#outerholder {
    max-width: 600px;
}


#imgholder img {
    position: absolute;
    width: auto;
    max-width: 100%;
    max-height: 100%;
    margin: auto;
    left: 0;
    right: 0;
    top: 0;
    bottom: 0;
}

#frontpic1 {
    mix-blend-mode: difference;
}

.opac {
    opacity: 1;
    transition-duration: 0s;
}

.transp {
    opacity: 0;
    transition-duration: 0s;
}

.toopac {
    opacity: 1;
    transition: opacity 1s linear;
}

.totransp {
    opacity: 0;
    transition: opacity 1s linear;
}