.postcard {
    width: 100vw;
    height: 100vh;

    background-attachment: fixed;
    background-size: cover;
    background-position: 50% 50%;
    z-index: -1;

    position: fixed;
    top: 0;
    left: 0;

    user-select: none;
    pointer-events: none;
}

.postcard-visible {
    z-index: 1;
    filter: none;
}