/* 基础样式重置 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #fafafa;
}

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

/* 导航栏样式 */
.navbar {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid #e5e5e5;
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 1000;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.nav-logo h1 {
    font-size: 24px;
    font-weight: 600;
    color: #2c3e50;
    margin-bottom: 2px;
}

.nav-logo h1 a {
    text-decoration: none;
    color: inherit;
}

.nav-subtitle {
    font-size: 12px;
    color: #7f8c8d;
    font-weight: 400;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 30px;
}

.nav-menu a {
    text-decoration: none;
    color: #555;
    font-weight: 500;
    transition: color 0.3s ease;
    position: relative;
}

.nav-menu a:hover,
.nav-menu a.active {
    color: #3498db;
}

.nav-menu a.active::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 100%;
    height: 2px;
    background: #3498db;
}

/* 主视觉区域 */
.hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 120px 0 80px;
    text-align: center;
    margin-top: 70px;
}

.hero-content {
    max-width: 800px;
    margin: 0 auto;
    padding: 0 20px;
}

.hero-title {
    font-size: 4rem;
    font-weight: 300;
    margin-bottom: 20px;
    letter-spacing: 2px;
}

.hero-subtitle {
    font-size: 1.5rem;
    margin-bottom: 40px;
    opacity: 0.9;
    font-weight: 300;
}

.hero-mission {
    max-width: 600px;
    margin: 0 auto;
}

.hero-mission p {
    font-size: 1.1rem;
    line-height: 1.8;
    opacity: 0.9;
}

/* 精选模块卡片 */
.featured-modules {
    padding: 80px 0;
    background: white;
}

.modules-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 40px;
    margin-top: 40px;
}

.module-card {
    background: white;
    border-radius: 12px;
    padding: 40px 30px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    border: 1px solid #f0f0f0;
}

.module-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.12);
}

.card-icon {
    font-size: 2.5rem;
    margin-bottom: 20px;
}

.module-card h3 {
    font-size: 1.5rem;
    margin-bottom: 15px;
    color: #2c3e50;
}

.module-card h3 a {
    text-decoration: none;
    color: inherit;
    transition: color 0.3s ease;
}

.module-card h3 a:hover {
    color: #3498db;
}

.module-card p {
    color: #666;
    line-height: 1.7;
}

/* 页面标题 */
.page-header {
    background: linear-gradient(135deg, #2c3e50 0%, #34495e 100%);
    color: white;
    padding: 120px 0 60px;
    text-align: center;
    margin-top: 70px;
}

.page-header h1 {
    font-size: 3rem;
    font-weight: 300;
    margin-bottom: 10px;
}

.page-subtitle {
    font-size: 1.2rem;
    opacity: 0.8;
    margin-bottom: 20px;
    font-style: italic;
}

.page-description {
    font-size: 1.1rem;
    opacity: 0.9;
    max-width: 600px;
    margin: 0 auto;
    line-height: 1.6;
}

/* 主要内容 */
.main-content {
    padding: 60px 0;
    background: white;
}

.content-section {
    margin-bottom: 80px;
}

.content-section h2 {
    font-size: 2.2rem;
    color: #2c3e50;
    margin-bottom: 30px;
    font-weight: 400;
    border-bottom: 3px solid #3498db;
    padding-bottom: 10px;
}

.content-section h3 {
    font-size: 1.4rem;
    color: #34495e;
    margin: 30px 0 15px;
    font-weight: 500;
}

.section-content p {
    font-size: 1.1rem;
    line-height: 1.8;
    color: #555;
    margin-bottom: 20px;
}

/* 时间线样式 */
.timeline {
    margin-top: 40px;
}

.timeline-item {
    background: #f8f9fa;
    border-radius: 8px;
    padding: 30px;
    margin-bottom: 25px;
    border-left: 4px solid #3498db;
    transition: transform 0.3s ease;
}

.timeline-item:hover {
    transform: translateX(5px);
}

.timeline-item h3 {
    color: #2c3e50;
    margin-bottom: 15px;
    font-size: 1.3rem;
}

/* 引擎卡片网格 */
.engines-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(500px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

.engine-card {
    background: #f8f9fa;
    border-radius: 12px;
    padding: 35px;
    border: 1px solid #e9ecef;
    transition: box-shadow 0.3s ease;
}

.engine-card:hover {
    box-shadow: 0 6px 25px rgba(0, 0, 0, 0.1);
}

.engine-card h3 {
    color: #2c3e50;
    font-size: 1.4rem;
    margin-bottom: 20px;
    border-bottom: 2px solid #3498db;
    padding-bottom: 8px;
}

.engine-content p {
    margin-bottom: 15px;
    font-size: 1rem;
    line-height: 1.7;
}

.engine-content strong {
    color: #2c3e50;
    font-weight: 600;
}

/* 术语卡片网格 */
.terms-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

.term-card {
    background: white;
    border-radius: 12px;
    padding: 30px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.08);
    border: 1px solid #e9ecef;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.term-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.12);
}

.term-card h3 {
    color: #2c3e50;
    font-size: 1.3rem;
    margin-bottom: 20px;
    border-bottom: 2px solid #e74c3c;
    padding-bottom: 8px;
}

.term-definition {
    margin-bottom: 20px;
}

.term-definition p {
    background: #f1f2f6;
    padding: 15px;
    border-radius: 6px;
    font-size: 1rem;
    line-height: 1.6;
}

.term-significance p {
    font-size: 1rem;
    line-height: 1.7;
    color: #555;
}

.term-definition strong,
.term-significance strong {
    color: #2c3e50;
    font-weight: 600;
}

/* 文章导航样式 */
.articles-navigation {
    padding: 2rem 0;
}

.nav-intro {
    text-align: center;
    margin-bottom: 3rem;
}

.nav-intro p {
    font-size: 1.2rem;
    color: #666;
    max-width: 600px;
    margin: 0 auto;
    line-height: 1.6;
}

.articles-grid {
    display: flex;
    flex-direction: column;
    gap: 3rem;
}

.article-category {
    background: white;
    border-radius: 16px;
    padding: 2.5rem;
    box-shadow: 0 4px 20px rgba(0,0,0,0.06);
    border: 1px solid #f0f0f0;
}

.category-title {
    font-size: 1.5rem;
    color: #3498db;
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 2px solid #f0f0f0;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.category-articles {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
    gap: 2rem;
}

.article-preview {
    background: #fafafa;
    border-radius: 12px;
    padding: 1.5rem;
    transition: all 0.3s ease;
    border: 1px solid #eee;
    display: flex;
    gap: 1.5rem;
    align-items: flex-start;
}

.article-preview:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(0,0,0,0.1);
    background: white;
}

.article-visual {
    flex-shrink: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 80px;
    height: 80px;
    background: white;
    border-radius: 12px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.08);
}

.article-info {
    flex: 1;
}

.article-info h4 {
    margin: 0 0 0.8rem 0;
    font-size: 1.1rem;
    line-height: 1.4;
}

.article-info h4 a {
    color: #3498db;
    text-decoration: none;
    transition: color 0.3s ease;
}

.article-info h4 a:hover {
    color: #2980b9;
}

.article-summary {
    color: #666;
    font-size: 0.95rem;
    line-height: 1.5;
    margin-bottom: 1rem;
}

.article-meta {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
    align-items: center;
}

.article-meta span {
    font-size: 0.85rem;
    padding: 0.3rem 0.8rem;
    border-radius: 20px;
    font-weight: 500;
}

.difficulty {
    background: #f8f9fa;
    color: #495057;
    border: 1px solid #dee2e6;
}

.read-time {
    background: #e3f2fd;
    color: #1976d2;
    border: 1px solid #bbdefb;
}

.article-type {
    background: #f3e5f5;
    color: #7b1fa2;
    border: 1px solid #ce93d8;
}

/* 页脚 */
.footer {
    background: #2c3e50;
    color: white;
    text-align: center;
    padding: 40px 0;
}

.footer p {
    opacity: 0.8;
}

.footer a {
    color: #3498db;
    text-decoration: none;
}

.footer a:hover {
    text-decoration: underline;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .hero-title {
        font-size: 2.5rem;
    }
    
    .hero-subtitle {
        font-size: 1.2rem;
    }
    
    .modules-grid {
        grid-template-columns: 1fr;
        gap: 30px;
    }
    
    .engines-grid {
        grid-template-columns: 1fr;
    }
    
    .terms-grid {
        grid-template-columns: 1fr;
    }
    
    .nav-menu {
        gap: 20px;
    }
    
    .page-header h1 {
        font-size: 2.2rem;
    }
    
    .module-card,
    .engine-card,
    .term-card {
        padding: 25px;
    }
}