/* ==========================================================================
   LearnWeb - Modern & Minimal Custom CSS
   Editorial Learning Aesthetic with Terracotta Accent
   ========================================================================== */

/* ==========================================================================
   1. CSS Reset & Custom Properties
   ========================================================================== */

/* Modern CSS Reset */
*,
*::before,
*::after {
  box-sizing: border-box;
}

* {
  margin: 0;
  padding: 0;
}

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  min-height: 100vh;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img,
picture,
video,
canvas,
svg {
  display: block;
  max-width: 100%;
}

input,
button,
textarea,
select {
  font: inherit;
}

p,
h1,
h2,
h3,
h4,
h5,
h6 {
  overflow-wrap: break-word;
}

/* Custom Properties */
:root {
  /* Colors - Backgrounds */
  --bg-primary: #FAFAF9;
  --bg-secondary: #F5F5F4;
  --bg-elevated: #FFFFFF;

  /* Colors - Text */
  --text-primary: #1C1917;
  --text-secondary: #57534E;
  --text-muted: #A8A29E;

  /* Colors - Accent (Terracotta/Rust) */
  --accent-primary: #C2410C;
  --accent-hover: #9A3412;
  --accent-light: #FFEDD5;
  --accent-subtle: #FFF7ED;

  /* Colors - Semantic */
  --border-color: #E7E5E4;
  --border-strong: #D6D3D1;
  --shadow-color: rgba(28, 25, 23, 0.08);
  --focus-ring: #C2410C;

  /* Typography - Fonts */
  --font-display: "DM Sans", system-ui, sans-serif;
  --font-body: "Source Sans 3", system-ui, sans-serif;
  --font-mono: "JetBrains Mono", ui-monospace, monospace;

  /* Typography - Scale (Fluid) */
  --text-xs: clamp(0.75rem, 0.7rem + 0.25vw, 0.8rem);
  --text-sm: clamp(0.875rem, 0.8rem + 0.35vw, 0.95rem);
  --text-base: clamp(1rem, 0.95rem + 0.25vw, 1.125rem);
  --text-lg: clamp(1.125rem, 1rem + 0.5vw, 1.25rem);
  --text-xl: clamp(1.25rem, 1.1rem + 0.75vw, 1.5rem);
  --text-2xl: clamp(1.5rem, 1.25rem + 1.25vw, 2rem);
  --text-3xl: clamp(2rem, 1.5rem + 2.5vw, 3rem);
  --text-4xl: clamp(2.5rem, 2rem + 3vw, 4rem);

  /* Spacing */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-24: 6rem;

  /* Layout */
  --max-width: 1200px;
  --content-width: 720px;
  --sidebar-width: 280px;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 200ms ease;
  --transition-slow: 300ms ease;

  /* Borders & Shadows */
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --shadow-sm: 0 1px 2px var(--shadow-color);
  --shadow-md: 0 4px 6px var(--shadow-color), 0 2px 4px var(--shadow-color);
  --shadow-lg: 0 10px 15px var(--shadow-color), 0 4px 6px var(--shadow-color);
}

/* ==========================================================================
   Dark Mode
   ========================================================================== */

[data-theme="dark"] {
  /* Colors - Backgrounds */
  --bg-primary: #171717;
  --bg-secondary: #262626;
  --bg-elevated: #1F1F1F;

  /* Colors - Text */
  --text-primary: #FAFAFA;
  --text-secondary: #A3A3A3;
  --text-muted: #737373;

  /* Colors - Accent (Terracotta - slightly lighter for dark mode) */
  --accent-primary: #EA580C;
  --accent-hover: #F97316;
  --accent-light: #431407;
  --accent-subtle: #1C1007;

  /* Colors - Semantic */
  --border-color: #404040;
  --border-strong: #525252;
  --shadow-color: rgba(0, 0, 0, 0.3);
  --focus-ring: #EA580C;
}

/* Dark mode code blocks - invert to light */
[data-theme="dark"] pre {
  background-color: #0A0A0A;
  color: #E5E5E5;
}

[data-theme="dark"] code {
  background-color: var(--bg-secondary);
}

/* Dark mode header gradient */
[data-theme="dark"] header[role="banner"] {
  background: linear-gradient(135deg, var(--accent-subtle) 0%, var(--bg-primary) 100%);
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }

  html {
    scroll-behavior: auto;
  }
}

/* ==========================================================================
   2. Base Typography
   ========================================================================== */

body {
  font-family: var(--font-body);
  font-size: var(--text-base);
  color: var(--text-primary);
  background-color: var(--bg-primary);
}

/* Headings */
h1,
h2,
h3,
h4,
h5,
h6 {
  font-family: var(--font-display);
  font-weight: 600;
  line-height: 1.25;
  color: var(--text-primary);
  margin-bottom: var(--space-4);
}

h1 {
  font-size: var(--text-4xl);
  font-weight: 700;
  letter-spacing: -0.02em;
}

h2 {
  font-size: var(--text-3xl);
  letter-spacing: -0.01em;
  margin-top: var(--space-12);
}

h3 {
  font-size: var(--text-2xl);
  margin-top: var(--space-8);
}

h4 {
  font-size: var(--text-xl);
  margin-top: var(--space-6);
}

h5 {
  font-size: var(--text-lg);
  margin-top: var(--space-4);
}

h6 {
  font-size: var(--text-base);
  font-weight: 600;
  margin-top: var(--space-4);
}

/* First heading after header shouldn't have top margin */
main>.container>h2:first-child,
article>h2:first-child,
.lesson-content>h2:first-child {
  margin-top: 0;
}

/* Paragraphs */
p {
  margin-bottom: var(--space-4);
  max-width: 65ch;
}

/* Links */
a {
  color: var(--accent-primary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--accent-hover);
  text-decoration: underline;
  text-underline-offset: 3px;
}

a:focus-visible {
  outline: 2px solid var(--focus-ring);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

/* Lists */
ul,
ol {
  margin-bottom: var(--space-4);
  padding-left: var(--space-6);
}

li {
  margin-bottom: var(--space-2);
}

li::marker {
  color: var(--accent-primary);
}

/* Nested lists */
ul ul,
ol ol,
ul ol,
ol ul {
  margin-top: var(--space-2);
  margin-bottom: var(--space-2);
}

/* Strong and emphasis */
strong,
b {
  font-weight: 600;
}

em,
i {
  font-style: italic;
}

/* Small text */
small {
  font-size: var(--text-sm);
  color: var(--text-secondary);
}

/* Code */
code {
  font-family: var(--font-mono);
  font-size: 0.9em;
  background-color: var(--bg-secondary);
  padding: 0.125em 0.375em;
  border-radius: var(--radius-sm);
  color: var(--text-primary);
}

/* Code blocks */
pre {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  background-color: var(--text-primary);
  color: var(--bg-primary);
  padding: var(--space-4);
  border-radius: var(--radius-md);
  overflow-x: auto;
  margin-bottom: var(--space-6);
  line-height: 1.5;
}

pre code {
  background: none;
  padding: 0;
  border-radius: 0;
  color: inherit;
  font-size: inherit;
}

/* Blockquotes */
blockquote {
  border-left: 4px solid var(--accent-primary);
  padding-left: var(--space-4);
  margin: var(--space-6) 0;
  font-style: italic;
  color: var(--text-secondary);
}

/* Horizontal rule */
hr {
  border: none;
  border-top: 1px solid var(--border-color);
  margin: var(--space-8) 0;
}

/* ==========================================================================
   3. Layout System
   ========================================================================== */

.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-4);
}

@media (min-width: 768px) {
  .container {
    padding: 0 var(--space-8);
  }
}

/* Guide Container - Two-column lesson layout */
.guide-container {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-8);
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-6) var(--space-4);
}

@media (min-width: 1024px) {
  .guide-container {
    grid-template-columns: var(--sidebar-width) 1fr;
    padding: var(--space-8);
    gap: var(--space-12);
  }
}

/* Guide Grid - Course cards on homepage */
.guide-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-6);
  margin-top: var(--space-6);
}

@media (min-width: 640px) {
  .guide-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .guide-grid {
    grid-template-columns: repeat(4, 1fr);
  }
}

/* Articles Grid */
.articles-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-6);
  margin-top: var(--space-6);
}

@media (min-width: 640px) {
  .articles-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .articles-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

/* ==========================================================================
   4. Navigation Components
   ========================================================================== */

/* Main Navigation */
nav[role="navigation"] {
  background-color: var(--bg-elevated);
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 100;
}

nav[role="navigation"] .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: var(--space-3);
  padding-bottom: var(--space-3);
}

.nav-logo {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: var(--text-lg);
  color: var(--text-primary);
  text-decoration: none;
}

.nav-logo:hover {
  color: var(--accent-primary);
  text-decoration: none;
}

.nav-list {
  display: none;
  list-style: none;
  margin: 0;
  padding: 0;
  gap: var(--space-1);
}

@media (min-width: 768px) {
  .nav-list {
    display: flex;
    align-items: center;
  }
}

.nav-list li {
  margin: 0;
}

.nav-list a {
  display: block;
  padding: var(--space-2) var(--space-3);
  color: var(--text-secondary);
  font-size: var(--text-sm);
  font-weight: 500;
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}

.nav-list a:hover {
  color: var(--text-primary);
  background-color: var(--bg-secondary);
  text-decoration: none;
}

.nav-list a[aria-current="page"] {
  color: var(--accent-primary);
  background-color: var(--accent-subtle);
}

/* Mobile Menu Toggle */
.mobile-menu-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  background: none;
  border: none;
  cursor: pointer;
  color: var(--text-primary);
  border-radius: var(--radius-md);
  transition: background-color var(--transition-fast);
}

.mobile-menu-toggle:hover {
  background-color: var(--bg-secondary);
}

@media (min-width: 768px) {
  .mobile-menu-toggle {
    display: none;
  }
}

/* Mobile menu open state */
.nav-list.is-open {
  display: flex;
  flex-direction: column;
  position: absolute;
  top: 100%;
  left: 0;
  right: 0;
  background-color: var(--bg-elevated);
  border-bottom: 1px solid var(--border-color);
  padding: var(--space-4);
  box-shadow: var(--shadow-lg);
}

.nav-list.is-open a {
  padding: var(--space-3) var(--space-4);
}

/* Theme Toggle */
.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  background: none;
  border: 1px solid var(--border-color);
  cursor: pointer;
  color: var(--text-secondary);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}

.theme-toggle:hover {
  background-color: var(--bg-secondary);
  border-color: var(--border-strong);
  color: var(--text-primary);
}

/* Logo Link */
.logo-link {
  text-decoration: none;
  color: inherit;
}

.logo-link:hover {
  text-decoration: none;
}

/* Breadcrumbs */
.breadcrumb {
  margin-bottom: var(--space-6);
}

.breadcrumb-list {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  list-style: none;
  margin: 0;
  padding: 0;
  font-size: var(--text-sm);
}

.breadcrumb-item {
  display: flex;
  align-items: center;
  margin: 0;
  color: var(--text-muted);
}

.breadcrumb-item:not(:last-child)::after {
  content: "/";
  margin: 0 var(--space-2);
  color: var(--border-strong);
}

.breadcrumb-item a {
  color: var(--text-secondary);
}

.breadcrumb-item a:hover {
  color: var(--accent-primary);
}

.breadcrumb-item:last-child {
  color: var(--text-primary);
  font-weight: 500;
}

/* ==========================================================================
   5. Header & Footer
   ========================================================================== */

/* Header */
header[role="banner"] {
  background: linear-gradient(135deg, var(--accent-subtle) 0%, var(--bg-primary) 100%);
  padding: var(--space-12) 0;
  text-align: center;
}

header[role="banner"] .container {
  max-width: 800px;
}

header[role="banner"] h1 {
  margin-bottom: var(--space-4);
}

/* Site Name with accent styling */
.site-name {
  font-family: var(--font-display);
  font-weight: 700;
}

.site-name-dot {
  color: var(--accent-primary);
}

.site-name-tld {
  color: var(--accent-primary);
}

/* Subpage Branding */
.subpage-branding {
  text-align: left;
}

.subpage-branding h1 {
  font-size: var(--text-2xl);
  margin-bottom: var(--space-2);
}

header[role="banner"].subpage-header {
  padding: var(--space-8) 0;
  background: var(--bg-secondary);
}

/* Tagline */
.tagline {
  font-size: var(--text-lg);
  color: var(--text-secondary);
  margin-bottom: 0;
  max-width: 60ch;
  margin-left: auto;
  margin-right: auto;
}

/* Footer */
footer[role="contentinfo"] {
  background-color: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: var(--space-8) 0;
  margin-top: var(--space-16);
  text-align: center;
}

footer[role="contentinfo"] .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
}

footer[role="contentinfo"] p {
  color: var(--text-secondary);
  font-size: var(--text-sm);
  margin: 0 auto;
}

footer[role="contentinfo"] a {
  color: var(--text-secondary);
  text-decoration: underline;
}

footer[role="contentinfo"] a:hover {
  color: var(--accent-primary);
}

/* ==========================================================================
   6. Card Components
   ========================================================================== */

/* Guide Card - Course cards on homepage */
.guide-card {
  background-color: var(--bg-elevated);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  transition: all var(--transition-base);
  display: flex;
  flex-direction: column;
}

.guide-card:hover {
  border-color: var(--border-strong);
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.guide-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  background-color: var(--accent-subtle);
  color: var(--accent-primary);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-4);
  font-size: 24px;
}

.guide-card h3 {
  font-size: var(--text-lg);
  margin-top: 0;
  margin-bottom: var(--space-2);
}

.guide-card h3 a {
  color: var(--text-primary);
}

.guide-card h3 a:hover {
  color: var(--accent-primary);
  text-decoration: none;
}

.guide-card p {
  font-size: var(--text-sm);
  color: var(--text-secondary);
  margin-bottom: var(--space-4);
  flex-grow: 1;
}

.guide-card>div:last-child {
  display: flex;
  gap: var(--space-2);
  flex-wrap: wrap;
}

/* Article Card */
.article-card {
  background-color: var(--bg-elevated);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  transition: all var(--transition-base);
  display: flex;
  flex-direction: column;
}

.article-card:hover {
  border-color: var(--border-strong);
  box-shadow: var(--shadow-md);
}

.article-card h3 {
  font-size: var(--text-lg);
  margin-top: 0;
  margin-bottom: var(--space-2);
}

.article-card h3 a {
  color: var(--text-primary);
}

.article-card h3 a:hover {
  color: var(--accent-primary);
  text-decoration: none;
}

.article-excerpt {
  font-size: var(--text-sm);
  color: var(--text-secondary);
  margin-bottom: var(--space-4);
  flex-grow: 1;
}

.article-card-meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  font-size: var(--text-xs);
  color: var(--text-muted);
  margin-bottom: var(--space-4);
}

.meta-item {
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.tag-badge-small {
  display: inline-block;
  background-color: var(--bg-secondary);
  color: var(--text-secondary);
  padding: 0.125rem 0.5rem;
  border-radius: 9999px;
  font-size: var(--text-xs);
}

.tag-more {
  color: var(--text-muted);
  font-size: var(--text-xs);
}

.article-link {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--accent-primary);
}

.article-link:hover {
  text-decoration: none;
  gap: var(--space-2);
}

/* ==========================================================================
   7. Lesson Layout
   ========================================================================== */

/* Lesson TOC Sidebar */
.lesson-toc {
  background-color: var(--bg-elevated);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--space-4);
  height: fit-content;
}

@media (min-width: 1024px) {
  .lesson-toc {
    position: sticky;
    top: calc(60px + var(--space-4));
  }
}

.lesson-toc-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-4);
}

.lesson-toc-title {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin: 0;
}

.lesson-toc-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  background: none;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  cursor: pointer;
  color: var(--text-secondary);
  transition: all var(--transition-fast);
}

.lesson-toc-toggle:hover {
  background-color: var(--bg-secondary);
  color: var(--text-primary);
}

@media (min-width: 1024px) {
  .lesson-toc-toggle {
    display: none;
  }
}

.lesson-toc-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

/* Mobile: collapsed by default */
@media (max-width: 1023px) {
  .lesson-toc-list {
    display: none;
  }

  .lesson-toc-list.is-open {
    display: block;
  }
}

.lesson-toc-item {
  margin-bottom: var(--space-1);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.lesson-toc-item a {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-2) var(--space-3);
  color: var(--text-secondary);
  font-size: var(--text-sm);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
  flex-grow: 1;
}

.lesson-toc-item a:hover {
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  text-decoration: none;
}

.lesson-toc-item-active a {
  background-color: var(--accent-subtle);
  color: var(--accent-primary);
  font-weight: 500;
}

.lesson-toc-current-indicator {
  display: flex;
  color: var(--accent-primary);
}

.lesson-toc-item:not(.lesson-toc-item-active) .lesson-toc-current-indicator {
  display: none;
}

/* Lesson Content */
.lesson-content {
  min-width: 0;
  /* Prevent grid blowout */
}

.lesson-content h2:first-of-type {
  margin-top: 0;
}

/* Lesson Meta */
.lesson-meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-4);
  margin-bottom: var(--space-6);
  padding-bottom: var(--space-4);
  border-bottom: 1px solid var(--border-color);
}

.lesson-meta-item {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-sm);
  color: var(--text-muted);
}

.lesson-meta-item .material-symbols-outlined {
  font-size: 18px;
  color: var(--accent-primary);
}

/* Lesson Navigation (Prev/Next) */
.lesson-navigation {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-4);
  margin-top: var(--space-12);
  padding-top: var(--space-8);
  border-top: 1px solid var(--border-color);
}

@media (min-width: 640px) {
  .lesson-navigation {
    grid-template-columns: 1fr 1fr;
  }
}

/* Navigation Card Links */
.lesson-nav-link {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  padding: var(--space-4) var(--space-5);
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  border-radius: var(--radius-lg);
  border: 1px solid transparent;
  text-decoration: none;
  min-height: 88px;
  transition: all var(--transition-base);
}

.lesson-nav-link:hover {
  background-color: var(--accent-subtle);
  border-color: var(--accent-light);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  text-decoration: none;
  color: var(--text-primary);
}

.lesson-nav-link:focus-visible {
  outline: 2px solid var(--focus-ring);
  outline-offset: 2px;
}

/* Direction label (Previous/Next with icon) */
.lesson-nav-direction {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-family: var(--font-display);
  font-size: var(--text-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--accent-primary);
}

.lesson-nav-direction .material-symbols-outlined {
  font-size: 16px;
  transition: transform var(--transition-fast);
}

/* Lesson title */
.lesson-nav-title {
  font-family: var(--font-display);
  font-size: var(--text-base);
  font-weight: 500;
  line-height: 1.4;
  color: var(--text-primary);
}

/* Previous link - left aligned */
.lesson-nav-prev {
  align-items: flex-start;
  text-align: left;
}

.lesson-nav-prev:hover .material-symbols-outlined {
  transform: translateX(-3px);
}

/* Next link - right aligned */
.lesson-nav-next {
  align-items: flex-end;
  text-align: right;
}

.lesson-nav-next .lesson-nav-direction {
  flex-direction: row;
}

.lesson-nav-next:hover .material-symbols-outlined {
  transform: translateX(3px);
}

/* ==========================================================================
   8. Progress & Completion
   ========================================================================== */

/* Course Progress */
.course-progress {
  margin-bottom: var(--space-6);
}

.progress-bar-container {
  background-color: var(--bg-secondary);
  border-radius: 9999px;
  height: 8px;
  overflow: hidden;
  margin-bottom: var(--space-2);
}

.progress-bar {
  background: linear-gradient(90deg, var(--accent-primary), var(--accent-hover));
  height: 100%;
  border-radius: 9999px;
  transition: width var(--transition-slow);
  width: 0%;
}

.progress-text {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-sm);
  color: var(--text-secondary);
}

.progress-text .material-symbols-outlined {
  font-size: 18px;
  color: var(--accent-primary);
}

/* Lesson Completion Checkbox */
.lesson-completion {
  margin-top: var(--space-8);
  padding: var(--space-4);
  background-color: var(--bg-secondary);
  border-radius: var(--radius-lg);
}

.lesson-completion-label {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  cursor: pointer;
  user-select: none;
}

.lesson-completion-checkbox {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  border: 2px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background-color: var(--bg-elevated);
  transition: all var(--transition-fast);
  flex-shrink: 0;
}

.lesson-completion-checkbox .material-symbols-outlined {
  font-size: 16px;
  color: transparent;
  transition: color var(--transition-fast);
}

.lesson-completion-label:hover .lesson-completion-checkbox {
  border-color: var(--accent-primary);
}

/* Checked state - controlled by JavaScript */
.lesson-completion.is-complete .lesson-completion-checkbox {
  background-color: var(--accent-primary);
  border-color: var(--accent-primary);
}

.lesson-completion.is-complete .lesson-completion-checkbox .material-symbols-outlined {
  color: white;
}

.lesson-completion-text {
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--text-secondary);
}

.lesson-completion.is-complete .lesson-completion-text {
  color: var(--accent-primary);
}

/* Lesson Complete Checkmark (Sidebar & Lists) */
.lesson-complete {
  color: var(--accent-primary);
  margin-left: var(--space-2);
  margin-right: var(--space-3);
  display: flex;
  align-items: center;
  flex-shrink: 0;
}

.guide-list .lesson-complete,
.lesson-list .lesson-complete {
  margin-right: var(--space-4);
}

/* ==========================================================================
   9. Content Components
   ========================================================================== */

/* Callout Box */
.callout {
  background-color: var(--accent-subtle);
  border-left: 4px solid var(--accent-primary);
  padding: var(--space-4) var(--space-6);
  margin: var(--space-6) 0;
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
}

.callout h3 {
  font-size: var(--text-lg);
  color: var(--accent-hover);
  margin-top: 0;
  margin-bottom: var(--space-2);
}

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

/* Tip Box */
.tip {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  padding: var(--space-4) var(--space-6);
  margin: var(--space-6) 0;
  border-radius: var(--radius-md);
}

.tip h3 {
  font-size: var(--text-base);
  font-weight: 600;
  color: var(--text-primary);
  margin-top: 0;
  margin-bottom: var(--space-2);
}

.tip p:last-child {
  margin-bottom: 0;
}

/* Key Takeaways Box */
.key-takeaways {
  background-color: var(--bg-elevated);
  border: 2px solid var(--accent-primary);
  padding: var(--space-6);
  margin: var(--space-8) 0;
  border-radius: var(--radius-lg);
}

.key-takeaways h3 {
  font-size: var(--text-lg);
  color: var(--accent-primary);
  margin-top: 0;
  margin-bottom: var(--space-4);
}

.key-takeaways ul {
  margin-bottom: 0;
}

.key-takeaways li:last-child {
  margin-bottom: 0;
}

/* Tables */
table {
  width: 100%;
  border-collapse: collapse;
  margin: var(--space-6) 0;
  font-size: var(--text-sm);
}

th,
td {
  padding: var(--space-3) var(--space-4);
  text-align: left;
  border-bottom: 1px solid var(--border-color);
}

th {
  font-weight: 600;
  color: var(--text-primary);
  background-color: var(--bg-secondary);
}

tr:hover {
  background-color: var(--bg-secondary);
}

/* ==========================================================================
   10. Buttons
   ========================================================================== */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-6);
  font-family: var(--font-display);
  font-size: var(--text-sm);
  font-weight: 600;
  color: white;
  background-color: var(--accent-primary);
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  text-decoration: none;
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.btn:hover {
  background-color: var(--accent-hover);
  color: white;
  text-decoration: none;
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.btn:focus-visible {
  outline: 2px solid var(--focus-ring);
  outline-offset: 2px;
}

.btn:active {
  transform: translateY(0);
}

/* Secondary Button */
.btn-secondary {
  background-color: transparent;
  color: var(--text-primary);
  border: 1px solid var(--border-strong);
}

.btn-secondary:hover {
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  border-color: var(--text-primary);
  box-shadow: none;
}

/* Resume/Play Button */
.btn-resume {
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-hover));
}

.btn-resume:hover {
  background: linear-gradient(135deg, var(--accent-hover), var(--accent-primary));
}

/* Button with icon */
.btn .material-symbols-outlined {
  font-size: 18px;
}

/* ==========================================================================
   11. Utilities & Helpers
   ========================================================================== */

/* Skip Link - Accessibility */
.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-4);
  padding: var(--space-3) var(--space-4);
  background-color: var(--accent-primary);
  color: white;
  font-weight: 600;
  border-radius: var(--radius-md);
  z-index: 1000;
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: var(--space-4);
  color: white;
  text-decoration: none;
}

/* Screen Reader Only */
.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;
}

/* Material Symbols Defaults */
.material-symbols-outlined {
  font-family: 'Material Symbols Outlined';
  font-weight: normal;
  font-style: normal;
  font-size: 48px;
  line-height: 1;
  letter-spacing: normal;
  text-transform: none;
  display: inline-block;
  white-space: nowrap;
  word-wrap: normal;
  direction: ltr;
  -webkit-font-smoothing: antialiased;
  vertical-align: middle;
}

/* Section Footer */
.section-footer {
  text-align: center;
  margin-top: var(--space-8);
}

/* Intro Section */
.intro {
  text-align: center;
  max-width: 700px;
  padding: var(--space-8) 0;
  margin: 0 auto var(--space-12);
}

.intro h2 {
  margin-top: 0;
}

/* Guides Section */
.guides {
  margin-bottom: var(--space-16);
}

.guides h2 {
  margin-top: 0;
}

/* Latest Articles Section */
.latest-articles {
  margin-bottom: var(--space-8);
}

.latest-articles h2 {
  margin-top: 0;
}

/* Guide Header (Course Index) */
.guide-header {
  margin: var(--space-8) 0;
}

.guide-header h2 {
  margin-top: 0;
}

/* Guide Nav (Course Index - Lesson List) */
.guide-nav {
  margin-top: var(--space-8);
}

.guide-nav h2 {
  margin-top: 0;
  font-size: var(--text-xl);
}

.guide-list {
  list-style: none;
  padding: 0;
  margin: var(--space-4) 0;
}

.guide-list li {
  margin-bottom: 0;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.guide-list li:first-child {
  border-top: 1px solid var(--border-color);
}

.guide-list a {
  display: block;
  padding: var(--space-4);
  color: var(--text-primary);
  transition: all var(--transition-fast);
}

.guide-list a:hover {
  background-color: var(--bg-secondary);
  color: var(--accent-primary);
  text-decoration: none;
}

/* Lesson List (variant) */
.lesson-list {
  list-style: none;
  padding: 0;
  margin: var(--space-4) 0;
}

.lesson-list li {
  margin-bottom: 0;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.lesson-list li:first-child {
  border-top: 1px solid var(--border-color);
}

.lesson-list a {
  display: block;
  padding: var(--space-4);
  color: var(--text-primary);
  transition: all var(--transition-fast);
}

.lesson-list a:hover {
  background-color: var(--bg-secondary);
  color: var(--accent-primary);
  text-decoration: none;
}

/* ==========================================================================
   12. Responsive Breakpoints & Adjustments
   ========================================================================== */

/* Tablet (768px) */
@media (min-width: 768px) {
  .tagline {
    font-size: var(--text-xl);
  }
}


/* Print Styles */
@media print {

  nav[role="navigation"],
  .skip-link,
  .lesson-toc,
  .lesson-completion,
  .lesson-navigation,
  .mobile-menu-toggle,
  .theme-toggle {
    display: none !important;
  }

  body {
    font-size: 12pt;
    color: black;
    background: white;
  }

  a {
    color: black;
    text-decoration: underline;
  }

  .container {
    max-width: 100%;
    padding: 0;
  }
}