/* ============================================
   CSS Variables & Base Styles
   ============================================ */

:root {
    /* Colors */
    --color-bg: #0a1128;
    --color-bg-secondary: #0f1936;
    --color-bg-tertiary: #162244;
    --color-text: #e8edf5;
    --color-text-secondary: #9ba8c4;
    --color-text-muted: #6b7a9a;
    --color-accent: #f4a261;
    --color-accent-dark: #e76f51;
    --color-accent-light: #f6bd8b;
    --color-border: rgba(255, 255, 255, 0.1);
    --color-overlay: rgba(10, 17, 40, 0.85);

    /* Typography */
    --font-display: 'Playfair Display', Georgia, serif;
    --font-body: 'IBM Plex Sans', sans-serif;
    --font-mono: 'IBM Plex Mono', monospace;

    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 2rem;
    --spacing-lg: 4rem;
    --spacing-xl: 6rem;
    --spacing-xxl: 8rem;

    /* Layout */
    --container-max: 1280px;
    --container-padding: 2rem;
    --nav-height: 80px;

    /* Animation */
    --transition-fast: 0.2s ease;
    --transition-base: 0.3s ease;
    --transition-slow: 0.5s ease;
    --transition-smooth: cubic-bezier(0.4, 0, 0.2, 1);
}

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

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

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

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

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

a {
    color: inherit;
    text-decoration: none;
    transition: all var(--transition-base);
}

/* ============================================
   Background Grid Overlay
   ============================================ */

.grid-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image:
        linear-gradient(rgba(255, 255, 255, 0.02) 1px, transparent 1px),
        linear-gradient(90deg, rgba(255, 255, 255, 0.02) 1px, transparent 1px);
    background-size: 50px 50px;
    pointer-events: none;
    z-index: 0;
    opacity: 0.5;
}

/* ============================================
   Container
   ============================================ */

.container {
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 var(--container-padding);
    position: relative;
    z-index: 1;
}

/* ============================================
   Navigation
   ============================================ */

.nav {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: var(--nav-height);
    background: var(--color-overlay);
    backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--color-border);
    z-index: 1000;
    transition: all var(--transition-base);
}

.nav-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: var(--nav-height);
}

.nav-logo {
    font-family: var(--font-display);
    font-size: 1.5rem;
    font-weight: 700;
    letter-spacing: 0.05em;
    color: var(--color-accent);
}

.nav-links {
    display: flex;
    gap: var(--spacing-md);
}

.nav-link {
    font-size: 0.95rem;
    font-weight: 500;
    letter-spacing: 0.02em;
    opacity: 0.8;
    transition: all var(--transition-base);
    position: relative;
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--color-accent);
    transition: width var(--transition-base);
}

.nav-link:hover {
    opacity: 1;
    color: var(--color-accent);
}

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

/* ============================================
   Hero Section
   ============================================ */

.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding-top: var(--nav-height);
    padding-bottom: var(--spacing-xxl);
    position: relative;
}

.hero-content {
    display: grid;
    grid-template-columns: 1.2fr 1fr;
    gap: var(--spacing-xl);
    align-items: center;
    padding-top: var(--spacing-lg);
}

.hero-label {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    letter-spacing: 0.15em;
    text-transform: uppercase;
    color: var(--color-accent);
    margin-bottom: var(--spacing-sm);
    font-weight: 500;
}

.hero-title {
    font-family: var(--font-display);
    font-size: clamp(3rem, 8vw, 5.5rem);
    font-weight: 800;
    line-height: 1.1;
    margin-bottom: var(--spacing-md);
    letter-spacing: -0.02em;
}

.hero-title-accent {
    display: block;
    color: var(--color-accent);
    font-style: italic;
}

.hero-tagline {
    font-size: clamp(1.1rem, 2vw, 1.3rem);
    line-height: 1.6;
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-lg);
    max-width: 600px;
}

.hero-tagline-accent {
    display: block;
    color: var(--color-text);
    font-weight: 500;
    margin-top: var(--spacing-xs);
}

.hero-cta {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-xl);
}

.hero-stats {
    display: flex;
    gap: var(--spacing-lg);
    padding-top: var(--spacing-lg);
    border-top: 1px solid var(--color-border);
}

.stat {
    flex: 1;
}

.stat-number {
    font-family: var(--font-display);
    font-size: 2rem;
    font-weight: 700;
    color: var(--color-accent);
    margin-bottom: var(--spacing-xs);
}

.stat-label {
    font-size: 0.85rem;
    color: var(--color-text-muted);
    letter-spacing: 0.05em;
}

/* Hero Image */
.hero-image {
    position: relative;
}

.image-frame {
    position: relative;
    border-radius: 8px;
    overflow: hidden;
    border: 1px solid var(--color-border);
    background: var(--color-bg-secondary);
}

.image-frame img {
    width: 100%;
    height: auto;
    display: block;
    transition: transform 0.6s var(--transition-smooth);
}

.image-frame:hover img {
    transform: scale(1.05);
}

.image-caption {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    padding: var(--spacing-sm) var(--spacing-md);
    background: linear-gradient(transparent, rgba(10, 17, 40, 0.95));
    font-size: 0.85rem;
    color: var(--color-text-secondary);
    letter-spacing: 0.02em;
}

/* Scroll Indicator */
.scroll-indicator {
    position: absolute;
    bottom: var(--spacing-lg);
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-xs);
    font-size: 0.75rem;
    letter-spacing: 0.15em;
    text-transform: uppercase;
    color: var(--color-text-muted);
    font-family: var(--font-mono);
}

.scroll-line {
    width: 1px;
    height: 40px;
    background: linear-gradient(to bottom, var(--color-accent), transparent);
    animation: scroll-pulse 2s ease-in-out infinite;
}

@keyframes scroll-pulse {
    0%, 100% {
        opacity: 0.3;
        transform: translateY(-10px);
    }
    50% {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ============================================
   Buttons
   ============================================ */

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.875rem 2rem;
    font-size: 0.95rem;
    font-weight: 500;
    letter-spacing: 0.02em;
    border-radius: 4px;
    cursor: pointer;
    transition: all var(--transition-base);
    border: 1px solid transparent;
    font-family: var(--font-body);
}

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

.btn-primary:hover {
    background: var(--color-accent-light);
    border-color: var(--color-accent-light);
    transform: translateY(-2px);
    box-shadow: 0 8px 20px rgba(244, 162, 97, 0.3);
}

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

.btn-secondary:hover {
    background: var(--color-bg-secondary);
    border-color: var(--color-accent);
    color: var(--color-accent);
    transform: translateY(-2px);
}

.btn-large {
    padding: 1.125rem 2.5rem;
    font-size: 1.05rem;
}

/* ============================================
   Section Styles
   ============================================ */

section {
    padding: var(--spacing-xxl) 0;
    position: relative;
}

.section-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-xl);
}

.section-number {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    letter-spacing: 0.15em;
    color: var(--color-accent);
    padding: 0.5rem 1rem;
    border: 1px solid var(--color-accent);
    border-radius: 4px;
    font-weight: 500;
}

.section-title {
    font-family: var(--font-display);
    font-size: clamp(2.5rem, 5vw, 3.5rem);
    font-weight: 700;
    letter-spacing: -0.02em;
}

/* ============================================
   About Section
   ============================================ */

.about {
    background: var(--color-bg-secondary);
}

.about-content {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xl);
}

.about-intro {
    max-width: 900px;
}

.about-text-large {
    font-size: clamp(1.3rem, 2.5vw, 1.6rem);
    line-height: 1.6;
    margin-bottom: var(--spacing-md);
    color: var(--color-text);
    font-weight: 400;
}

.about-text {
    font-size: 1.1rem;
    line-height: 1.8;
    color: var(--color-text-secondary);
}

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

/* Experience Grid */
.experience-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-md);
    margin-top: var(--spacing-lg);
}

.experience-item {
    padding: var(--spacing-md);
    background: var(--color-bg-tertiary);
    border: 1px solid var(--color-border);
    border-radius: 8px;
    transition: all var(--transition-base);
}

.experience-item:hover {
    border-color: var(--color-accent);
    transform: translateY(-4px);
    box-shadow: 0 12px 24px rgba(0, 0, 0, 0.3);
}

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

.experience-company {
    font-family: var(--font-display);
    font-size: 1.3rem;
    font-weight: 600;
    color: var(--color-accent);
}

.experience-period {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    color: var(--color-text-muted);
    letter-spacing: 0.05em;
    white-space: nowrap;
}

.experience-role {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
}

.experience-location {
    font-size: 0.85rem;
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-sm);
}

.experience-desc {
    font-size: 0.95rem;
    line-height: 1.6;
    color: var(--color-text-secondary);
}

/* Credentials Section */
.credentials-section {
    margin-top: var(--spacing-xl);
}

.credentials-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-md);
}

.credential-card {
    padding: var(--spacing-md);
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: 8px;
}

.credential-icon {
    font-size: 2rem;
    margin-bottom: var(--spacing-sm);
}

.credential-title {
    font-family: var(--font-display);
    font-size: 1.3rem;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
}

.credential-detail {
    font-size: 0.95rem;
    line-height: 1.7;
    color: var(--color-text-secondary);
}

.skills-tags {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-xs);
    margin-top: var(--spacing-sm);
}

.skill-tag {
    padding: 0.4rem 0.9rem;
    background: var(--color-bg-tertiary);
    border: 1px solid var(--color-border);
    border-radius: 20px;
    font-size: 0.85rem;
    font-family: var(--font-mono);
    letter-spacing: 0.02em;
    transition: all var(--transition-fast);
}

.skill-tag:hover {
    background: var(--color-bg-secondary);
    border-color: var(--color-accent);
    color: var(--color-accent);
}

/* ============================================
   Book Section
   ============================================ */

.book-section {
    background: var(--color-bg);
}

.book-content {
    display: grid;
    grid-template-columns: 1fr 1.5fr;
    gap: var(--spacing-xl);
    align-items: start;
}

.book-cover-wrapper {
    position: sticky;
    top: calc(var(--nav-height) + var(--spacing-md));
}

.book-cover-frame {
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-border);
    border-radius: 8px;
    padding: var(--spacing-md);
    transition: all 0.4s var(--transition-smooth);
}

.book-cover-frame:hover {
    transform: translateY(-8px);
    box-shadow: 0 20px 40px rgba(244, 162, 97, 0.15);
    border-color: var(--color-accent);
}

.book-cover-image {
    width: 100%;
    border-radius: 4px;
}

.book-info {
    padding-top: var(--spacing-sm);
}

.book-badge {
    display: inline-block;
    padding: 0.5rem 1rem;
    background: var(--color-accent);
    color: var(--color-bg);
    font-size: 0.75rem;
    font-weight: 600;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    border-radius: 4px;
    margin-bottom: var(--spacing-md);
    font-family: var(--font-mono);
}

.book-title {
    font-family: var(--font-display);
    font-size: clamp(2rem, 4vw, 3rem);
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: var(--spacing-sm);
    letter-spacing: -0.01em;
}

.book-subtitle {
    font-size: 1.2rem;
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-md);
    font-weight: 500;
}

.book-description {
    font-size: 1.05rem;
    line-height: 1.8;
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-lg);
}

.book-highlights {
    padding: var(--spacing-md);
    background: var(--color-bg-secondary);
    border-left: 3px solid var(--color-accent);
    border-radius: 4px;
    margin-bottom: var(--spacing-lg);
}

.highlights-title {
    font-family: var(--font-display);
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
}

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

.highlights-list li {
    padding-left: 1.5rem;
    margin-bottom: var(--spacing-xs);
    position: relative;
    line-height: 1.7;
    color: var(--color-text-secondary);
}

.highlights-list li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--color-accent);
    font-weight: bold;
}

.book-cta {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.book-meta {
    display: flex;
    gap: var(--spacing-sm);
    align-items: center;
    font-size: 0.9rem;
    color: var(--color-text-muted);
    font-family: var(--font-mono);
}

.separator {
    color: var(--color-accent);
}

/* ============================================
   Academic Papers Section
   ============================================ */

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

.papers-content {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-lg);
}

.paper-card {
    padding: var(--spacing-lg);
    background: var(--color-bg-tertiary);
    border: 1px solid var(--color-border);
    border-radius: 8px;
    transition: all var(--transition-base);
}

.paper-card:hover {
    border-color: var(--color-accent);
    transform: translateY(-4px);
    box-shadow: 0 12px 24px rgba(0, 0, 0, 0.3);
}

.paper-meta {
    display: flex;
    gap: var(--spacing-sm);
    align-items: center;
    margin-bottom: var(--spacing-sm);
}

.paper-badge {
    display: inline-block;
    padding: 0.4rem 0.8rem;
    background: var(--color-accent);
    color: var(--color-bg);
    font-size: 0.7rem;
    font-weight: 600;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    border-radius: 4px;
    font-family: var(--font-mono);
}

.paper-year {
    font-family: var(--font-mono);
    font-size: 0.85rem;
    color: var(--color-text-muted);
    letter-spacing: 0.05em;
}

.paper-title {
    font-family: var(--font-display);
    font-size: 1.6rem;
    font-weight: 600;
    line-height: 1.3;
    margin-bottom: var(--spacing-sm);
    color: var(--color-text);
}

.paper-venue {
    font-size: 0.95rem;
    color: var(--color-accent);
    font-weight: 500;
    margin-bottom: var(--spacing-sm);
}

.paper-description {
    font-size: 1rem;
    line-height: 1.7;
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-md);
}

.paper-links {
    display: flex;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
}

.btn-outline {
    background: transparent;
    color: var(--color-text);
    border: 1px solid var(--color-border);
    padding: 0.75rem 1.5rem;
    font-size: 0.9rem;
}

.btn-outline:hover {
    background: var(--color-accent);
    border-color: var(--color-accent);
    color: var(--color-bg);
    transform: translateY(-2px);
    box-shadow: 0 8px 20px rgba(244, 162, 97, 0.3);
}

/* ============================================
   Contact Section
   ============================================ */

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

.contact-intro {
    margin-bottom: var(--spacing-xl);
    max-width: 800px;
}

.contact-text-large {
    font-size: clamp(1.3rem, 2.5vw, 1.6rem);
    line-height: 1.6;
    color: var(--color-text);
}

.contact-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: var(--spacing-md);
}

.contact-card {
    padding: var(--spacing-md);
    background: var(--color-bg-tertiary);
    border: 1px solid var(--color-border);
    border-radius: 8px;
    transition: all var(--transition-base);
    cursor: pointer;
}

.contact-card:hover {
    border-color: var(--color-accent);
    transform: translateY(-4px);
    box-shadow: 0 12px 24px rgba(0, 0, 0, 0.3);
}

.contact-icon {
    font-size: 2rem;
    margin-bottom: var(--spacing-sm);
}

.contact-label {
    font-size: 0.85rem;
    color: var(--color-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin-bottom: var(--spacing-xs);
    font-weight: 500;
}

.contact-value {
    font-size: 1.1rem;
    font-weight: 500;
    color: var(--color-accent);
}

/* ============================================
   Footer
   ============================================ */

.footer {
    padding: var(--spacing-xl) 0 var(--spacing-lg);
    border-top: 1px solid var(--color-border);
    background: var(--color-bg);
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: var(--spacing-lg);
}

.footer-logo {
    font-family: var(--font-display);
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
}

.footer-tagline {
    font-size: 0.95rem;
    color: var(--color-text-muted);
}

.footer-right {
    text-align: right;
}

.footer-links {
    display: flex;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-sm);
}

.footer-link {
    font-size: 0.9rem;
    color: var(--color-text-secondary);
    transition: color var(--transition-base);
}

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

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

/* ============================================
   Animations
   ============================================ */

.fade-in {
    opacity: 0;
    animation: fadeIn 0.8s ease forwards;
}

.fade-in-delay-1 {
    opacity: 0;
    animation: fadeIn 0.8s ease 0.2s forwards;
}

.fade-in-delay-2 {
    opacity: 0;
    animation: fadeIn 0.8s ease 0.4s forwards;
}

.fade-in-delay-3 {
    opacity: 0;
    animation: fadeIn 0.8s ease 0.6s forwards;
}

.fade-in-delay-4 {
    opacity: 0;
    animation: fadeIn 0.8s ease 0.8s forwards;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.reveal-on-scroll {
    opacity: 0;
    transform: translateY(30px);
    transition: all 0.8s var(--transition-smooth);
}

.reveal-on-scroll.revealed {
    opacity: 1;
    transform: translateY(0);
}

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

@media (max-width: 1024px) {
    :root {
        --spacing-lg: 3rem;
        --spacing-xl: 4rem;
        --spacing-xxl: 6rem;
        --container-padding: 1.5rem;
    }

    .hero-content {
        grid-template-columns: 1fr;
        gap: var(--spacing-lg);
    }

    .hero-image {
        order: -1;
        max-width: 500px;
        margin: 0 auto;
    }

    .book-content {
        grid-template-columns: 1fr;
        gap: var(--spacing-lg);
    }

    .book-cover-wrapper {
        position: relative;
        top: 0;
        max-width: 400px;
        margin: 0 auto;
    }
}

@media (max-width: 768px) {
    :root {
        --nav-height: 70px;
        --spacing-md: 1.5rem;
        --spacing-lg: 2.5rem;
        --spacing-xl: 3rem;
        --spacing-xxl: 4rem;
        --container-padding: 1.25rem;
    }

    .nav-links {
        gap: var(--spacing-sm);
    }

    .nav-link {
        font-size: 0.85rem;
    }

    .hero {
        min-height: auto;
        padding-top: calc(var(--nav-height) + var(--spacing-md));
    }

    .hero-cta {
        flex-direction: column;
    }

    .btn {
        width: 100%;
    }

    .hero-stats {
        gap: var(--spacing-md);
    }

    .stat-number {
        font-size: 1.5rem;
    }

    .stat-label {
        font-size: 0.75rem;
    }

    .section-header {
        flex-direction: column;
        align-items: flex-start;
        gap: var(--spacing-sm);
    }

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

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

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

    .paper-links {
        flex-direction: column;
    }

    .paper-links .btn-outline {
        width: 100%;
    }

    .footer-content {
        flex-direction: column;
    }

    .footer-right {
        text-align: left;
        width: 100%;
    }

    .footer-links {
        justify-content: flex-start;
    }

    .scroll-indicator {
        display: none;
    }
}

@media (max-width: 480px) {
    .nav-logo {
        font-size: 1.2rem;
    }

    .hero-title {
        font-size: 2.5rem;
    }

    .about-text-large {
        font-size: 1.2rem;
    }

    .book-title {
        font-size: 1.8rem;
    }

    .contact-text-large {
        font-size: 1.2rem;
    }
}

/* ============================================
   Print Styles
   ============================================ */

@media print {
    .nav,
    .scroll-indicator,
    .btn,
    .footer {
        display: none;
    }

    body {
        background: white;
        color: black;
    }

    section {
        page-break-inside: avoid;
    }
}