console 命令行工具 X clear

console

<div data-msg="hello world!">
  hover
</div>

div{
  width:100px;
  position:absolute;
  border:1px solid #ccc;
}
div:hover:after{
  content: attr(data-msg);
  position:absolute;
  font-size: 12px;
  width:200%;
  line-height:30px;
  text-align:center;
  left:0;
  top:25px;
  border:1px solid green;
}