/* ═══════════════════════════════════════════════════════════════════════════
   DIGITAL PHYSICS ACADEMY - OrthoSystem Atelier Style
   Elegant, editorial design with gold accents
   ═══════════════════════════════════════════════════════════════════════════ */

/* ─────────────────────────────────────────────────────────────────────────────
   CSS VARIABLES
   ───────────────────────────────────────────────────────────────────────────── */
:root {
    /* Core Colors - Elegant Gold Palette */
    --color-gold: #C9A962;
    --color-gold-dark: #A8893F;
    --color-gold-light: #D4BC7D;
    --color-charcoal: #2E2E2E;
    --color-white: #FFFFFF;
    --color-black: #1A1A1A;
    --color-gray-light: #F8F8F6;
    --color-gray-medium: #666666;
    --color-gray-border: rgba(0, 0, 0, 0.08);

    /* Semantic Colors */
    --color-success: #4A7C59;
    --color-success-bg: rgba(74, 124, 89, 0.08);
    --color-warning: #B8860B;
    --color-warning-bg: rgba(184, 134, 11, 0.08);
    --color-error: #8B4049;
    --color-error-bg: rgba(139, 64, 73, 0.08);
    --color-info: #4A6B8A;
    --color-info-bg: rgba(74, 107, 138, 0.08);

    /* Code Colors */
    --code-bg: #1a1a1a;
    --code-bg-light: #F8F8F6;
    --code-border: rgba(0, 0, 0, 0.1);
    --code-keyword: #C9A962;
    --code-function: #6B8E8E;
    --code-string: #87CEAB;
    --code-number: #DDA0DD;
    --code-comment: #6B6B6B;
    --code-builtin: #D4A574;
    --code-variable: #CC7777;

    /* Typography */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-serif: 'Newsreader', Georgia, serif;
    --font-mono: 'JetBrains Mono', 'SF Mono', Consolas, monospace;

    /* Spacing */
    --sidebar-width: 280px;
    --content-max-width: 720px;
    --spacing-xs: 4px;
    --spacing-sm: 8px;
    --spacing-md: 16px;
    --spacing-lg: 24px;
    --spacing-xl: 32px;
    --spacing-2xl: 48px;
    --spacing-3xl: 64px;

    /* Border Radius */
    --radius-sm: 3px;
    --radius-md: 6px;
    --radius-lg: 8px;

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
}

/* ─────────────────────────────────────────────────────────────────────────────
   RESET & BASE STYLES
   ───────────────────────────────────────────────────────────────────────────── */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 17px;
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-sans);
    font-size: 1rem;
    line-height: 1.8;
    color: var(--color-charcoal);
    background-color: var(--color-white);
}

/* ─────────────────────────────────────────────────────────────────────────────
   TYPOGRAPHY
   ───────────────────────────────────────────────────────────────────────────── */
h1, h2, h3 {
    font-family: var(--font-serif);
    font-weight: 400;
    line-height: 1.3;
    color: var(--color-black);
    letter-spacing: -0.3px;
}

h4, h5, h6 {
    font-family: var(--font-sans);
    font-weight: 600;
    line-height: 1.4;
    color: var(--color-black);
}

h1 { font-size: clamp(32px, 5vw, 48px); }
h2 { font-size: clamp(24px, 3.5vw, 32px); margin: 56px 0 24px; }
h3 { font-size: clamp(20px, 2.5vw, 24px); margin: 40px 0 16px; }
h4 { font-size: 18px; margin: 32px 0 12px; }

p {
    margin-bottom: 1.5em;
    color: var(--color-charcoal);
}

a {
    color: var(--color-gold-dark);
    text-decoration: underline;
    text-decoration-color: rgba(201, 169, 98, 0.4);
    text-underline-offset: 3px;
    transition: all var(--transition-fast);
}

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

strong {
    color: inherit;
    font-weight: 600;
}

em {
    font-style: italic;
}

code {
    font-family: var(--font-mono);
    font-size: 0.85em;
    background: var(--color-gray-light);
    padding: 2px 6px;
    border-radius: var(--radius-sm);
    color: var(--color-charcoal);
}

kbd {
    font-family: var(--font-mono);
    font-size: 0.75em;
    background: var(--color-gray-light);
    color: var(--color-gray-medium);
    padding: 3px 8px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--color-gray-border);
    box-shadow: 0 1px 0 var(--color-gray-border);
}

/* ─────────────────────────────────────────────────────────────────────────────
   LAYOUT
   ───────────────────────────────────────────────────────────────────────────── */
.app-container {
    display: flex;
    min-height: 100vh;
}

/* ─────────────────────────────────────────────────────────────────────────────
   NAVIGATION
   ───────────────────────────────────────────────────────────────────────────── */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--color-gray-border);
    padding: 0 40px;
    height: 64px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-logo {
    font-size: 15px;
    font-weight: 600;
    letter-spacing: 2px;
    color: var(--color-charcoal);
    text-decoration: none;
}

.nav-logo span {
    color: var(--color-gold);
}

.nav-links {
    display: flex;
    gap: 32px;
}

.nav-links a {
    font-size: 14px;
    color: var(--color-gray-medium);
    text-decoration: none;
    transition: color var(--transition-fast);
}

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

/* ─────────────────────────────────────────────────────────────────────────────
   SIDEBAR
   ───────────────────────────────────────────────────────────────────────────── */
.sidebar {
    width: var(--sidebar-width);
    background: var(--color-gray-light);
    border-right: 1px solid var(--color-gray-border);
    position: fixed;
    top: 64px;
    left: 0;
    bottom: 0;
    display: flex;
    flex-direction: column;
    z-index: 100;
    transition: transform var(--transition-normal);
}

.sidebar-header {
    padding: var(--spacing-lg);
    border-bottom: 1px solid var(--color-gray-border);
}

.sidebar-logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

.logo-icon {
    width: 40px;
    height: 40px;
    flex-shrink: 0;
}

.sidebar-title {
    font-size: 16px;
    font-weight: 600;
    color: var(--color-black);
    line-height: 1.2;
}

.sidebar-subtitle {
    font-size: 11px;
    font-weight: 500;
    letter-spacing: 2px;
    text-transform: uppercase;
    color: var(--color-gold-dark);
}

/* Sidebar Progress */
.sidebar-progress {
    padding: var(--spacing-md) var(--spacing-lg);
    border-bottom: 1px solid var(--color-gray-border);
}

.progress-label {
    display: flex;
    justify-content: space-between;
    font-size: 12px;
    color: var(--color-gray-medium);
    margin-bottom: var(--spacing-xs);
}

.progress-track {
    height: 4px;
    background: rgba(0, 0, 0, 0.08);
    border-radius: 2px;
    overflow: hidden;
}

.sidebar-progress .progress-fill {
    height: 100%;
    background: var(--color-gold);
    border-radius: 2px;
    width: 0%;
    transition: width var(--transition-normal);
}

.progress-stats {
    font-size: 12px;
    color: var(--color-gray-medium);
    margin-top: var(--spacing-xs);
    text-align: center;
}

.reset-progress-btn {
    width: 100%;
    margin-top: var(--spacing-sm);
    padding: 6px 12px;
    font-size: 11px;
    font-family: var(--font-sans);
    color: var(--color-gray-medium);
    background: transparent;
    border: 1px solid var(--color-gray-border);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.reset-progress-btn:hover {
    color: var(--color-error);
    border-color: var(--color-error);
    background: rgba(139, 64, 73, 0.1);
}

.reset-progress-btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

/* Search Box */
.search-box {
    padding: var(--spacing-md) var(--spacing-lg);
    border-bottom: 1px solid var(--color-gray-border);
    position: relative;
}

.search-icon {
    position: absolute;
    left: calc(var(--spacing-lg) + 12px);
    top: 50%;
    transform: translateY(-50%);
    color: var(--color-gray-medium);
    pointer-events: none;
}

.search-input {
    width: 100%;
    padding: 10px 12px 10px 40px;
    background: var(--color-white);
    border: 1px solid var(--color-gray-border);
    border-radius: var(--radius-md);
    color: var(--color-charcoal);
    font-size: 14px;
    font-family: var(--font-sans);
    transition: all var(--transition-fast);
}

.search-input::placeholder {
    color: var(--color-gray-medium);
}

.search-input:focus {
    outline: none;
    border-color: var(--color-gold);
    box-shadow: 0 0 0 3px rgba(201, 169, 98, 0.15);
}

/* Sidebar Navigation */
.sidebar-nav {
    flex: 1;
    overflow-y: auto;
    padding: var(--spacing-md) 0;
}

.nav-section {
    margin-bottom: var(--spacing-sm);
}

.nav-section-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-sm) var(--spacing-lg);
    cursor: pointer;
    transition: background var(--transition-fast);
}

.nav-section-header:hover {
    background: rgba(0, 0, 0, 0.03);
}

.nav-section-title {
    font-size: 11px;
    font-weight: 600;
    letter-spacing: 1.5px;
    text-transform: uppercase;
    color: var(--color-gray-medium);
}

.nav-section-count {
    font-size: 11px;
    color: var(--color-gray-medium);
    background: var(--color-white);
    padding: 2px 8px;
    border-radius: 10px;
}

.nav-section.collapsed .nav-items {
    display: none;
}

.nav-items {
    padding: var(--spacing-xs) 0;
}

.nav-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-lg);
    padding-left: calc(var(--spacing-lg) + 8px);
    font-size: 14px;
    color: var(--color-gray-medium);
    cursor: pointer;
    transition: all var(--transition-fast);
    border-left: 2px solid transparent;
    text-decoration: none;
}

.nav-item:hover {
    background: rgba(0, 0, 0, 0.03);
    color: var(--color-charcoal);
}

.nav-item.active {
    background: rgba(201, 169, 98, 0.08);
    color: var(--color-gold-dark);
    border-left-color: var(--color-gold);
}

.nav-item.completed {
    color: var(--color-success);
}

.nav-item-number {
    font-family: var(--font-mono);
    font-size: 12px;
    color: var(--color-gray-medium);
    min-width: 32px;
}

.nav-item-title {
    flex: 1;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.nav-item-check {
    width: 14px;
    height: 14px;
    color: var(--color-success);
    opacity: 0;
}

.nav-item.completed .nav-item-check {
    opacity: 1;
}

/* Sidebar Footer */
.sidebar-footer {
    padding: var(--spacing-md) var(--spacing-lg);
    border-top: 1px solid var(--color-gray-border);
}

.keyboard-hints {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-md);
    justify-content: center;
}

.hint {
    font-size: 12px;
    color: var(--color-gray-medium);
    display: flex;
    align-items: center;
    gap: 4px;
}

/* ─────────────────────────────────────────────────────────────────────────────
   MAIN CONTENT
   ───────────────────────────────────────────────────────────────────────────── */
.main-content {
    flex: 1;
    margin-left: var(--sidebar-width);
    margin-top: 64px;
    min-height: calc(100vh - 64px);
    display: flex;
    flex-direction: column;
}

/* Progress Bar */
.progress-bar {
    position: fixed;
    top: 64px;
    left: var(--sidebar-width);
    right: 0;
    height: 2px;
    background: var(--color-gray-border);
    z-index: 90;
}

.progress-bar .progress-fill {
    height: 100%;
    background: var(--color-gold);
    width: 0%;
    transition: width var(--transition-fast);
}

/* ─────────────────────────────────────────────────────────────────────────────
   HERO SECTION
   ───────────────────────────────────────────────────────────────────────────── */
.hero {
    padding: 80px 40px 60px;
    background: linear-gradient(180deg, #FAFAF8 0%, #FFFFFF 100%);
    text-align: center;
    border-bottom: 1px solid var(--color-gray-border);
}

.hero-background {
    display: none;
}

.hero-content {
    max-width: 800px;
    margin: 0 auto;
}

.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: 11px;
    font-weight: 600;
    letter-spacing: 3px;
    text-transform: uppercase;
    color: var(--color-gold-dark);
    margin-bottom: var(--spacing-lg);
}

.badge-icon {
    display: none;
}

.hero-title {
    margin-bottom: var(--spacing-lg);
}

.title-line {
    display: block;
    font-family: var(--font-serif);
    font-size: clamp(36px, 6vw, 54px);
    font-weight: 400;
    letter-spacing: -0.5px;
    color: var(--color-black);
    line-height: 1.1;
}

.gradient-text {
    color: var(--color-gold-dark);
}

.hero-subtitle {
    font-family: var(--font-serif);
    font-size: 20px;
    font-style: italic;
    color: var(--color-gray-medium);
    margin-bottom: var(--spacing-xl);
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
    line-height: 1.6;
}

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

.feature-card {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: 14px;
    color: var(--color-gray-medium);
}

.feature-icon {
    font-size: 18px;
}

.feature-text {
    display: flex;
    flex-direction: column;
    text-align: left;
}

.feature-text strong {
    font-size: 14px;
    color: var(--color-charcoal);
}

.feature-text span {
    font-size: 12px;
    color: var(--color-gray-medium);
}

.hero-cta {
    display: flex;
    justify-content: center;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-2xl);
}

.btn-primary, .btn-secondary {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: 14px 28px;
    font-size: 14px;
    font-weight: 500;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    border: none;
    font-family: var(--font-sans);
    text-decoration: none;
}

.btn-primary {
    background: var(--color-charcoal);
    color: var(--color-white);
}

.btn-primary:hover {
    background: var(--color-black);
    transform: translateY(-1px);
}

.btn-secondary {
    background: transparent;
    color: var(--color-charcoal);
    border: 1px solid var(--color-gray-border);
}

.btn-secondary:hover {
    border-color: var(--color-charcoal);
    background: var(--color-gray-light);
}

.hero-stats {
    display: flex;
    justify-content: center;
    gap: var(--spacing-2xl);
    padding-top: var(--spacing-xl);
    border-top: 1px solid var(--color-gray-border);
}

.stat {
    text-align: center;
}

.stat-value {
    font-family: var(--font-serif);
    font-size: 32px;
    color: var(--color-gold-dark);
}

.stat-label {
    font-size: 13px;
    color: var(--color-gray-medium);
    text-transform: uppercase;
    letter-spacing: 1px;
}

/* ─────────────────────────────────────────────────────────────────────────────
   CURRICULUM SECTION
   ───────────────────────────────────────────────────────────────────────────── */
.curriculum {
    padding: var(--spacing-3xl) var(--spacing-2xl);
    max-width: 1000px;
    margin: 0 auto;
}

.curriculum-header {
    text-align: center;
    margin-bottom: var(--spacing-2xl);
}

.curriculum-header h2 {
    font-family: var(--font-serif);
    margin-bottom: var(--spacing-md);
}

.curriculum-header p {
    color: var(--color-gray-medium);
    max-width: 600px;
    margin: 0 auto;
}

.curriculum-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
}

.section-card {
    background: var(--color-gray-light);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.section-card:hover {
    background: rgba(201, 169, 98, 0.1);
    transform: translateY(-2px);
}

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

.section-number {
    font-family: var(--font-mono);
    font-size: 12px;
    font-weight: 600;
    color: var(--color-white);
    background: var(--color-gold-dark);
    padding: 4px 10px;
    border-radius: var(--radius-sm);
}

.section-title {
    font-size: 16px;
    font-weight: 600;
    color: var(--color-black);
}

.section-description {
    font-size: 14px;
    color: var(--color-gray-medium);
    margin-bottom: var(--spacing-md);
    line-height: 1.6;
}

.section-topics {
    font-size: 13px;
    color: var(--color-gray-medium);
}

.section-topics strong {
    color: var(--color-gold-dark);
}

/* ─────────────────────────────────────────────────────────────────────────────
   LESSON CONTAINER
   ───────────────────────────────────────────────────────────────────────────── */
.lesson-container {
    max-width: var(--content-max-width);
    margin: 0 auto;
    padding: 60px 24px 80px;
    flex: 1;
}

.lesson-header {
    margin-bottom: var(--spacing-2xl);
    padding-bottom: var(--spacing-xl);
    border-bottom: 1px solid var(--color-gray-border);
    text-align: center;
}

.lesson-breadcrumb {
    font-size: 14px;
    color: var(--color-gray-medium);
    margin-bottom: var(--spacing-lg);
}

.lesson-breadcrumb a {
    color: var(--color-gray-medium);
    text-decoration: none;
}

.lesson-breadcrumb a:hover {
    color: var(--color-gold-dark);
}

.lesson-title {
    font-family: var(--font-serif);
    font-size: clamp(28px, 5vw, 40px);
    font-weight: 400;
    margin-bottom: var(--spacing-md);
    line-height: 1.2;
    color: var(--color-black);
}

.lesson-meta {
    font-size: 14px;
    color: var(--color-gray-medium);
}

.lesson-content {
    font-size: 17px;
    line-height: 1.8;
}

.lesson-content h2 {
    font-family: var(--font-sans);
    font-size: 26px;
    font-weight: 500;
    margin: 56px 0 24px;
    color: var(--color-black);
    letter-spacing: -0.3px;
}

.lesson-content h3 {
    font-family: var(--font-sans);
    font-size: 20px;
    font-weight: 500;
    margin: 40px 0 16px;
    color: var(--color-black);
}

.lesson-content h4 {
    font-family: var(--font-sans);
    font-size: 17px;
    font-weight: 600;
    margin: 32px 0 12px;
    color: var(--color-black);
}

.lesson-content ul, .lesson-content ol {
    margin: var(--spacing-md) 0 var(--spacing-lg);
    padding-left: var(--spacing-xl);
    color: var(--color-charcoal);
}

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

/* Lesson Navigation */
.lesson-navigation {
    display: flex;
    justify-content: space-between;
    padding: var(--spacing-xl) 0;
    margin-top: var(--spacing-2xl);
    border-top: 1px solid var(--color-gray-border);
}

.nav-btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md) var(--spacing-lg);
    background: var(--color-gray-light);
    border: 1px solid var(--color-gray-border);
    border-radius: var(--radius-md);
    color: var(--color-charcoal);
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-fast);
    font-family: var(--font-sans);
    text-decoration: none;
}

.nav-btn:hover {
    background: rgba(201, 169, 98, 0.1);
    border-color: var(--color-gold);
}

.nav-btn:disabled {
    opacity: 0.4;
    cursor: not-allowed;
}

/* ─────────────────────────────────────────────────────────────────────────────
   CONTENT COMPONENTS
   ───────────────────────────────────────────────────────────────────────────── */

/* Epigraph / Question Box */
.question-box, .epigraph {
    font-family: var(--font-serif);
    font-style: italic;
    font-size: 19px;
    color: var(--color-gray-medium);
    border-left: 3px solid var(--color-gold);
    padding: var(--spacing-lg);
    padding-left: var(--spacing-lg);
    margin: 40px 0;
    line-height: 1.7;
    background: transparent;
}

.question-box-title {
    font-family: var(--font-sans);
    font-style: normal;
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 1px;
    text-transform: uppercase;
    color: var(--color-gold-dark);
    margin-bottom: var(--spacing-md);
}

.question-box p {
    color: var(--color-gray-medium);
    margin-bottom: 0;
}

/* Key Point / Callout */
.key-point, .callout {
    background: linear-gradient(135deg, rgba(201, 169, 98, 0.08) 0%, rgba(201, 169, 98, 0.04) 100%);
    border-left: 3px solid var(--color-gold);
    padding: var(--spacing-lg);
    margin: 32px 0;
    border-radius: 0 var(--radius-lg) var(--radius-lg) 0;
}

.key-point-title {
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 1px;
    text-transform: uppercase;
    color: var(--color-gold-dark);
    margin-bottom: var(--spacing-md);
}

.key-point p, .callout p {
    margin-bottom: var(--spacing-sm);
    font-size: 15px;
    color: var(--color-charcoal);
}

.key-point p:last-child, .callout p:last-child {
    margin-bottom: 0;
}

/* Under The Hood */
.under-the-hood {
    background: var(--code-bg);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    margin: 32px 0;
}

.under-the-hood-title {
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 1px;
    text-transform: uppercase;
    color: var(--color-gold);
    margin-bottom: var(--spacing-md);
}

.under-the-hood p {
    color: #d0d0d0;
    margin-bottom: var(--spacing-md);
    font-size: 15px;
}

.under-the-hood li {
    color: #d0d0d0;
    font-size: 15px;
    margin-bottom: var(--spacing-sm);
}

.under-the-hood ul, .under-the-hood ol {
    margin: var(--spacing-md) 0;
    padding-left: var(--spacing-lg);
}

.under-the-hood p:last-child {
    margin-bottom: 0;
}

.under-the-hood code {
    background: rgba(255, 255, 255, 0.1);
    color: var(--code-keyword);
}

/* Try It */
.try-it {
    background: var(--color-gray-light);
    border-left: 3px solid var(--color-success);
    padding: var(--spacing-lg);
    margin: 32px 0;
    border-radius: 0 var(--radius-lg) var(--radius-lg) 0;
}

.try-it-title {
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 1px;
    text-transform: uppercase;
    color: var(--color-success);
    margin-bottom: var(--spacing-md);
}

.try-it p {
    color: var(--color-charcoal);
    margin-bottom: var(--spacing-md);
    font-size: 15px;
}

.try-it pre {
    background: var(--code-bg);
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    font-family: var(--font-mono);
    font-size: 13px;
    line-height: 1.6;
    color: #e8e8e8;
    overflow-x: auto;
    white-space: pre-wrap;
    word-wrap: break-word;
    margin: 0;
}

/* Warning Box */
.warning-box {
    background: var(--color-warning-bg);
    border-left: 3px solid var(--color-warning);
    padding: var(--spacing-lg);
    margin: 32px 0;
    border-radius: 0 var(--radius-lg) var(--radius-lg) 0;
}

.warning-box-title {
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 1px;
    text-transform: uppercase;
    color: var(--color-warning);
    margin-bottom: var(--spacing-md);
}

.warning-box p {
    color: var(--color-charcoal);
    margin-bottom: 0;
    font-size: 15px;
}

/* Success Box */
.success-box {
    background: var(--color-success-bg);
    border-left: 3px solid var(--color-success);
    padding: var(--spacing-lg);
    margin: 32px 0;
    border-radius: 0 var(--radius-lg) var(--radius-lg) 0;
}

.success-box-title {
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 1px;
    text-transform: uppercase;
    color: var(--color-success);
    margin-bottom: var(--spacing-md);
}

.success-box p {
    color: var(--color-charcoal);
    margin-bottom: 0;
    font-size: 15px;
}

/* ─────────────────────────────────────────────────────────────────────────────
   CODE BLOCKS
   ───────────────────────────────────────────────────────────────────────────── */

/* Memory Diagram */
.memory-diagram {
    background: var(--code-bg);
    border-radius: var(--radius-lg);
    margin: 32px 0;
    overflow: hidden;
}

.memory-diagram-title {
    padding: var(--spacing-md) var(--spacing-lg);
    background: rgba(255, 255, 255, 0.03);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 1px;
    text-transform: uppercase;
    color: var(--color-gold);
}

.memory-diagram pre {
    padding: var(--spacing-lg);
    font-family: var(--font-mono);
    font-size: 14px;
    line-height: 1.6;
    color: #e8e8e8;
    overflow-x: auto;
    margin: 0;
}

/* Code Comparison (Before/After) */
.code-comparison {
    border: 1px solid var(--color-gray-border);
    border-radius: var(--radius-lg);
    overflow: hidden;
    margin: 32px 0;
}

.code-comparison-header {
    display: grid;
    grid-template-columns: 1fr 1fr;
}

.code-tab {
    padding: var(--spacing-md) var(--spacing-lg);
    font-size: 12px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 1px;
    text-align: center;
    border-bottom: 2px solid transparent;
}

.code-tab.before-tab {
    color: var(--color-error);
    background: var(--color-error-bg);
    border-bottom-color: var(--color-error);
}

.code-tab.after-tab {
    color: var(--color-success);
    background: var(--color-success-bg);
    border-bottom-color: var(--color-success);
}

.code-panels {
    display: grid;
    grid-template-columns: 1fr 1fr;
    background: var(--code-bg);
}

.code-panel {
    padding: var(--spacing-lg);
    border-right: 1px solid rgba(255, 255, 255, 0.1);
}

.code-panel:last-child {
    border-right: none;
}

.code-panel pre {
    font-family: var(--font-mono);
    font-size: 13px;
    line-height: 1.6;
    color: #e8e8e8;
    margin: 0;
    white-space: pre-wrap;
    word-break: break-word;
}

.code-result {
    margin-top: var(--spacing-md);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    font-size: 13px;
    font-weight: 500;
}

.code-result.slow {
    background: rgba(139, 64, 73, 0.2);
    border: 1px solid rgba(139, 64, 73, 0.4);
    color: #e8a0a8;
}

.code-result.fast {
    background: rgba(74, 124, 89, 0.2);
    border: 1px solid rgba(74, 124, 89, 0.4);
    color: #a8d4b0;
}

/* Drill-Down Code (Python → C → Assembly) */
.drill-down {
    border: 1px solid var(--color-gray-border);
    border-radius: var(--radius-lg);
    overflow: hidden;
    margin: 32px 0;
}

.drill-down-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-md) var(--spacing-lg);
    background: var(--color-gray-light);
    border-bottom: 1px solid var(--color-gray-border);
}

.drill-down-title {
    font-size: 13px;
    font-weight: 600;
    letter-spacing: 0.5px;
    text-transform: uppercase;
    color: var(--color-charcoal);
}

.drill-down-badge {
    font-size: 11px;
    font-weight: 600;
    padding: 4px 10px;
    border-radius: 10px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.drill-down-badge.fast {
    background: var(--color-success-bg);
    color: var(--color-success);
}

.drill-down-badge.slow {
    background: var(--color-error-bg);
    color: var(--color-error);
}

.drill-down-level {
    border-top: 1px solid var(--color-gray-border);
}

.drill-down-level:first-of-type {
    border-top: none;
}

.drill-down-level-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    padding: var(--spacing-sm) var(--spacing-lg);
    background: var(--color-gray-light);
    border-bottom: 1px solid var(--color-gray-border);
}

.level-icon {
    width: 28px;
    height: 28px;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 11px;
    font-weight: 700;
    font-family: var(--font-mono);
}

.level-icon.python {
    background: #3776ab;
    color: #ffd43b;
}

.level-icon.c {
    background: #555555;
    color: #ffffff;
}

.level-icon.asm {
    background: var(--color-gold-dark);
    color: #ffffff;
}

.level-label {
    font-size: 12px;
    font-weight: 500;
    color: var(--color-gray-medium);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.drill-down-code {
    padding: var(--spacing-md) var(--spacing-lg);
    background: var(--code-bg);
}

.drill-down-code pre {
    font-family: var(--font-mono);
    font-size: 13px;
    line-height: 1.6;
    color: #e8e8e8;
    margin: 0;
    overflow-x: auto;
    white-space: pre-wrap;
    word-wrap: break-word;
}

/* Assembly Columns (x86 / ARM) */
.asm-columns {
    display: grid;
    grid-template-columns: 1fr 1fr;
}

.asm-column {
    border-right: 1px solid var(--color-gray-border);
    min-width: 0; /* Allow column to shrink for overflow scroll */
}

.asm-column:last-child {
    border-right: none;
}

.asm-column-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--color-gray-light);
    border-bottom: 1px solid var(--color-gray-border);
}

.asm-chip {
    font-size: 10px;
    font-weight: 700;
    padding: 3px 8px;
    border-radius: var(--radius-sm);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.asm-chip.x86 {
    background: var(--color-charcoal);
    color: #ffffff;
}

.asm-chip.arm {
    background: var(--color-gold-dark);
    color: #ffffff;
}

.asm-column-label {
    font-size: 11px;
    color: var(--color-gray-medium);
}

.asm-column-code {
    padding: var(--spacing-md);
    background: var(--code-bg);
    overflow-x: auto;
}

.asm-column-code pre {
    font-family: var(--font-mono);
    font-size: 12px;
    line-height: 1.6;
    color: #e8e8e8;
    margin: 0;
    white-space: pre;
}

.drill-down-footer {
    padding: var(--spacing-sm) var(--spacing-lg);
    background: rgba(201, 169, 98, 0.08);
    border-top: 1px solid var(--color-gray-border);
}

.drill-down-footer p {
    margin: 0;
    font-size: 13px;
    font-weight: 500;
    color: var(--color-gold-dark);
}

/* Language Tabs */
.language-tabs-container {
    border: 1px solid var(--color-gray-border);
    border-radius: var(--radius-lg);
    overflow: hidden;
    margin: 32px 0;
}

.language-tabs {
    display: flex;
    background: var(--color-gray-light);
    border-bottom: 1px solid var(--color-gray-border);
}

.language-tab {
    flex: 1;
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: 13px;
    font-weight: 500;
    text-align: center;
    color: var(--color-gray-medium);
    cursor: pointer;
    border-bottom: 2px solid transparent;
    transition: all var(--transition-fast);
    background: transparent;
    border: none;
    border-bottom: 2px solid transparent;
    font-family: var(--font-sans);
}

.language-tab:hover {
    color: var(--color-charcoal);
    background: rgba(0, 0, 0, 0.03);
}

.language-tab.active {
    color: var(--color-gold-dark);
    border-bottom-color: var(--color-gold);
    background: rgba(201, 169, 98, 0.05);
}

.language-panel {
    display: none;
    padding: var(--spacing-lg);
    background: var(--code-bg);
}

.language-panel.active {
    display: block;
}

.language-panel pre {
    font-family: var(--font-mono);
    font-size: 14px;
    line-height: 1.6;
    color: #e8e8e8;
    margin: 0;
    overflow-x: auto;
    white-space: pre-wrap;
    word-wrap: break-word;
}

/* Syntax Highlighting */
.comment { color: var(--code-comment); }
.keyword { color: var(--code-keyword); }
.function { color: var(--code-function); }
.string { color: var(--code-string); }
.number { color: var(--code-number); }
.builtin { color: var(--code-builtin); }
.variable { color: var(--code-variable); }
.operator { color: #89ddff; }
.highlight { color: var(--color-gold); font-weight: 600; }
.address { color: #7eb6d4; }
.data { color: var(--code-string); }
.pointer { color: #dda0dd; }

/* ─────────────────────────────────────────────────────────────────────────────
   SVG DIAGRAMS - Quiet Luxury Aesthetic
   ───────────────────────────────────────────────────────────────────────────── */
.svg-diagram {
    margin: 64px -48px;
    padding: 48px;
    background: #141418;
    border-radius: 12px;
    overflow: hidden;
    border: 1px solid #2E2E2E;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
}

.svg-diagram-title {
    font-size: 11px;
    font-weight: 500;
    letter-spacing: 3px;
    text-transform: uppercase;
    color: #D4AF37;
    margin-bottom: 32px;
    text-align: center;
}

.svg-diagram svg {
    display: block;
    max-width: 100%;
    height: auto;
    margin: 0 auto;
}

/* ─────────────────────────────────────────────────────────────────────────────
   TABLE STYLES
   ───────────────────────────────────────────────────────────────────────────── */
.data-table {
    width: 100%;
    border-collapse: collapse;
    margin: 32px 0;
    font-size: 15px;
}

.data-table th,
.data-table td {
    padding: 12px 16px;
    text-align: left;
    border-bottom: 1px solid var(--color-gray-border);
}

.data-table th {
    font-weight: 600;
    font-size: 13px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--color-charcoal);
    border-bottom: 2px solid var(--color-charcoal);
}

.data-table td {
    color: var(--color-charcoal);
}

.data-table tr:hover td {
    background: rgba(201, 169, 98, 0.04);
}

.data-table .highlight {
    color: var(--color-gold-dark);
    font-weight: 600;
}

.data-table code {
    font-size: 13px;
}

/* Section Divider */
.section-divider {
    text-align: center;
    margin: 48px 0;
    color: var(--color-gold);
    font-size: 18px;
    letter-spacing: 8px;
}

/* ─────────────────────────────────────────────────────────────────────────────
   FOOTER
   ───────────────────────────────────────────────────────────────────────────── */
.footer {
    text-align: center;
    padding: 48px 24px;
    background: var(--color-charcoal);
    color: rgba(255, 255, 255, 0.6);
    font-size: 14px;
}

.footer a {
    color: rgba(255, 255, 255, 0.8);
    text-decoration: none;
}

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

.footer-content {
    max-width: 600px;
    margin: 0 auto;
}

.footer-logo {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    color: var(--color-white);
}

.footer p {
    color: rgba(255, 255, 255, 0.6);
    margin-bottom: var(--spacing-md);
}

.footer-links {
    display: flex;
    justify-content: center;
    gap: var(--spacing-lg);
}

/* ─────────────────────────────────────────────────────────────────────────────
   MOBILE TOGGLE
   ───────────────────────────────────────────────────────────────────────────── */
.mobile-toggle {
    display: none;
    position: fixed;
    bottom: var(--spacing-lg);
    right: var(--spacing-lg);
    width: 52px;
    height: 52px;
    background: var(--color-charcoal);
    border: none;
    border-radius: 50%;
    color: var(--color-white);
    cursor: pointer;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
    z-index: 101;
    transition: all var(--transition-fast);
}

.mobile-toggle:hover {
    background: var(--color-black);
    transform: scale(1.05);
}

/* ─────────────────────────────────────────────────────────────────────────────
   RESPONSIVE
   ───────────────────────────────────────────────────────────────────────────── */
@media (max-width: 1024px) {
    .sidebar {
        transform: translateX(-100%);
    }

    .sidebar.open {
        transform: translateX(0);
    }

    .main-content {
        margin-left: 0;
    }

    .progress-bar {
        left: 0;
    }

    .mobile-toggle {
        display: flex;
        align-items: center;
        justify-content: center;
    }

    .nav {
        padding: 0 20px;
    }

    .hero {
        padding: 60px 20px 48px;
    }

    .code-panels,
    .code-comparison-header,
    .asm-columns {
        grid-template-columns: 1fr;
    }

    .code-panel {
        border-right: none;
        border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    }

    .code-panel:last-child {
        border-bottom: none;
    }

    .asm-column {
        border-right: none;
        border-bottom: 1px solid var(--color-gray-border);
    }

    .asm-column:last-child {
        border-bottom: none;
    }
}

@media (max-width: 768px) {
    .hero-stats {
        flex-wrap: wrap;
        gap: var(--spacing-lg);
    }

    .hero-cta {
        flex-direction: column;
        align-items: center;
    }

    .btn-primary, .btn-secondary {
        width: 100%;
        max-width: 280px;
        justify-content: center;
    }

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

    .lesson-container {
        padding: 40px 20px 60px;
    }

    .lesson-navigation {
        flex-direction: column;
        gap: var(--spacing-md);
    }

    .nav-btn {
        width: 100%;
        justify-content: center;
    }

    .data-table {
        font-size: 13px;
    }

    .data-table th,
    .data-table td {
        padding: 10px 12px;
    }
}

/* ─────────────────────────────────────────────────────────────────────────────
   PRINT STYLES
   ───────────────────────────────────────────────────────────────────────────── */
@media print {
    .sidebar,
    .mobile-toggle,
    .progress-bar,
    .lesson-navigation,
    .nav {
        display: none;
    }

    .main-content {
        margin-left: 0;
        margin-top: 0;
    }

    .lesson-container {
        max-width: none;
        padding: 0;
    }
}