/* Enhanced CSS for Python Course - Responsive, Accessible, and Modern */

/* ===========================
   Import existing base styles
   =========================== */
@import url('main.css');

/* ===========================
   Responsive Design
   =========================== */

/* Container for responsive content */
.responsive-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Responsive Canvas/SVG wrapper */
.canvas-wrapper, .svg-wrapper {
    position: relative;
    width: 100%;
    max-width: 600px;
    margin: 20px auto;
    background: #f8f9fa;
    border-radius: 8px;
    padding: 10px;
}

.responsive-svg {
    width: 100%;
    height: auto;
    display: block;
}

/* Mobile-first responsive breakpoints */
@media (max-width: 768px) {
    body {
        margin-left: 10px;
        margin-right: 10px;
        font-size: 14px;
    }
    
    h1 {
        font-size: 1.5rem;
        padding: 0.75rem;
        margin: 0.5rem;
    }
    
    h2 {
        font-size: 1.25rem;
        margin-left: 10px;
        margin-right: 10px;
    }
    
    h3 {
        font-size: 1.1rem;
        margin-left: 15px;
        margin-right: 15px;
    }
    
    pre {
        margin-left: 10px;
        margin-right: 10px;
        font-size: 12px;
        overflow-x: auto;
    }
    
    p {
        margin-left: 15px;
        margin-right: 15px;
    }
    
    /* Hide canvas on mobile, show mobile message */
    /* !important is required to beat per-canvas inline `display: inline-block`/`display: block` */
    /* attributes that some lessons set for layout. Without it, those canvases stay visible */
    /* on mobile and the .canvas-fallback figures render as duplicate content. */
    canvas {
        display: none !important;
    }
    
    .mobile-diagram-note {
        display: block;
        padding: 15px;
        background: #e8f4f8;
        border-radius: 5px;
        text-align: center;
        color: #2c3e50;
        margin: 20px 10px;
    }
    
    /* Stack navigation elements vertically on mobile */
    .lesson-nav {
        flex-direction: column;
        gap: 10px;
    }
    
    .lesson-nav a {
        width: 100%;
        text-align: center;
    }
}

@media (min-width: 769px) {
    .mobile-diagram-note {
        display: none;
    }
}

@media (max-width: 480px) {
    /* Even smaller screens */
    blockquote {
        margin-left: 20px;
        margin-right: 20px;
    }
    
    table {
        font-size: 12px;
    }
}

/* ===========================
   Accessibility Improvements
   =========================== */

/* Skip to main content link */
.skip-to-main {
    position: absolute;
    left: -10000px;
    top: 30px;
    z-index: 999;
    padding: 10px;
    background: rgb(59, 130, 246);
    color: white;
    text-decoration: none;
    border-radius: 0 5px 5px 0;
}

.skip-to-main:focus {
    left: 0;
}

/* Focus indicators */
a:focus,
button:focus,
input:focus,
textarea:focus,
select:focus {
    outline: 3px solid rgb(59, 130, 246);
    outline-offset: 2px;
}

/* High contrast mode support */
@media (prefers-contrast: high) {
    body {
        background-color: white;
        color: black;
    }
    
    h1, h2, h3, h4 {
        background-color: black;
        color: white;
    }
    
    a {
        color: blue;
        text-decoration: underline;
    }
}

/* Reduced motion support */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
}

/* Screen reader only content */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* Improve link visibility */
a {
    text-decoration: underline;
    text-underline-offset: 2px;
}

a:hover {
    text-decoration-thickness: 2px;
}

/* ===========================
   Code Highlighting (Prism.js compatible)
   =========================== */

/* Better code block styling */
pre[class*="language-"],
code[class*="language-"] {
    color: #383a42;
    background: #fafafa;
    font-family: 'Consolas', 'Monaco', 'Andale Mono', 'Ubuntu Mono', monospace;
    font-size: 14px;
    text-align: left;
    white-space: pre;
    word-spacing: normal;
    word-break: normal;
    word-wrap: normal;
    line-height: 1.5;
    tab-size: 4;
    hyphens: none;
}

/* Code blocks */
pre[class*="language-"] {
    padding: 1em;
    margin: 1em 0;
    overflow: auto;
    border-radius: 8px;
    border: 1px solid #e1e4e8;
}

/* Inline code */
:not(pre) > code[class*="language-"] {
    padding: .1em .3em;
    border-radius: .3em;
    white-space: normal;
    background: #f6f8fa;
}

/* Line numbers */
.line-numbers {
    position: relative;
    padding-left: 3.8em !important;
    counter-reset: linenumber;
}

.line-numbers > code {
    position: relative;
    white-space: inherit;
}

.line-numbers .line-numbers-rows {
    position: absolute;
    pointer-events: none;
    top: 0;
    font-size: 100%;
    left: -3.8em;
    width: 3em;
    letter-spacing: -1px;
    border-right: 1px solid #e1e4e8;
    user-select: none;
}

.line-numbers-rows > span {
    display: block;
    counter-increment: linenumber;
}

.line-numbers-rows > span:before {
    content: counter(linenumber);
    color: #6a737d;
    display: block;
    padding-right: 0.8em;
    text-align: right;
}

/* Token colors for syntax highlighting */
.token.comment,
.token.prolog,
.token.doctype,
.token.cdata {
    color: #6a737d;
    font-style: italic;
}

.token.punctuation {
    color: #383a42;
}

.token.property,
.token.tag,
.token.boolean,
.token.number,
.token.constant,
.token.symbol,
.token.deleted {
    color: #e45649;
}

.token.selector,
.token.attr-name,
.token.string,
.token.char,
.token.builtin,
.token.inserted {
    color: #50a14f;
}

.token.operator,
.token.entity,
.token.url,
.language-css .token.string,
.style .token.string {
    color: #a626a4;
}

.token.atrule,
.token.attr-value,
.token.keyword {
    color: #4078f2;
}

.token.function,
.token.class-name {
    color: #c18401;
}

.token.regex,
.token.important,
.token.variable {
    color: #e06c75;
}

/* Override the green color that's hard to read */
code, pre {
    color: #383a42 !important;
    background-color: #f6f8fa !important;
}

/* Python-specific highlighting when not using Prism */
.python-code {
    background: #f6f8fa !important;
    border: 1px solid #e1e4e8;
    border-radius: 6px;
}

/* ===========================
   Navigation Improvements
   =========================== */

/* Lesson navigation */
.lesson-nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin: 40px 0;
    padding: 20px;
    background: #f8f9fa;
    border-radius: 8px;
    border: 1px solid #e1e4e8;
}

.lesson-nav a {
    display: inline-flex;
    align-items: center;
    padding: 10px 20px;
    background: rgb(59, 130, 246);
    color: white;
    text-decoration: none;
    border-radius: 5px;
    transition: background-color 0.3s ease;
    font-weight: bold;
}

.lesson-nav a:hover {
    background: rgb(37, 99, 235);
    text-decoration: none;
}

.lesson-nav a:focus {
    outline: 3px solid rgb(37, 99, 235);
    outline-offset: 2px;
}

.lesson-nav .prev-lesson::before {
    content: "← ";
    margin-right: 5px;
}

.lesson-nav .next-lesson::after {
    content: " →";
    margin-left: 5px;
}

.lesson-nav .current-lesson {
    font-weight: bold;
    color: #2c3e50;
}

/* Breadcrumb navigation */
.breadcrumb {
    display: flex;
    align-items: center;
    padding: 10px 0;
    margin-bottom: 20px;
    font-size: 14px;
}

.breadcrumb a {
    color: rgb(59, 130, 246);
    text-decoration: none;
}

.breadcrumb a:hover {
    text-decoration: underline;
}

.breadcrumb .separator {
    margin: 0 10px;
    color: #6a737d;
}

.breadcrumb .current {
    color: #2c3e50;
    font-weight: bold;
}

/* Reading time indicator */
.reading-time {
    display: inline-block;
    padding: 5px 10px;
    background: #e8f4f8;
    border-radius: 20px;
    font-size: 14px;
    color: #2c3e50;
    margin: 10px 0;
}

.reading-time::before {
    content: "⏱️ ";
    margin-right: 5px;
}

/* Progress indicator */
.progress-indicator {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 4px;
    background: #e1e4e8;
    z-index: 1000;
}

.progress-bar {
    height: 100%;
    background: linear-gradient(90deg, rgb(59, 130, 246), rgb(37, 99, 235));
    width: 0;
    transition: width 0.3s ease;
}

/* ===========================
   Enhanced Exercise Cards
   =========================== */

.exercise-card {
    border: 1px solid #e1e4e8;
    border-radius: 8px;
    margin: 20px 0;
    overflow: hidden;
}

.exercise-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 15px;
    background: #f8f9fa;
    border-bottom: 1px solid #e1e4e8;
}

.exercise-header h3 {
    margin: 0;
    padding: 0;
    background: none;
    color: #2c3e50;
}

.difficulty-badge {
    padding: 3px 10px;
    border-radius: 12px;
    font-size: 12px;
    font-weight: bold;
}

.difficulty-badge.easy {
    background: #d4edda;
    color: #155724;
}

.difficulty-badge.medium {
    background: #fff3cd;
    color: #856404;
}

.difficulty-badge.hard {
    background: #f8d7da;
    color: #721c24;
}

.time-estimate {
    font-size: 12px;
    color: #6a737d;
}

.exercise-body {
    padding: 15px;
}

.exercise-actions {
    padding: 15px;
    background: #f8f9fa;
    border-top: 1px solid #e1e4e8;
    display: flex;
    gap: 10px;
}

.exercise-actions button {
    padding: 8px 16px;
    border: 1px solid #e1e4e8;
    background: white;
    border-radius: 5px;
    cursor: pointer;
    transition: all 0.3s ease;
}

.exercise-actions button:hover {
    background: #f8f9fa;
    border-color: rgb(59, 130, 246);
}

/* ===========================
   Print Styles
   =========================== */

@media print {
    body {
        background: white;
        color: black;
    }
    
    .lesson-nav,
    .progress-indicator,
    .skip-to-main,
    canvas,
    .mobile-diagram-note {
        display: none !important;
    }
    
    h1, h2, h3, h4 {
        background: none !important;
        color: black !important;
        border-bottom: 2px solid black;
    }
    
    a {
        color: black;
        text-decoration: underline;
    }
    
    pre {
        border: 1px solid #ccc;
        page-break-inside: avoid;
    }
}

/* ===========================
   Dark Mode Support
   Applies when the OS prefers dark AND the user has not manually picked light
   via the data-theme attribute. The manual [data-theme="dark"] block below
   mirrors these rules for explicit user choice.
   =========================== */

@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) body {
        background-color: #1e1e1e;
        color: #d4d4d4;
    }
    :root:not([data-theme="light"]) h1,
    :root:not([data-theme="light"]) h2,
    :root:not([data-theme="light"]) h3,
    :root:not([data-theme="light"]) h4 {
        background-color: #2d53a3;
    }
    :root:not([data-theme="light"]) pre,
    :root:not([data-theme="light"]) code {
        background-color: #2d2d30 !important;
        color: #d4d4d4 !important;
        border-color: #3e3e42;
    }
    :root:not([data-theme="light"]) .lesson-nav,
    :root:not([data-theme="light"]) .breadcrumb,
    :root:not([data-theme="light"]) .exercise-header,
    :root:not([data-theme="light"]) .exercise-actions {
        background: #2d2d30;
        border-color: #3e3e42;
    }
    :root:not([data-theme="light"]) a {
        color: #569cd6;
    }
    :root:not([data-theme="light"]) blockquote {
        background-color: #2d2d30;
        color: #d4d4d4;
    }
}

/* ===========================
   Theme System (added 2026)
   CSS variables + manual dark/light toggle via data-theme on <html>
   - data-theme="dark"  → force dark (overrides OS preference)
   - data-theme="light" → force light (overrides OS preference)
   - no attribute       → fall through to @media (prefers-color-scheme: dark) above
   =========================== */

:root {
    --bg-color: rgb(248, 250, 252);
    --card-bg: #ffffff;
    --nav-bg: #ffffff;
    --text-color: rgb(51, 65, 85);
    --text-light: #6a737d;
    --border-color: #e1e4e8;
    --primary-color: rgb(59, 130, 246);
    --primary-hover: rgb(37, 99, 235);
    --primary-light: rgba(59, 130, 246, 0.08);
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --radius-sm: 6px;
    --radius-md: 10px;
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.07), 0 2px 4px -2px rgba(0,0,0,0.05);
    color-scheme: light dark;
}

/* Variable overrides when OS prefers dark and user hasn't chosen light */
@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
        --bg-color: #1e1e1e;
        --card-bg: #2d2d30;
        --nav-bg: #2d2d30;
        --text-color: #d4d4d4;
        --text-light: #b0b0b0;
        --border-color: #3e3e42;
        --primary-color: #569cd6;
        --primary-hover: #75b3d6;
        --primary-light: rgba(86, 156, 214, 0.15);
        --shadow-sm: 0 1px 2px rgba(0,0,0,0.3);
        --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.4), 0 2px 4px -2px rgba(0,0,0,0.3);
    }
}

/* Variable overrides for explicit dark mode */
:root[data-theme="dark"] {
    --bg-color: #1e1e1e;
    --card-bg: #2d2d30;
    --nav-bg: #2d2d30;
    --text-color: #d4d4d4;
    --text-light: #b0b0b0;
    --border-color: #3e3e42;
    --primary-color: #569cd6;
    --primary-hover: #75b3d6;
    --primary-light: rgba(86, 156, 214, 0.15);
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.3);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.4), 0 2px 4px -2px rgba(0,0,0,0.3);
}

/* Apply manual dark theme to existing content (mirror of @media block) */
:root[data-theme="dark"] body {
    background-color: #1e1e1e;
    color: #d4d4d4;
}
:root[data-theme="dark"] h1,
:root[data-theme="dark"] h2,
:root[data-theme="dark"] h3,
:root[data-theme="dark"] h4 {
    background-color: #2d53a3;
}
:root[data-theme="dark"] pre,
:root[data-theme="dark"] code {
    background-color: #2d2d30 !important;
    color: #d4d4d4 !important;
    border-color: #3e3e42;
}
:root[data-theme="dark"] .lesson-nav,
:root[data-theme="dark"] .breadcrumb,
:root[data-theme="dark"] .exercise-header,
:root[data-theme="dark"] .exercise-actions {
    background: #2d2d30;
    border-color: #3e3e42;
}
:root[data-theme="dark"] a { color: #569cd6; }
:root[data-theme="dark"] blockquote {
    background-color: #2d2d30;
    color: #d4d4d4;
}

/* ===========================
   Sticky Top Navigation (added 2026)
   Sits inside body's existing left/right margins (30–40px desktop, 10px mobile).
   Uses negative margins to span the body's content area edge-to-edge so the
   sticky header reads as a real bar.
   =========================== */

.main-nav {
    background-color: var(--nav-bg);
    border-bottom: 1px solid var(--border-color);
    padding: var(--spacing-sm) var(--spacing-md);
    position: sticky;
    top: 0;
    z-index: 200;
    box-shadow: var(--shadow-sm);
    transition: background-color 0.3s ease, border-color 0.3s ease;
    margin: 0 -40px var(--spacing-md) -30px;
}

@media (max-width: 768px) {
    .main-nav {
        margin: 0 -10px var(--spacing-md) -10px;
    }
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: relative;
    padding: 0 var(--spacing-md);
}

.nav-logo {
    font-size: 1.15rem;
    font-weight: 700;
    color: var(--primary-color);
    text-decoration: none;
    white-space: nowrap;
    background: none;
    padding: 0;
    margin: 0;
}
.nav-logo:hover { text-decoration: none; }

.main-nav .nav-links {
    display: flex;
    gap: var(--spacing-md);
    align-items: center;
    list-style: none;
    margin: 0;
    padding: 0;
}

.main-nav .nav-links a {
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
    font-size: 0.92rem;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-sm);
    transition: color 0.2s, background-color 0.2s;
}
.main-nav .nav-links a:hover {
    color: var(--primary-color);
    background-color: var(--primary-light);
    text-decoration: none;
}

.main-nav .nav-divider {
    width: 1px;
    height: 1.2rem;
    background-color: var(--border-color);
    flex-shrink: 0;
}

#theme-toggle {
    background: var(--primary-light);
    border: 1px solid var(--border-color);
    border-radius: 50%;
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: 1.1rem;
    padding: 0;
    color: var(--text-color);
    transition: background-color 0.2s, transform 0.2s;
    line-height: 1;
}
#theme-toggle:hover {
    transform: scale(1.1);
    background-color: var(--primary-color);
    color: #fff;
}

.mobile-menu-toggle {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--primary-color);
    padding: var(--spacing-xs);
    line-height: 1;
}

@media (max-width: 768px) {
    .mobile-menu-toggle { display: block; }

    .main-nav .nav-links {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--nav-bg);
        border-top: 1px solid var(--border-color);
        flex-direction: column;
        padding: var(--spacing-md);
        box-shadow: var(--shadow-md);
        z-index: 300;
    }
    .main-nav .nav-links.active { display: flex; }
    .main-nav .nav-divider { display: none; }
}

/* ===========================
   Phase 3 — Dark Mode Polish (added 2026)
   Overrides for hard-coded light backgrounds that don't flip with the theme:
     - Inline-styled boxes: #f0f8ff (info), #fff5f5 (note), #f9f9f9 (neutral)
     - Class-based: .canvas-wrapper, .svg-wrapper, .reading-time, .mobile-diagram-note
     - Mermaid container/node/text overrides (main.css uses !important on text fills)
   Each rule is duplicated under [data-theme="dark"] AND under
   @media (prefers-color-scheme: dark) :root:not([data-theme="light"]) so the
   styling holds during the brief pre-JS render on dark-OS systems and after
   the user manually picks dark.
   =========================== */

/* ---- Inline-style info boxes (#f0f8ff) ---- */
:root[data-theme="dark"] [style*="background-color: #f0f8ff" i],
:root[data-theme="dark"] [style*="background-color:#f0f8ff" i],
:root[data-theme="dark"] [style*="background: #f0f8ff" i],
:root[data-theme="dark"] [style*="background:#f0f8ff" i] {
    background-color: rgba(86, 156, 214, 0.15) !important;
    color: #d4d4d4 !important;
}

/* ---- Inline-style note/analogy boxes (#fff5f5) ---- */
:root[data-theme="dark"] [style*="background-color: #fff5f5" i],
:root[data-theme="dark"] [style*="background-color:#fff5f5" i],
:root[data-theme="dark"] [style*="background: #fff5f5" i],
:root[data-theme="dark"] [style*="background:#fff5f5" i] {
    background-color: rgba(239, 68, 68, 0.12) !important;
    color: #d4d4d4 !important;
}

/* ---- Inline-style neutral boxes (#f9f9f9) ---- */
:root[data-theme="dark"] [style*="background-color: #f9f9f9" i],
:root[data-theme="dark"] [style*="background-color:#f9f9f9" i],
:root[data-theme="dark"] [style*="background: #f9f9f9" i],
:root[data-theme="dark"] [style*="background:#f9f9f9" i] {
    background-color: rgba(255, 255, 255, 0.05) !important;
    color: #d4d4d4 !important;
}

/* ---- Class-based light backgrounds ---- */
:root[data-theme="dark"] .canvas-wrapper,
:root[data-theme="dark"] .svg-wrapper {
    background: #2d2d30;
    border: 1px solid #3e3e42;
}
:root[data-theme="dark"] .reading-time {
    background: rgba(86, 156, 214, 0.2);
    color: #d4d4d4;
}
:root[data-theme="dark"] .mobile-diagram-note {
    background: #2d2d30;
    color: #d4d4d4;
}

/* ---- Mermaid container & node overrides ---- */
:root[data-theme="dark"] .mermaid_container,
:root[data-theme="dark"] .mermaid-diagram,
:root[data-theme="dark"] .mermaid {
    background-color: #2d2d30;
    color: #d4d4d4;
    border-color: #3e3e42;
}
:root[data-theme="dark"] .mermaid .node rect,
:root[data-theme="dark"] .mermaid .node circle,
:root[data-theme="dark"] .mermaid .node ellipse,
:root[data-theme="dark"] .mermaid .node polygon,
:root[data-theme="dark"] .mermaid .node path {
    fill: #1e1e1e;
    stroke: #569cd6;
}
:root[data-theme="dark"] .mermaid .edgePath .path {
    stroke: #94a3b8;
}
:root[data-theme="dark"] .mermaid .cluster rect {
    fill: #1e1e1e;
    stroke: #569cd6;
}
/* main.css forces these to dark text via !important; need !important to win */
:root[data-theme="dark"] .mermaid .label text,
:root[data-theme="dark"] .mermaid text,
:root[data-theme="dark"] .mermaid .flowchart-label text,
:root[data-theme="dark"] .mermaid .mindmap-node text,
:root[data-theme="dark"] .mermaid .mindmap-node .nodeText,
:root[data-theme="dark"] .mermaid .nodeLabel {
    fill: #d4d4d4 !important;
    color: #d4d4d4 !important;
}
:root[data-theme="dark"] .mermaid .label {
    color: #d4d4d4;
    fill: #d4d4d4;
}

/* ---- Same overrides during pre-JS render on dark-OS systems ---- */
@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) [style*="background-color: #f0f8ff" i],
    :root:not([data-theme="light"]) [style*="background-color:#f0f8ff" i],
    :root:not([data-theme="light"]) [style*="background: #f0f8ff" i],
    :root:not([data-theme="light"]) [style*="background:#f0f8ff" i] {
        background-color: rgba(86, 156, 214, 0.15) !important;
        color: #d4d4d4 !important;
    }
    :root:not([data-theme="light"]) [style*="background-color: #fff5f5" i],
    :root:not([data-theme="light"]) [style*="background-color:#fff5f5" i],
    :root:not([data-theme="light"]) [style*="background: #fff5f5" i],
    :root:not([data-theme="light"]) [style*="background:#fff5f5" i] {
        background-color: rgba(239, 68, 68, 0.12) !important;
        color: #d4d4d4 !important;
    }
    :root:not([data-theme="light"]) [style*="background-color: #f9f9f9" i],
    :root:not([data-theme="light"]) [style*="background-color:#f9f9f9" i],
    :root:not([data-theme="light"]) [style*="background: #f9f9f9" i],
    :root:not([data-theme="light"]) [style*="background:#f9f9f9" i] {
        background-color: rgba(255, 255, 255, 0.05) !important;
        color: #d4d4d4 !important;
    }
    :root:not([data-theme="light"]) .canvas-wrapper,
    :root:not([data-theme="light"]) .svg-wrapper {
        background: #2d2d30;
        border: 1px solid #3e3e42;
    }
    :root:not([data-theme="light"]) .reading-time {
        background: rgba(86, 156, 214, 0.2);
        color: #d4d4d4;
    }
    :root:not([data-theme="light"]) .mobile-diagram-note {
        background: #2d2d30;
        color: #d4d4d4;
    }
    :root:not([data-theme="light"]) .mermaid_container,
    :root:not([data-theme="light"]) .mermaid-diagram,
    :root:not([data-theme="light"]) .mermaid {
        background-color: #2d2d30;
        color: #d4d4d4;
        border-color: #3e3e42;
    }
    :root:not([data-theme="light"]) .mermaid .node rect,
    :root:not([data-theme="light"]) .mermaid .node circle,
    :root:not([data-theme="light"]) .mermaid .node ellipse,
    :root:not([data-theme="light"]) .mermaid .node polygon,
    :root:not([data-theme="light"]) .mermaid .node path {
        fill: #1e1e1e;
        stroke: #569cd6;
    }
    :root:not([data-theme="light"]) .mermaid .edgePath .path {
        stroke: #94a3b8;
    }
    :root:not([data-theme="light"]) .mermaid .cluster rect {
        fill: #1e1e1e;
        stroke: #569cd6;
    }
    :root:not([data-theme="light"]) .mermaid .label text,
    :root:not([data-theme="light"]) .mermaid text,
    :root:not([data-theme="light"]) .mermaid .flowchart-label text,
    :root:not([data-theme="light"]) .mermaid .mindmap-node text,
    :root:not([data-theme="light"]) .mermaid .mindmap-node .nodeText,
    :root:not([data-theme="light"]) .mermaid .nodeLabel {
        fill: #d4d4d4 !important;
        color: #d4d4d4 !important;
    }
    :root:not([data-theme="light"]) .mermaid .label {
        color: #d4d4d4;
        fill: #d4d4d4;
    }
}

/* ===========================
   Phase 5 — Auto-TOC (added 2026)
   Built at runtime by nav-enhancements.js / initAutoTOC() from <h2 id> elements.
   Open: full sticky card under the main-nav.
   Closed: 44px circular FAB in upper-left, just below the main-nav.
   =========================== */

.toc-card.auto-toc {
    position: sticky;
    top: calc(60px + env(safe-area-inset-top));
    z-index: 100;
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
    margin: 0 0 var(--spacing-lg) 0;
    padding: 0;
    transition: background-color 0.3s ease, box-shadow 0.3s ease, transform 0.2s ease;
}

/* Hide native disclosure marker — we render our own chevron */
.toc-card.auto-toc summary { list-style: none; }
.toc-card.auto-toc summary::-webkit-details-marker { display: none; }
.toc-card.auto-toc summary::marker { content: ''; }

.toc-card.auto-toc summary {
    cursor: pointer;
    padding: var(--spacing-sm) var(--spacing-md);
    user-select: none;
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    background: transparent;
    color: var(--text-color);
}
.toc-card.auto-toc .toc-icon { font-size: 1.25rem; line-height: 1; }
.toc-card.auto-toc .toc-label { font-size: 1.1rem; font-weight: 700; }
.toc-card.auto-toc .toc-chevron {
    margin-left: auto;
    font-size: 0.85rem;
    color: var(--text-light);
    transition: transform 0.3s ease;
}
.toc-card.auto-toc[open] .toc-chevron { transform: rotate(180deg); }

.toc-card.auto-toc nav {
    padding: 0 var(--spacing-md) var(--spacing-md);
}
.toc-card.auto-toc ol {
    list-style: decimal;
    padding-left: var(--spacing-xl);
    margin: 0;
}
.toc-card.auto-toc li {
    padding: 2px 0;
    margin: 0;
}
.toc-card.auto-toc .toc-link {
    color: var(--text-color);
    text-decoration: none;
    transition: color 0.2s;
    display: inline-block;
    padding: 2px 0;
}
.toc-card.auto-toc .toc-link:hover {
    color: var(--primary-color);
    text-decoration: underline;
}
.toc-card.auto-toc .toc-link.active {
    color: var(--primary-color);
    font-weight: 600;
}

/* ---- Collapsed state: floating action button in upper-left ----
   Sits just below the sticky main-nav (~60px tall) at left: spacing-lg.
   --- */
.toc-card.auto-toc:not([open]) {
    position: fixed;
    top: calc(70px + env(safe-area-inset-top));
    left: var(--spacing-lg);
    bottom: auto;
    right: auto;
    width: 44px;
    height: 44px;
    padding: 0;
    margin: 0;
    border: none;
    border-radius: 50%;
    background: var(--primary-color);
    box-shadow: var(--shadow-md);
    z-index: 150;
    overflow: hidden;
}
.toc-card.auto-toc:not([open]):hover {
    transform: scale(1.08);
    box-shadow: var(--shadow-lg);
    filter: brightness(1.1);
}
.toc-card.auto-toc:not([open]) summary {
    width: 100%;
    height: 100%;
    padding: 0;
    justify-content: center;
    color: #fff;
}
.toc-card.auto-toc:not([open]) .toc-icon {
    font-size: 1.25rem;
    color: #fff;
}
.toc-card.auto-toc:not([open]) .toc-label,
.toc-card.auto-toc:not([open]) .toc-chevron {
    /* Visually hidden but still accessible to screen readers via summary */
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* On small screens, hug the left edge a bit tighter */
@media (max-width: 768px) {
    .toc-card.auto-toc:not([open]) {
        top: calc(62px + env(safe-area-inset-top));
        left: var(--spacing-md);
        width: 40px;
        height: 40px;
    }
    .toc-card.auto-toc:not([open]) .toc-icon { font-size: 1.1rem; }
}

/* ===========================
   Phase 8 — Pedagogy Upgrade (added 2026)
   Practice Exercise card + Quick Quiz interactive card.

   Ported from python_intro precedent (chat-37 M1 audit). Adds three new
   semantic classes to python_gamedev:
     - .lesson-section  (outer wrapper around an exercise + quiz pair)
     - .card / .card-info  (matches python_intro design-system shape;
                            previously only .exercise-card existed here)
     - .quiz-container / .quiz-question / .quiz-options /
       .quiz-option / .quiz-feedback  (interactive quiz block)

   Markup pattern:

     <section class="lesson-section">
       <h2>🏋️ Practice Exercise: …</h2>
       <div class="card card-info">
         <h3>Exercise N: …</h3>
         <p><strong>Objective:</strong> …</p>
         <h4>Instructions:</h4>
         <ol>…</ol>
         <details><summary>💡 Hint</summary>…</details>
         <details><summary>✅ Example Solution</summary><pre><code>…</code></pre></details>
       </div>
       <div class="card quiz-container">
         <h3>🎯 Quick Quiz</h3>
         <div class="quiz-question">
           <p><strong>Question N:</strong> …</p>
           <div class="quiz-options">
             <button class="quiz-option" data-correct="true|false"
                     data-hint="…" data-explanation="…">A) …</button>
             …
           </div>
           <div class="quiz-feedback"></div>
         </div>
         …
       </div>
     </section>

   JS hook in nav-enhancements.js / initQuizInteractivity() (Phase 8).
   Success/danger colours hardcoded here (these CSS-variables aren't in
   python_gamedev's :root; can be promoted to vars in a future Phase-9 lint).
   =========================== */

.lesson-section {
    margin: var(--spacing-xl) 0;
}

.card {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
    margin: var(--spacing-md) 0;
    box-shadow: var(--shadow-sm);
    transition: box-shadow 0.3s ease, background-color 0.3s ease;
}
.card:hover { box-shadow: var(--shadow-md); }

.card-info {
    background: #eff6ff;
    border-left: 4px solid #3b82f6;
}
:root[data-theme="dark"] .card-info {
    background: rgba(86, 156, 214, 0.10);
    border-left-color: #569cd6;
}
@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) .card-info {
        background: rgba(86, 156, 214, 0.10);
        border-left-color: #569cd6;
    }
}

.card-info h3,
.card-info h4 {
    background: none;
    padding: 0;
    margin: 0 0 var(--spacing-sm) 0;
    color: var(--text-color);
    border: none;
}
.card-info p { margin-bottom: var(--spacing-sm); }
.card-info ol {
    margin: var(--spacing-sm) 0 var(--spacing-md) var(--spacing-lg);
    padding-left: var(--spacing-md);
}
.card-info ol li { margin-bottom: var(--spacing-xs); }
.card-info details {
    margin-top: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
}
.card-info details summary {
    cursor: pointer;
    font-weight: 600;
    color: var(--text-color);
    padding: var(--spacing-xs) 0;
}
.card-info details[open] summary { margin-bottom: var(--spacing-sm); }
.card-info details pre {
    margin: var(--spacing-sm) 0 0;
    border-radius: var(--radius-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    overflow-x: auto;
}

/* Quiz container + question shell */
.quiz-container { padding: var(--spacing-lg); }
.quiz-container h3 {
    background: none;
    padding: 0;
    margin: 0 0 var(--spacing-md) 0;
    color: var(--text-color);
    border: none;
}
.quiz-question {
    margin: var(--spacing-md) 0;
    padding-bottom: var(--spacing-md);
    border-bottom: 1px solid var(--border-color);
}
.quiz-question:last-of-type {
    border-bottom: none;
    padding-bottom: 0;
}
.quiz-question p { margin-bottom: var(--spacing-sm); }
.quiz-options {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
    margin: var(--spacing-sm) 0;
}

/* Quiz options — buttons. Override the global button styling deliberately:
   the global .button/button rules paint primary-blue + white; quiz options
   need to look like neutral selectable cards until clicked. */
.quiz-option {
    display: block;
    width: 100%;
    text-align: left;
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--card-bg);
    color: var(--text-color);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 0.95rem;
    font-weight: 400;
    transition: border-color 0.2s, background-color 0.2s, color 0.2s;
}
.quiz-option:hover {
    border-color: var(--primary-color);
    background-color: var(--primary-light);
    color: var(--text-color);
    transform: none;
    box-shadow: none;
}
.quiz-option.correct {
    border-color: #22c55e;
    background-color: #f0fdf4;
    color: #14532d;
}
.quiz-option.incorrect {
    border-color: #ef4444;
    background-color: #fef2f2;
    color: #7f1d1d;
}
:root[data-theme="dark"] .quiz-option.correct {
    background-color: rgba(34, 197, 94, 0.15);
    color: #86efac;
    border-color: #22c55e;
}
:root[data-theme="dark"] .quiz-option.incorrect {
    background-color: rgba(239, 68, 68, 0.15);
    color: #fca5a5;
    border-color: #ef4444;
}
@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) .quiz-option.correct {
        background-color: rgba(34, 197, 94, 0.15);
        color: #86efac;
        border-color: #22c55e;
    }
    :root:not([data-theme="light"]) .quiz-option.incorrect {
        background-color: rgba(239, 68, 68, 0.15);
        color: #fca5a5;
        border-color: #ef4444;
    }
}

/* Quiz feedback — surfaces hint or explanation after a click. */
.quiz-feedback {
    padding: var(--spacing-sm) var(--spacing-md);
    margin-top: var(--spacing-sm);
    border-radius: var(--radius-sm);
    font-weight: 500;
    min-height: 1.5em;
    transition: background-color 0.2s, color 0.2s;
}
.quiz-feedback.correct {
    color: #14532d;
    background-color: #f0fdf4;
}
.quiz-feedback.incorrect {
    color: #7f1d1d;
    background-color: #fef2f2;
}
:root[data-theme="dark"] .quiz-feedback.correct {
    color: #86efac;
    background-color: rgba(34, 197, 94, 0.12);
}
:root[data-theme="dark"] .quiz-feedback.incorrect {
    color: #fca5a5;
    background-color: rgba(239, 68, 68, 0.12);
}
@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) .quiz-feedback.correct {
        color: #86efac;
        background-color: rgba(34, 197, 94, 0.12);
    }
    :root:not([data-theme="light"]) .quiz-feedback.incorrect {
        color: #fca5a5;
        background-color: rgba(239, 68, 68, 0.12);
    }
}

/* ===========================
   Phase 7 — Mobile Canvas Fallbacks (added 2026)
   On viewports where canvas is hidden by the existing
     @media (max-width: 768px) { canvas { display: none; } }
   rule, show a static SVG fallback inside the same .canvas-wrapper.

   Markup pattern (injected by wrap_canvas_fallbacks.py per the catalog at
   phase7-canvas-fallback-catalog.json):

     <div class="canvas-wrapper">
       <canvas id="…" …></canvas>
       <figure class="canvas-fallback">
         <img class="responsive-svg" src="/images/components/….svg" alt="…" loading="lazy">
         <figcaption>…</figcaption>
       </figure>
     </div>

   Hidden by default on desktop. Only flips visible at ≤ 768px so it never
   competes with the live canvas demo. Theming inherits from .canvas-wrapper
   (Phase 3 already polishes that for dark mode).
   =========================== */

.canvas-fallback {
    display: none;
    margin: 0;
    padding: 0;
}

@media (max-width: 768px) {
    .canvas-fallback {
        display: block;
        text-align: center;
        margin: 0;
    }
    .canvas-fallback .responsive-svg {
        width: 100%;
        max-width: 600px;
        height: auto;
        margin: 0 auto;
    }
    .canvas-fallback figcaption {
        font-size: 0.92rem;
        color: var(--text-light);
        margin-top: 0.5rem;
        font-style: italic;
        padding: 0 0.5rem;
        text-align: center;
        line-height: 1.45;
    }
}

/* Print: hide fallbacks (canvas is already hidden in print) */
@media print {
    .canvas-fallback { display: none !important; }
}