/* =====================
   CSS Variables
   ===================== */
:root {
    /* Colors */
    --color-text: #2c3e50;
    --color-text-light: #5a6c7d;
    --color-text-meta: #7f8c9a;
    --color-bg: #ffffff;
    --color-bg-alt: #f8f9fa;
    --color-border: #e1e4e8;
    --color-border-accent: #3b7ea1;
    --color-accent: #2c5282;
    --color-link: #0366d6;
    
    /* Spacing */
    --spacing-xs: 8px;
    --spacing-sm: 16px;
    --spacing-md: 24px;
    --spacing-lg: 32px;
    --spacing-xl: 48px;
    --spacing-section: 60px;
    
    /* Typography */
    --font-size-xs: 13px;
    --font-size-sm: 14px;
    --font-size-base: 16px;
    --font-size-lg: 18px;
    --font-size-xl: 22px;
    --font-size-2xl: 28px;
    --font-size-3xl: 36px;
    
    /* Container */
    --container-width: 900px;
}

/* =====================
   General Styles
   ===================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Helvetica Neue', 'Arial', sans-serif;
    line-height: 1.7;
    color: var(--color-text);
    background-color: var(--color-bg-alt);
    font-size: var(--font-size-base);
}

/* =====================
   Header & Navigation
   ===================== */
header {
    background-color: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.05);
}

nav {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

nav ul {
    list-style: none;
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: var(--spacing-xs);
}

nav a {
    display: block;
    padding: var(--spacing-sm) var(--spacing-md);
    text-decoration: none;
    color: var(--color-text-light);
    font-weight: 500;
    font-size: var(--font-size-base);
    transition: color 0.2s ease, border-color 0.2s ease;
    border-bottom: 2px solid transparent;
}

nav a:hover {
    color: var(--color-text);
}

nav a.active {
    color: var(--color-accent);
    border-bottom-color: var(--color-accent);
}

/* =====================
   Main Content & Container
   ===================== */
main {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: var(--spacing-xl) var(--spacing-md);
}

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

/* Hero Section */
.hero {
    text-align: center;
    padding: var(--spacing-xl) 0;
    margin-bottom: var(--spacing-section);
}

.hero h1 {
    font-size: var(--font-size-3xl);
    margin-bottom: var(--spacing-sm);
    font-weight: 700;
    letter-spacing: -0.5px;
    color: var(--color-text);
    line-height: 1.2;
}

.subtitle {
    font-size: var(--font-size-lg);
    color: var(--color-text-light);
    margin-bottom: var(--spacing-lg);
    font-weight: 400;
    line-height: 1.5;
}

.introduction {
    font-size: var(--font-size-base);
    color: var(--color-text-light);
    max-width: 700px;
    margin: 0 auto;
    line-height: 1.8;
}

/* Page Header (for non-home pages) */
.page-header {
    text-align: center;
    padding: var(--spacing-lg) 0;
    margin-bottom: var(--spacing-lg);
}

.page-header h1 {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    color: var(--color-text);
    margin-bottom: var(--spacing-sm);
}

/* Content Sections */
.section,
.content-section {
    margin-bottom: var(--spacing-xl);
    padding: var(--spacing-lg);
    background-color: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: 6px;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.05);
}

.section h2,
.content-section h2 {
    font-size: var(--font-size-xl);
    margin-bottom: var(--spacing-md);
    font-weight: 600;
    color: var(--color-text);
    padding-bottom: var(--spacing-sm);
    border-bottom: 2px solid var(--color-bg-alt);
}

.section p,
.content-section p {
    font-size: var(--font-size-base);
    color: var(--color-text-light);
    line-height: 1.8;
    margin-bottom: var(--spacing-sm);
}

.section p:last-child,
.content-section p:last-child {
    margin-bottom: 0;
}

/* Quick Links Grid */
.quick-links {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-md);
    margin-top: var(--spacing-md);
}

.quick-link-card {
    padding: var(--spacing-md);
    background-color: var(--color-bg);
    border: 2px solid var(--color-border);
    border-radius: 6px;
    text-align: center;
    text-decoration: none;
    color: var(--color-text);
    transition: all 0.2s ease;
}

.quick-link-card:hover {
    border-color: var(--color-accent);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.quick-link-card .card-title {
    font-size: var(--font-size-lg);
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
    color: var(--color-accent);
}

.quick-link-card .card-description {
    font-size: var(--font-size-sm);
    color: var(--color-text-meta);
    line-height: 1.5;
}

/* Interests List */
.interests-list {
    list-style: none;
    padding: 0;
    margin: 0;
    display: grid;
    gap: var(--spacing-sm);
}

.interests-list li {
    padding-left: var(--spacing-md);
    position: relative;
    color: var(--color-text-light);
    font-size: var(--font-size-base);
    line-height: 1.6;
}

.interests-list li::before {
    content: "▸";
    position: absolute;
    left: 0;
    color: var(--color-accent);
    font-weight: bold;
}

/* Publications */
.publication-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.publication {
    padding: var(--spacing-md);
    background-color: var(--color-bg-alt);
    border-left: 4px solid var(--color-border-accent);
    border-radius: 4px;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.publication:hover {
    transform: translateX(4px);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
}

.pub-title {
    font-weight: 600;
    font-size: var(--font-size-base);
    color: var(--color-text);
    margin-bottom: var(--spacing-xs);
    line-height: 1.5;
}

.pub-authors {
    font-size: var(--font-size-sm);
    color: var(--color-text-light);
    margin-bottom: var(--spacing-xs);
}

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

.pub-doi {
    font-size: var(--font-size-sm);
    margin-top: var(--spacing-sm);
    padding-top: var(--spacing-sm);
    border-top: 1px solid var(--color-border);
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
}

.pub-links {
    flex: 1;
}

.pub-doi a {
    color: var(--color-link);
    text-decoration: none;
    font-weight: 500;
}

.pub-doi a:hover {
    text-decoration: underline;
}

.section-link {
    margin-top: var(--spacing-md);
    text-align: center;
}

.section-link a {
    color: var(--color-accent);
    text-decoration: none;
    font-weight: 600;
    font-size: var(--font-size-base);
    transition: color 0.2s ease;
}

.section-link a:hover {
    color: var(--color-text);
    text-decoration: underline;
}

/* BibTeX Inline Viewer */
.bibtex-viewer {
    display: none;
    margin-top: var(--spacing-sm);
    padding: var(--spacing-sm);
    background-color: #f6f8fa;
    border: 1px solid #d1d5da;
    border-radius: 4px;
    font-family: 'Courier New', Courier, monospace;
    font-size: var(--font-size-xs);
    line-height: 1.5;
    white-space: pre-wrap;
    overflow-x: auto;
    color: #24292e;
}

.bibtex-viewer.show {
    display: block;
}

.bibtex-toggle {
    cursor: pointer;
    padding: 6px 12px;
    background-color: var(--color-bg);
    border: 1px solid var(--color-border-accent);
    border-radius: 4px;
    color: var(--color-accent);
    text-decoration: none;
    font-weight: 500;
    font-size: var(--font-size-sm);
    white-space: nowrap;
    transition: all 0.2s ease;
}

.bibtex-toggle:hover {
    background-color: var(--color-accent);
    color: var(--color-bg);
    text-decoration: none;
}

.bibtex-error {
    color: #d73a49;
    font-style: italic;
}

/* CV Styles */
.cv-entry {
    margin-bottom: var(--spacing-lg);
    padding-bottom: var(--spacing-lg);
    border-bottom: 1px solid var(--color-border);
}

.cv-entry:last-child {
    border-bottom: none;
    margin-bottom: 0;
    padding-bottom: 0;
}

.entry-title {
    font-weight: 600;
    font-size: var(--font-size-lg);
    color: var(--color-text);
    margin-bottom: var(--spacing-xs);
    line-height: 1.4;
}

.entry-subtitle {
    font-size: var(--font-size-base);
    color: var(--color-accent);
    margin-bottom: var(--spacing-xs);
    font-weight: 500;
}

.entry-meta {
    font-size: var(--font-size-sm);
    color: var(--color-text-meta);
    margin-bottom: var(--spacing-sm);
    font-style: italic;
}

.entry-description {
    font-size: var(--font-size-base);
    color: var(--color-text-light);
    line-height: 1.7;
    margin-bottom: var(--spacing-xs);
}

.entry-list {
    list-style: none;
    padding: 0;
    margin: var(--spacing-sm) 0 0 0;
}

.entry-list li {
    padding: var(--spacing-xs) 0;
    padding-left: var(--spacing-md);
    position: relative;
    color: var(--color-text-light);
    font-size: var(--font-size-base);
    line-height: 1.6;
}

.entry-list li::before {
    content: "▸";
    position: absolute;
    left: 0;
    color: var(--color-accent);
    font-weight: bold;
}

/* Contact Styles */
.contact-links {
    display: grid;
    gap: var(--spacing-md);
}

.contact-item {
    padding: var(--spacing-md);
    background-color: var(--color-bg-alt);
    border-radius: 6px;
    border-left: 4px solid var(--color-border-accent);
    transition: transform 0.2s ease;
}

.contact-item:hover {
    transform: translateX(4px);
}

.contact-label {
    font-weight: 600;
    font-size: var(--font-size-sm);
    color: var(--color-text-meta);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: var(--spacing-xs);
}

.contact-value {
    font-size: var(--font-size-base);
    color: var(--color-text);
    line-height: 1.6;
}

.contact-value a {
    color: var(--color-link);
    text-decoration: none;
    font-weight: 500;
}

.contact-value a:hover {
    text-decoration: underline;
}

/* Compact Contact Styles */
.contact-compact {
    display: grid;
    gap: var(--spacing-md);
}

.contact-compact-item {
    display: flex;
    gap: var(--spacing-sm);
    padding: var(--spacing-md);
    background-color: var(--color-bg-alt);
    border-radius: 6px;
    align-items: flex-start;
}

.contact-compact-item-with-logo {
    gap: var(--spacing-md);
    align-items: center;
}

.contact-logo-card {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-md);
    background-color: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: 8px;
    text-decoration: none;
    transition: all 0.2s ease;
    flex-shrink: 0;
    min-width: 100px;
    min-height: 100px;
}

.contact-logo-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    border-color: var(--color-border-accent);
}

.contact-logo-img {
    width: 64px;
    height: 64px;
    object-fit: contain;
}

.contact-text-content {
    display: flex;
    gap: var(--spacing-sm);
    align-items: flex-start;
    flex: 1;
}

.contact-icon {
    width: 24px;
    height: 24px;
    flex-shrink: 0;
    color: var(--color-accent);
    margin-top: 2px;
}

.contact-compact-label {
    font-weight: 600;
    font-size: var(--font-size-sm);
    color: var(--color-text-meta);
    margin-bottom: 4px;
}

.contact-compact-item a {
    color: var(--color-link);
    text-decoration: none;
}

.contact-compact-item a:hover {
    text-decoration: underline;
}

/* Profile Grid */
.profile-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-sm);
}

.profile-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-md);
    background-color: var(--color-bg-alt);
    border: 1px solid var(--color-border);
    border-radius: 8px;
    text-decoration: none;
    color: var(--color-text);
    transition: all 0.2s ease;
    min-height: 100px;
}

.profile-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    border-color: var(--color-border-accent);
}

.profile-icon {
    width: 32px;
    height: 32px;
    margin-bottom: var(--spacing-xs);
}

.profile-card span {
    font-size: var(--font-size-sm);
    font-weight: 500;
    text-align: center;
}

.profile-note {
    font-size: var(--font-size-sm);
    color: var(--color-text-meta);
    font-style: italic;
    text-align: center;
}

/* Compact profile section for homepage */
.profile-links-section {
    padding: var(--spacing-md) 0;
    margin-bottom: var(--spacing-lg);
}

.profile-links-section .profile-grid {
    margin-bottom: 0;
}

/* Hero profile links - compact inline style */
.hero-profiles {
    display: flex;
    gap: var(--spacing-sm);
    margin-top: var(--spacing-md);
    justify-content: center;
    flex-wrap: wrap;
}

.hero-profile-link {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 52px;
    height: 52px;
    border-radius: 50%;
    background-color: var(--color-bg-alt);
    border: 1px solid var(--color-border);
    transition: all 0.2s ease;
    text-decoration: none;
}

.hero-profile-link:hover {
    transform: translateY(-2px);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    border-color: var(--color-border-accent);
}

.hero-profile-icon {
    width: 28px;
    height: 28px;
}


/* Buttons & Links */
.btn-download,
.button-link {
    display: inline-block;
    padding: 12px 28px;
    background-color: var(--color-accent);
    color: var(--color-bg);
    text-decoration: none;
    border-radius: 6px;
    font-weight: 600;
    font-size: var(--font-size-base);
    transition: all 0.2s ease;
    border: 2px solid var(--color-accent);
}

.btn-download:hover,
.button-link:hover {
    background-color: var(--color-text);
    border-color: var(--color-text);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.15);
}

.center-text {
    text-align: center;
}

/* =====================
   Footer
   ===================== */
footer {
    background-color: var(--color-bg);
    border-top: 2px solid var(--color-border);
    margin-top: var(--spacing-section);
    padding: var(--spacing-lg) var(--spacing-md);
    text-align: center;
}

footer p {
    font-size: var(--font-size-sm);
    color: var(--color-text-meta);
    margin-bottom: var(--spacing-xs);
}

footer p:last-child {
    margin-bottom: 0;
}

.footer-name {
    font-weight: 600;
    color: var(--color-text);
    font-size: var(--font-size-base);
    margin-bottom: var(--spacing-xs);
}

.footer-tagline {
    color: var(--color-text-meta);
    font-size: var(--font-size-sm);
}

/* =====================
   Responsive Design
   ===================== */
@media (max-width: 768px) {
    :root {
        --font-size-3xl: 28px;
        --font-size-2xl: 24px;
        --font-size-xl: 20px;
        --spacing-xl: 32px;
        --spacing-section: 40px;
    }
    
    nav ul {
        gap: 0;
    }

    nav a {
        padding: 12px var(--spacing-sm);
        font-size: var(--font-size-sm);
    }

    main {
        padding: var(--spacing-md) var(--spacing-sm);
    }

    .hero {
        padding: var(--spacing-lg) 0;
        margin-bottom: var(--spacing-xl);
    }

    .section,
    .content-section {
        padding: var(--spacing-md);
        margin-bottom: var(--spacing-md);
    }
    
    .quick-links {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    :root {
        --font-size-3xl: 24px;
        --font-size-2xl: 20px;
        --font-size-xl: 18px;
        --font-size-lg: 16px;
        --spacing-md: 16px;
        --spacing-lg: 20px;
    }
    
    nav a {
        padding: 10px 12px;
        font-size: var(--font-size-xs);
    }

    .section,
    .content-section {
        padding: var(--spacing-sm);
    }
    
    .publication,
    .contact-item {
        padding: var(--spacing-sm);
    }
    
    .pub-doi {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .bibtex-toggle {
        width: 100%;
        text-align: center;
    }
    
    .profile-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .contact-compact-item-with-logo {
        flex-direction: column;
        align-items: stretch;
    }
    
    .contact-logo-card {
        min-width: auto;
        width: 100%;
    }
}