要使用CSS在top 属性上实现动画，您可以尝试运行以下代码-
<!DOCTYPE html>
<html>
<head>
<style>
div {
position: absolute;
width: 300px;
height: 200px;
background-color: orange;
color: white;
top: 0;
animation: myanim 3s infinite;
}
@keyframes myanim {
30% {
top: 300px;
}
}
</style>
</head>
<body>
<h1>CSS top property</h1>
<div>
<h1>This is demo text!</h1>
</div>
</body>
</html>