/* ===== CSS Variables & Design System ===== */
:root {
    /* Colors */
    --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --secondary-gradient: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --accent-gradient: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);

    --bg-primary: #0a0e27;
    --bg-secondary: #141b3d;
    --bg-tertiary: #1e2749;
    --bg-card: rgba(30, 39, 73, 0.6);

    --text-primary: #ffffff;
    --text-secondary: #a0aec0;
    --text-muted: #718096;

    --border-color: rgba(255, 255, 255, 0.1);
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.2);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.3);
    --shadow-glow: 0 0 40px rgba(102, 126, 234, 0.3);

    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;

    /* Typography */
    --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-mono: 'JetBrains Mono', 'Courier New', monospace;

    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;

    /* Transitions */
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);
}

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

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

/* Animated Background */
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background:
        radial-gradient(circle at 20% 50%, rgba(102, 126, 234, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 80% 80%, rgba(118, 75, 162, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 40% 20%, rgba(79, 172, 254, 0.08) 0%, transparent 50%);
    z-index: -1;
    animation: backgroundPulse 15s ease-in-out infinite;
}

@keyframes backgroundPulse {

    0%,
    100% {
        opacity: 1;
    }

    50% {
        opacity: 0.8;
    }
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

/* ===== Navigation ===== */
.navbar {
    position: sticky;
    top: 0;
    background: rgba(10, 14, 39, 0.8);
    backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border-color);
    padding: var(--spacing-md) 0;
    z-index: 1000;
    animation: slideDown 0.5s ease-out;
}

@keyframes slideDown {
    from {
        transform: translateY(-100%);
        opacity: 0;
    }

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

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

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: 1.25rem;
    font-weight: 700;
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

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

.nav-link {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-sm);
    transition: all var(--transition-base);
    position: relative;
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    width: 0;
    height: 2px;
    background: var(--primary-gradient);
    transform: translateX(-50%);
    transition: width var(--transition-base);
}

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

.nav-link:hover::after,
.nav-link.active::after {
    width: 80%;
}

/* ===== Hero Section ===== */
.hero {
    padding: var(--spacing-2xl) 0;
    text-align: center;
    position: relative;
}

.hero-content {
    animation: fadeInUp 0.8s ease-out;
}

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

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

.hero-title {
    font-size: clamp(2.5rem, 5vw, 4rem);
    font-weight: 800;
    background: linear-gradient(135deg, #ffffff 0%, #a0aec0 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-md);
    line-height: 1.2;
}

.hero-subtitle {
    font-size: clamp(1rem, 2vw, 1.25rem);
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto var(--spacing-xl);
}

.hero-stats {
    display: flex;
    justify-content: center;
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
    flex-wrap: wrap;
}

.stat-card {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-md) var(--spacing-lg);
    min-width: 120px;
    transition: all var(--transition-base);
}

.stat-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-glow);
    border-color: rgba(102, 126, 234, 0.5);
}

.stat-number {
    font-size: 2.5rem;
    font-weight: 800;
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.stat-label {
    color: var(--text-secondary);
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.cta-button {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    background: var(--primary-gradient);
    color: white;
    border: none;
    padding: var(--spacing-md) var(--spacing-xl);
    border-radius: var(--radius-lg);
    font-size: 1.125rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-base);
    box-shadow: var(--shadow-md);
}

.cta-button:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg), var(--shadow-glow);
}

.cta-button:active {
    transform: translateY(0);
}

/* ===== Topics Section ===== */
.topics-section {
    padding: var(--spacing-2xl) 0;
}

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

.section-subtitle {
    text-align: center;
    color: var(--text-secondary);
    font-size: 1.125rem;
    margin-bottom: var(--spacing-xl);
}

.topics-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-xl);
}

.topic-card {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    cursor: pointer;
    transition: all var(--transition-base);
    position: relative;
    overflow: hidden;
}

.topic-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, rgba(102, 126, 234, 0.1) 0%, transparent 100%);
    opacity: 0;
    transition: opacity var(--transition-base);
}

.topic-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-lg);
    border-color: rgba(102, 126, 234, 0.5);
}

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

.topic-icon {
    width: 64px;
    height: 64px;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: var(--spacing-md);
    box-shadow: var(--shadow-md);
    transition: transform var(--transition-base);
}

.topic-card:hover .topic-icon {
    transform: scale(1.1) rotate(5deg);
}

.topic-title {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-xs);
}

.topic-description {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
    line-height: 1.5;
}

.topic-meta {
    display: flex;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-md);
    font-size: 0.875rem;
    color: var(--text-muted);
}

.lesson-count::before {
    content: '📚 ';
}

.question-count::before {
    content: '❓ ';
}

.progress-bar {
    width: 100%;
    height: 6px;
    background: var(--bg-tertiary);
    border-radius: 3px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--primary-gradient);
    border-radius: 3px;
    transition: width var(--transition-slow);
}

/* ===== Learning View ===== */
.learning-view {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: var(--bg-primary);
    z-index: 2000;
    overflow-y: auto;
    transition: opacity var(--transition-base);
}

.learning-view.hidden {
    display: none;
    opacity: 0;
}

.learning-container {
    max-width: 900px;
    margin: 0 auto;
    padding: var(--spacing-lg);
}

.back-button {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-md);
    font-size: 1rem;
    cursor: pointer;
    transition: all var(--transition-base);
    margin-bottom: var(--spacing-lg);
}

.back-button:hover {
    background: var(--bg-tertiary);
    transform: translateX(-4px);
}

.learning-header {
    margin-bottom: var(--spacing-xl);
}

.learning-title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-md);
}

.learning-tabs {
    display: flex;
    gap: var(--spacing-sm);
    border-bottom: 2px solid var(--border-color);
}

.tab-button {
    background: none;
    border: none;
    color: var(--text-secondary);
    padding: var(--spacing-sm) var(--spacing-lg);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    position: relative;
    transition: all var(--transition-base);
}

.tab-button::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 100%;
    height: 2px;
    background: var(--primary-gradient);
    transform: scaleX(0);
    transition: transform var(--transition-base);
}

.tab-button.active {
    color: var(--text-primary);
}

.tab-button.active::after {
    transform: scaleX(1);
}

.tab-content {
    display: none;
    animation: fadeIn 0.3s ease-out;
}

.tab-content.active {
    display: block;
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }

    to {
        opacity: 1;
    }
}

/* ===== Lessons ===== */
.lesson-item {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
}

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

.lesson-number {
    display: inline-block;
    background: var(--primary-gradient);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
}

.lesson-title {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
}

.lesson-content {
    color: var(--text-secondary);
    line-height: 1.8;
}

.lesson-content h4 {
    color: var(--text-primary);
    margin-top: var(--spacing-md);
    margin-bottom: var(--spacing-sm);
    font-size: 1.125rem;
}

.lesson-content ul,
.lesson-content ol {
    margin-left: var(--spacing-lg);
    margin-bottom: var(--spacing-md);
}

.lesson-content li {
    margin-bottom: var(--spacing-xs);
}

.lesson-content code {
    background: var(--bg-tertiary);
    color: #4facfe;
    padding: 0.2rem 0.5rem;
    border-radius: 4px;
    font-family: var(--font-mono);
    font-size: 0.9em;
}

.lesson-content pre {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    overflow-x: auto;
    margin: var(--spacing-md) 0;
}

.lesson-content pre code {
    background: none;
    padding: 0;
}

.example-box {
    background: var(--bg-tertiary);
    border-left: 4px solid #667eea;
    border-radius: var(--radius-sm);
    padding: var(--spacing-md);
    margin: var(--spacing-md) 0;
}

.example-box strong {
    color: #667eea;
}

/* ===== Questions ===== */
.question-item {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
}

.question-header {
    margin-bottom: var(--spacing-md);
}

.question-number {
    display: inline-block;
    background: var(--secondary-gradient);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
}

.difficulty-badge {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-weight: 600;
    margin-left: var(--spacing-sm);
}

.difficulty-easy {
    background: rgba(72, 187, 120, 0.2);
    color: #48bb78;
}

.difficulty-medium {
    background: rgba(237, 137, 54, 0.2);
    color: #ed8936;
}

.difficulty-hard {
    background: rgba(245, 101, 101, 0.2);
    color: #f56565;
}

.question-text {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: var(--spacing-md);
    line-height: 1.6;
}

.question-context {
    background: var(--bg-tertiary);
    border-radius: var(--radius-sm);
    padding: var(--spacing-md);
    margin-bottom: var(--spacing-md);
    color: var(--text-secondary);
    line-height: 1.6;
}

.reveal-button {
    background: var(--accent-gradient);
    color: white;
    border: none;
    padding: var(--spacing-sm) var(--spacing-lg);
    border-radius: var(--radius-md);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-base);
    margin-top: var(--spacing-md);
}

.reveal-button:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.answer-section {
    margin-top: var(--spacing-md);
    padding-top: var(--spacing-md);
    border-top: 1px solid var(--border-color);
    display: none;
}

.answer-section.visible {
    display: block;
    animation: fadeIn 0.3s ease-out;
}

.answer-label {
    display: inline-block;
    background: linear-gradient(135deg, #48bb78 0%, #38a169 100%);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
}

.answer-content {
    color: var(--text-secondary);
    line-height: 1.8;
}

.answer-content h4 {
    color: var(--text-primary);
    margin-top: var(--spacing-md);
    margin-bottom: var(--spacing-sm);
}

.answer-content code {
    background: var(--bg-tertiary);
    color: #4facfe;
    padding: 0.2rem 0.5rem;
    border-radius: 4px;
    font-family: var(--font-mono);
    font-size: 0.9em;
}

.answer-content pre {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    overflow-x: auto;
    margin: var(--spacing-md) 0;
}

.answer-content pre code {
    background: none;
    padding: 0;
}

/* ===== Responsive Design ===== */
@media (max-width: 768px) {
    .hero-stats {
        flex-direction: column;
        align-items: center;
    }

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

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

    .learning-title {
        font-size: 2rem;
    }
}

/* ===== Code Editor ===== */
.code-editor-section {
    margin-top: var(--spacing-md);
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
}

.code-editor-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-sm);
}

.code-editor-label {
    font-weight: 600;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.code-editor-label svg {
    color: #4facfe;
}

.code-editor {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: var(--spacing-md);
    font-family: var(--font-mono);
    font-size: 0.9rem;
    color: var(--text-primary);
    min-height: 150px;
    resize: vertical;
    width: 100%;
    line-height: 1.5;
}

.code-editor:focus {
    outline: none;
    border-color: #667eea;
    box-shadow: 0 0 0 2px rgba(102, 126, 234, 0.2);
}

.run-code-button {
    background: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    color: white;
    border: none;
    padding: var(--spacing-sm) var(--spacing-lg);
    border-radius: var(--radius-md);
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-base);
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.run-code-button:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.code-output {
    margin-top: var(--spacing-md);
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: var(--spacing-md);
    font-family: var(--font-mono);
    font-size: 0.875rem;
    color: var(--text-secondary);
    display: none;
}

.code-output.visible {
    display: block;
}

.code-output-success {
    color: #48bb78;
}

.code-output-error {
    color: #f56565;
}

/* ===== Footer ===== */
.footer {
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    padding: var(--spacing-2xl) 0 var(--spacing-lg);
    margin-top: var(--spacing-2xl);
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-xl);
    margin-bottom: var(--spacing-xl);
}

.footer-section {
    display: flex;
    flex-direction: column;
}

.footer-title {
    font-size: 1.5rem;
    font-weight: 700;
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-sm);
}

.footer-description {
    color: var(--text-secondary);
    line-height: 1.6;
}

.footer-heading {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: var(--spacing-md);
}

.footer-links {
    list-style: none;
    padding: 0;
    margin: 0;
}

.footer-links li {
    margin-bottom: var(--spacing-xs);
}

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

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

.footer-contact {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xs);
    line-height: 1.6;
}

.footer-contact strong {
    color: var(--text-primary);
}

.footer-contact a {
    color: #4facfe;
    text-decoration: none;
    transition: color var(--transition-base);
}

.footer-contact a:hover {
    color: #667eea;
}

.footer-social {
    display: flex;
    gap: var(--spacing-md);
    margin-top: var(--spacing-md);
}

.social-link {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    transition: all var(--transition-base);
}

.social-link:hover {
    background: var(--primary-gradient);
    color: white;
    border-color: transparent;
    transform: translateY(-2px);
}

.footer-bottom {
    text-align: center;
    padding-top: var(--spacing-lg);
    border-top: 1px solid var(--border-color);
    color: var(--text-muted);
    font-size: 0.875rem;
}

/* ===== Auth Panel ===== */
.auth-panel {
    margin-top: var(--spacing-xl);
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    text-align: center;
}

.auth-title {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-xs);
}

.auth-subtitle {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
}

.auth-status {
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
}

.auth-form {
    display: grid;
    gap: var(--spacing-sm);
    max-width: 420px;
    margin: 0 auto;
}

.auth-form input {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    color: var(--text-primary);
    font-size: 1rem;
}

.auth-form input:focus {
    outline: none;
    border-color: #667eea;
    box-shadow: 0 0 0 2px rgba(102, 126, 234, 0.2);
}

.auth-actions {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
    justify-content: center;
    margin-top: var(--spacing-sm);
}

.auth-message {
    min-height: 1.5rem;
    color: var(--text-secondary);
    font-size: 0.95rem;
}

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

/* ===== Footer Logo (Centered) ===== */
.footer-logo-section {
    display: flex;
    justify-content: center;
    align-items: center;
    margin-bottom: var(--spacing-lg);
    padding-top: var(--spacing-lg);
    border-top: 1px solid var(--border-color);
}

.footer-logo-centered {
    height: 100px;
    width: auto;
    border-radius: 8px;
    transition: transform var(--transition-base);
}

.footer-logo-centered:hover {
    transform: scale(1.05);
}

/* ===== Case Studies ===== */
.case-studies-container {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-lg);
}

.case-study-item {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
}

.case-study-header {
    margin-bottom: var(--spacing-md);
}

.case-number {
    display: inline-block;
    background: var(--primary-gradient);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
}

.case-scenario {
    margin-bottom: var(--spacing-md);
    padding: var(--spacing-md);
    background: rgba(102, 126, 234, 0.05);
    border-left: 3px solid var(--primary-color);
    border-radius: var(--radius-sm);
}

.case-scenario p {
    margin: 0;
    line-height: 1.6;
    color: var(--text-secondary);
}

.case-question {
    margin-bottom: var(--spacing-md);
    font-weight: 600;
    color: var(--text-primary);
}

.case-options {
    margin-bottom: var(--spacing-md);
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.case-option {
    display: flex;
    align-items: center;
    padding: var(--spacing-sm);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: background-color var(--transition-base);
}

.case-option:hover {
    background-color: rgba(102, 126, 234, 0.1);
}

.case-option input[type="radio"] {
    margin-right: var(--spacing-sm);
    cursor: pointer;
}

.case-option label {
    cursor: pointer;
    flex: 1;
    margin: 0;
}
/* ===== Track-based Card Theme Overrides ===== */

.topic-card.track--data-analyst .topic-icon { background: linear-gradient(135deg, #667eea 0%, #764ba2 100%); }
.topic-card.track--data-engineer .topic-icon { background: linear-gradient(135deg, #f5576c 0%, #f093fb 100%); }
.topic-card.track--data-scientist .topic-icon { background: linear-gradient(135deg, #00d4aa 0%, #00a896 100%); }
.topic-card.track--core .topic-icon { background: linear-gradient(135deg, #f59e0b 0%, #d97706 100%); }


/* ===== Role-Track Filters ===== */
.topic-filters { display: flex; flex-wrap: wrap; gap: var(--spacing-sm); justify-content: center; margin-bottom: var(--spacing-lg); }
.filter-button {
    padding: 0.6rem 1.4rem;
    border: 1px solid var(--border-color);
    border-radius: 999px;
    background: rgba(255,255,255,0.03);
    color: var(--text-secondary);
    font-family: var(--font-primary);
    font-weight: 500;
    font-size: 0.95rem;
    cursor: pointer;
    transition: all var(--transition-base);
}
.filter-button:hover { border-color: #667eea; color: var(--text-primary); background: rgba(102,126,234,0.12); }
.filter-button.active { background: var(--primary-gradient); color: #fff; border-color: transparent; font-weight: 600; }

.category-badge {
    display: inline-block;
    font-size: 0.7rem;
    font-weight: 600;
    letter-spacing: 0.5px;
    text-transform: uppercase;
    color: var(--text-muted);
    background: rgba(255,255,255,0.05);
    padding: 0.15rem 0.6rem;
    border-radius: 999px;
    margin-bottom: var(--spacing-sm);
}

/* ===== Learning Toolbar + Breadcrumb ===== */
.learning-toolbar { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: var(--spacing-sm); padding: var(--spacing-sm) 0; border-bottom: 1px solid var(--border-color); margin-bottom: var(--spacing-md); }
.breadcrumb { font-size: 0.85rem; color: var(--text-muted); }
.nav-topic-buttons { display: flex; gap: var(--spacing-sm); }
.nav-topic-button {
    display: inline-flex; align-items: center; gap: 0.35rem;
    padding: 0.45rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    background: transparent;
    color: var(--text-secondary);
    font-family: var(--font-primary);
    font-size: 0.9rem;
    cursor: pointer;
    transition: all var(--transition-base);
}
.nav-topic-button:hover { color: var(--text-primary); border-color: #667eea; background: rgba(102,126,234,0.10); }

/* ===== Lesson Done Button ===== */
.lesson-header { display: flex; justify-content: space-between; align-items: flex-start; gap: var(--spacing-sm); }
.lesson-done-button {
    padding: 0.35rem 0.85rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    background: transparent;
    color: var(--text-muted);
    font-size: 0.8rem;
    cursor: pointer;
    transition: all var(--transition-base);
    white-space: nowrap;
}
.lesson-done-button:hover { color: var(--text-primary); border-color: #4facfe; }
.lesson-done-button.done { background: rgba(0,212,170,0.15); border-color: #00d4aa; color: #00d4aa; }

/* ===== Inline SVG diagrams ===== */
.lesson-content .diagram,
.answer-content .diagram {
    display: flex; justify-content: center;
    padding: var(--spacing-md);
    background: rgba(255,255,255,0.02);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    margin: var(--spacing-md) 0;
    overflow-x: auto;
}
.diagram svg { max-width: 100%; height: auto; display: block; }

/* ===== Polish: track accent, diagram captions, small refinements ===== */

.topic-card {
    border-top: 3px solid rgba(102,126,234,0.35);
}
.topic-card.track--data-engineer { border-top-color: rgba(245,87,108,0.45); }
.topic-card.track--data-scientist { border-top-color: rgba(0,212,170,0.45); }
.topic-card.track--core { border-top-color: rgba(245,158,11,0.45); }

.topic-card .lesson-count,
.topic-card .question-count {
    display: inline-block;
    padding: 0.2rem 0.6rem;
    border-radius: 999px;
    font-size: 0.75rem;
    background: rgba(255,255,255,0.05);
}

.diagram figcaption {
    text-align: center;
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-top: var(--spacing-sm);
    font-style: italic;
}

/* better focus visibility for accessibility */
.topic-card:focus-visible,
.filter-button:focus-visible,
.nav-topic-button:focus-visible {
    outline: 2px solid #667eea;
    outline-offset: 2px;
}

/* ===== About Section ===== */
.about-section {
    padding: var(--spacing-xl) 0;
}
.about-content {
    display: flex;
    gap: var(--spacing-lg);
    align-items: center;
    max-width: 900px;
    margin: 0 auto;
    flex-wrap: wrap;
    justify-content: center;
}
.about-photo {
    flex: 0 0 auto;
}
.about-photo-img {
    width: 220px;
    height: 220px;
    border-radius: 50%;
    object-fit: cover;
    border: 3px solid var(--primary-gradient);
    border: 3px solid #667eea;
    box-shadow: var(--shadow-glow);
}
.about-text {
    flex: 1 1 400px;
    color: var(--text-secondary);
    line-height: 1.7;
}
.about-text p { margin-bottom: var(--spacing-sm); }
@media (max-width: 768px) {
    .about-photo-img { width: 160px; height: 160px; }
}
/* ===== Portfolio Project Cards & Modal ===== */

.project-card-item {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    position: relative;
    overflow: hidden;
    border-top: 3px solid rgba(102,126,234,0.35);
    transition: transform var(--transition-base), box-shadow var(--transition-base), border-color var(--transition-base);
}

/* ===== Project Card Polish: tool accents, hover, tags, result highlight ===== */
.project-card-portfolio { display: flex; flex-direction: column; }
.project-card-portfolio:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 32px rgba(0,0,0,0.35);
}

/* Per-tool accent colors: border, badge, buttons */
.project-card-portfolio { --tool-accent: #667eea; }
.project-card-portfolio.tool-tableau  { --tool-accent: #e879f9; border-top-color: #e879f9; }
.project-card-portfolio.tool-powerbi { --tool-accent: #fbbf24; border-top-color: #fbbf24; }
.project-card-portfolio.tool-python  { --tool-accent: #60a5fa; border-top-color: #60a5fa; }

.tool-badge {
    display: inline-block;
    font-size: 0.7rem;
    font-weight: 700;
    letter-spacing: 0.6px;
    text-transform: uppercase;
    padding: 0.25rem 0.75rem;
    border-radius: 999px;
    color: #fff;
    background: var(--tool-accent);
    white-space: nowrap;
    box-shadow: 0 2px 8px color-mix(in srgb, var(--tool-accent) 45%, transparent);
}

.category-badge {
    background: color-mix(in srgb, var(--tool-accent) 16%, transparent);
    color: var(--tool-accent);
    border: 1px solid color-mix(in srgb, var(--tool-accent) 35%, transparent);
}

/* Result line pops as key takeaway */
.project-card-portfolio .star-method p {
    font-size: 0.9rem;
    line-height: 1.55;
    color: var(--text-secondary);
}
.project-card-portfolio .star-method p strong {
    color: var(--tool-accent);
}
.project-card-portfolio .star-method p:last-child {
    background: color-mix(in srgb, var(--tool-accent) 10%, transparent);
    border-left: 3px solid var(--tool-accent);
    border-radius: 0 8px 8px 0;
    padding: 0.5rem 0.75rem;
    margin-top: 0.5rem;
    color: var(--text-primary);
}

/* Buttons: gradient + accent, footer push to bottom */
.project-links { margin-top: auto !important; }
.reveal-button {
    background: linear-gradient(135deg, color-mix(in srgb, var(--tool-accent) 75%, #667eea), color-mix(in srgb, var(--tool-accent) 60%, #764ba2));
    border: none;
    color: #fff !important;
    font-weight: 600;
    padding: 0.5rem 1.1rem;
    border-radius: 999px;
    transition: filter var(--transition-base), transform var(--transition-base);
}
.reveal-button:hover {
    filter: brightness(1.12);
    transform: translateY(-1px);
}

.dashboard-modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.85);
    z-index: 9999;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 0;
    box-sizing: border-box;
}

.modal-content-wrapper {
    background: #1a202c;
    border-radius: 12px;
    /* Height always less than viewport height -> guaranteed on-screen fit */
    width: min(1100px, calc(100vw - 2rem));
    height: calc(100vh - 2rem);
    max-width: calc(100vw - 2rem);
    display: flex;
    flex-direction: column;
    box-shadow: 0 10px 30px rgba(0,0,0,0.5);
    overflow: hidden;
}

.modal-close-btn {
    background: #e53e3e;
    color: white;
    border: none;
    padding: 0.5rem 1.2rem;
    border-radius: 0 0 0 8px;
    font-weight: 600;
    cursor: pointer;
    align-self: flex-end;
    margin: 0;
    flex-shrink: 0;
}

.modal-iframe-container {
    flex-grow: 1;
    min-height: 0; /* Allow flex child to shrink, keeping iframe under viewport */
    border-radius: 8px 8px 0 0;
    overflow: hidden;
    margin: 0;
    background: white;
}

.modal-footnote {
    margin: 0.5rem 0.75rem 0.75rem;
    padding: 0.4rem 0.75rem;
    background: #f0f9ff;
    border-left: 4px solid #0ea5e9;
    border-radius: 6px;
    display: flex;
    align-items: flex-start;
    gap: 8px;
    flex-shrink: 0;
    box-sizing: border-box;
}

.modal-footnote-icon {
    font-size: 1rem;
    line-height: 1;
}

.modal-footnote-title {
    margin: 0 0 2px 0;
    font-weight: 600;
    color: #0369a1;
    font-size: 0.8rem;
}

.modal-footnote-text {
    margin: 0;
    color: #334155;
    font-size: 0.78rem;
    line-height: 1.45;
}