#page-container {
    position: relative;
    width: 100%;
    height: 100vh;
}

#page-flip {
    position: absolute;
    width: 100%;
    height: 100%;
}

#page-front,
#page-back {
    position: absolute;
    width: 100%;
    height: 100%;
    overflow-y: auto;
}

#page-back {
    display: none;
}