.demo-viewport {
    /*border: 2px solid red;*/
}

.demo-viewport .center-page-part .show .demo-block {
    width: 83%;
    height: 100%;
}

.demo-block > img {
    display: block;
    position: absolute;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    transition: opacity 2.0s;
    opacity: 0;
}

.demo-block > #img0 {
    opacity: 1;
}