/* CSS Variables for Theme */
:root {
    --primary-color: #2563eb;
    --secondary-color: #7c3aed;
    --accent-color: #10b981;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --bg-primary: #ffffff;
    --bg-secondary: #f9fafb;
    --bg-tertiary: #f3f4f6;
    --border-color: #e5e7eb;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Dark Mode Variables */
[data-theme="dark"] {
    --primary-color: #3b82f6;
    --secondary-color: #8b5cf6;
    --accent-color: #34d399;
    --text-primary: #f9fafb;
    --text-secondary: #d1d5db;
    --bg-primary: #111827;
    --bg-secondary: #1f2937;
    --bg-tertiary: #374151;
    --border-color: #4b5563;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.5);
}

/* Reset & Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
    transition: var(--transition);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 16px;
}

/* Navigation */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background-color: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
    transition: var(--transition);
    backdrop-filter: blur(10px);
    background-color: rgba(255, 255, 255, 0.9);
}

[data-theme="dark"] .navbar {
    background-color: rgba(17, 24, 39, 0.9);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-logo {
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary-color);
}

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

.nav-link {
    color: var(--text-primary);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
    position: relative;
}

.nav-link:hover {
    color: var(--primary-color);
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--primary-color);
    transition: var(--transition);
}

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

.nav-controls {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.theme-toggle {
    background: none;
    border: 1px solid var(--border-color);
    border-radius: 50%;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: var(--transition);
    font-size: 1.2rem;
}

.theme-toggle:hover {
    background-color: var(--bg-secondary);
    transform: rotate(15deg);
}

.mobile-menu-toggle {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
}

.mobile-menu-toggle span {
    width: 25px;
    height: 3px;
    background-color: var(--text-primary);
    transition: var(--transition);
    border-radius: 2px;
}

/* Hero Section */
.hero {
    min-height: auto;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: 40px 16px 30px;
    background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-primary) 100%);
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle, var(--primary-color) 0%, transparent 70%);
    opacity: 0.05;
    animation: pulse 20s infinite;
}

@keyframes pulse {
    0%, 100% { transform: scale(1); opacity: 0.05; }
    50% { transform: scale(1.1); opacity: 0.08; }
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 800px;
}

.hero-title {
    font-size: clamp(2rem, 4vw, 3rem);
    font-weight: 800;
    margin-bottom: 0.75rem;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    animation: fadeInUp 0.8s ease-out;
}

.hero-subtitle {
    font-size: clamp(1.25rem, 3vw, 2rem);
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
    animation: fadeInUp 0.8s ease-out 0.2s both;
}

.hero-description {
    font-size: clamp(0.9375rem, 1.5vw, 1.125rem);
    color: var(--text-secondary);
    margin-bottom: 0;
    animation: fadeInUp 0.8s ease-out 0.4s both;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.countdown-container {
    display: flex;
    justify-content: center;
    gap: 2rem;
    margin: 3rem 0;
    flex-wrap: wrap;
    animation: fadeInUp 0.8s ease-out 0.6s both;
}

.countdown-item {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 1.5rem 2rem;
    min-width: 100px;
    box-shadow: var(--shadow-md);
    transition: var(--transition);
}

.countdown-item:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.countdown-value {
    display: block;
    font-size: 2.5rem;
    font-weight: bold;
    color: var(--primary-color);
    font-variant-numeric: tabular-nums;
}

.countdown-label {
    display: block;
    font-size: 0.875rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-top: 0.5rem;
}

.hero-stats {
    display: flex;
    justify-content: center;
    gap: 3rem;
    margin-top: 3rem;
    flex-wrap: wrap;
    animation: fadeInUp 0.8s ease-out 0.8s both;
}

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

.stat-value {
    display: block;
    font-size: 2rem;
    font-weight: bold;
    color: var(--accent-color);
}

.stat-label {
    display: block;
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-top: 0.5rem;
}

/* Section Styles */
section {
    padding: 40px 0;
    position: relative;
}

.section-title {
    font-size: clamp(2rem, 4vw, 3rem);
    font-weight: 700;
    text-align: center;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.section-subtitle {
    text-align: center;
    color: var(--text-secondary);
    font-size: 1rem;
    margin-bottom: 2rem;
}

/* Timeline Section */
.timeline-section {
    background-color: var(--bg-secondary);
}

.timeline {
    position: relative;
    padding: 2rem 0;
    max-width: 900px;
    margin: 0 auto;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 50%;
    top: 0;
    bottom: 0;
    width: 3px;
    background: linear-gradient(to bottom, var(--primary-color), var(--secondary-color));
    transform: translateX(-50%);
}

.timeline-item {
    position: relative;
    margin-bottom: 3rem;
    display: flex;
    align-items: center;
    opacity: 0;
    animation: fadeInUp 0.6s ease-out forwards;
}

.timeline-item:nth-child(even) {
    flex-direction: row-reverse;
}

.timeline-content {
    width: 45%;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 1.5rem;
    box-shadow: var(--shadow-md);
    transition: var(--transition);
}

.timeline-item:nth-child(odd) .timeline-content {
    margin-right: auto;
}

.timeline-item:nth-child(even) .timeline-content {
    margin-left: auto;
}

.timeline-content:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.timeline-marker {
    position: absolute;
    left: 50%;
    transform: translateX(-50%);
    width: 20px;
    height: 20px;
    background-color: var(--primary-color);
    border: 4px solid var(--bg-secondary);
    border-radius: 50%;
    z-index: 1;
}

.timeline-date {
    font-size: 0.875rem;
    color: var(--text-secondary);
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.timeline-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.timeline-description {
    color: var(--text-secondary);
    font-size: 0.9375rem;
}

.timeline-status {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.75rem;
    font-weight: 600;
    margin-top: 0.5rem;
}

.timeline-status.completed {
    background-color: var(--accent-color);
    color: white;
}

.timeline-status.in-progress {
    background-color: var(--primary-color);
    color: white;
}

.timeline-status.upcoming {
    background-color: var(--bg-tertiary);
    color: var(--text-secondary);
}

/* Papers Section */
.papers-section {
    background-color: var(--bg-primary);
}

.search-filter-container {
    max-width: 800px;
    margin: 0 auto 2rem;
}

.search-input {
    width: 100%;
    padding: 1rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    background-color: var(--bg-secondary);
    color: var(--text-primary);
    margin-bottom: 1.5rem;
    transition: var(--transition);
}

.search-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.tag-filters {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.tag-filter {
    padding: 0.5rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: 20px;
    background-color: var(--bg-secondary);
    color: var(--text-primary);
    cursor: pointer;
    transition: var(--transition);
    font-size: 0.875rem;
}

.tag-filter:hover {
    background-color: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.tag-filter.active {
    background-color: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.papers-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1.5rem;
}

.paper-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 1.25rem;
    transition: var(--transition);
    cursor: pointer;
}

.paper-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.paper-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.paper-authors {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: 0.75rem;
}

.paper-year {
    display: inline-block;
    padding: 0.25rem 0.5rem;
    background-color: var(--bg-tertiary);
    border-radius: 4px;
    font-size: 0.75rem;
    color: var(--text-secondary);
    margin-bottom: 0.75rem;
}

.paper-notes {
    font-size: 0.9375rem;
    color: var(--text-secondary);
    margin-bottom: 1rem;
    line-height: 1.6;
}

.paper-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.paper-tag {
    padding: 0.25rem 0.75rem;
    background-color: var(--bg-tertiary);
    border-radius: 12px;
    font-size: 0.75rem;
    color: var(--text-primary);
}

.paper-link {
    display: inline-block;
    margin-top: 1rem;
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    font-size: 0.875rem;
}

.paper-link:hover {
    text-decoration: underline;
}

/* Learning Section */
.learning-section {
    background-color: var(--bg-secondary);
}

.progress-summary {
    max-width: 600px;
    margin: 0 auto 2rem;
}

.progress-card {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 1.5rem;
    box-shadow: var(--shadow-md);
}

.progress-card h3 {
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.progress-bar-container {
    width: 100%;
    height: 30px;
    background-color: var(--bg-tertiary);
    border-radius: 15px;
    overflow: hidden;
    position: relative;
}

.progress-bar {
    height: 100%;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    border-radius: 15px;
    transition: width 1s ease-out;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
}

.progress-text {
    color: white;
    font-weight: 600;
    font-size: 0.875rem;
    z-index: 1;
}

.courses-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1.5rem;
}

.course-card {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 1.25rem;
    transition: var(--transition);
}

.course-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.course-header {
    display: flex;
    justify-content: space-between;
    align-items: start;
    margin-bottom: 1rem;
}

.course-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
    flex: 1;
}

.course-platform {
    font-size: 0.75rem;
    color: var(--text-secondary);
    padding: 0.25rem 0.5rem;
    background-color: var(--bg-tertiary);
    border-radius: 4px;
}

.course-progress-container {
    margin-top: 1rem;
}

.course-progress-bar {
    width: 100%;
    height: 8px;
    background-color: var(--bg-tertiary);
    border-radius: 4px;
    overflow: hidden;
    margin-bottom: 0.5rem;
}

.course-progress-fill {
    height: 100%;
    background-color: var(--accent-color);
    border-radius: 4px;
    transition: width 0.5s ease-out;
}

.course-progress-text {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

/* Build Section */
.build-section {
    background-color: var(--bg-primary);
}

.build-phases {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 3rem;
    flex-wrap: wrap;
}

.build-phase {
    padding: 0.75rem 1.5rem;
    border: 2px solid var(--border-color);
    border-radius: 20px;
    background-color: var(--bg-secondary);
    color: var(--text-primary);
    cursor: pointer;
    transition: var(--transition);
    font-weight: 500;
}

.build-phase:hover,
.build-phase.active {
    background-color: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.gallery-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 1.5rem;
}

.gallery-item {
    position: relative;
    aspect-ratio: 1;
    border-radius: 12px;
    overflow: hidden;
    cursor: pointer;
    transition: var(--transition);
}

.gallery-item:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow-lg);
}

.gallery-item img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.gallery-item-placeholder {
    background: linear-gradient(135deg, var(--bg-secondary), var(--bg-tertiary));
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.gallery-caption {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    background: linear-gradient(to top, rgba(0, 0, 0, 0.8), transparent);
    color: white;
    padding: 1rem;
    font-size: 0.875rem;
    transform: translateY(100%);
    transition: var(--transition);
}

.gallery-item:hover .gallery-caption {
    transform: translateY(0);
}

/* Blog Section */
.blog-section {
    background-color: var(--bg-secondary);
}

.blog-posts {
    display: grid;
    gap: 2rem;
    max-width: 800px;
    margin: 0 auto;
}

.blog-post {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 2rem;
    transition: var(--transition);
}

.blog-post:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.blog-post-date {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
}

.blog-post-title {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 1rem;
}

.blog-post-content {
    color: var(--text-secondary);
    line-height: 1.8;
    margin-bottom: 1rem;
}

.blog-post-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-top: 1rem;
}

/* Resources Section */
.resources-section {
    background-color: var(--bg-primary);
}

.resources-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1.5rem;
}

.resource-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 1.25rem;
    transition: var(--transition);
}

.resource-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.resource-type {
    font-size: 0.75rem;
    text-transform: uppercase;
    color: var(--text-secondary);
    letter-spacing: 1px;
    margin-bottom: 0.5rem;
}

.resource-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.resource-description {
    font-size: 0.9375rem;
    color: var(--text-secondary);
    margin-bottom: 1rem;
}

.resource-link {
    display: inline-block;
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    font-size: 0.875rem;
}

.resource-link:hover {
    text-decoration: underline;
}

/* About Section */
.about-section {
    background-color: var(--bg-secondary);
}

.about-content {
    max-width: 800px;
    margin: 0 auto;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 3rem;
    box-shadow: var(--shadow-md);
}

.about-content p {
    color: var(--text-secondary);
    line-height: 1.8;
    margin-bottom: 1.5rem;
    font-size: 1.0625rem;
}

.about-content h3 {
    color: var(--text-primary);
    margin-top: 2rem;
    margin-bottom: 1rem;
    font-size: 1.5rem;
}

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

.footer-links {
    margin-top: 1rem;
}

.footer-links a {
    color: var(--primary-color);
    text-decoration: none;
    transition: var(--transition);
}

.footer-links a:hover {
    text-decoration: underline;
}

.social-links {
    margin-top: 1.5rem;
    display: flex;
    justify-content: center;
    gap: 1rem;
    flex-wrap: wrap;
}

.social-links a {
    color: var(--text-secondary);
    text-decoration: none;
    transition: var(--transition);
    padding: 0.5rem;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    background-color: var(--bg-secondary);
}

.social-links a:hover {
    color: var(--primary-color);
    background-color: var(--bg-tertiary);
    transform: translateY(-3px);
}

.social-links a svg {
    width: 20px;
    height: 20px;
}

/* Desktop Enhancements */
@media (min-width: 769px) {
    .container {
        padding: 0 20px;
    }

    /* Section Styles */
    section {
        padding: 80px 0;
    }

    .section-subtitle {
        font-size: 1.125rem;
        margin-bottom: 3rem;
    }

    /* Hero Section */
    .hero {
        padding: 60px 20px 40px;
    }

    /* Search and Filter */
    .search-filter-container {
        margin: 0 auto 3rem;
    }

    /* Progress Summary */
    .progress-summary {
        margin: 0 auto 3rem;
    }

    .progress-card {
        padding: 2rem;
    }

    /* Grids - Multi-column on desktop */
    .papers-grid {
        grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
        gap: 2rem;
    }

    .courses-grid {
        grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
        gap: 2rem;
    }

    .resources-grid {
        grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
        gap: 2rem;
    }

    .gallery-grid {
        grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    }

    /* Cards - More padding on desktop */
    .paper-card,
    .course-card,
    .resource-card {
        padding: 1.5rem;
    }
}

/* Utility Classes */
.hidden {
    display: none !important;
}

.fade-in {
    animation: fadeInUp 0.6s ease-out forwards;
}