html, body { padding: 0; margin: 0; position: relative; height: 100%; }

rotation iframe {
    position: absolute; width: 100%; height: 100%; border: 0;
    visibility: hidden;
}

rotation iframe.previous, rotation iframe.before, rotation iframe.after {
    visibility: visible;
}

rotation iframe.previous { z-index: 0; }
rotation iframe.before { z-index: 1; opacity: 0; }
rotation iframe.after { z-index: 1; opacity: 1; transition: opacity 0.5s }