/* ============================================
   Xun's Portal - Root Stylesheet
   A warm, academic light theme
   ============================================ */

/* CSS Custom Properties */
:root {
    --color-bg: #faf9f7;
    --color-bg-secondary: #ffffff;
    --color-text: #2d3748;
    --color-text-muted: #64748b;
    --color-accent-research: #2563eb;
    --color-accent-teaching: #059669;
    --color-accent-blog: #c026d3;
    --color-border: rgba(0, 0, 0, 0.08);
    --font-display: 'Crimson Pro', Georgia, serif;
    --font-body: 'Source Sans 3', -apple-system, BlinkMacSystemFont, sans-serif;
    --transition-smooth: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Reset and base styles */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

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

body {
    font-family: var(--font-body);
    line-height: 1.6;
    color: var(--color-text);
    background: var(--color-bg);
    min-height: 100vh;
}

/* Subtle background pattern */
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: 
        radial-gradient(ellipse at 20% 30%, rgba(37, 99, 235, 0.04) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 70%, rgba(5, 150, 105, 0.04) 0%, transparent 50%),
        radial-gradient(ellipse at 50% 90%, rgba(192, 38, 211, 0.03) 0%, transparent 40%);
    pointer-events: none;
    z-index: -1;
}

.page-wrapper {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Container */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

/* Header */
header {
    padding: 1rem 2rem;
    border-bottom: 1px solid var(--color-border);
}

header nav {
    max-width: 1000px;
    margin: 0 auto;
}

header .logo {
    font-family: var(--font-display);
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--color-text);
    letter-spacing: -0.02em;
}

header .nav-links {
    display: flex;
    gap: 2rem;
}

header .nav-links a {
    color: var(--color-text-muted);
    text-decoration: none;
    font-weight: 500;
    transition: color var(--transition-smooth);
}

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

/* Main content */
main {
    flex: 1;
    padding: 4rem 0;
}

/* Hero section */
.hero {
    text-align: center;
    margin-bottom: 4rem;
}

.hero h1 {
    font-family: var(--font-display);
    font-size: clamp(2.5rem, 6vw, 4rem);
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: 0.75rem;
    letter-spacing: -0.03em;
}

.hero .subtitle {
    font-size: 1.125rem;
    color: var(--color-text-muted);
    font-weight: 400;
}

/* Portal Cards */
.portal-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 2rem;
    margin-top: 2rem;
}

.portal-card {
    position: relative;
    display: block;
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-border);
    border-radius: 16px;
    padding: 2.5rem;
    text-decoration: none;
    color: inherit;
    transition: 
        transform var(--transition-smooth),
        border-color var(--transition-smooth),
        box-shadow var(--transition-smooth);
    overflow: hidden;
}

.portal-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    opacity: 0;
    transition: opacity var(--transition-smooth);
}

.research-card::before {
    background: linear-gradient(90deg, var(--color-accent-research), transparent);
}

.teaching-card::before {
    background: linear-gradient(90deg, var(--color-accent-teaching), transparent);
}

.blog-card::before {
    background: linear-gradient(90deg, var(--color-accent-blog), transparent);
}

.portal-card:hover {
    transform: translateY(-4px);
    border-color: rgba(0, 0, 0, 0.12);
    box-shadow: 0 20px 40px -15px rgba(0, 0, 0, 0.15);
}

.portal-card:hover::before {
    opacity: 1;
}

.card-icon {
    margin-bottom: 1.5rem;
    transition: transform var(--transition-smooth);
}

.research-card .card-icon {
    color: var(--color-accent-research);
}

.teaching-card .card-icon {
    color: var(--color-accent-teaching);
}

.blog-card .card-icon {
    color: var(--color-accent-blog);
}

.portal-card:hover .card-icon {
    transform: scale(1.1);
}

.portal-card h2 {
    font-family: var(--font-display);
    font-size: 1.75rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
    letter-spacing: -0.02em;
}

.research-card h2 {
    color: var(--color-accent-research);
}

.teaching-card h2 {
    color: var(--color-accent-teaching);
}

.blog-card h2 {
    color: var(--color-accent-blog);
}

.portal-card p {
    color: var(--color-text-muted);
    font-size: 1rem;
    line-height: 1.7;
    margin-bottom: 1.5rem;
}

.card-arrow {
    position: absolute;
    bottom: 2rem;
    right: 2rem;
    font-size: 1.5rem;
    opacity: 0;
    transform: translateX(-10px);
    transition: 
        opacity var(--transition-smooth),
        transform var(--transition-smooth);
}

.research-card .card-arrow {
    color: var(--color-accent-research);
}

.teaching-card .card-arrow {
    color: var(--color-accent-teaching);
}

.blog-card .card-arrow {
    color: var(--color-accent-blog);
}

.portal-card:hover .card-arrow {
    opacity: 1;
    transform: translateX(0);
}

/* Content sections (for sub-pages) */
.content-section {
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-border);
    border-radius: 12px;
    padding: 2rem;
    margin-bottom: 2rem;
}

.content-section h2 {
    font-family: var(--font-display);
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: 1rem;
    letter-spacing: -0.01em;
}

.content-section p {
    color: var(--color-text-muted);
}

/* Link cards for sub-pages */
.link-card {
    background: rgba(0, 0, 0, 0.02);
    border: 1px solid var(--color-border);
    border-radius: 8px;
    padding: 1.25rem;
    margin: 1rem 0;
    transition: 
        background var(--transition-smooth),
        border-color var(--transition-smooth);
}

.link-card:hover {
    background: rgba(0, 0, 0, 0.04);
    border-color: rgba(0, 0, 0, 0.12);
}

.link-card a {
    color: var(--color-accent-research);
    text-decoration: none;
    font-weight: 500;
    transition: color var(--transition-smooth);
}

.link-card a:hover {
    text-decoration: underline;
}

.link-card p {
    color: var(--color-text-muted);
    font-size: 0.9rem;
    margin-top: 0.5rem;
}

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

footer p {
    color: var(--color-text-muted);
    font-size: 0.875rem;
}

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

footer .footer-links a {
    color: var(--color-text-muted);
    text-decoration: none;
    margin-left: 1.5rem;
    font-size: 0.875rem;
    transition: color var(--transition-smooth);
}

footer .footer-links a:hover {
    color: var(--color-text);
}

/* Responsive design */
@media (max-width: 768px) {
    .portal-cards {
        grid-template-columns: 1fr;
    }

    .portal-card {
        padding: 2rem;
    }

    .hero h1 {
        font-size: 2.25rem;
    }

    header nav {
        text-align: center;
    }

    footer .footer-content {
        flex-direction: column;
        gap: 1rem;
    }

    footer .footer-links a {
        margin: 0 0.75rem;
    }
}

/* ============================================
   Card Sections (Courses, Blog, etc.)
   ============================================ */

.card-section {
    margin-bottom: 3rem;
}

.section-header-link {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    text-decoration: none;
    color: inherit;
    margin-bottom: 1.5rem;
    width: fit-content;
    transition: gap var(--transition-smooth);
}

.section-header-link:hover {
    gap: 0.75rem;
}

.section-header-link h2 {
    font-family: var(--font-display);
    font-size: 1.75rem;
    font-weight: 600;
    color: var(--color-text);
    letter-spacing: -0.02em;
    margin: 0;
}

.section-header-link:hover h2 {
    color: var(--color-accent-teaching);
}

.section-arrow {
    font-size: 1.25rem;
    color: var(--color-text-muted);
    transition: 
        transform var(--transition-smooth),
        color var(--transition-smooth);
}

.section-header-link:hover .section-arrow {
    transform: translateX(4px);
    color: var(--color-accent-teaching);
}

/* Card Grid */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1.25rem;
}

/* Mini Cards */
.mini-card {
    display: block;
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-border);
    border-radius: 12px;
    padding: 1.5rem;
    text-decoration: none;
    color: inherit;
    transition: 
        transform var(--transition-smooth),
        border-color var(--transition-smooth),
        box-shadow var(--transition-smooth);
}

.mini-card:hover {
    transform: translateY(-3px);
    border-color: rgba(0, 0, 0, 0.12);
    box-shadow: 0 12px 24px -8px rgba(0, 0, 0, 0.12);
}

.mini-card-tag {
    display: inline-block;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--color-accent-teaching);
    background: rgba(5, 150, 105, 0.1);
    padding: 0.25rem 0.6rem;
    border-radius: 4px;
    margin-bottom: 0.75rem;
}

.mini-card h3 {
    font-family: var(--font-display);
    font-size: 1.15rem;
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: 0.5rem;
    letter-spacing: -0.01em;
    transition: color var(--transition-smooth);
}

.mini-card:hover h3 {
    color: var(--color-accent-teaching);
}

.mini-card p {
    font-size: 0.9rem;
    color: var(--color-text-muted);
    line-height: 1.6;
    margin: 0;
}

/* Show More Link */
.show-more-link {
    display: inline-block;
    margin-top: 1.25rem;
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--color-accent-teaching);
    text-decoration: none;
    transition: color var(--transition-smooth);
}

.show-more-link:hover {
    color: #047857;
    text-decoration: underline;
}

/* Resource List */
.resource-list {
    list-style: none;
    margin-top: 1rem;
}

.resource-list li {
    position: relative;
    padding: 0.5rem 0 0.5rem 1.5rem;
    color: var(--color-text-muted);
}

.resource-list li::before {
    content: '→';
    position: absolute;
    left: 0;
    color: var(--color-accent-teaching);
    font-weight: 500;
}

/* ============================================
   Responsive Adjustments for Card Sections
   ============================================ */

@media (max-width: 768px) {
    .card-grid {
        grid-template-columns: 1fr;
    }
    
    .section-header-link h2 {
        font-size: 1.5rem;
    }
}

/* Selection color */
::selection {
    background: rgba(37, 99, 235, 0.2);
    color: var(--color-text);
}