console 命令行工具 X clear

console

<div class="main-div">
  <div class="sub-div">
    fff
  </div>
</div>

.main-div {
  line-height:3px;
  border:1px solid green;
}

.sub-div {
  //line-height:30px;
  font-size:20px;
  //width:100px;
  //height:100px;
  border:1px solid red;
}