小编Bob*_*Bob的帖子

div{
  display: block;
  width: 500px;
  height: 200px;
  border: 1px solid black;
  border-radius: 5px;
  transition: box-shadow 1s;
}

div:hover{
    box-shadow: 25px 25px 0px #000;
}

<div>Test</div>