怎么在一定时间内让d2从d1的底部从下往上的盖住d1
<div id="d1" style="width: 100%; height:200px;">
我是d1的内容
</div>
<div id="d2">
<img src="images/153535.jpg" width="100%" height="200">
</div>
<div id="d1" style="width: 100%; height:200px;">
我是d1的内容
</div>
<div id="d2">
<img src="images/153535.jpg" width="100%" height="200">
</div>
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
<title> 页面名称 </title>
<style type="text/css">
@keyframes anim{
0% {top: 0px;}
100% {top: -200px;}
}
#d2 {
background-color: #ff0;
position: relative;
z-index: 99;
animation: anim 2s forwards;
}
</style>
</head>
<body>
<div id="d1" style="width: 100%; height:200px;">
我是d1的内容
</div>
<div id="d2">
<img src="images/153535.jpg" width="100%" height="200">
</div>
</body>
</html>