console 命令行工具 X clear

console

<div class="box-shadow"></div>
<div class="border"></div>

.border{
  width:100px;
  height:100px;
  position:relative;
  left:300px;
  border-radius:50%;
  border:3px solid red;
}

.box-shadow{
  width:100px;
  height:100px;
  position:relative;
  left:100px;
  top:100px;
  border-radius:50%;
  box-shadow:0 0 0 3px red;
}