/* ===================================
   Learn Without Walls - Free Learning Platform
   Modern, Professional Stylesheet
   =================================== */

/* CSS Variables for Easy Theming */
:root {
  /* Color Palette - Professional Academic */
  --primary-color: #2C5F7C;        /* Deep blue - trust, academic */
  --primary-light: #3A7CA5;        /* Lighter blue */
  --primary-dark: #1A3A4D;         /* Darker blue */
  --accent-color: #D97D54;          /* Warm terracotta - approachable */
  --accent-light: #E89B7B;         /* Lighter terracotta */

  /* Neutrals */
  --text-primary: #2D2D2D;         /* Near black for text */
  --text-secondary: #5A5A5A;       /* Medium gray */
  --text-light: #767676;           /* Light gray */
  --background: #FFFFFF;           /* White */
  --background-alt: #F8F9FA;       /* Off-white */
  --border-color: #E1E4E8;         /* Light gray border */

  /* Functional Colors */
  --success: #28A745;
  --info: #17A2B8;
  --warning: #FFC107;

  /* Typography */
  --font-primary: 'Segoe UI', -apple-system, BlinkMacSystemFont, 'Roboto', 'Helvetica Neue', Arial, sans-serif;
  --font-mono: 'Consolas', 'Monaco', 'Courier New', monospace;

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

  /* Border Radius */
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;

  /* Shadows */
  --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.08);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.12);

  /* Transitions */
  --transition: all 0.3s ease;
}

/* ===================================
   Reset & Base Styles
   =================================== */

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-primary);
  font-size: 1rem;
  line-height: 1.7;
  color: var(--text-primary);
  background-color: var(--background);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* ===================================
   Typography
   =================================== */

h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.3;
  margin-bottom: var(--spacing-md);
  color: var(--primary-dark);
}

h1 {
  font-size: 2.5rem;
  margin-bottom: var(--spacing-lg);
}

h2 {
  font-size: 2rem;
  margin-top: var(--spacing-xl);
  padding-bottom: var(--spacing-sm);
  border-bottom: 3px solid var(--accent-color);
  display: inline-block;
}

h3 {
  font-size: 1.5rem;
  color: var(--primary-color);
  margin-top: var(--spacing-lg);
}

h4 {
  font-size: 1.25rem;
  color: var(--primary-color);
}

p {
  margin-bottom: var(--spacing-md);
}

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

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

strong {
  font-weight: 600;
  color: var(--text-primary);
}

em {
  font-style: italic;
}

/* ===================================
   Layout
   =================================== */

.container {
  max-width: 1000px;
  margin: 0 auto;
  padding: var(--spacing-lg);
}

.container-narrow {
  max-width: 800px;
  margin: 0 auto;
  padding: var(--spacing-lg);
}

/* ===================================
   Header & Navigation
   =================================== */

header {
  background: linear-gradient(135deg, var(--primary-dark) 0%, var(--primary-color) 100%);
  color: white;
  padding: var(--spacing-md) 0;
  box-shadow: var(--shadow-md);
  position: sticky;
  top: 0;
  z-index: 1000;
}

.site-title {
  font-size: 1.5rem;
  font-weight: 700;
  color: white;
  margin: 0;
  padding: 0 var(--spacing-lg);
}

nav {
  padding: var(--spacing-sm) var(--spacing-lg);
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-md);
  align-items: center;
}

nav a {
  color: white;
  text-decoration: none;
  padding: var(--spacing-xs) var(--spacing-sm);
  border-radius: var(--radius-sm);
  transition: var(--transition);
  font-weight: 500;
}

nav a:hover {
  background-color: rgba(255, 255, 255, 0.15);
  text-decoration: none;
}

nav a.active {
  background-color: var(--accent-color);
  color: white;
}

/* ===================================
   Hero Section
   =================================== */

.hero {
  background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-light) 100%);
  color: white;
  padding: var(--spacing-xl) var(--spacing-lg);
  margin-bottom: var(--spacing-xl);
  border-radius: var(--radius-lg);
  text-align: center;
}

.hero h1 {
  color: white;
  font-size: 2.8rem;
  margin-bottom: var(--spacing-md);
}

.hero p {
  font-size: 1.2rem;
  opacity: 0.95;
  max-width: 800px;
  margin: 0 auto var(--spacing-md) auto;
}

.hero-subtitle {
  font-size: 1.1rem;
  opacity: 0.9;
  font-weight: 300;
}

/* ===================================
   Cards & Sections
   =================================== */

.card {
  background: white;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: var(--spacing-lg);
  margin-bottom: var(--spacing-lg);
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
}

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

.card-header {
  border-bottom: 2px solid var(--border-color);
  padding-bottom: var(--spacing-sm);
  margin-bottom: var(--spacing-md);
}

.card-title {
  color: var(--primary-color);
  font-size: 1.5rem;
  margin: 0;
}

.highlight-box {
  background: var(--background-alt);
  border-left: 4px solid var(--accent-color);
  padding: var(--spacing-md);
  margin: var(--spacing-lg) 0;
  border-radius: var(--radius-sm);
}

.info-box {
  background: #E7F3F8;
  border-left: 4px solid var(--info);
  padding: var(--spacing-md);
  margin: var(--spacing-lg) 0;
  border-radius: var(--radius-sm);
}

.research-box {
  background: linear-gradient(135deg, #F0F7FA 0%, #E7F3F8 100%);
  border: 2px solid var(--primary-light);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  margin: var(--spacing-xl) 0;
}

/* ===================================
   Buttons & CTAs
   =================================== */

.btn {
  display: inline-block;
  padding: var(--spacing-sm) var(--spacing-lg);
  border-radius: var(--radius-md);
  font-weight: 600;
  text-decoration: none;
  transition: var(--transition);
  cursor: pointer;
  border: none;
  font-size: 1rem;
  text-align: center;
}

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

.btn-primary:hover {
  background: var(--primary-dark);
  text-decoration: none;
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

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

.btn-accent:hover {
  background: var(--accent-light);
  text-decoration: none;
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.btn-outline {
  background: transparent;
  border: 2px solid var(--primary-color);
  color: var(--primary-color);
}

.btn-outline:hover {
  background: var(--primary-color);
  color: white;
  text-decoration: none;
}

.cta-group {
  display: flex;
  gap: var(--spacing-md);
  flex-wrap: wrap;
  margin: var(--spacing-lg) 0;
}

/* ===================================
   Lists
   =================================== */

ul, ol {
  margin: var(--spacing-md) 0 var(--spacing-md) var(--spacing-lg);
}

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

ul.no-bullets {
  list-style: none;
  margin-left: 0;
}

ul.icon-list {
  list-style: none;
}

ul.icon-list li::before {
  content: "▸";
  color: var(--accent-color);
  font-weight: bold;
  margin-right: var(--spacing-xs);
}

/* ===================================
   Tables
   =================================== */

table {
  width: 100%;
  border-collapse: collapse;
  margin: var(--spacing-lg) 0;
  background: white;
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}

thead {
  background: var(--primary-color);
  color: white;
}

th {
  padding: var(--spacing-md);
  text-align: left;
  font-weight: 600;
}

td {
  padding: var(--spacing-md);
  border-bottom: 1px solid var(--border-color);
}

tbody tr:hover {
  background: var(--background-alt);
}

/* ===================================
   Badges & Tags
   =================================== */

.badge {
  display: inline-block;
  padding: 0.25rem 0.75rem;
  border-radius: 20px;
  font-size: 0.875rem;
  font-weight: 600;
  margin-right: var(--spacing-xs);
}

.badge-primary {
  background: var(--primary-light);
  color: white;
}

.badge-accent {
  background: var(--accent-color);
  color: white;
}

.badge-success {
  background: var(--success);
  color: white;
}

/* ===================================
   Course Cards
   =================================== */

.course-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: var(--spacing-lg);
  margin: var(--spacing-xl) 0;
}

.course-card {
  background: white;
  border: 2px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  transition: var(--transition);
}

.course-card:hover {
  border-color: var(--primary-color);
  box-shadow: var(--shadow-lg);
  transform: translateY(-4px);
}

.course-emoji {
  font-size: 3rem;
  margin-bottom: var(--spacing-md);
}

.course-title {
  color: var(--primary-color);
  font-size: 1.3rem;
  margin-bottom: var(--spacing-sm);
}

.course-meta {
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: var(--spacing-md);
}

/* ===================================
   Footer
   =================================== */

footer {
  background: var(--background-alt);
  border-top: 1px solid var(--border-color);
  padding: var(--spacing-xl) var(--spacing-lg);
  margin-top: var(--spacing-xl);
  color: var(--text-secondary);
  text-align: center;
}

footer a {
  color: var(--primary-color);
}

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

/* ===================================
   Utilities
   =================================== */

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

.text-muted {
  color: var(--text-secondary);
}

.mt-0 { margin-top: 0; }
.mt-1 { margin-top: var(--spacing-sm); }
.mt-2 { margin-top: var(--spacing-md); }
.mt-3 { margin-top: var(--spacing-lg); }

.mb-0 { margin-bottom: 0; }
.mb-1 { margin-bottom: var(--spacing-sm); }
.mb-2 { margin-bottom: var(--spacing-md); }
.mb-3 { margin-bottom: var(--spacing-lg); }

.back-link {
  display: inline-block;
  margin-bottom: var(--spacing-lg);
  color: var(--text-secondary);
  font-weight: 500;
}

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

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

@media (max-width: 768px) {
  html {
    font-size: 14px;
  }

  h1 {
    font-size: 2rem;
  }

  h2 {
    font-size: 1.75rem;
  }

  .hero h1 {
    font-size: 2rem;
  }

  .container,
  .container-narrow {
    padding: var(--spacing-md);
  }

  nav {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--spacing-sm);
  }

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

  .cta-group {
    flex-direction: column;
  }

  .btn {
    width: 100%;
  }
}

@media (max-width: 480px) {
  .hero {
    padding: var(--spacing-lg) var(--spacing-md);
  }

  .card {
    padding: var(--spacing-md);
  }
}

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

@media print {
  header,
  nav,
  footer {
    display: none;
  }

  body {
    font-size: 12pt;
    line-height: 1.5;
  }

  .card {
    box-shadow: none;
    border: 1px solid #ddd;
    page-break-inside: avoid;
  }
}

/* ============================================
   ACCESSIBILITY SYSTEM
   ============================================ */

/* Dark Mode */
body.dark-mode {
  --background: #1a1a2e;
  --background-alt: #16213e;
  --text-primary: #e8e8e8;
  --text-secondary: #b0b0b0;
  --border-color: #2a2a4a;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.4);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.4);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.5);
}
body.dark-mode { background: #1a1a2e; color: #e8e8e8; }
body.dark-mode header { background: #0f0f1e; border-bottom: 1px solid #2a2a4a; }
body.dark-mode footer { background: #0f0f1e; border-top: 1px solid #2a2a4a; }
body.dark-mode .card, body.dark-mode .course-card-yl, body.dark-mode .course-card-fc,
body.dark-mode .exercise-block, body.dark-mode .grade-card { background: #16213e; border-color: #2a2a4a; color: #e8e8e8; }
body.dark-mode .card h3, body.dark-mode .card h2 { color: #90CAF9; }
body.dark-mode nav a { color: #90CAF9; }
body.dark-mode nav a:hover { color: #ffffff; }
body.dark-mode .btn-outline { border-color: #90CAF9; color: #90CAF9; }
body.dark-mode input, body.dark-mode textarea, body.dark-mode select { background: #16213e; color: #e8e8e8; border-color: #2a2a4a; }
body.dark-mode .highlight-box, body.dark-mode .info-box { background: #16213e; border-color: #2a2a4a; }
body.dark-mode .concept-recap { background: #0d1b2e; }
body.dark-mode .worked-example { background: #1a0d2e; }
body.dark-mode .big-idea { background: #2a1f00; }
body.dark-mode .try-it { background: #0d1f0d; }
body.dark-mode .brain-break { background: #1f1200; }
body.dark-mode .wrap-up { background: #0d1f0d; }

/* Font Size Controls */
body.font-large { font-size: 1.15rem; line-height: 1.8; }
body.font-xl { font-size: 1.3rem; line-height: 1.9; }
body.font-large h1 { font-size: 2.4rem; }
body.font-large h2 { font-size: 1.9rem; }
body.font-large h3 { font-size: 1.5rem; }
body.font-xl h1 { font-size: 2.8rem; }
body.font-xl h2 { font-size: 2.2rem; }
body.font-xl h3 { font-size: 1.7rem; }

/* Dyslexia-Friendly Font (Lexend — proven to help dyslexic readers) */
@import url('https://fonts.googleapis.com/css2?family=Lexend:wght@300;400;500;600;700&display=swap');
body.dyslexia-font, body.dyslexia-font * {
  font-family: 'Lexend', sans-serif !important;
  letter-spacing: 0.05em;
  word-spacing: 0.1em;
  line-height: 1.9;
}

/* Reading Mode */
body.reading-mode main.container { max-width: 720px !important; }
body.reading-mode .course-grid { display: block !important; }
body.reading-mode .course-grid > * { margin-bottom: 1.5rem; }

/* Accessibility Toolbar */
#a11y-trigger {
  position: fixed; bottom: 24px; right: 24px; z-index: 9999;
  width: 52px; height: 52px; border-radius: 50%;
  background: #1565C0; color: white; border: none;
  font-size: 1.4rem; cursor: pointer;
  box-shadow: 0 4px 16px rgba(21,101,192,0.5);
  transition: all 0.2s; display: flex; align-items: center; justify-content: center;
}
#a11y-trigger:hover { background: #0D47A1; transform: scale(1.05); }
#a11y-panel {
  position: fixed; bottom: 88px; right: 24px; z-index: 9998;
  background: white; border-radius: 16px; padding: 1.25rem;
  box-shadow: 0 8px 32px rgba(0,0,0,0.2);
  width: 260px; display: none; border: 2px solid #e0e0e0;
}
body.dark-mode #a11y-panel { background: #16213e; border-color: #2a2a4a; }
#a11y-panel h3 { margin: 0 0 1rem; font-size: 0.9rem; text-transform: uppercase; letter-spacing: 0.05em; color: #666; }
body.dark-mode #a11y-panel h3 { color: #90CAF9; }
.a11y-row { display: flex; align-items: center; justify-content: space-between; margin-bottom: 0.875rem; font-size: 0.925rem; font-weight: 500; }
.a11y-row:last-child { margin-bottom: 0; }
.a11y-toggle {
  width: 44px; height: 24px; border-radius: 12px; border: none;
  background: #e0e0e0; cursor: pointer; position: relative; transition: background 0.2s; flex-shrink: 0;
}
.a11y-toggle::after {
  content: ''; position: absolute; width: 18px; height: 18px; border-radius: 50%;
  background: white; top: 3px; left: 3px; transition: left 0.2s;
  box-shadow: 0 1px 3px rgba(0,0,0,0.2);
}
.a11y-toggle.on { background: #1565C0; }
.a11y-toggle.on::after { left: 23px; }
.a11y-btn-group { display: flex; gap: 4px; }
.a11y-btn {
  padding: 4px 10px; border-radius: 6px; border: 2px solid #e0e0e0;
  background: white; cursor: pointer; font-weight: 600; transition: all 0.15s; font-size: 0.85rem;
}
body.dark-mode .a11y-btn { background: #1a1a2e; color: #e8e8e8; border-color: #2a2a4a; }
.a11y-btn.active { background: #1565C0; color: white; border-color: #1565C0; }
.a11y-reset { width: 100%; margin-top: 1rem; padding: 0.5rem; border-radius: 8px; border: 1px solid #e0e0e0; background: white; cursor: pointer; font-size: 0.85rem; color: #666; }
body.dark-mode .a11y-reset { background: #1a1a2e; color: #90CAF9; border-color: #2a2a4a; }
.a11y-reset:hover { background: #f5f5f5; }

/* ===================================
   Mobile Navigation - Hamburger Menu
   =================================== */

.mobile-nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
  z-index: 1001;
  position: absolute;
  right: var(--spacing-sm);
  top: 50%;
  transform: translateY(-50%);
}

.hamburger-icon {
  display: block;
  width: 26px;
  height: 3px;
  background: white;
  border-radius: 2px;
  position: relative;
  transition: background 0.3s;
}

.hamburger-icon::before,
.hamburger-icon::after {
  content: '';
  display: block;
  width: 26px;
  height: 3px;
  background: white;
  border-radius: 2px;
  position: absolute;
  transition: transform 0.3s, top 0.3s;
}

.hamburger-icon::before { top: -8px; }
.hamburger-icon::after { top: 8px; }

/* Animate to X when open */
.mobile-nav-toggle.active .hamburger-icon { background: transparent; }
.mobile-nav-toggle.active .hamburger-icon::before { top: 0; transform: rotate(45deg); }
.mobile-nav-toggle.active .hamburger-icon::after { top: 0; transform: rotate(-45deg); }

/* ===================================
   Responsive - Tablet (max-width: 768px)
   =================================== */

@media (max-width: 768px) {

  /* -- Header & Navigation -- */
  header {
    position: relative;
    padding-bottom: var(--spacing-sm);
  }

  .mobile-nav-toggle {
    display: block;
  }

  header nav {
    display: none;
    flex-direction: column;
    width: 100%;
    background: var(--primary-dark);
    border-radius: var(--radius-md);
    margin-top: var(--spacing-sm);
    padding: var(--spacing-xs) 0;
    box-shadow: var(--shadow-lg);
  }

  header nav.nav-open {
    display: flex;
  }

  header nav a {
    padding: 0.75rem var(--spacing-md);
    border-radius: 0;
    font-size: 1rem;
    min-height: 48px;
    display: flex;
    align-items: center;
    border-bottom: 1px solid rgba(255,255,255,0.1);
  }

  header nav a:last-child {
    border-bottom: none;
  }

  header nav a:hover,
  header nav a.active {
    background: rgba(255,255,255,0.15);
  }

  /* -- Typography -- */
  h1 { font-size: 1.75rem; }
  h2 { font-size: 1.4rem; }
  h3 { font-size: 1.15rem; }

  /* -- Container -- */
  .container {
    padding: 0 var(--spacing-sm);
  }

  /* -- Hero -- */
  .hero {
    padding: var(--spacing-lg) var(--spacing-sm);
    border-radius: var(--radius-md);
  }

  .hero h1 {
    font-size: 1.75rem;
  }

  .hero p, .hero-subtitle {
    font-size: 0.95rem;
  }

  /* -- Grids -- */
  .course-grid,
  .feature-grid {
    grid-template-columns: 1fr;
    gap: var(--spacing-sm);
  }

  /* -- Buttons -- */
  .btn {
    width: 100%;
    text-align: center;
    min-height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
  }

  .cta-group {
    flex-direction: column;
    gap: var(--spacing-sm) !important;
  }

  /* -- Tables -- */
  table {
    font-size: 0.85rem;
  }

  th, td {
    padding: var(--spacing-xs) var(--spacing-sm);
  }

  /* Scrollable table wrapper */
  .table-wrapper {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    margin: var(--spacing-md) 0;
  }

  /* -- Cards -- */
  .highlight-box,
  .info-box {
    padding: var(--spacing-md);
  }

  /* -- Accessibility Panel -- */
  #a11y-panel {
    width: calc(100vw - 48px);
    right: 24px;
    max-width: 300px;
  }

  #a11y-trigger {
    width: 44px;
    height: 44px;
    bottom: 16px;
    right: 16px;
    font-size: 1.2rem;
  }

  /* -- Print bar -- */
  .print-bar {
    flex-direction: column;
    text-align: center;
  }

  /* -- Module/Lesson navigation -- */
  .lesson-nav {
    flex-direction: column;
    gap: var(--spacing-xs);
    text-align: center;
  }
}

/* ===================================
   Responsive - Mobile (max-width: 480px)
   =================================== */

@media (max-width: 480px) {

  html { font-size: 15px; }

  h1 { font-size: 1.5rem; }
  h2 { font-size: 1.25rem; margin-top: var(--spacing-lg); }

  .hero h1 { font-size: 1.5rem; }
  .hero { padding: var(--spacing-md) var(--spacing-sm); }

  .container {
    padding: 0 0.75rem;
  }

  /* Stack inline flex containers */
  [style*="display:flex"],
  [style*="display: flex"] {
    flex-wrap: wrap !important;
  }

  /* Smaller card padding */
  .course-card-fc,
  .module-card {
    padding: var(--spacing-md);
  }

  .course-card-fc h3 {
    padding-right: 0 !important;
    font-size: 1.1rem;
  }

  .available-badge,
  .module-badge {
    position: static;
    display: inline-block;
    margin-bottom: var(--spacing-xs);
  }

  /* Table font smaller */
  table { font-size: 0.8rem; }
  th, td { padding: 0.35rem 0.5rem; }

  /* Code blocks */
  pre, code {
    font-size: 0.78rem;
  }

  pre {
    padding: var(--spacing-sm);
  }

  /* Spacing reductions */
  section { margin-bottom: var(--spacing-lg); }
}

/* ===================================
   Responsive - Small phones (max-width: 360px)
   =================================== */

@media (max-width: 360px) {
  html { font-size: 14px; }
  h1 { font-size: 1.35rem; }

  .hero h1 { font-size: 1.3rem; }

  header .site-title { font-size: 1.1rem; }

  .container { padding: 0 0.5rem; }

  #a11y-panel {
    width: calc(100vw - 24px);
    right: 12px;
  }

  #a11y-trigger {
    width: 40px;
    height: 40px;
    bottom: 12px;
    right: 12px;
  }
}