/* ============================================
   Zihua Wang - Academic Personal Homepage
   Modern, clean design with subtle animations
   ============================================ */

/* --- CSS Variables --- */
:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --primary-light: #dbeafe;
    --accent: #0ea5e9;
    --text: #1e293b;
    --text-secondary: #64748b;
    --text-light: #94a3b8;
    --bg: #ffffff;
    --bg-alt: #f8fafc;
    --bg-card: #ffffff;
    --border: #e2e8f0;
    --shadow: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.07), 0 2px 4px -2px rgba(0,0,0,0.05);
    --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.08), 0 4px 6px -4px rgba(0,0,0,0.05);
    --radius: 12px;
    --radius-sm: 8px;
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-serif: 'Source Serif 4', Georgia, serif;
    --max-width: 1100px;
    --nav-height: 64px;
}

/* --- Reset & Base --- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; scroll-padding-top: var(--nav-height); }
body {
    font-family: var(--font-sans);
    color: var(--text);
    background: var(--bg);
    line-height: 1.7;
    font-size: 15px;
    -webkit-font-smoothing: antialiased;
}
a { color: var(--primary); text-decoration: none; transition: color 0.2s; }
a:hover { color: var(--primary-dark); }
ul { list-style: none; }
img { max-width: 100%; display: block; }

.container { max-width: var(--max-width); margin: 0 auto; padding: 0 24px; }

/* --- Navigation --- */
.navbar {
    position: fixed; top: 0; left: 0; right: 0; z-index: 100;
    background: rgba(255,255,255,0.85);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid transparent;
    transition: border-color 0.3s, box-shadow 0.3s;
    height: var(--nav-height);
}
.navbar.scrolled {
    border-bottom-color: var(--border);
    box-shadow: 0 1px 3px rgba(0,0,0,0.04);
}
.nav-container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 100%;
}
.nav-logo {
    font-weight: 700;
    font-size: 1.15rem;
    color: var(--text);
    letter-spacing: -0.02em;
}
.nav-menu {
    display: flex;
    gap: 32px;
}
.nav-menu a {
    color: var(--text-secondary);
    font-size: 0.9rem;
    font-weight: 500;
    transition: color 0.2s;
    position: relative;
}
.nav-menu a::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0; right: 0;
    height: 2px;
    background: var(--primary);
    transform: scaleX(0);
    transition: transform 0.25s ease;
}
.nav-menu a:hover, .nav-menu a.active { color: var(--text); }
.nav-menu a:hover::after, .nav-menu a.active::after { transform: scaleX(1); }

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 4px;
}
.nav-toggle span {
    display: block; width: 22px; height: 2px;
    background: var(--text);
    border-radius: 2px;
    transition: transform 0.3s, opacity 0.3s;
}

/* --- Hero Section --- */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    position: relative;
    padding-top: var(--nav-height);
    overflow: hidden;
}
.hero-bg {
    position: absolute;
    inset: 0;
    background:
        radial-gradient(ellipse 80% 50% at 50% -20%, rgba(37,99,235,0.08), transparent),
        radial-gradient(ellipse 60% 40% at 80% 80%, rgba(14,165,233,0.06), transparent);
}
.hero-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 60px;
    position: relative;
    z-index: 1;
}
.hero-text { flex: 1; }
.hero-greeting {
    font-size: 1rem;
    color: var(--primary);
    font-weight: 500;
    margin-bottom: 8px;
    letter-spacing: 0.05em;
    text-transform: uppercase;
}
.hero-name {
    font-size: 3.2rem;
    font-weight: 700;
    letter-spacing: -0.03em;
    line-height: 1.15;
    margin-bottom: 12px;
    color: var(--text);
}
.hero-name-cn {
    display: inline-block;
    font-size: 1.8rem;
    font-weight: 400;
    color: var(--text-secondary);
    margin-left: 8px;
    vertical-align: baseline;
}
.hero-title {
    font-size: 1.2rem;
    color: var(--text-secondary);
    margin-bottom: 4px;
}
.hero-affiliation {
    font-size: 1.05rem;
    color: var(--text-light);
    margin-bottom: 8px;
}
.hero-research {
    font-size: 0.95rem;
    color: var(--primary);
    font-weight: 500;
    padding: 6px 14px;
    background: var(--primary-light);
    border-radius: 20px;
    display: inline-block;
    margin-bottom: 28px;
}
.hero-links { display: flex; gap: 12px; flex-wrap: wrap; }

.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 22px;
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    font-weight: 500;
    transition: all 0.2s ease;
    cursor: pointer;
    border: none;
}
.btn-primary {
    background: var(--primary);
    color: #fff;
}
.btn-primary:hover {
    background: var(--primary-dark);
    color: #fff;
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}
.btn-outline {
    background: var(--bg);
    color: var(--text);
    border: 1px solid var(--border);
}
.btn-outline:hover {
    border-color: var(--primary);
    color: var(--primary);
    transform: translateY(-1px);
    box-shadow: var(--shadow);
}

.hero-avatar {
    flex-shrink: 0;
}
.avatar-img {
    width: 220px; height: 220px;
    border-radius: 50%;
    object-fit: cover;
    object-position: center top;
    box-shadow: var(--shadow-lg);
    border: 4px solid #fff;
}

.scroll-indicator {
    position: absolute;
    bottom: 32px;
    left: 50%;
    transform: translateX(-50%);
    animation: float 2s ease-in-out infinite;
}
.scroll-indicator a {
    color: var(--text-light);
    font-size: 1.2rem;
}
@keyframes float {
    0%, 100% { transform: translateX(-50%) translateY(0); }
    50% { transform: translateX(-50%) translateY(8px); }
}

/* --- Sections --- */
.section { padding: 80px 0; }
.section-alt { background: var(--bg-alt); }
.section-title {
    font-size: 1.8rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    margin-bottom: 12px;
    position: relative;
    display: inline-block;
}
.section-title::after {
    content: '';
    display: block;
    width: 40px; height: 3px;
    background: var(--primary);
    border-radius: 2px;
    margin-top: 8px;
}
.section-subtitle {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: 40px;
}

/* --- About --- */
.about-content {
    display: grid;
    grid-template-columns: 1.5fr 1fr;
    gap: 48px;
    margin-top: 32px;
}
.about-text p { margin-bottom: 16px; color: var(--text); }
.research-list { margin-top: 12px; }
.research-list li {
    display: flex; align-items: center; gap: 12px;
    padding: 8px 0;
    color: var(--text);
    font-size: 0.95rem;
}
.research-list li i {
    color: var(--primary);
    width: 20px;
    text-align: center;
    font-size: 0.85rem;
}
.info-card {
    background: var(--bg-alt);
    border-radius: var(--radius);
    padding: 24px;
    margin-bottom: 16px;
}
.info-card h3 {
    font-size: 0.85rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-light);
    margin-bottom: 14px;
}
.info-list li {
    display: flex; align-items: center; gap: 10px;
    padding: 6px 0;
    font-size: 0.9rem;
}
.info-list li i {
    color: var(--primary);
    width: 18px;
    text-align: center;
    font-size: 0.8rem;
}
.skill-tags { display: flex; flex-wrap: wrap; gap: 8px; }
.tag {
    padding: 4px 12px;
    background: var(--primary-light);
    color: var(--primary);
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 500;
}

/* --- News --- */
.news-list { margin-top: 32px; }
.news-item {
    display: flex;
    gap: 20px;
    padding: 14px 0;
    border-bottom: 1px solid var(--border);
    align-items: baseline;
}
.news-item:last-child { border-bottom: none; }
.news-date {
    flex-shrink: 0;
    font-size: 0.85rem;
    color: var(--primary);
    font-weight: 600;
    min-width: 80px;
    font-variant-numeric: tabular-nums;
}
.news-text {
    font-size: 0.93rem;
    color: var(--text);
}

/* --- Publications --- */
.pub-list { margin-top: 16px; }
.pub-item {
    padding: 24px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    margin-bottom: 16px;
    background: var(--bg-card);
    transition: box-shadow 0.2s, transform 0.2s;
}
.pub-item:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-1px);
}
.pub-venue {
    display: flex; align-items: center; gap: 10px;
    margin-bottom: 10px;
}
.venue-badge {
    font-size: 0.75rem;
    font-weight: 700;
    padding: 3px 10px;
    border-radius: 4px;
    text-transform: uppercase;
    letter-spacing: 0.04em;
}
.venue-journal { background: #dcfce7; color: #166534; }
.venue-conf { background: #dbeafe; color: #1e40af; }
.venue-preprint { background: #fef3c7; color: #92400e; }
.venue-rank { font-size: 0.8rem; color: var(--text-light); }
.pub-title {
    font-family: var(--font-serif);
    font-size: 1.08rem;
    font-weight: 600;
    line-height: 1.45;
    margin-bottom: 6px;
    color: var(--text);
}
.pub-authors {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: 8px;
}
.pub-desc {
    font-size: 0.87rem;
    color: var(--text-secondary);
    line-height: 1.6;
}
.pub-links {
    display: flex; gap: 10px; margin-top: 12px; flex-wrap: wrap;
}
.pub-tag {
    display: inline-flex; align-items: center; gap: 5px;
    font-size: 0.78rem;
    padding: 3px 10px;
    border-radius: 20px;
    font-weight: 500;
}
.pub-tag.first-author { background: #fef3c7; color: #92400e; }
.pub-link {
    display: inline-flex; align-items: center; gap: 5px;
    font-size: 0.82rem;
    padding: 4px 12px;
    border: 1px solid var(--border);
    border-radius: 20px;
    color: var(--text-secondary);
    transition: all 0.2s;
}
.pub-link:hover { border-color: var(--primary); color: var(--primary); }
.pub-coauthor { opacity: 0.8; }
.pub-coauthor:hover { opacity: 1; }

/* --- Experience Timeline --- */
.timeline { margin-top: 32px; position: relative; padding-left: 32px; }
.timeline::before {
    content: '';
    position: absolute;
    left: 7px; top: 8px; bottom: 8px;
    width: 2px;
    background: var(--border);
}
.timeline-item {
    position: relative;
    padding-bottom: 32px;
}
.timeline-item:last-child { padding-bottom: 0; }
.timeline-marker {
    position: absolute;
    left: -32px; top: 6px;
    width: 16px; height: 16px;
    border-radius: 50%;
    background: var(--bg);
    border: 3px solid var(--primary);
    z-index: 1;
}
.timeline-header {
    display: flex;
    justify-content: space-between;
    align-items: baseline;
    gap: 16px;
    flex-wrap: wrap;
}
.timeline-content h3 {
    font-size: 1.1rem;
    font-weight: 600;
}
.timeline-date {
    font-size: 0.85rem;
    color: var(--primary);
    font-weight: 500;
    white-space: nowrap;
}
.timeline-role {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin: 4px 0 10px;
}
.timeline-content ul {
    padding-left: 18px;
    list-style: disc;
}
.timeline-content li {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 4px;
}

/* --- Education --- */
.edu-grid {
    display: grid;
    gap: 20px;
    margin-top: 32px;
}
.edu-card {
    display: flex;
    gap: 20px;
    padding: 24px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    transition: box-shadow 0.2s;
}
.edu-card:hover { box-shadow: var(--shadow-md); }
.edu-icon {
    flex-shrink: 0;
    width: 48px; height: 48px;
    background: var(--primary-light);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--primary);
    font-size: 1.2rem;
}
.edu-info h3 { font-size: 1.05rem; font-weight: 600; }
.edu-degree { font-size: 0.93rem; color: var(--text); margin: 2px 0; }
.edu-dept { font-size: 0.85rem; color: var(--text-secondary); }
.edu-date { font-size: 0.82rem; color: var(--text-light); margin-top: 4px; }

/* --- Awards --- */
.awards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 16px;
    margin-top: 32px;
}
.award-item {
    display: flex;
    align-items: center;
    gap: 14px;
    padding: 18px 20px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: 0.93rem;
    transition: box-shadow 0.2s;
}
.award-item:hover { box-shadow: var(--shadow-md); }
.award-item i {
    color: #f59e0b;
    font-size: 1.1rem;
    flex-shrink: 0;
}

/* --- Footer --- */
.footer {
    padding: 40px 0;
    border-top: 1px solid var(--border);
}
.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.footer-content p { font-size: 0.85rem; color: var(--text-light); }
.visit-counter {
    margin-left: 16px;
    padding: 2px 10px;
    background: var(--bg-alt);
    border-radius: 12px;
    font-size: 0.8rem;
    color: var(--text-secondary);
}
.visit-counter i { margin-right: 4px; font-size: 0.75rem; }
.footer-links {
    display: flex; gap: 18px;
}
.footer-links a {
    color: var(--text-light);
    font-size: 1.1rem;
    transition: color 0.2s;
}
.footer-links a:hover { color: var(--primary); }

/* --- Animations --- */
.fade-in {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.6s ease, transform 0.6s ease;
}
.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}

/* --- Responsive --- */
@media (max-width: 768px) {
    :root { --nav-height: 56px; }
    .nav-toggle { display: flex; }
    .nav-menu {
        position: fixed;
        top: var(--nav-height); left: 0; right: 0;
        background: rgba(255,255,255,0.98);
        backdrop-filter: blur(12px);
        flex-direction: column;
        padding: 20px 24px;
        gap: 16px;
        border-bottom: 1px solid var(--border);
        transform: translateY(-100%);
        opacity: 0;
        pointer-events: none;
        transition: transform 0.3s, opacity 0.3s;
    }
    .nav-menu.open {
        transform: translateY(0);
        opacity: 1;
        pointer-events: auto;
    }
    .hero-content { flex-direction: column-reverse; text-align: center; gap: 32px; }
    .hero-links { justify-content: center; }
    .hero-name { font-size: 2.2rem; }
    .hero-name-cn { display: block; margin-left: 0; margin-top: 4px; }
    .avatar-img { width: 160px; height: 160px; }
    .about-content { grid-template-columns: 1fr; gap: 32px; }
    .section { padding: 56px 0; }
    .section-title { font-size: 1.5rem; }
    .news-item { flex-direction: column; gap: 4px; }
    .timeline-header { flex-direction: column; gap: 2px; }
    .footer-content { flex-direction: column; gap: 16px; text-align: center; }
    .awards-grid { grid-template-columns: 1fr; }
    .pub-item { padding: 18px; }
}

@media (max-width: 480px) {
    .hero-name { font-size: 1.8rem; }
    .btn { padding: 8px 16px; font-size: 0.85rem; }
    .hero-links { gap: 8px; }
}