:root {
    --primary-color: #0056b3;
    --primary-hover: #004494;
    --secondary-color: #6c757d;
    --text-color: #333;
    --light-bg: #f8f9fa;
    --white: #ffffff;
    --border-color: #dee2e6;
    --container-width: 1000px;
    --font-main: 'Calibri', 'Candara', 'Segoe UI', 'Optima', Arial, sans-serif;
    --font-heading: 'Calibri', 'Candara', 'Segoe UI', 'Optima', Arial, sans-serif;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: var(--font-main);
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--white);
    scroll-behavior: smooth;
}

.container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 2rem;
}

/* Header & Nav */
header {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
    border-bottom: 1px solid var(--border-color);
}

nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.logo {
    font-family: var(--font-heading);
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

nav ul {
    display: flex;
    list-style: none;
}

nav ul li {
    margin-left: 2rem;
}

nav ul li a {
    text-decoration: none;
    color: var(--text-color);
    font-weight: 600;
    font-size: 0.9rem;
    transition: color 0.3s;
}

nav ul li a:hover {
    color: var(--primary-color);
}

/* Hero Section */
.hero {
    padding: 160px 0 100px;
    background: linear-gradient(135deg, #f0f4f8 0%, #d9e2ec 100%);
    text-align: center;
}

.hero h1 {
    font-family: var(--font-heading);
    font-size: 3.5rem;
    margin-bottom: 1rem;
    color: #102a43;
}

.subtitle {
    font-size: 1.25rem;
    color: #486581;
    margin-bottom: 2.5rem;
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
}

.hero-actions {
    display: flex;
    justify-content: center;
    gap: 1rem;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    padding: 0.8rem 2rem;
    border-radius: 8px;
    text-decoration: none;
    font-weight: 600;
    transition: all 0.3s;
    cursor: pointer;
}

.btn-primary {
    background-color: var(--primary-color);
    color: var(--white);
}

.btn-primary:hover {
    background-color: var(--primary-hover);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 86, 179, 0.2);
}

.btn-secondary {
    background-color: var(--white);
    color: var(--text-color);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    background-color: var(--light-bg);
}

.btn-outline {
    border: 2px solid var(--primary-color);
    color: var(--primary-color);
    gap: 0.5rem;
}

.btn-outline:hover {
    background-color: var(--primary-color);
    color: var(--white);
}

/* Sections */
.section {
    padding: 80px 0;
}

.bg-light {
    background-color: var(--light-bg);
}

h2 {
    font-family: var(--font-heading);
    font-size: 2.25rem;
    margin-bottom: 2.5rem;
    text-align: center;
    color: #102a43;
}

/* Content Grid */
.content-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    align-items: start;
}

.text-content p {
    margin-bottom: 1.5rem;
    font-size: 1.1rem;
}

.image-gallery {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}

.gallery-item {
    border-radius: 8px;
    overflow: hidden;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
    border: 1px solid var(--border-color);
    background: var(--white);
}

.gallery-item img {
    width: 100%;
    height: 150px;
    object-fit: cover;
    display: block;
    transition: transform 0.3s;
}

.gallery-item img:hover {
    transform: scale(1.05);
}

.gallery-caption {
    padding: 0.5rem;
    font-size: 0.8rem;
    text-align: center;
    color: var(--secondary-color);
    background: var(--white);
}

/* Stats Grid */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 2rem;
    text-align: center;
}

.stat-card {
    background: var(--white);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.05);
    border: 1px solid var(--border-color);
}

.stat-value {
    display: block;
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.stat-label {
    font-size: 1rem;
    color: var(--secondary-color);
    text-transform: uppercase;
    letter-spacing: 1px;
}

/* Class Grid */
.class-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 2rem;
}

.class-item {
    text-align: center;
}

.class-item img {
    width: 100%;
    height: 200px;
    object-fit: cover;
    border-radius: 12px;
    margin-bottom: 1.5rem;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
    border: 1px solid var(--border-color);
    transition: transform 0.3s;
}

.class-item img:hover {
    transform: scale(1.05);
}

.class-item h3 {
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
    color: #102a43;
}

.class-item p {
    font-size: 0.9rem;
    color: var(--secondary-color);
}

.text-center {
    text-align: center;
}

.mb-4 {
    margin-bottom: 2rem;
}

/* License Box */
.license-box {
    background: var(--white);
    padding: 3rem;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    max-height: 600px;
    overflow-y: auto;
    box-shadow: inset 0 2px 4px rgba(0,0,0,0.05);
}

.license-box h3 {
    margin: 2rem 0 1rem;
    font-family: var(--font-heading);
    color: #102a43;
}

.license-box h3:first-child {
    margin-top: 0;
}

.license-box p {
    margin-bottom: 1rem;
}

.license-box ol {
    padding-left: 1.5rem;
}

.license-box li {
    margin-bottom: 1rem;
}

/* Contact Card */
.contact-card {
    background: #e1e8f0;
    padding: 2rem;
    border-radius: 12px;
    margin: 2rem auto;
    max-width: 600px;
    border-left: 5px solid var(--primary-color);
}

.email-subject {
    font-size: 1.1rem;
    margin-bottom: 0.5rem;
}

.email-to a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 700;
    font-size: 1.2rem;
}

.download-links {
    display: flex;
    justify-content: center;
    gap: 2rem;
    margin-top: 3rem;
}

/* Citation Box */
.citation-box {
    background: #243b53;
    color: #f0f4f8;
    padding: 2rem;
    border-radius: 8px;
    font-family: 'Courier New', Courier, monospace;
    overflow-x: auto;
}

.citation-box code {
    display: block;
    line-height: 1.4;
}

/* Footer */
footer {
    padding: 60px 0;
    background: #102a43;
    color: #bcccdc;
    text-align: center;
}

footer p {
    margin-bottom: 0.5rem;
}

/* Responsive */
@media (max-width: 768px) {
    .hero h1 {
        font-size: 2.5rem;
    }
    
    .content-grid {
        grid-template-columns: 1fr;
    }
    
    .image-gallery {
        grid-template-columns: 1fr 1fr;
    }

    .stats-grid {
        grid-template-columns: 1fr 1fr;
    }

    .class-grid {
        grid-template-columns: 1fr 1fr;
    }
    
    .download-links {
        flex-direction: column;
        align-items: center;
        gap: 1rem;
    }
    
    nav ul {
        display: none;
    }
}