/* 全局样式 */
:root {
    --primary-color: #2563eb;
    --primary-light: #3b82f6;
    --primary-dark: #1d4ed8;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --bg-primary: #ffffff;
    --bg-secondary: #f9fafb;
    --bg-alt: #f3f4f6;
    --border-color: #e5e7eb;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --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;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Noto Sans SC', 'Noto Sans', -apple-system, BlinkMacSystemFont, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background: var(--bg-primary);
}

body.en {
    font-family: 'Noto Sans', 'Noto Sans SC', -apple-system, BlinkMacSystemFont, sans-serif;
}

/* 导航栏 */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    z-index: 1000;
    box-shadow: var(--shadow-sm);
}

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

.nav-logo {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-primary);
    text-decoration: none;
    font-family: 'Noto Serif SC', 'Noto Serif', serif;
}

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

.nav-menu a {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
}

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

.lang-toggle {
    background: var(--bg-alt);
    border: 1px solid var(--border-color);
    padding: 0.4rem 0.8rem;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.875rem;
    font-weight: 500;
    transition: var(--transition);
}

.lang-toggle:hover {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

/* 首页 */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 6rem 2rem 4rem;
    background: linear-gradient(135deg, #f8fafc 0%, #e2e8f0 100%);
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -20%;
    width: 600px;
    height: 600px;
    background: radial-gradient(circle, rgba(37, 99, 235, 0.1) 0%, transparent 70%);
    border-radius: 50%;
}

.hero-content {
    text-align: center;
    max-width: 700px;
    position: relative;
    z-index: 1;
}

.avatar-container {
    margin-bottom: 2rem;
}

.avatar {
    width: 160px;
    height: 160px;
    border-radius: 50%;
    object-fit: cover;
    border: 4px solid white;
    box-shadow: var(--shadow-lg);
    background: linear-gradient(135deg, #e2e8f0, #cbd5e1);
}

.hero-title {
    font-size: 3rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
    font-family: 'Noto Serif SC', 'Noto Serif', serif;
}

body.en .hero-title {
    font-family: 'Noto Serif', 'Noto Serif SC', serif;
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--primary-color);
    font-weight: 500;
    margin-bottom: 1rem;
}

.hero-description {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: 2rem;
    line-height: 1.8;
}

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

.btn {
    display: inline-block;
    padding: 0.875rem 2rem;
    border-radius: 8px;
    font-weight: 500;
    text-decoration: none;
    transition: var(--transition);
    font-size: 1rem;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
    border: 2px solid var(--primary-color);
}

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

.btn-outline {
    background: transparent;
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
}

.btn-outline:hover {
    background: var(--primary-color);
    color: white;
    transform: translateY(-2px);
}

/* 通用区块 */
.section {
    padding: 5rem 2rem;
}

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

.container {
    max-width: 1000px;
    margin: 0 auto;
}

.section-title {
    font-size: 2rem;
    font-weight: 600;
    text-align: center;
    margin-bottom: 3rem;
    color: var(--text-primary);
    font-family: 'Noto Serif SC', 'Noto Serif', serif;
    position: relative;
}

body.en .section-title {
    font-family: 'Noto Serif', 'Noto Serif SC', serif;
}

.section-title::after {
    content: '';
    display: block;
    width: 60px;
    height: 3px;
    background: var(--primary-color);
    margin: 1rem auto 0;
}

/* 关于 */
.about-content {
    display: grid;
    grid-template-columns: 1.5fr 1fr;
    gap: 3rem;
    align-items: start;
}

.about-text p {
    margin-bottom: 1.5rem;
    color: var(--text-secondary);
    line-height: 1.8;
    font-size: 1.05rem;
}

.about-info h3 {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.info-list {
    list-style: none;
    margin-bottom: 2rem;
}

.info-list li {
    display: flex;
    gap: 1rem;
    padding: 0.75rem 0;
    border-bottom: 1px solid var(--border-color);
}

.info-list .year {
    color: var(--text-secondary);
    font-size: 0.9rem;
    min-width: 80px;
}

.info-list .degree {
    color: var(--text-primary);
}

/* 研究方向 */
.research-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
}

.research-card {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: var(--shadow-md);
    transition: var(--transition);
    border: 1px solid var(--border-color);
}

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

.research-icon {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.research-card h3 {
    font-size: 1.15rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
}

.research-card p {
    color: var(--text-secondary);
    font-size: 0.95rem;
    line-height: 1.7;
}

/* publications */
.pub-section {
    margin-bottom: 3rem;
}

.pub-section h3 {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--primary-color);
    display: inline-block;
}

.pub-list, .project-list {
    list-style: none;
}

.pub-item, .project-item {
    display: flex;
    gap: 1.5rem;
    padding: 1.25rem 0;
    border-bottom: 1px solid var(--border-color);
    transition: var(--transition);
}

.pub-item:hover, .project-item:hover {
    background: var(--bg-secondary);
    margin: 0 -1rem;
    padding-left: 1rem;
    padding-right: 1rem;
}

.pub-year, .project-year {
    color: var(--primary-color);
    font-weight: 600;
    min-width: 60px;
}

.pub-title, .project-title {
    font-weight: 500;
    color: var(--text-primary);
    margin-bottom: 0.25rem;
}

.pub-journal {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.project-role {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-top: 0.25rem;
}

/* teaching */
.teaching-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.course-card {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: var(--shadow-md);
    transition: var(--transition);
    border: 1px solid var(--border-color);
}

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

.course-card h3 {
    font-size: 1.15rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
}

.course-info {
    color: var(--primary-color);
    font-size: 0.9rem;
    font-weight: 500;
    margin-bottom: 0.75rem;
}

.course-desc {
    color: var(--text-secondary);
    font-size: 0.95rem;
    line-height: 1.7;
}

/* 联系 */
.contact-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 3rem;
    text-align: center;
}

.contact-item {
    padding: 2rem;
}

.contact-icon {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.contact-item h3 {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
}

.contact-item p {
    color: var(--text-secondary);
}

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

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

.social-links {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
}

.social-links a {
    color: var(--primary-color);
    font-weight: 500;
}

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

.footer p {
    opacity: 0.8;
    font-size: 0.9rem;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .nav-menu {
        display: none;
    }

    .hero-title {
        font-size: 2.25rem;
    }

    .hero-subtitle {
        font-size: 1.1rem;
    }

    .about-content {
        grid-template-columns: 1fr;
    }

    .section {
        padding: 3rem 1.5rem;
    }

    .hero-links {
        flex-direction: column;
        align-items: center;
    }

    .btn {
        width: 100%;
        max-width: 250px;
    }
}

/* 滚动动画 */
.fade-in {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}