SOURCE

console 命令行工具 X clear

                    
>
console
  <div class="box">
  </div>
.box {
      position: relative;
      width: 600px;
      height: 400px;
      background: #fff;
      border: 1px solid #ccc;
      box-shadow: 2px 2px 2px #ccc;
margin:50px;
    }
    .box:after {
      position: absolute;
      display: inline-block;
      top: 380px;
      left: 300px;
      width: 0;
      height: 0px;
      content: '';
      border-style: solid;
      border-width: 20px;
      border-color: #fff #fff transparent transparent;
      transform: rotate(135deg);
      box-shadow: 2px -2px 2px #ccc;
    }