* {
    margin: 0;
    padding: 0;
    border: 0;
}

body {
    width: 640px;
    height: 960px;
}

img {
    position: absolute;
    top: 0px;
    left: 640px;
    width: 640px;
    height: 960px;
    -webkit-transition-property: left;
    -webkit-transition-duration: 3s;
}

img.out {
    left: -640px;
}

img.in {
    left: 0;
}
