/* ===== CSS RESET ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* ===== CSS VARIABLES ===== */
:root {
    /* Light theme */
    --bg-light: #fafafa;
    --text-light: #111111;
    --text-secondary-light: #555555;
    --border-light: #e0e0e0;
    --hover-light: #f0f0f0;
    --card-light: #ffffff;
    --accent-light: #2563eb;

    /* Dark theme */
    --bg-dark: #0a0a0a;
    --text-dark: #f0f0f0;
    --text-secondary-dark: #a0a0a0;
    --border-dark: #1e1e1e;
    --hover-dark: #151515;
    --card-dark: #111111;
    --accent-dark: #60a5fa;

    /* Active theme (default light) */
    --bg: var(--bg-light);
    --text: var(--text-light);
    --text-secondary: var(--text-secondary-light);
    --border: var(--border-light);
    --hover: var(--hover-light);
    --card: var(--card-light);
    --accent: var(--accent-light);

    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-size-sm: 14px;
    --font-size-base: 16px;
    --font-size-lg: 18px;
    --font-size-xl: 24px;
    --font-size-2xl: 28px;
    --font-size-3xl: 36px;

    /* Spacing */
    --space-xs: 8px;
    --space-sm: 16px;
    --space-md: 24px;
    --space-lg: 32px;
    --space-xl: 48px;
    --space-2xl: 64px;

    /* Layout */
    --content-width: 880px;
    --nav-height: 64px;
    --border-radius: 8px;
    --border-radius-lg: 12px;

    /* Transitions */
    --transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: all 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Dark theme */
[data-theme="dark"] {
    --bg: var(--bg-dark);
    --text: var(--text-dark);
    --text-secondary: var(--text-secondary-dark);
    --border: var(--border-dark);
    --hover: var(--hover-dark);
    --card: var(--card-dark);
    --accent: var(--accent-dark);
}

/* ===== BASE STYLES ===== */
html {
    font-size: var(--font-size-base);
    line-height: 1.6;
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    background-color: var(--bg);
    color: var(--text);
    transition: var(--transition);
    font-weight: 400;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

a:hover {
    opacity: 0.8;
}

/* ===== LAYOUT ===== */
.container {
    max-width: var(--content-width);
    margin: 0 auto;
    padding: 0 var(--space-md);
    min-height: 100vh;
    position: relative;
}

/* ===== NAVBAR (full-width) ===== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--nav-height);
    background: rgba(250, 250, 250, 0.85);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
    z-index: 1000;
    transition: var(--transition);
}

[data-theme="dark"] .navbar {
    background: rgba(10, 10, 10, 0.85);
}

.navbar-inner {
    max-width: var(--content-width);
    margin: 0 auto;
    padding: 0 var(--space-md);
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.navbar-brand a {
    font-size: var(--font-size-xl);
    font-weight: 500;
    color: var(--text);
    text-decoration: none;
    letter-spacing: -0.02em;
}

.navbar-brand a:hover {
    opacity: 0.7;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: var(--space-lg);
}

.nav-item {
    font-size: var(--font-size-base);
    font-weight: 400;
    color: var(--text-secondary);
    text-decoration: none;
    position: relative;
    padding: var(--space-xs) 0;
    transition: var(--transition);
}

.nav-item:hover,
.nav-item:focus-visible {
    color: var(--text);
    opacity: 1;
}

.nav-item.active {
    color: var(--text);
    font-weight: 500;
}

.nav-item.active::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--text);
    border-radius: 1px;
}

.nav-controls {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
}

/* Hamburger button */
.hamburger {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--space-xs);
    color: var(--text);
    font-size: 24px;
    line-height: 1;
    z-index: 1001;
}

.hamburger-icon {
    display: block;
    width: 22px;
    height: 2px;
    background: var(--text);
    position: relative;
    transition: var(--transition);
}

.hamburger-icon::before,
.hamburger-icon::after {
    content: '';
    position: absolute;
    width: 22px;
    height: 2px;
    background: var(--text);
    transition: var(--transition);
}

.hamburger-icon::before {
    top: -7px;
}

.hamburger-icon::after {
    bottom: -7px;
}

/* Hamburger open state */
.hamburger.open .hamburger-icon {
    background: transparent;
}

.hamburger.open .hamburger-icon::before {
    top: 0;
    transform: rotate(45deg);
}

.hamburger.open .hamburger-icon::after {
    bottom: 0;
    transform: rotate(-45deg);
}

/* ===== THEME TOGGLE ===== */
.theme-toggle {
    width: 40px;
    height: 20px;
    background: var(--border);
    border: none;
    border-radius: 10px;
    cursor: pointer;
    transition: var(--transition);
    outline: none;
    position: relative;
    flex-shrink: 0;
}

.theme-toggle:hover {
    background: var(--text-secondary);
}

.theme-toggle:focus-visible {
    outline: 2px solid var(--text);
    outline-offset: 2px;
}

.toggle-circle {
    display: block;
    width: 16px;
    height: 16px;
    background: var(--text);
    border-radius: 50%;
    transition: var(--transition);
    transform: translateX(2px);
}

[data-theme="dark"] .toggle-circle {
    transform: translateX(22px);
}

/* ===== LANGUAGE TOGGLE ===== */
.lang-toggle {
    background: var(--hover);
    color: var(--text);
    border: 1px solid var(--border);
    border-radius: 4px;
    padding: 4px 8px;
    font-size: 12px;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    outline: none;
    font-family: inherit;
    text-transform: uppercase;
    flex-shrink: 0;
}

.lang-toggle:hover {
    background: var(--text);
    color: var(--bg);
}

.lang-toggle:focus-visible {
    outline: 2px solid var(--text);
    outline-offset: 2px;
}

/* ===== MAIN CONTENT ===== */
.main {
    min-height: 60vh;
    padding-top: calc(var(--nav-height) + var(--space-xl));
    padding-bottom: var(--space-2xl);
}

.section {
    display: none;
    animation: fadeIn 0.4s ease-in-out;
}

.section.active {
    display: block;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(12px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ===== HERO SECTION (Option A: Side-by-Side) ===== */
.hero {
    display: flex;
    align-items: flex-start;
    gap: var(--space-xl);
    margin-bottom: var(--space-xl);
    padding: var(--space-lg) 0;
}

.hero-image {
    flex-shrink: 0;
}

.hero-image img {
    width: 150px;
    height: 150px;
    border-radius: 50%;
    object-fit: cover;
    border: 3px solid var(--border);
}



.hero-content {
    flex: 1;
    min-width: 0;
}

.hero-name {
    font-size: var(--font-size-3xl);
    font-weight: 600;
    letter-spacing: -0.03em;
    margin-bottom: var(--space-xs);
    line-height: 1.2;
}

.hero-title {
    font-size: var(--font-size-lg);
    color: var(--text-secondary);
    margin-bottom: var(--space-md);
    font-weight: 400;
}

.hero-bio {
    font-size: var(--font-size-base);
    line-height: 1.75;
    color: var(--text-secondary);
    margin-bottom: var(--space-lg);
}

.hero-bio a {
    color: var(--text);
    text-decoration: none;
    border-bottom: 1px solid var(--text);
    transition: var(--transition);
}

.hero-bio a:hover {
    opacity: 0.6;
    color: var(--text);
}

/* Contact Links (centered at bottom) */
.contact-section {
    margin-top: var(--space-lg);
    text-align: center;
}

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

.contact-link {
    color: var(--text);
    text-decoration: none;
    font-weight: 400;
    font-size: var(--font-size-sm);
    padding: var(--space-xs) var(--space-sm);
    border: 1px solid var(--border);
    border-radius: var(--border-radius);
    transition: var(--transition);
    display: inline-flex;
    align-items: center;
    gap: var(--space-xs);
}

.contact-link:hover {
    background: var(--hover);
    border-color: var(--text-secondary);
    color: var(--text);
    opacity: 1;
}

.contact-icon {
    font-size: 16px;
    width: 16px;
    text-align: center;
    flex-shrink: 0;
}

/* ===== DEVELOPMENT NOTICE ===== */
.warning {
    margin-bottom: var(--space-lg);
    padding: var(--space-sm) var(--space-md);
    border: 1px solid var(--border);
    border-radius: var(--border-radius);
    background: var(--hover);
    color: var(--text);
    font-size: var(--font-size-sm);
}

/* ===== PROJECTS SECTION ===== */
.loading {
    color: var(--text-secondary);
    text-align: center;
    padding: var(--space-xl) 0;
}

.project-tech {
    display: flex;
    gap: var(--space-xs);
    flex-wrap: wrap;
}

.tech-tag {
    background: var(--hover);
    color: var(--text-secondary);
    padding: 4px var(--space-xs);
    border-radius: 4px;
    font-size: var(--font-size-sm);
    font-weight: 500;
    border: 1px solid var(--border);
}

.collab-badge {
    background: var(--text);
    color: var(--bg);
    padding: 2px 8px;
    border-radius: 4px;
    font-size: 12px;
    font-weight: 600;
    margin-left: var(--space-xs);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

/* ===== PUBLICATIONS SECTION ===== */
.publications,
.duolingo-section {
    margin-bottom: var(--space-xl);
}

.section-title {
    font-size: var(--font-size-xl);
    font-weight: 500;
    margin-bottom: var(--space-lg);
    letter-spacing: -0.01em;
}

.pub-card {
    padding: var(--space-md);
    margin-bottom: var(--space-sm);
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--border-radius-lg);
    transition: var(--transition);
}

.pub-card:hover {
    border-color: var(--text-secondary);
}

.pub-card:last-child {
    margin-bottom: 0;
}

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

.pub-title {
    font-weight: 500;
    font-size: var(--font-size-base);
    color: var(--text);
    line-height: 1.4;
}

.pub-title a {
    color: var(--text);
    text-decoration: none;
    border-bottom: 1px solid transparent;
    transition: var(--transition);
}

.pub-title a:hover {
    border-bottom-color: var(--accent);
    color: var(--accent);
    opacity: 1;
}

.pub-year-badge {
    flex-shrink: 0;
    font-size: 12px;
    font-weight: 600;
    padding: 2px 8px;
    background: var(--hover);
    border: 1px solid var(--border);
    border-radius: 4px;
    color: var(--text-secondary);
}

.pub-meta {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: var(--space-xs);
    margin-top: 6px;
}

.pub-venue {
    font-size: var(--font-size-sm);
    color: var(--text-secondary);
}

.pub-venue a {
    color: var(--text-secondary);
    text-decoration: none;
    border-bottom: 1px solid var(--border);
    transition: var(--transition);
}

.pub-venue a:hover {
    color: var(--text);
    border-bottom-color: var(--text);
    opacity: 1;
}

.pub-status {
    font-size: 12px;
    font-style: italic;
    color: var(--text-secondary);
    padding: 2px 8px;
    background: var(--hover);
    border-radius: 4px;
}

.pub-abstract-toggle {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    font-size: var(--font-size-sm);
    color: var(--accent);
    background: none;
    border: none;
    cursor: pointer;
    padding: 4px 0;
    margin-top: var(--space-xs);
    font-family: inherit;
    transition: var(--transition);
}

.pub-abstract-toggle:hover {
    opacity: 0.7;
}

.pub-abstract-toggle i {
    font-size: 12px;
    transition: transform 0.2s ease;
}

.pub-abstract-toggle.expanded i {
    transform: rotate(180deg);
}

.pub-abstract {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.35s ease, padding 0.35s ease;
}

.pub-abstract.expanded {
    max-height: 400px;
    padding-top: var(--space-sm);
}

.pub-abstract p {
    font-size: var(--font-size-sm);
    line-height: 1.7;
    color: var(--text-secondary);
    padding: var(--space-sm);
    background: var(--hover);
    border-radius: var(--border-radius);
    border-left: 3px solid var(--accent);
}

/* ===== DUOLINGO SECTION ===== */
.duolingo-section {
    margin-bottom: var(--space-xl);
}

.duolingo-highlight {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    padding: var(--space-md);
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--border-radius-lg);
    margin-bottom: var(--space-md);
}

.streak-display {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
}

.streak-number {
    font-size: var(--font-size-3xl);
    font-weight: 700;
    color: var(--text);
    line-height: 1;
}

.streak-label {
    font-size: var(--font-size-sm);
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.streak-fire {
    font-size: 28px;
    line-height: 1;
}

.duolingo-stat-row {
    display: flex;
    gap: var(--space-sm);
    margin-bottom: var(--space-md);
}

.duo-stat-chip {
    flex: 1;
    text-align: center;
    padding: var(--space-sm);
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--border-radius);
}

.duo-stat-value {
    display: block;
    font-size: var(--font-size-lg);
    font-weight: 600;
    color: var(--text);
}

.duo-stat-label {
    font-size: 12px;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.duolingo-top-languages {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
    gap: var(--space-sm);
    margin-bottom: var(--space-sm);
}

.lang-card {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    padding: var(--space-sm);
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--border-radius);
    transition: var(--transition);
}

.lang-card:hover {
    border-color: var(--text-secondary);
}

.lang-flag {
    font-size: var(--font-size-lg);
    width: 28px;
    text-align: center;
}

.lang-name {
    font-weight: 500;
    font-size: var(--font-size-sm);
    color: var(--text);
}

.lang-xp {
    font-size: 12px;
    color: var(--text-secondary);
}

.show-all-toggle {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    font-size: var(--font-size-sm);
    color: var(--accent);
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--space-xs) 0;
    font-family: inherit;
    transition: var(--transition);
}

.show-all-toggle:hover {
    opacity: 0.7;
}

.duolingo-notice {
    margin-top: var(--space-sm);
    text-align: center;
}

.duolingo-notice small {
    color: var(--text-secondary);
    font-style: italic;
    font-size: 12px;
}

/* ===== COLLAPSIBLE SECTIONS ===== */
.collapsible-section {
    margin-top: var(--space-md);
}

.collapsible-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--space-sm);
    cursor: pointer;
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--border-radius);
    transition: var(--transition);
    user-select: none;
}

.collapsible-header:hover {
    border-color: var(--text-secondary);
}

.collapsible-header h4 {
    margin: 0;
    font-size: var(--font-size-base);
    font-weight: 500;
    color: var(--text);
}

.collapsible-header i {
    color: var(--text-secondary);
    transition: transform 0.3s ease;
    font-size: var(--font-size-sm);
}

.collapsible-section.expanded .collapsible-header i {
    transform: rotate(180deg);
}

.collapsible-content {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.35s ease;
    border-left: 1px solid var(--border);
    border-right: 1px solid var(--border);
    border-bottom: 1px solid var(--border);
    border-top: none;
    border-radius: 0 0 var(--border-radius) var(--border-radius);
}

.collapsible-section.expanded .collapsible-content {
    max-height: 800px;
    padding: var(--space-md);
    overflow-y: auto;
}

/* ===== TIMELINE SECTION ===== */
/* ===== PAGE LOAD TRANSITION (prevents jitter) ===== */
body {
    opacity: 0;
    animation: bodyFadeIn 0.3s ease forwards;
}

@keyframes bodyFadeIn {
    to {
        opacity: 1;
    }
}

/* ===== TIMELINE SECTION ===== */
.timeline-intro {
    margin-bottom: var(--space-lg);
    font-size: var(--font-size-base);
    color: var(--text-secondary);
    line-height: 1.7;
}

.timeline {
    position: relative;
    padding: 0;
}

/* Year groups */
.timeline-year-group {
    display: grid;
    grid-template-columns: 80px 1fr;
    gap: 0;
    margin-bottom: var(--space-md);
}

.timeline-year-label {
    position: sticky;
    top: calc(var(--nav-height) + var(--space-md));
    align-self: start;
    padding-top: var(--space-sm);
}

.timeline-year-label span {
    font-size: var(--font-size-xl);
    font-weight: 600;
    color: var(--text);
    letter-spacing: -0.02em;
}

.timeline-year-events {
    border-left: 2px solid var(--border);
    padding-left: var(--space-lg);
}

.timeline-event {
    position: relative;
    margin-bottom: var(--space-lg);
    padding-bottom: var(--space-md);
    border-bottom: 1px solid var(--border);
}

.timeline-event:last-child {
    margin-bottom: 0;
    border-bottom: none;
    padding-bottom: 0;
}

.timeline-event::before {
    content: '';
    position: absolute;
    left: calc(-1 * var(--space-lg) - 5px);
    top: 8px;
    width: 8px;
    height: 8px;
    background: var(--text-secondary);
    border-radius: 50%;
    z-index: 1;
}

/* Scroll reveal animation */
.timeline-hidden {
    opacity: 0;
    transform: translateY(20px);
}

.timeline-visible {
    opacity: 1;
    transform: translateY(0);
    transition: opacity 0.5s ease, transform 0.5s ease;
}

.timeline-date {
    font-size: var(--font-size-sm);
    color: var(--text-secondary);
    font-weight: 500;
    margin-bottom: 4px;
}

.timeline-title {
    font-size: var(--font-size-base);
    font-weight: 500;
    color: var(--text);
    margin-bottom: 4px;
    line-height: 1.5;
}

.timeline-description {
    font-size: var(--font-size-sm);
    color: var(--text-secondary);
    line-height: 1.6;
}

/* ===== RESPONSIVE DESIGN ===== */

/* Mobile menu overlay */
.mobile-menu {
    display: none;
}

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

    .hamburger {
        display: flex;
        align-items: center;
        justify-content: center;
    }

    .mobile-menu {
        display: none;
        position: fixed;
        top: var(--nav-height);
        left: 0;
        right: 0;
        background: var(--bg);
        border-bottom: 1px solid var(--border);
        padding: var(--space-md);
        z-index: 999;
        animation: slideDown 0.25s ease;
    }

    .mobile-menu.open {
        display: flex;
        flex-direction: column;
        gap: var(--space-sm);
    }

    @keyframes slideDown {
        from {
            opacity: 0;
            transform: translateY(-8px);
        }

        to {
            opacity: 1;
            transform: translateY(0);
        }
    }

    .mobile-menu .nav-item {
        font-size: var(--font-size-lg);
        padding: var(--space-sm) 0;
        border-bottom: 1px solid var(--border);
    }

    .mobile-menu .nav-item:last-of-type {
        border-bottom: none;
    }

    .mobile-menu .nav-controls {
        padding-top: var(--space-sm);
        border-top: 1px solid var(--border);
        justify-content: flex-start;
    }

    /* Hero responsive */
    .hero {
        flex-direction: column;
        align-items: center;
        text-align: center;
        gap: var(--space-md);
    }

    .hero-name {
        font-size: var(--font-size-2xl);
    }

    .hero-bio {
        text-align: left;
    }

    /* Projects */
    .project-item {
        margin-bottom: var(--space-md);
        padding-bottom: var(--space-md);
    }

    /* Duolingo */
    .duolingo-highlight {
        flex-direction: column;
        align-items: flex-start;
    }

    .duolingo-stat-row {
        flex-direction: column;
    }

    .duolingo-top-languages {
        grid-template-columns: 1fr;
    }

    /* Timeline */
    .timeline-year-group {
        grid-template-columns: 1fr;
    }

    .timeline-year-label {
        position: relative;
        top: 0;
        padding-bottom: var(--space-xs);
        border-bottom: 1px solid var(--border);
        margin-bottom: var(--space-sm);
    }

    .timeline-year-events {
        padding-left: var(--space-md);
    }

    .timeline-event::before {
        left: calc(-1 * var(--space-md) - 4px);
        width: 6px;
        height: 6px;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 var(--space-sm);
    }

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

    .contact-link {
        width: 100%;
        justify-content: center;
    }
}

/* ===== SITE FOOTER ===== */
.site-footer {
    text-align: center;
    padding: var(--space-lg) var(--space-md);
    border-top: 1px solid var(--border);
    margin-top: var(--space-xl);
}

.footer-inner {
    max-width: var(--content-width);
    margin: 0 auto;
    font-size: 13px;
    color: var(--text-secondary);
}

.footer-inner a {
    color: var(--text-secondary);
    border-bottom: 1px solid var(--border);
    transition: var(--transition);
}

.footer-inner a:hover {
    color: var(--text);
    border-bottom-color: var(--text);
    opacity: 1;
}

/* ===== WIP NOTICE ===== */
.wip-notice {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    padding: var(--space-sm) var(--space-md);
    background: var(--hover);
    border: 1px solid var(--border);
    border-radius: var(--border-radius);
    margin-bottom: var(--space-xl);
    color: var(--text-secondary);
    font-size: var(--font-size-sm);
}

.wip-notice i {
    font-size: var(--font-size-lg);
    opacity: 0.6;
}

/* ===== PUB AUTHORS ===== */
.pub-authors {
    font-size: var(--font-size-sm);
    color: var(--text-secondary);
    margin-top: 4px;
    line-height: 1.5;
}