/* ========================================
   Style 2: Minimalist Academic
   Clean, typography-focused, scholarly
   ======================================== */

:root {
    /* Light Theme (Default for Academic) */
    --bg-primary: #ffffff;
    --bg-secondary: #f9fafb;
    --bg-tertiary: #f3f4f6;
    --bg-card: #ffffff;

    --text-primary: #111827;
    --text-secondary: #374151;
    --text-muted: #6b7280;

    --accent-primary: #2563eb;
    --accent-secondary: #1d4ed8;
    --accent-gradient: linear-gradient(135deg, #2563eb 0%, #1d4ed8 100%);

    --border-color: #e5e7eb;
    --border-hover: #d1d5db;

    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 2px 4px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 4px 8px rgba(0, 0, 0, 0.08);
    --shadow-glow: none;

    /* Typography - Clean Academic */
    --font-display: 'Source Sans 3', 'Helvetica Neue', sans-serif;
    --font-body: 'Source Sans 3', 'Helvetica Neue', sans-serif;
    --font-mono: 'IBM Plex Mono', monospace;

    /* Compact Spacing */
    --space-xs: 0.125rem;
    --space-sm: 0.25rem;
    --space-md: 0.5rem;
    --space-lg: 0.75rem;
    --space-xl: 1rem;
    --space-2xl: 1.5rem;
    --space-3xl: 2rem;

    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;

    --radius-sm: 2px;
    --radius-md: 4px;
    --radius-lg: 6px;
    --radius-xl: 8px;

    /* Sidebar width */
    --sidebar-width: 280px;
}

/* Dark Theme */
[data-theme="dark"] {
    --bg-primary: #1a1a1a;
    --bg-secondary: #242424;
    --bg-tertiary: #2a2a2a;
    --bg-card: #222222;

    --text-primary: #f5f5f5;
    --text-secondary: #b0b0b0;
    --text-muted: #707070;

    --border-color: #333333;
    --border-hover: #444444;
}

/* ========================================
   Reset & Base
   ======================================== */

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

html {
    scroll-behavior: smooth;
    scroll-padding-top: 80px;
    font-size: 18px;
}

body {
    font-family: var(--font-body);
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    font-size: 20px;
    transition: background-color var(--transition-base), color var(--transition-base);
}

a {
    color: var(--accent-primary);
    text-decoration: none;
    transition: color var(--transition-fast);
}

a:hover {
    text-decoration: underline;
}

/* ========================================
   Navigation - Simple Top Bar
   ======================================== */

.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    transition: all var(--transition-base);
}

.nav-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--space-md) var(--space-xl);
    max-width: 1000px;
    margin: 0 auto;
}

.nav-logo {
    font-family: var(--font-display);
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
    text-decoration: none;
}

.nav-logo:hover {
    text-decoration: none;
}

.logo-bracket, .logo-text {
    color: var(--text-primary);
    -webkit-text-fill-color: var(--text-primary);
    background: none;
}

.nav-links {
    display: flex;
    gap: 2.5rem;
}

.nav-links a {
    font-size: 0.9rem;
    color: var(--text-secondary);
    text-decoration: none;
}

.nav-links a:hover {
    color: var(--text-primary);
    text-decoration: none;
}

.nav-controls {
    display: flex;
    align-items: center;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 2px;
}

.nav-btn {
    display: flex;
    align-items: center;
    gap: 4px;
    padding: 4px 10px;
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--text-secondary);
    background: transparent;
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.nav-btn:hover {
    color: var(--accent-primary);
    background: var(--bg-tertiary);
}

.nav-btn-icon {
    width: 14px;
    height: 14px;
    flex-shrink: 0;
}

.nav-btn-label {
    white-space: nowrap;
}

.nav-divider {
    width: 1px;
    height: 16px;
    background: var(--border-color);
    margin: 0 2px;
}

.sun-icon { display: block; }
.moon-icon { display: none; }

[data-theme="dark"] .sun-icon { display: none; }
[data-theme="dark"] .moon-icon { display: block; }

[data-theme="dark"] .theme-label::after { content: "Light"; }
[data-theme="light"] .theme-label::after { content: "Dark"; }

.theme-label {
    font-size: 0;
}

.theme-label::after {
    font-size: 0.8rem;
}

/* ========================================
   Hero - Compact Sidebar Layout
   ======================================== */

.hero {
    min-height: auto;
    display: flex;
    align-items: flex-start;
    padding: 110px var(--space-xl) var(--space-2xl);
}

.hero-bg {
    display: none;
}

.hero-content {
    max-width: 1000px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: var(--sidebar-width) 1fr;
    gap: var(--space-2xl);
    align-items: center;
    width: 100%;
}

.hero-greeting {
    display: none;
}

.hero-name {
    font-family: var(--font-display);
    font-size: 1.5rem;
    font-weight: 600;
    line-height: 1.3;
    margin-bottom: var(--space-sm);
    color: var(--text-primary);
}

.hero-title {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: var(--space-lg);
    font-style: normal;
    line-height: 1.5;
}

.hero-description {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: var(--space-xl);
}

.highlight {
    color: var(--accent-primary);
    font-weight: 500;
}

.hero-stats {
    display: flex;
    gap: var(--space-xl);
    margin-bottom: var(--space-xl);
    padding: var(--space-lg) 0;
    border-top: 1px solid var(--border-color);
    border-bottom: 1px solid var(--border-color);
}

.stat-number {
    font-family: var(--font-display);
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
}

.stat-label {
    font-size: 0.7rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.hero-cta {
    display: flex;
    gap: var(--space-md);
}

.btn {
    padding: var(--space-sm) var(--space-lg);
    font-size: 0.85rem;
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
    cursor: pointer;
}

.btn-primary {
    background: var(--accent-primary);
    color: white;
    border: none;
}

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

.btn-secondary {
    background: transparent;
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    border-color: var(--text-primary);
}

.hero-image {
    order: -1;
}

.image-frame {
    width: 200px;
    height: 200px;
    border-radius: 50%;
    overflow: hidden;
    border: 2px solid var(--border-color);
    padding: 0;
    background: none;
    box-shadow: none;
}

.profile-photo {
    width: 100%;
    height: 100%;
    object-fit: cover;
    object-position: center;
}

.image-placeholder {
    width: 100%;
    height: 100%;
    background: var(--bg-tertiary);
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
}

.image-placeholder svg {
    width: 50px;
    height: 50px;
    color: var(--text-muted);
}

/* ========================================
   Sections Base
   ======================================== */

.section {
    padding: var(--space-2xl) var(--space-xl);
}

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

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

.section-title {
    font-family: var(--font-display);
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: var(--space-xl);
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    border-bottom: 2px solid var(--accent-primary);
    padding-bottom: var(--space-md);
}

.title-icon {
    color: var(--accent-primary);
    font-weight: 400;
}

/* ========================================
   Publications - Compact List
   ======================================== */

.publications-filter {
    display: flex;
    gap: var(--space-sm);
    margin-bottom: var(--space-lg);
}

.filter-btn {
    padding: 2px var(--space-md);
    font-size: 0.8rem;
    color: var(--text-secondary);
    background: transparent;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.filter-btn:hover {
    border-color: var(--accent-primary);
    color: var(--accent-primary);
}

.filter-btn.active {
    background: var(--accent-primary);
    color: white;
    border-color: var(--accent-primary);
}

.publications-list {
    display: flex;
    flex-direction: column;
    gap: var(--space-lg);
}

.pub-card {
    display: grid;
    grid-template-columns: 50px 1fr;
    gap: var(--space-lg);
    padding-bottom: var(--space-lg);
    border-bottom: 1px solid var(--border-color);
}

.pub-card:last-child {
    border-bottom: none;
}

.pub-card:hover {
    transform: none;
    box-shadow: none;
}

.pub-year {
    font-family: var(--font-mono);
    font-size: 0.8rem;
    color: var(--text-muted);
}

.pub-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: var(--space-md);
    margin-bottom: 2px;
}

.pub-title {
    font-family: var(--font-display);
    font-size: 0.95rem;
    font-weight: 600;
    line-height: 1.4;
    color: var(--text-primary);
    flex: 1;
    min-width: 0;
}

.pub-authors {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: 2px;
}

.pub-venue {
    font-size: 0.8rem;
    color: var(--text-muted);
    font-style: italic;
    margin-bottom: var(--space-sm);
}

.pub-links {
    display: flex;
    gap: var(--space-sm);
    flex-shrink: 0;
    white-space: nowrap;
}

.pub-link {
    font-size: 0.75rem;
    padding: 1px var(--space-sm);
    color: var(--accent-primary);
    border: 1px solid var(--accent-primary);
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
}

.pub-link:hover {
    background: var(--accent-primary);
    color: white;
    text-decoration: none;
}

/* ========================================
   Projects - Compact Cards
   ======================================== */

.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: var(--space-lg);
}

.project-card {
    padding: var(--space-lg);
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    transition: border-color var(--transition-fast);
    cursor: pointer;
}

.project-card:hover {
    border-color: var(--accent-primary);
}

.project-icon {
    width: 32px;
    height: 32px;
    margin-bottom: var(--space-md);
    color: var(--accent-primary);
}

.project-icon svg {
    width: 100%;
    height: 100%;
}

.project-title {
    font-family: var(--font-display);
    font-size: 0.95rem;
    font-weight: 600;
    margin-bottom: var(--space-sm);
}

.project-desc {
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.5;
    margin-bottom: var(--space-md);
}

.project-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 4px;
    margin-bottom: var(--space-md);
}

.tag {
    font-family: var(--font-mono);
    font-size: 0.65rem;
    padding: 1px var(--space-sm);
    background: var(--bg-tertiary);
    border-radius: var(--radius-sm);
    color: var(--text-muted);
}

.project-links {
    display: flex;
    gap: var(--space-md);
}

.project-link {
    display: flex;
    align-items: center;
    gap: 4px;
    font-size: 0.8rem;
    color: var(--accent-primary);
}

.project-link:hover {
    text-decoration: underline;
}

.project-link svg {
    width: 14px;
    height: 14px;
}

.project-stars {
    font-size: 0.8rem;
    color: var(--text-muted);
}

/* ========================================
   News - Compact Timeline
   ======================================== */

.news-timeline {
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
}

.news-item {
    display: grid;
    grid-template-columns: 85px 1fr;
    gap: var(--space-md);
    padding: var(--space-md) 0;
    border-bottom: 1px solid var(--border-color);
}

.news-item:last-child {
    border-bottom: none;
}

.news-date {
    font-family: var(--font-mono);
    font-size: 0.85rem;
    color: var(--text-muted);
}

.news-content {
    display: flex;
    flex-direction: row;
    align-items: baseline;
    gap: var(--space-sm);
    flex-wrap: wrap;
}

.news-badge {
    display: inline-block;
    font-size: 0.7rem;
    padding: 1px 6px;
    border-radius: var(--radius-sm);
    background: var(--accent-primary);
    color: white;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    flex-shrink: 0;
    min-width: 45px;
    text-align: center;
}

.news-text {
    color: var(--text-secondary);
    line-height: 1.5;
    font-size: 0.9rem;
}

/* ========================================
   Experience - Compact Two Column
   ======================================== */

.experience-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-xl);
}

.exp-category {
    font-family: var(--font-display);
    font-size: 1rem;
    font-weight: 600;
    color: var(--accent-primary);
    margin-bottom: var(--space-lg);
    padding-bottom: var(--space-sm);
    border-bottom: 2px solid var(--accent-primary);
}

.exp-item {
    padding: var(--space-md) 0;
    border-bottom: 1px solid var(--border-color);
}

.exp-item:last-child {
    border-bottom: none;
}

.exp-period {
    font-family: var(--font-mono);
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-bottom: 2px;
}

.exp-title {
    font-size: 0.95rem;
    font-weight: 600;
    margin-bottom: 2px;
}

.exp-org {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 2px;
}

.exp-desc {
    font-size: 0.85rem;
    color: var(--text-muted);
}

/* ========================================
   Contact - Compact Centered
   ======================================== */

.contact-content {
    text-align: center;
    max-width: 500px;
    margin: 0 auto;
}

.contact-intro {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: var(--space-lg);
}

.contact-links {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: var(--space-sm);
}

.contact-item {
    display: flex;
    align-items: center;
    gap: 4px;
    padding: 4px var(--space-md);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    font-size: 0.8rem;
    transition: all var(--transition-fast);
    cursor: pointer;
}

.contact-item:hover {
    border-color: var(--accent-primary);
    color: var(--accent-primary);
    text-decoration: none;
}

.contact-item svg {
    width: 14px;
    height: 14px;
}

/* ========================================
   Footer - Compact
   ======================================== */

.footer {
    padding: var(--space-md) var(--space-xl);
    border-top: 1px solid var(--border-color);
    text-align: center;
}

.footer-content p {
    font-size: 0.75rem;
    color: var(--text-muted);
}

.visitor-stats {
    margin-top: var(--space-sm);
    font-size: 0.7rem;
    display: flex;
    justify-content: center;
    align-items: center;
    gap: var(--space-sm);
}

.visitor-stats svg {
    opacity: 0.7;
}

.stat-divider {
    color: var(--border-color);
}

/* ========================================
   Responsive Design
   ======================================== */

@media (max-width: 768px) {
    .nav-links {
        display: none;
    }

    .hero {
        padding: 70px var(--space-md) var(--space-xl);
    }

    .hero-content {
        grid-template-columns: 1fr;
        text-align: center;
    }

    .hero-image {
        order: -1;
        display: flex;
        justify-content: center;
    }

    .image-frame {
        width: 120px;
        height: 120px;
    }

    .hero-name {
        font-size: 1.5rem;
    }

    .hero-stats {
        justify-content: center;
        gap: var(--space-md);
    }

    .hero-cta {
        justify-content: center;
    }

    .section {
        padding: var(--space-xl) var(--space-md);
    }

    .pub-card {
        grid-template-columns: 1fr;
    }

    .pub-year {
        margin-bottom: var(--space-xs);
    }

    .news-item {
        grid-template-columns: 1fr;
    }

    .news-date {
        margin-bottom: var(--space-xs);
    }

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

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

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

/* ========================================
   Scroll-Triggered Animations
   ======================================== */

/* 基础滚动动画类 - 简洁淡入 */
.scroll-animate {
    opacity: 0;
    transform: translateY(15px);
    transition: opacity 0.4s ease-out, transform 0.4s ease-out;
}

.scroll-animate.visible {
    opacity: 1;
    transform: translateY(0);
}

/* Section 滚动动画 */
.section.scroll-animate {
    transform: translateY(20px);
}

.section.scroll-animate.visible {
    transform: translateY(0);
}

/* 卡片滚动动画 - 简洁风格 */
.pub-card.scroll-animate,
.project-card.scroll-animate,
.news-item.scroll-animate {
    opacity: 0;
    transform: translateY(10px);
    transition: opacity 0.35s ease-out, transform 0.35s ease-out;
}

.pub-card.scroll-animate.visible,
.project-card.scroll-animate.visible,
.news-item.scroll-animate.visible {
    opacity: 1;
    transform: translateY(0);
}

/* 经验项滚动动画 */
.exp-item.scroll-animate {
    opacity: 0;
    transform: translateY(10px);
    transition: opacity 0.3s ease-out, transform 0.3s ease-out;
}

.exp-item.scroll-animate.visible {
    opacity: 1;
    transform: translateY(0);
}

/* 联系项滚动动画 */
.contact-item.scroll-animate {
    opacity: 0;
    transform: translateY(8px);
    transition: opacity 0.25s ease-out, transform 0.25s ease-out;
}

.contact-item.scroll-animate.visible {
    opacity: 1;
    transform: translateY(0);
}

/* Section 标题滚动动画 */
.section-title.scroll-animate {
    opacity: 0;
    transform: translateY(8px);
    transition: opacity 0.4s ease-out, transform 0.4s ease-out;
}

.section-title.scroll-animate.visible {
    opacity: 1;
    transform: translateY(0);
}

/* 筛选按钮滚动动画 */
.filter-btn.scroll-animate {
    opacity: 0;
    transition: opacity 0.25s ease-out;
}

.filter-btn.scroll-animate.visible {
    opacity: 1;
}

/* ========================================
   Navbar Scroll Effect
   ======================================== */

.navbar.scrolled {
    background: var(--bg-primary);
    box-shadow: var(--shadow-md);
}

.navbar.scrolled .nav-container {
    padding: var(--space-xs) var(--space-lg);
}

.navbar.scrolled .nav-logo {
    font-size: 0.9rem;
}

/* ========================================
   Theme Transition Animation
   ======================================== */

.theme-transitioning,
.theme-transitioning *,
.theme-transitioning *::before,
.theme-transitioning *::after {
    transition: background-color 0.5s ease,
                color 0.5s ease,
                border-color 0.5s ease,
                box-shadow 0.5s ease !important;
}

/* ========================================
   Back to Top Button
   ======================================== */

.back-to-top {
    position: fixed;
    bottom: 24px;
    right: 24px;
    width: 40px;
    height: 40px;
    border-radius: var(--radius-sm);
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    color: var(--accent-primary);
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transform: translateY(15px);
    transition: all 0.25s ease;
    z-index: 999;
    display: flex;
    align-items: center;
    justify-content: center;
}

.back-to-top svg {
    width: 18px;
    height: 18px;
}

.back-to-top.visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.back-to-top:hover {
    background: var(--accent-primary);
    color: white;
    border-color: var(--accent-primary);
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {
    *, *::before, *::after {
        animation-duration: 0.01ms !important;
        transition-duration: 0.01ms !important;
    }
}

/* ========================================
   Hide SPA-specific elements
   ======================================== */

.spa-layout {
    display: block;
}

.sidebar {
    display: none;
}

.content-area {
    margin-left: 0;
    padding: 0;
    min-height: auto;
}

.content-section {
    display: block !important;
}

.about-cards,
.about-news-card {
    display: none;
}

.scroll-arrow {
    display: none;
}