*{
    margin: 0;
    padding: 0;
}

html,body{
    width: 100%;
    height: 100%;
    overflow: hidden;
}

#main{    width: 640px;
    height: 960px;
    position: absolute;
    left: 50%;
    top: 0;
    margin-left: -320px;
    transform-origin: top;
    -webkit-transform-origin: top;/*改变缩放基准点*/
}

#list li{
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    background-size: cover;


}
#list li:nth-child(1){
    background: url(1.jpeg) no-repeat;
}
#list li:nth-child(2){
    background: url(1.jpeg) no-repeat;
}
#list li:nth-child(3){
    background: url(1.jpeg) no-repeat;
}
#list li:nth-child(4){
    background: url(1.jpeg) no-repeat;
}