-space: nowrap;
}
.circle::before {
  content: "";
  display: inline-block;
  vertical-align: middle;
  padding-top: 100%;
  height: 0;
}
.circle span {
  display: inline-block;
  vertical-align: middle;
}