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

:root {
    --primary-color: #2563eb;
    --primary-dark: #1e40af;
    --secondary-color: #64748b;
    --background: #f8fafc;
    --surface: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--background);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Navigation */
.navbar {
    background-color: var(--surface);
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

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

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

.nav-link {
    text-decoration: none;
    color: var(--text-secondary);
    font-weight: 500;
    transition: color 0.2s;
    padding: 0.5rem 0;
    position: relative;
}

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

.nav-link.active {
    color: var(--primary-color);
}

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    height: 2px;
    background-color: var(--primary-color);
}

/* Main Content */
main {
    flex: 1;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: white;
    padding: 5rem 0;
    text-align: center;
}

.hero-title {
    font-size: 3rem;
    font-weight: 700;
    margin-bottom: 1rem;
}

.hero-subtitle {
    font-size: 1.25rem;
    margin-bottom: 2rem;
    opacity: 0.95;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    text-decoration: none;
    border-radius: 0.5rem;
    font-weight: 500;
    transition: all 0.2s;
    cursor: pointer;
    border: none;
    font-size: 1rem;
}

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

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

.btn-large {
    padding: 1rem 2rem;
    font-size: 1.125rem;
}

/* Features Section */
.features {
    padding: 5rem 0;
    background-color: var(--surface);
}

.section-title {
    font-size: 2.5rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: 3rem;
    color: var(--text-primary);
}

.feature-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-top: 2rem;
}

.feature-card {
    background-color: var(--surface);
    padding: 2rem;
    border-radius: 0.75rem;
    box-shadow: var(--shadow);
    transition: transform 0.2s, box-shadow 0.2s;
    text-align: center;
}

.feature-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.feature-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.feature-card h3 {
    font-size: 1.25rem;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
}

.feature-card p {
    color: var(--text-secondary);
    line-height: 1.6;
}

/* About Section */
.about {
    padding: 5rem 0;
    background-color: var(--background);
}

.about-content {
    max-width: 800px;
    margin: 0 auto;
    text-align: center;
}

.about-content p {
    font-size: 1.125rem;
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
    line-height: 1.8;
}

/* CTA Section */
.cta {
    padding: 5rem 0;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: white;
    text-align: center;
}

.cta .section-title {
    color: white;
    margin-bottom: 1rem;
}

.cta p {
    font-size: 1.25rem;
    margin-bottom: 2rem;
    opacity: 0.95;
}

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

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

footer p {
    opacity: 0.8;
}

/* PDF List Styles */
.pdf-list {
    display: grid;
    gap: 1.5rem;
    margin-top: 2rem;
}

.pdf-item {
    background-color: var(--surface);
    padding: 2rem;
    border-radius: 0.75rem;
    box-shadow: var(--shadow);
    transition: transform 0.2s, box-shadow 0.2s;
    border-left: 4px solid var(--primary-color);
}

.pdf-item:hover {
    transform: translateX(4px);
    box-shadow: var(--shadow-lg);
}

.pdf-item h3 {
    font-size: 1.5rem;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
}

.pdf-description {
    color: var(--text-secondary);
    margin-bottom: 1rem;
    line-height: 1.6;
}

.pdf-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    margin-bottom: 1.5rem;
    padding-top: 1rem;
    border-top: 1px solid var(--border-color);
}

.meta-item {
    font-size: 0.875rem;
    color: var(--text-secondary);
    display: inline-flex;
    align-items: center;
    gap: 0.25rem;
}

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

.pdf-item .btn:hover {
    background-color: var(--primary-dark);
}

.empty-state {
    text-align: center;
    padding: 4rem 2rem;
    background-color: var(--surface);
    border-radius: 0.75rem;
    box-shadow: var(--shadow);
}

.empty-state p {
    font-size: 1.125rem;
    color: var(--text-secondary);
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-container {
        flex-direction: column;
        gap: 1rem;
    }

    .nav-menu {
        gap: 1rem;
    }

    .hero-title {
        font-size: 2rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    .section-title {
        font-size: 2rem;
    }

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

    .container {
        padding: 0 1rem;
    }
}