【需求描述】假设有一张非常长的宽幅照片，但它的容器只是一个尺寸为150*150的正方形区域。默认显示这张图片的左边缘，当鼠标悬停或聚焦在图片上时，图片滚动显露出剩余的部分（本例摘自《CSS揭秘》）。
【相关链接】【css】animation、MDN animatation。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
@keyframes panoramic {
to {
background-position: 100% 0; }
}
.panoramic {
width: 150px; height: 150px;
background: url('http://c3.staticflickr.com/3/2671/3904743709_74bc76d5ac_b.jpg');
background-size: auto 100%;
animation: panoramic 10s linear infinite alternate;
animation-play-state: paused;
}
.panoramic:hover, .panoramic:focus {
animation-play-state: running;
}
</style>
</head>
<body>
<div class="panoramic"></div>
</body>
</html>