/* ========================================
   CSS Custom Properties
   ======================================== */
:root {
    /* Colors */
    --color-bg: #fafafa;
    --color-bg-alt: #ffffff;
    --color-surface: #f0f0f0;
    --color-text: #1a1a2e;
    --color-text-secondary: #555570;
    --color-text-muted: #8888a0;
    --color-accent: #2d5a7b;
    --color-accent-light: #3a7ca5;
    --color-accent-glow: rgba(45, 90, 123, 0.15);
    --color-border: #e0e0e8;
    --color-hero-bg: #0f1624;
    --color-hero-text: #e8eaf0;
    --color-hero-muted: #8892a8;
    --color-tag-proficient: #2d5a7b;
    --color-tag-working: #6b7c93;

    /* Typography */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-serif: 'Source Serif 4', Georgia, 'Times New Roman', serif;

    /* Spacing */
    --section-padding: 6rem 0;
    --container-width: 1080px;

    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-medium: 0.4s ease;
    --transition-slow: 0.6s ease;
}

/* ========================================
   Reset & Base
   ======================================== */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: var(--font-sans);
    color: var(--color-text);
    background-color: var(--color-bg);
    line-height: 1.7;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    overflow-x: hidden;
}

img {
    max-width: 100%;
    display: block;
}

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

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

/* ========================================
   Utility
   ======================================== */
.container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 2rem;
}

.section {
    padding: var(--section-padding);
}

.section-title {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    letter-spacing: -0.02em;
}

.section-subtitle {
    color: var(--color-text-secondary);
    font-size: 1.05rem;
    max-width: 640px;
    margin-bottom: 3rem;
    line-height: 1.7;
}

/* ========================================
   Reveal Animation
   ======================================== */
.reveal {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.7s cubic-bezier(0.16, 1, 0.3, 1),
                transform 0.7s cubic-bezier(0.16, 1, 0.3, 1);
}

.reveal.visible {
    opacity: 1;
    transform: translateY(0);
}

/* Stagger children */
.reveal-delay-1 { transition-delay: 0.1s; }
.reveal-delay-2 { transition-delay: 0.2s; }
.reveal-delay-3 { transition-delay: 0.3s; }

/* ========================================
   Navigation
   ======================================== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    padding: 1rem 0;
    transition: background-color var(--transition-medium),
                padding var(--transition-medium),
                box-shadow var(--transition-medium);
}

.navbar.scrolled {
    background-color: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    padding: 0.6rem 0;
    box-shadow: 0 1px 12px rgba(0, 0, 0, 0.06);
}

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

.nav-logo {
    font-weight: 700;
    font-size: 1.25rem;
    color: var(--color-hero-text);
    letter-spacing: 0.04em;
    transition: color var(--transition-fast);
}

.navbar.scrolled .nav-logo {
    color: var(--color-text);
}

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

.nav-link {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-hero-muted);
    letter-spacing: 0.02em;
    position: relative;
    padding: 0.25rem 0;
    transition: color var(--transition-fast);
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--color-accent);
    transition: width var(--transition-medium);
}

.nav-link:hover,
.nav-link.active {
    color: var(--color-hero-text);
}

.nav-link:hover::after,
.nav-link.active::after {
    width: 100%;
}

.navbar.scrolled .nav-link {
    color: var(--color-text-muted);
}

.navbar.scrolled .nav-link:hover,
.navbar.scrolled .nav-link.active {
    color: var(--color-text);
}

/* Mobile toggle */
.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 4px;
}

.nav-toggle span {
    display: block;
    width: 24px;
    height: 2px;
    background-color: var(--color-hero-text);
    transition: all var(--transition-fast);
}

.navbar.scrolled .nav-toggle span {
    background-color: var(--color-text);
}

/* ========================================
   Hero
   ======================================== */
.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: var(--color-hero-bg);
    overflow: hidden;
}

#network-canvas {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    opacity: 0.4;
}

.hero-content {
    position: relative;
    z-index: 2;
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 2rem;
    display: flex;
    align-items: center;
    gap: 4rem;
    width: 100%;
}

.hero-text {
    flex: 1;
}

.hero-greeting {
    font-size: 1rem;
    font-weight: 500;
    color: var(--color-accent-light);
    letter-spacing: 0.08em;
    text-transform: uppercase;
    margin-bottom: 0.5rem;
}

.hero-name {
    font-size: clamp(2.5rem, 5vw, 3.5rem);
    font-weight: 700;
    color: var(--color-hero-text);
    line-height: 1.1;
    letter-spacing: -0.03em;
    margin-bottom: 0.75rem;
}

.accent-dot {
    color: var(--color-accent-light);
}

.hero-title {
    font-family: var(--font-serif);
    font-size: 1.2rem;
    color: var(--color-hero-muted);
    margin-bottom: 1.25rem;
    font-style: italic;
}

.hero-tagline {
    font-size: 1.1rem;
    color: var(--color-hero-muted);
    max-width: 520px;
    line-height: 1.7;
    margin-bottom: 2rem;
}

.hero-cta {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    padding: 0.75rem 1.75rem;
    border-radius: 6px;
    font-size: 0.9rem;
    font-weight: 600;
    letter-spacing: 0.02em;
    transition: all var(--transition-fast);
    cursor: pointer;
    border: none;
}

.btn-primary {
    background-color: var(--color-accent);
    color: #fff;
}

.btn-primary:hover {
    background-color: var(--color-accent-light);
    color: #fff;
    transform: translateY(-1px);
    box-shadow: 0 4px 20px rgba(45, 90, 123, 0.35);
}

.btn-outline {
    background-color: transparent;
    color: var(--color-hero-muted);
    border: 1.5px solid rgba(136, 146, 168, 0.3);
}

.btn-outline:hover {
    color: var(--color-hero-text);
    border-color: rgba(136, 146, 168, 0.6);
    transform: translateY(-1px);
}

/* Hero portrait */
.hero-portrait {
    flex-shrink: 0;
}

.portrait-img {
    width: 260px;
    height: 320px;
    border-radius: 12px;
    object-fit: cover;
    object-position: center top;
    border: 2px solid rgba(58, 124, 165, 0.25);
    box-shadow: 0 16px 48px rgba(0, 0, 0, 0.3);
}

/* Scroll indicator */
.scroll-indicator {
    position: absolute;
    bottom: 2rem;
    left: 50%;
    transform: translateX(-50%);
    z-index: 2;
}

.scroll-arrow {
    width: 24px;
    height: 24px;
    border-right: 2px solid var(--color-hero-muted);
    border-bottom: 2px solid var(--color-hero-muted);
    transform: rotate(45deg);
    animation: scrollBounce 2s ease-in-out infinite;
    opacity: 0.5;
}

@keyframes scrollBounce {
    0%, 100% { transform: rotate(45deg) translate(0, 0); opacity: 0.5; }
    50% { transform: rotate(45deg) translate(5px, 5px); opacity: 1; }
}

/* ========================================
   About
   ======================================== */
.about {
    background-color: var(--color-bg-alt);
}

.about-grid {
    display: grid;
    grid-template-columns: 1.3fr 1fr;
    gap: 3rem;
    align-items: start;
}

.about-text p {
    margin-bottom: 1rem;
    color: var(--color-text-secondary);
    font-size: 1.02rem;
}

.about-text strong {
    color: var(--color-text);
    font-weight: 600;
}

.about-highlights {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}

.highlight-card {
    background-color: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: 10px;
    padding: 1.5rem;
    text-align: center;
    transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.highlight-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.06);
}

.highlight-number {
    font-size: 2rem;
    font-weight: 700;
    color: var(--color-accent);
    line-height: 1;
    margin-bottom: 0.35rem;
}

.highlight-label {
    font-size: 0.8rem;
    color: var(--color-text-muted);
    font-weight: 500;
    line-height: 1.3;
}

/* ========================================
   Research
   ======================================== */
.research {
    background-color: var(--color-bg);
}

.research-areas {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1.5rem;
    margin-bottom: 3rem;
}

.research-card {
    background-color: var(--color-bg-alt);
    border: 1px solid var(--color-border);
    border-radius: 12px;
    padding: 2rem;
    transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.research-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.07);
}

.research-icon {
    width: 48px;
    height: 48px;
    color: var(--color-accent);
    margin-bottom: 1.25rem;
}

.research-card h3 {
    font-size: 1.1rem;
    font-weight: 650;
    margin-bottom: 0.75rem;
    color: var(--color-text);
}

.research-card p {
    font-size: 0.925rem;
    color: var(--color-text-secondary);
    line-height: 1.65;
}

.research-card em {
    font-style: italic;
}

/* Dissertation highlight */
.dissertation-highlight {
    background: linear-gradient(135deg, var(--color-accent), var(--color-accent-light));
    border-radius: 12px;
    padding: 2rem 2.5rem;
    color: #fff;
    position: relative;
    overflow: hidden;
}

.dissertation-highlight::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -20%;
    width: 300px;
    height: 300px;
    background: rgba(255, 255, 255, 0.05);
    border-radius: 50%;
}

.dissertation-badge {
    display: inline-block;
    background-color: rgba(255, 255, 255, 0.2);
    padding: 0.25rem 0.75rem;
    border-radius: 4px;
    font-size: 0.75rem;
    font-weight: 600;
    letter-spacing: 0.06em;
    text-transform: uppercase;
    margin-bottom: 1rem;
}

.dissertation-highlight h3 {
    font-size: 1.25rem;
    font-weight: 650;
    margin-bottom: 0.5rem;
}

.dissertation-highlight p {
    opacity: 0.9;
    font-size: 0.95rem;
    line-height: 1.6;
}

.dissertation-meta {
    margin-top: 0.75rem;
    font-size: 0.85rem !important;
    opacity: 0.7 !important;
}

/* ========================================
   Publications
   ======================================== */
.publications {
    background-color: var(--color-bg-alt);
}

.pub-list {
    max-width: 820px;
}

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

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

.pub-year {
    flex-shrink: 0;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--color-accent);
    padding-top: 0.15rem;
    width: 48px;
}

.pub-content {
    flex: 1;
}

.pub-title {
    font-weight: 600;
    font-size: 0.975rem;
    color: var(--color-text);
    margin-bottom: 0.3rem;
    line-height: 1.45;
}

.pub-authors {
    font-size: 0.875rem;
    color: var(--color-text-secondary);
    margin-bottom: 0.2rem;
}

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

.pub-link {
    display: inline-block;
    margin-top: 0.35rem;
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--color-accent);
    letter-spacing: 0.02em;
}

.pub-link:hover {
    color: var(--color-accent-light);
}

/* ========================================
   Teaching
   ======================================== */
.teaching {
    background-color: var(--color-bg);
}

.teaching-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    margin-bottom: 2.5rem;
}

.teaching-category {
    background-color: var(--color-bg-alt);
    border: 1px solid var(--color-border);
    border-radius: 12px;
    padding: 2rem;
}

.teaching-category h3 {
    font-size: 1.1rem;
    font-weight: 650;
    margin-bottom: 0.25rem;
    color: var(--color-text);
}

.teaching-institution {
    font-size: 0.85rem;
    color: var(--color-text-muted);
    margin-bottom: 1rem;
}

.course-list {
    list-style: none;
    padding: 0;
}

.course-list li {
    padding: 0.4rem 0;
    padding-left: 1.25rem;
    position: relative;
    font-size: 0.925rem;
    color: var(--color-text-secondary);
}

.course-list li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background-color: var(--color-accent);
    opacity: 0.5;
    transform: translateY(-50%);
}

.mentorship-note {
    background-color: var(--color-bg-alt);
    border: 1px solid var(--color-border);
    border-left: 3px solid var(--color-accent);
    border-radius: 0 12px 12px 0;
    padding: 1.5rem 2rem;
}

.mentorship-note h3 {
    font-size: 1rem;
    font-weight: 650;
    margin-bottom: 0.5rem;
}

.mentorship-note p {
    font-size: 0.925rem;
    color: var(--color-text-secondary);
    line-height: 1.65;
}

/* ========================================
   Skills
   ======================================== */
.skills {
    background-color: var(--color-bg);
}

.skills-two-col {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
}

.skill-column {
    background-color: var(--color-bg-alt);
    border: 1px solid var(--color-border);
    border-radius: 12px;
    padding: 2rem;
}

.skill-column h3 {
    font-size: 1.1rem;
    font-weight: 650;
    margin-bottom: 1rem;
    color: var(--color-accent);
    text-transform: uppercase;
    letter-spacing: 0.04em;
    font-size: 0.85rem;
}

.skill-list-clean {
    list-style: none;
    padding: 0;
}

.skill-list-clean li {
    padding: 0.55rem 0;
    border-bottom: 1px solid var(--color-border);
    font-size: 0.925rem;
    color: var(--color-text-secondary);
    line-height: 1.55;
}

.skill-list-clean li:last-child {
    border-bottom: none;
}

.skill-list-clean li strong {
    color: var(--color-text);
    font-weight: 600;
}

@media (max-width: 640px) {
    .skills-two-col {
        grid-template-columns: 1fr;
    }
}

/* ========================================
   Contact
   ======================================== */
.contact {
    background-color: var(--color-bg);
}

.contact-links {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1.25rem;
}

.contact-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    padding: 2rem 1.5rem;
    border: 1px solid var(--color-border);
    border-radius: 12px;
    background-color: var(--color-bg-alt);
    transition: transform var(--transition-fast), box-shadow var(--transition-fast), border-color var(--transition-fast);
}

.contact-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.07);
    border-color: var(--color-accent);
    color: var(--color-text);
}

.contact-icon {
    width: 40px;
    height: 40px;
    color: var(--color-accent);
    margin-bottom: 1rem;
}

.contact-label {
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--color-text);
    margin-bottom: 0.25rem;
}

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

/* ========================================
   Footer
   ======================================== */
.footer {
    padding: 2rem 0;
    text-align: center;
    border-top: 1px solid var(--color-border);
    background-color: var(--color-bg);
}

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

/* ========================================
   Responsive
   ======================================== */
@media (max-width: 900px) {
    .hero-content {
        flex-direction: column;
        text-align: center;
        padding-top: 6rem;
    }

    .hero-tagline {
        margin-left: auto;
        margin-right: auto;
    }

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

    .portrait-img {
        width: 200px;
        height: 250px;
    }

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

    .about-highlights {
        grid-template-columns: repeat(4, 1fr);
    }

    .research-areas {
        grid-template-columns: 1fr;
    }

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

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

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

@media (max-width: 640px) {
    :root {
        --section-padding: 4rem 0;
    }

    .section-title {
        font-size: 1.6rem;
    }

    /* Mobile nav */
    .nav-toggle {
        display: flex;
    }

    .nav-menu {
        position: fixed;
        top: 0;
        right: -100%;
        width: 70%;
        max-width: 300px;
        height: 100vh;
        background-color: var(--color-bg-alt);
        flex-direction: column;
        padding: 5rem 2rem;
        gap: 1.5rem;
        transition: right var(--transition-medium);
        box-shadow: -4px 0 30px rgba(0, 0, 0, 0.1);
    }

    .nav-menu.open {
        right: 0;
    }

    .nav-menu .nav-link {
        color: var(--color-text);
        font-size: 1rem;
    }

    .hero-content {
        padding-top: 5rem;
    }

    .hero-name {
        font-size: 2rem;
    }

    .portrait-img {
        width: 180px;
        height: 220px;
    }

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

    .pub-item {
        flex-direction: column;
        gap: 0.25rem;
    }

    .pub-year {
        width: auto;
    }

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