//count down from 5 to 1, a useful animation. show the code to you:
<!DOCTYPE html>
<html>
<style>
#contain {
}
#pic {
height: 1200px;
}
#pic > img {
}
@keyframes switch {
}
</style>
<body>
<div id="contain">
<div id="pic">
<img src="5.png" />
<img src="4.png" />
</div>
</div>
</body>
</html>