```css
/* =========================
   GENERAL PAGE STYLING
   ========================= */

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: Arial, Helvetica, sans-serif;
    background-color: #f4f1ea;
    color: #333;
}

/* =========================
   TOP HEADER
   ========================= */

header {
    background-color: #222;
    border-bottom: 4px solid #c9a227;
    position: sticky;
    top: 0;
    z-index: 1000;
}

.header-inner {
    max-width: 1100px;
    margin: auto;
    padding: 15px 25px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

/* Logo */

.logo {
    height: 70px;
    width: auto;
    object-fit: contain;
}

/* Navigation */

nav {
    display: flex;
    gap: 10px;
}

nav a {
    color: white;
    text-decoration: none;
    padding: 12px 18px;
    border-radius: 6px;
    transition: background-color 0.25s ease;
}

nav a:hover {
    background-color: #444;
}

nav a.active {
    background-color: #c9a227;
    color: #222;
}

/* =========================
   MAIN CONTENT
   ========================= */

main {
    max-width: 1100px;
    margin: auto;
    padding: 50px 25px;
}

h1 {
    font-size: 42px;
    margin-top: 0;
    margin-bottom: 15px;
}

.intro {
    max-width: 800px;
    font-size: 18px;
    line-height: 1.7;
    margin-bottom: 40px;
}

/* =========================
   GALLERY
   ========================= */

.gallery {
    max-width: 900px;
    margin: auto;
}

/* Large image */

.gallery-display {
    position: relative;
    background: #111;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 8px 25px rgba(0,0,0,0.25);
}

.gallery-display img {
    display: block;
    width: 100%;
    height: 500px;
    object-fit: cover;
}

/* Previous/Next buttons */

.gallery-button {
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    width: 50px;
    height: 50px;
    border: none;
    border-radius: 50%;
    background: rgba(0,0,0,0.7);
    color: white;
    font-size: 25px;
    cursor: pointer;
    transition: background-color 0.2s;
}

.gallery-button:hover {
    background: rgba(201,162,39,0.95);
    color: #222;
}

.previous {
    left: 15px;
}

.next {
    right: 15px;
}

/* Image counter */

.image-counter {
    position: absolute;
    bottom: 15px;
    left: 50%;
    transform: translateX(-50%);
    background: rgba(0,0,0,0.7);
    color: white;
    padding: 7px 14px;
    border-radius: 20px;
}

/* =========================
   THUMBNAILS
   ========================= */

.thumbnails {
    display: flex;
    gap: 12px;
    margin-top: 15px;
    overflow-x: auto;
    padding-bottom: 10px;
}

.thumbnail {
    flex: 0 0 130px;
    height: 90px;
    object-fit: cover;
    border-radius: 7px;
    cursor: pointer;
    opacity: 0.6;
    border: 3px solid transparent;
    transition: all 0.2s;
}

.thumbnail:hover {
    opacity: 1;
}

.thumbnail.selected {
    opacity: 1;
    border-color: #c9a227;
}

/* =========================
   FOOTER
   ========================= */

footer {
    text-align: center;
    padding: 30px;
    margin-top: 50px;
    background-color: #222;
    color: white;
}

/* =========================
   MOBILE
   ========================= */

@media (max-width: 700px) {

    .header-inner {
        flex-direction: column;
        gap: 15px;
    }

    nav {
        width: 100%;
        justify-content: center;
    }

    nav a {
        padding: 10px;
        font-size: 14px;
    }

    .logo {
        height: 55px;
    }

    h1 {
        font-size: 32px;
    }

    .gallery-display img {
        height: 350px;
    }

    .thumbnail {
        flex-basis: 100px;
        height: 70px;
    }
}
```