/* Xiang Li - Academic Blue-Gray Theme */
/* Clean, restrained, theory-oriented academic style */

:root {
    --primary: #1f3a5f;
    --secondary: #2c4d73;
    --accent: #6f8fb8;
    --accent-dark: #4f6f96;
    --background: #fcfcfd;
    --surface: #f5f7fa;
    --surface-dark: #e6ebf2;
    --text: #243447;
    --text-muted: #5f6f82;
    --text-bright: #162535;
    --gradient: linear-gradient(135deg, #1f3a5f 0%, #314f77 100%);
    --transition: all 0.28s ease;
    --shadow: 0 4px 18px rgba(31, 58, 95, 0.06);
    --shadow-lg: 0 10px 30px rgba(31, 58, 95, 0.10);
    --border-radius: 10px;
    --content-width: 760px;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', Georgia, serif;
    background-color: var(--background);
    color: var(--text);
    line-height: 1.8;
    letter-spacing: 0.01em;
}

h1, h2, h3, h4 {
    font-weight: 600;
    line-height: 1.3;
    color: var(--text-bright);
    letter-spacing: -0.01em;
}

h1 {
    font-size: clamp(2.4rem, 5vw, 3.8rem);
}

h2 {
    font-size: clamp(1.75rem, 4vw, 2.35rem);
}

h3 {
    font-size: 1.1rem;
}

p {
    color: var(--text-muted);
    margin-bottom: 1rem;
}

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

a:hover {
    color: var(--accent-dark);
}

.container {
    max-width: 1120px;
    margin: 0 auto;
    padding: 0 2rem;
}

.container.narrow {
    max-width: 860px;
}

/* Navigation */
nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    padding: 1rem 0;
    background: rgba(252, 252, 253, 0.94);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--surface-dark);
}

nav .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1rem;
    font-weight: 700;
    color: var(--primary);
    padding: 0.45rem 0.75rem;
    background: transparent;
    border: 1px solid var(--surface-dark);
    border-radius: 8px;
    letter-spacing: 0.03em;
}

.nav-links {
    display: flex;
    gap: 1.8rem;
    list-style: none;
}

.nav-links a {
    color: var(--text-muted);
    font-weight: 500;
    font-size: 0.92rem;
}

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

.menu-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    cursor: pointer;
}

.menu-toggle span {
    width: 22px;
    height: 2px;
    background: var(--primary);
    border-radius: 2px;
}

/* Hero */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding: 8.5rem 0 5.5rem;
    background: linear-gradient(180deg, #f7f9fc 0%, var(--background) 60%);
}

.hero-layout {
    display: grid;
    grid-template-columns: 260px minmax(0, 1fr);
    gap: 3.5rem;
    align-items: center;
}

.hero-image img {
    width: 100%;
    border-radius: 12px;
    display: block;
    box-shadow: var(--shadow-lg);
    border: 1px solid var(--surface-dark);
}

.hero-content {
    max-width: 720px;
}

.hero-subtitle {
    color: var(--accent-dark);
    font-size: 0.98rem;
    font-weight: 600;
    margin-bottom: 0.9rem;
    display: flex;
    align-items: center;
    gap: 0.6rem;
    text-transform: none;
    letter-spacing: 0.02em;
}

.hero-subtitle::before {
    content: '';
    width: 28px;
    height: 1.5px;
    background: var(--accent-dark);
}

.hero h1 {
    margin-bottom: 0.4rem;
    color: var(--text-bright);
}

.hero h2 {
    color: var(--text-muted);
    font-weight: 400;
    font-size: 1.2rem;
    margin-bottom: 1.35rem;
}

.hero-description {
    font-size: 1.04rem;
    margin-bottom: 2rem;
    line-height: 1.9;
    max-width: 680px;
}

.hero-links,
.cta-buttons {
    display: flex;
    gap: 0.9rem;
    flex-wrap: wrap;
    margin-bottom: 1.35rem;
}

.hero-meta {
    display: flex;
    gap: 1.2rem;
    flex-wrap: wrap;
    color: var(--text-muted);
    font-size: 0.92rem;
}

.hero-meta span {
    display: inline-flex;
    align-items: center;
    gap: 0.45rem;
}

.btn {
    padding: 0.82rem 1.45rem;
    border-radius: 8px;
    font-weight: 600;
    font-size: 0.92rem;
    border: 1.5px solid;
    cursor: pointer;
    transition: var(--transition);
}

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

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

.btn-outline {
    background: transparent;
    border-color: var(--surface-dark);
    color: var(--primary);
}

.btn-outline:hover {
    background: var(--surface);
    border-color: var(--primary);
    color: var(--primary);
}

.hero-visual {
    display: none;
}

/* Sections */
section {
    padding: 5.5rem 0;
}

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

.section-header {
    text-align: center;
    margin-bottom: 3.25rem;
}

.section-header h2 {
    color: var(--text-bright);
    display: inline-flex;
    align-items: center;
    gap: 0.9rem;
}

.section-header h2::before,
.section-header h2::after {
    content: '';
    width: 32px;
    height: 1.5px;
    background: #c4d0df;
}

/* About */
.about-content,
.academic-about {
    max-width: var(--content-width);
    margin: 0 auto;
}

.about-content h3,
.academic-about h3 {
    color: var(--primary);
    margin-bottom: 1rem;
}

.about-summary-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1rem;
    margin-top: 2.4rem;
}

.summary-card {
    background: white;
    padding: 1.35rem 1.25rem;
    border: 1px solid var(--surface-dark);
    border-radius: var(--border-radius);
    box-shadow: none;
}

.summary-card h3 {
    font-size: 0.98rem;
    margin-bottom: 0.55rem;
    color: var(--text-bright);
}

.summary-card p {
    font-size: 0.9rem;
    line-height: 1.7;
    margin-bottom: 0;
}

/* Optional old education cards */
.education-cards {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1.25rem;
    margin-top: 2.5rem;
}

.edu-card {
    padding: 1.35rem;
    background: white;
    border-radius: var(--border-radius);
    border: 1px solid var(--surface-dark);
    box-shadow: none;
    display: flex;
    gap: 1rem;
    transition: var(--transition);
}

.edu-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow);
}

.edu-icon {
    width: 44px;
    height: 44px;
    background: var(--surface);
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--primary);
    font-size: 1.15rem;
    flex-shrink: 0;
}

.edu-info h4 {
    font-size: 0.95rem;
    margin-bottom: 0.25rem;
}

.edu-info p {
    font-size: 0.82rem;
    margin-bottom: 0.25rem;
}

.edu-year {
    font-size: 0.76rem;
    color: var(--accent-dark);
    font-weight: 600;
}

/* Timeline */
.timeline {
    max-width: 760px;
    margin: 0 auto;
    position: relative;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 2px;
    background: var(--surface-dark);
    border-radius: 2px;
}

.timeline-item {
    padding-left: 32px;
    margin-bottom: 2rem;
    position: relative;
}

.timeline-marker {
    position: absolute;
    left: -5px;
    top: 6px;
    width: 12px;
    height: 12px;
    background: var(--accent);
    border-radius: 50%;
    border: 2px solid var(--background);
}

.timeline-content {
    background: white;
    padding: 1.35rem 1.4rem;
    border-radius: var(--border-radius);
    border: 1px solid var(--surface-dark);
    box-shadow: none;
}

.timeline-header h3 {
    font-size: 1.05rem;
    margin-bottom: 0.2rem;
}

.timeline-header .company {
    color: var(--primary);
    font-weight: 500;
}

.timeline-header .date {
    color: var(--text-muted);
    font-size: 0.84rem;
}

.timeline-details {
    padding-left: 1.1rem;
    margin-top: 0.9rem;
}

.timeline-details li {
    margin-bottom: 0.45rem;
    color: var(--text-muted);
    font-size: 0.94rem;
}

/* Research */
.research-grid,
.academic-research-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1.25rem;
}

.research-card {
    padding: 1.7rem;
    background: white;
    border-radius: var(--border-radius);
    border: 1px solid var(--surface-dark);
    box-shadow: none;
    border-left: 3px solid #c7d5e6;
    transition: var(--transition);
}

.research-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow);
    border-left-color: var(--accent-dark);
}

.research-icon {
    width: 50px;
    height: 50px;
    background: var(--surface);
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.35rem;
    color: var(--primary);
    margin-bottom: 1.2rem;
}

.research-card h3 {
    font-size: 1.02rem;
    margin-bottom: 0.55rem;
}

.research-venue {
    color: var(--accent-dark);
    font-size: 0.84rem;
    font-weight: 500;
    margin-bottom: 0.9rem;
}

.research-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.45rem;
    margin-top: 1rem;
}

.research-tags span {
    background: #f3f6fa;
    color: var(--secondary);
    padding: 0.28rem 0.68rem;
    border-radius: 999px;
    font-size: 0.74rem;
    font-weight: 500;
    border: 1px solid #dbe4ef;
}

/* Publications */
.publications-list,
.academic-publications {
    max-width: 760px;
    margin: 0 auto;
}

.pub-category {
    margin-bottom: 2rem;
}

.pub-category h3 {
    color: var(--text-bright);
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.65rem;
    font-size: 1rem;
    font-weight: 600;
}

.pub-category h3 i {
    color: var(--accent-dark);
}

.pub-item {
    background: white;
    padding: 1.35rem 1.4rem;
    border-radius: var(--border-radius);
    margin-bottom: 0.9rem;
    border: 1px solid var(--surface-dark);
    box-shadow: none;
    border-left: 3px solid transparent;
    transition: var(--transition);
}

.pub-item:hover {
    border-left-color: var(--accent-dark);
    box-shadow: var(--shadow);
}

.pub-content h4 {
    font-size: 0.96rem;
    margin-bottom: 0.45rem;
    line-height: 1.65;
    font-weight: 600;
}

.pub-journal {
    color: var(--text-muted);
    font-size: 0.85rem;
    font-style: italic;
}

/* Optional conferences section */
.conferences-section {
    margin-top: 3rem;
}

.conferences-section h3 {
    color: var(--text-bright);
    margin-bottom: 1.25rem;
    font-size: 1rem;
}

.conferences-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 0.9rem;
}

.conf-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 0.8rem 1rem;
    background: white;
    border-radius: 8px;
    border: 1px solid var(--surface-dark);
    box-shadow: none;
}

.conf-year {
    background: var(--primary);
    color: white;
    padding: 0.24rem 0.58rem;
    border-radius: 4px;
    font-weight: 600;
    font-size: 0.78rem;
}

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

/* Teaching */
.teaching-list {
    max-width: 760px;
    margin: 0 auto;
}

.teaching-item {
    background: white;
    padding: 1.45rem 1.5rem;
    border-radius: var(--border-radius);
    border: 1px solid var(--surface-dark);
}

.teaching-item h3 {
    margin-bottom: 0.35rem;
}

.teaching-meta {
    color: var(--primary);
    font-size: 0.9rem;
    margin-bottom: 0.75rem;
}

/* Skills (kept compatible, but visually toned down) */
.skills-container {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1.25rem;
}

.skill-category {
    padding: 1.7rem;
    background: white;
    border-radius: var(--border-radius);
    border: 1px solid var(--surface-dark);
    box-shadow: none;
    transition: var(--transition);
}

.skill-category:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow);
}

.skill-icon {
    width: 52px;
    height: 52px;
    background: var(--surface);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.35rem;
    color: var(--primary);
    margin-bottom: 1.2rem;
}

.skill-category h3 {
    margin-bottom: 0.9rem;
    color: var(--text-bright);
}

.skill-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.45rem;
}

.skill-tag {
    background: #f4f7fb;
    color: var(--text);
    padding: 0.38rem 0.82rem;
    border-radius: 999px;
    font-size: 0.79rem;
    font-weight: 500;
    border: 1px solid #dde6f1;
    transition: var(--transition);
}

.skill-tag:hover {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

/* Contact */
.contact-content,
.academic-contact {
    max-width: 760px;
    margin: 0 auto;
}

.contact-content {
    display: block;
}

.contact-content p {
    margin-bottom: 1.4rem;
}

.contact-links,
.simple-contact-links {
    display: flex;
    flex-direction: column;
    gap: 0.7rem;
}

.contact-link {
    display: flex;
    align-items: center;
    gap: 0.95rem;
    padding: 0.95rem 1rem;
    background: white;
    border-radius: 8px;
    color: var(--text-muted);
    border: 1px solid var(--surface-dark);
    box-shadow: none;
    transition: var(--transition);
}

.contact-link:hover {
    color: var(--primary);
    transform: translateX(3px);
    box-shadow: var(--shadow);
}

.contact-link i {
    color: var(--accent-dark);
    width: 18px;
    text-align: center;
}

/* Legacy contact form support */
.contact-info h3 {
    color: var(--primary);
    margin-bottom: 1.2rem;
}

.contact-form {
    display: flex;
    flex-direction: column;
    gap: 1.1rem;
    margin-top: 2rem;
}

.form-group label {
    font-size: 0.84rem;
    color: var(--text-muted);
    margin-bottom: 0.45rem;
    display: block;
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: 0.95rem 1rem;
    background: white;
    border: 1.5px solid var(--surface-dark);
    border-radius: 8px;
    color: var(--text);
    font-size: 0.98rem;
    transition: var(--transition);
}

.form-group input:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(111, 143, 184, 0.12);
}

.form-group textarea {
    min-height: 120px;
    resize: vertical;
}

/* Footer */
footer {
    padding: 2.5rem 0;
    text-align: center;
    background: var(--surface);
    border-top: 1px solid var(--surface-dark);
}

.social-links {
    display: flex;
    justify-content: center;
    gap: 0.9rem;
    margin-bottom: 1.2rem;
}

.social-link {
    width: 42px;
    height: 42px;
    background: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--primary);
    font-size: 1rem;
    border: 1px solid var(--surface-dark);
    box-shadow: none;
    transition: var(--transition);
}

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

footer p {
    font-size: 0.84rem;
    color: var(--text-muted);
    margin-bottom: 0;
}

/* About Image */
.about-image img {
    width: 100%;
    border-radius: 12px;
    box-shadow: var(--shadow);
    border: 1px solid var(--surface-dark);
}

/* Animations */
.animate {
    animation: fadeInUp 0.6s ease-out forwards;
    opacity: 0;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(18px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.animate-delay-1 { animation-delay: 0.08s; }
.animate-delay-2 { animation-delay: 0.16s; }
.animate-delay-3 { animation-delay: 0.24s; }
.animate-delay-4 { animation-delay: 0.32s; }

/* Responsive */
@media (max-width: 900px) {
    .hero-layout {
        grid-template-columns: 1fr;
        gap: 2rem;
    }

    .hero-image {
        max-width: 240px;
    }

    .about-summary-grid,
    .research-grid,
    .academic-research-grid,
    .skills-container,
    .education-cards {
        grid-template-columns: 1fr;
    }
}

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

    .menu-toggle {
        display: flex;
    }

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

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

    .about-image {
        max-width: 250px;
        margin: 0 auto 2rem;
    }

    .container {
        padding: 0 1.25rem;
    }

    section {
        padding: 4.5rem 0;
    }

    .hero {
        padding: 7.5rem 0 4.5rem;
    }

    .hero-links,
    .cta-buttons,
    .hero-meta {
        gap: 0.75rem;
    }
}