#back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    display: none;
    background: #222;
    color: #fff;
    border-radius: 50%;
    width: 48px;
    height: 48px;
    text-align: center;
    line-height: 48px;
    font-size: 24px;
    z-index: 999;
    box-shadow: 0 2px 8px rgba(0,0,0,0.2);
}
#back-to-top:hover {
    background: #444;
    color: #fff;
    text-decoration: none;
}

body { margin: 0; background: #fafafa; }
        header { background: #333; color: #fff; padding: 1rem; text-align: center; }
        .container { max-width: 1200px; margin: 2rem auto; padding: 0 1rem; }
        h2 { color: #444; margin-top: 2rem; }
        .gallery-group {
            margin-bottom: 2rem;
        }
        .gallery {
            display: flex;
            flex-wrap: wrap;
            gap: 1rem;
        }
        .gallery img {
            width: 300px;
            height: 200px;
            object-fit: cover;
            border-radius: 8px;
            box-shadow: 0 2px 8px rgba(0,0,0,0.08);
            background: #eee;
        }

        @media (max-width: 700px) {
            .gallery img { width: 100%; height: 160px; }
        }

                    .gallery img {
                cursor: pointer;
                transition: transform 0.2s;
            }
            .gallery img:hover {
                transform: scale(1.03);
            }
            .lightbox-overlay {
                display: none;
                position: fixed;
                z-index: 9999;
                top: 0; left: 0; right: 0; bottom: 0;
                background: rgba(0,0,0,0.8);
                justify-content: center;
                align-items: center;
            }
            .lightbox-overlay.active {
                display: flex;
            }
            .lightbox-overlay img {
                max-width: 90vw;
                max-height: 90vh;
                border-radius: 8px;
                box-shadow: 0 0 20px #000;
            }
            .lightbox-overlay .close-btn {
                position: absolute;
                top: 30px;
                right: 40px;
                color: #fff;
                font-size: 2.5rem;
                cursor: pointer;
                z-index: 10001;
            }