2-9 CSS3 <animation>动画 - <steps>案例之小熊奔跑 - 《Web前端进阶》

核心思路：body加冰山背景图片，定义动画0到-1600px的移动，30s的动画时长，实现背景移动；div加小熊背景图片，定义动画0到-1600px的移动实现小熊奔跑，再定义动画小熊跑body的50%的x轴。

    <style>
        body {
            background: url(media/bg1.png) no-repeat;
            animation: bg 20s 2.9s linear;
        }
        @keyframes bg {
            0% {
                background-position: 0 0;
            }
            100% {
                background-position: -1600px 0;
            }
        }
        @keyframes go {
            0% {
                background-position: 0 0;
            }
            100% {
                background-position: -1600px 0;
            }
        }
        @keyframes stop {
            0% {
                left: 0;
            }
            100% {
                position: absolute;
                left: 50%;
                margin-left: -100px;
            }
        }
        div {
            position: relative;
            transform: translateY(237px);
            width: 200px;
            height: 100px;
            background: url(media/bear.png) no-repeat;
            animation: go 0.5s steps(8) infinite, stop 3s linear forwards;
        }
    </style>
</head>
<body>
    <div></div>
</body>