body {
    transition: background-color .8s ease;
}

body.christmas-mode::before {
    content: "";
    position: fixed;
    inset: 0;

    background: rgba(0,0,0,.45);

    pointer-events: none;

    z-index: 9998;
}

body.christmas-mode .tree {
    filter:
        brightness(1.08)
        drop-shadow(0 0 18px rgba(255,230,140,.5));

    transition: filter .8s ease;
}

body.christmas-mode {
    background-color: #111;
}

#popup {
    z-index: 30000;
}

#dark-overlay {
    position: fixed;
    inset: 0;

    background: rgba(0, 0, 0, 0);

    pointer-events: none;

    transition: background 1s ease;

    z-index: 9998;
}

#dark-overlay.active {
    background: rgba(5, 15, 40, 0.5);
}