/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #2c5aa0;
    --secondary-color: #4a90e2;
    --accent-color: #27ae60;
    --text-dark: #2c3e50;
    --text-light: #7f8c8d;
    --bg-light: #f8f9fa;
    --bg-white: #ffffff;
    --border-color: #e1e8ed;
    --shadow: 0 2px 10px rgba(0,0,0,0.1);
    --shadow-hover: 0 4px 20px rgba(0,0,0,0.15);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-dark);
    background-color: var(--bg-white);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header and Navigation */
header {
    background-color: var(--bg-white);
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 1000;
}

nav {
    padding: 1rem 0;
}

nav .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
}

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

.nav-links {
    display: flex;
    list-style: none;
    gap: 2rem;
    flex-wrap: wrap;
}

.nav-links a {
    color: var(--text-dark);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s;
}

.nav-links a:hover {
    color: var(--primary-color);
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    padding: 4rem 0;
    text-align: center;
}

.hero h2 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    line-height: 1.2;
}

.subtitle {
    font-size: 1.2rem;
    margin-bottom: 2rem;
    opacity: 0.95;
}

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

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    text-decoration: none;
    border-radius: 5px;
    font-weight: 600;
    transition: all 0.3s;
    cursor: pointer;
}

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

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-hover);
}

.btn-secondary {
    background-color: transparent;
    color: white;
    border: 2px solid white;
}

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

.btn-download {
    background-color: var(--accent-color);
    color: white;
    width: 100%;
    text-align: center;
}

.btn-download:hover {
    background-color: #229954;
    transform: translateY(-2px);
}

/* Sections */
.section {
    padding: 4rem 0;
}

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

.section h2 {
    color: var(--primary-color);
    font-size: 2rem;
    margin-bottom: 1.5rem;
}

.section h3 {
    color: var(--text-dark);
    font-size: 1.5rem;
    margin-top: 2rem;
    margin-bottom: 1rem;
}

/* Highlight Cards */
.highlights {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 2rem;
    margin: 3rem 0;
}

.highlight-card {
    background: white;
    padding: 2rem;
    border-radius: 10px;
    text-align: center;
    box-shadow: var(--shadow);
    transition: transform 0.3s;
}

.highlight-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-hover);
}

.highlight-card h3 {
    font-size: 3rem;
    color: var(--primary-color);
    margin: 0;
}

.highlight-card p {
    color: var(--text-light);
    margin-top: 0.5rem;
    font-weight: 500;
}

/* Lists */
.value-list, .city-list, .data-fields, .author-list {
    list-style-position: inside;
    margin: 1rem 0;
}

.value-list li, .city-list li, .data-fields li {
    margin: 0.75rem 0;
    line-height: 1.8;
}

/* Data Download Section */
.data-download {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
    margin: 2rem 0;
}

.download-card {
    background: white;
    padding: 2rem;
    border-radius: 10px;
    box-shadow: var(--shadow);
    text-align: center;
}

.download-card h3 {
    margin-top: 0;
    color: var(--primary-color);
}

.download-card p {
    color: var(--text-light);
    margin: 1rem 0 1.5rem 0;
}

/* Documentation Links */
.doc-links {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin: 2rem 0;
}

.doc-card {
    background: white;
    padding: 2rem;
    border-radius: 10px;
    box-shadow: var(--shadow);
    text-decoration: none;
    color: inherit;
    transition: all 0.3s;
    border-left: 4px solid var(--primary-color);
}

.doc-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-hover);
}

.doc-card h3 {
    margin-top: 0;
    color: var(--primary-color);
}

.doc-card p {
    color: var(--text-light);
    margin: 0;
}

/* Citation */
.citation-box {
    background: white;
    padding: 2rem;
    border-radius: 10px;
    border-left: 4px solid var(--primary-color);
    margin: 2rem 0;
    box-shadow: var(--shadow);
}

.citation-box p {
    line-height: 1.8;
    margin: 0;
}

.author-list {
    list-style: none;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 0.5rem;
}

.affiliations {
    margin-top: 1.5rem;
    color: var(--text-light);
    font-size: 0.9rem;
    line-height: 1.8;
}

/* Contact Section */
.contact-info {
    background: white;
    padding: 2rem;
    border-radius: 10px;
    box-shadow: var(--shadow);
}

.contact-info a {
    color: var(--primary-color);
    text-decoration: none;
}

.contact-info a:hover {
    text-decoration: underline;
}

/* Footer */
footer {
    background-color: var(--text-dark);
    color: white;
    padding: 2rem 0;
    text-align: center;
}

footer p {
    margin: 0.5rem 0;
    opacity: 0.9;
}

/* Responsive Design */
@media (max-width: 768px) {
    .hero h2 {
        font-size: 1.8rem;
    }

    .subtitle {
        font-size: 1rem;
    }

    nav .container {
        flex-direction: column;
        gap: 1rem;
    }

    .nav-links {
        justify-content: center;
    }

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