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

:root {
    --primary-color: #1e3a8a;
    --secondary-color: #3b82f6;
    --accent-color: #60a5fa;
    --bg-color: #f3f4f6;
    --card-bg: #ffffff;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --transition: all 0.3s ease;
}

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

.container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.hero {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
    padding: 80px 20px;
    text-align: center;
}

.hero-content {
    max-width: 800px;
    margin: 0 auto;
}

.hero-title {
    font-size: 3rem;
    font-weight: 700;
    margin-bottom: 16px;
    letter-spacing: -0.02em;
}

.hero-subtitle {
    font-size: 1.25rem;
    font-weight: 500;
    margin-bottom: 8px;
    opacity: 0.95;
}

.hero-major {
    font-size: 1.1rem;
    font-weight: 400;
    opacity: 0.9;
}

.main-content {
    flex: 1;
    padding: 60px 20px;
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
}

.courses-section {
    width: 100%;
}

.section-title {
    font-size: 2rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 40px;
    text-align: center;
}

.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 24px;
}

.course-card {
    background: var(--card-bg);
    border-radius: 12px;
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    cursor: pointer;
}

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

.course-card-header {
    background: linear-gradient(135deg, var(--secondary-color) 0%, var(--accent-color) 100%);
    padding: 24px;
    color: white;
}

.course-icon {
    width: 48px;
    height: 48px;
    background: rgba(255, 255, 255, 0.2);
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 16px;
    font-size: 24px;
}

.course-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 4px;
}

.course-card-body {
    padding: 20px 24px 24px;
}

.course-description {
    color: var(--text-secondary);
    font-size: 0.95rem;
    margin-bottom: 16px;
}

.course-details {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.4s ease, padding 0.4s ease;
}

.course-details.expanded {
    max-height: 500px;
    padding-top: 20px;
    border-top: 1px solid var(--bg-color);
}

.details-title {
    font-size: 1rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 12px;
}

.details-content {
    color: var(--text-secondary);
    font-size: 0.9rem;
    line-height: 1.8;
}

.details-content p {
    margin-bottom: 12px;
}

.details-content ul {
    padding-left: 20px;
    margin-top: 8px;
}

.details-content li {
    margin-bottom: 6px;
}

.expand-hint {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    color: var(--secondary-color);
    font-size: 0.85rem;
    font-weight: 500;
    margin-top: 12px;
    transition: var(--transition);
}

.course-card:hover .expand-hint {
    color: var(--primary-color);
}

.footer {
    background: var(--primary-color);
    color: white;
    padding: 24px;
    text-align: center;
    margin-top: auto;
}

.footer p {
    opacity: 0.9;
    font-size: 0.9rem;
}

/* 课程详情页面样式 */
.course-detail-page {
    max-width: 800px;
    margin: 0 auto;
}

.back-link {
    display: inline-block;
    color: var(--secondary-color);
    font-weight: 500;
    margin-bottom: 32px;
    cursor: pointer;
    transition: var(--transition);
}

.back-link:hover {
    color: var(--primary-color);
    transform: translateX(-4px);
}

.course-detail-header {
    text-align: center;
    margin-bottom: 48px;
}

.course-icon-large {
    font-size: 4rem;
    margin-bottom: 16px;
}

.course-title-large {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 12px;
}

.course-detail-content {
    background: var(--card-bg);
    padding: 40px;
    border-radius: 12px;
    box-shadow: var(--shadow-sm);
}

.course-detail-content h2 {
    font-size: 1.8rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 24px;
}

.course-detail-content h3 {
    font-size: 1.4rem;
    font-weight: 600;
    color: var(--text-primary);
    margin: 32px 0 16px 0;
}

.course-detail-content h4 {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--secondary-color);
    margin: 24px 0 12px 0;
}

.course-detail-content p {
    margin-bottom: 16px;
    line-height: 1.7;
}

.course-detail-content ul {
    margin: 16px 0;
    padding-left: 24px;
}

.course-detail-content li {
    margin-bottom: 8px;
    line-height: 1.6;
}

@media (max-width: 768px) {
    .hero {
        padding: 60px 20px;
    }
    
    .hero-title {
        font-size: 2rem;
    }
    
    .hero-subtitle {
        font-size: 1.1rem;
    }
    
    .hero-major {
        font-size: 1rem;
    }
    
    .main-content {
        padding: 40px 20px;
    }
    
    .section-title {
        font-size: 1.5rem;
        margin-bottom: 32px;
    }
    
    .courses-grid {
        grid-template-columns: 1fr;
    }
    
    .course-detail-content {
        padding: 24px;
    }
    
    .course-title-large {
        font-size: 2rem;
    }
}