immich-public-proxy/public/style.css

html {
    background: #191919;
}

#lightgallery img {
    height: 250px;
    margin: 4px;
}

#lightgallery a {
    position: relative; /* Establishes a positioning context */
    display: inline-block; /* Allows the container to wrap around the image */
    text-decoration: none;
    margin: 0;
    padding: 0;
    cursor: pointer;
}

.play-icon {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 50px;
    height: 50px;
    background-image: url('/images/play.png');
    background-size: contain;
    background-repeat: no-repeat;
    opacity: 0.5;
}
#lightgallery a:has(.play-icon):hover .play-icon {
    opacity: 1;
}