/* ========================================
   VARIABLES & RESET
   ======================================== */
:root {
  /* Design System - Professional Chinese Learning Platform */
  
  /* Primary Accent Color */
  --accent: #4a9d6f;
  --accent-hover: #3a8259;
  --accent-light: #6ab88f;
  
  /* Semantic Colors */
  --success: #4a9d6f;
  --error: #d64550;
  --warning: #f5a623;
  
  /* Background Colors */
  --bg-primary: #f0e8d8;
  --bg-secondary: #faf5eb;
  --bg-tertiary: #e5ead5;
  --bg-card: #fdfaf3;
  
  /* Text Colors */
  --text-primary: #1a1410;
  --text-secondary: #3d3528;
  --text-tertiary: #5a5045;
  
  /* Typography */
  --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
  --font-size-base: 1rem;
  --line-height-base: 1.6;
  
  /* Spacing (Mobile-First) */
  --spacing-xs: 0.5rem;   /* 8px */
  --spacing-sm: 1rem;     /* 16px */
  --spacing-md: 1.5rem;   /* 24px */
  --spacing-lg: 2rem;     /* 32px */
  --spacing-xl: 3rem;     /* 48px */
  --spacing-2xl: 4rem;    /* 64px */
  
  /* Border Radius */
  --radius-sm: 0.5rem;
  --radius-md: 0.75rem;
  --radius-lg: 1rem;
  --radius-xl: 1.5rem;
  
  /* Shadows */
  --shadow-sm: 0 1px 3px rgba(74, 157, 111, 0.08);
  --shadow-md: 0 4px 6px rgba(74, 157, 111, 0.1);
  --shadow-lg: 0 10px 20px rgba(74, 157, 111, 0.12);
  --shadow-xl: 0 20px 40px rgba(74, 157, 111, 0.15);
  --shadow-accent: 0 10px 30px rgba(74, 157, 111, 0.2);
  
  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-base: 0.3s ease;
  --transition-slow: 0.5s ease;
}

/* Dark Mode Variables */
body.dark-mode {
  --bg-primary: #0d1f0f;
  --bg-secondary: #1a2e1a;
  --bg-tertiary: #2d4a32;
  --bg-card: #1a2e1a;
  --text-primary: #e8f5e8;
  --text-secondary: #b8d4bd;
  --text-tertiary: #8ab18f;
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 10px 20px rgba(0, 0, 0, 0.5);
  --shadow-xl: 0 20px 40px rgba(0, 0, 0, 0.6);
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-family);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  letter-spacing: 0.3px;
  /* Prevent text size adjustment on mobile */
  -webkit-text-size-adjust: 100%;
  -moz-text-size-adjust: 100%;
  text-size-adjust: 100%;
  /* Improve tap highlighting */
  -webkit-tap-highlight-color: rgba(74, 157, 111, 0.2);
  /* Prevent horizontal scroll */
  overflow-x: hidden;
  width: 100%;
  /* Better font rendering on mobile */
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  /* Improve scrolling performance on iOS */
  -webkit-overflow-scrolling: touch;
  /* Prevent user selection on UI elements (better for app feel) */
  user-select: none;
  -webkit-user-select: none;
}

/* Allow selection on text content */
p, span, li, h1, h2, h3, h4, h5, h6,
.question, .option-btn, .card {
  user-select: text;
  -webkit-user-select: text;
}

/* Ensure all elements respect container width */
img,
video,
iframe {
  max-width: 100%;
  height: auto;
  display: block;
}

/* Better button press feedback on mobile */
button,
.btn,
.option-btn,
.tab-btn {
  cursor: pointer;
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;
  touch-action: manipulation;
}

/* Prevent zoom on double-tap for buttons */
button, .btn, a {
  touch-action: manipulation;
}

/* Smooth scrolling with offset for sticky nav */
html {
  scroll-padding-top: 80px;
  overflow-x: hidden;
  width: 100%;
}

section {
  padding: var(--spacing-xl) 0;
}

/* ========================================
   NAVIGATION
   ======================================== */
.navbar {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--bg-tertiary);
  backdrop-filter: blur(10px);
}

.nav-wrapper {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--spacing-md) 0;
}

.logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--accent);
  letter-spacing: -0.5px;
  z-index: 101;
}

.nav-links {
  list-style: none;
  display: flex;
  gap: var(--spacing-lg);
  align-items: center;
}

.nav-link {
  color: var(--text-secondary);
  text-decoration: none;
  font-weight: 500;
  transition: color 0.3s ease;
  padding: var(--spacing-xs) var(--spacing-sm);
  display: inline-block;
  /* Touch-friendly sizing */
  min-height: 44px;
  display: flex;
  align-items: center;
}

.nav-link:hover {
  color: var(--accent);
}

/* Navigation controls wrapper */
.nav-controls {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

/* Mobile menu toggle (hidden by default) */
.mobile-menu-toggle {
  display: none;
  background: none;
  border: none;
  color: var(--text-primary);
  font-size: 1.5rem;
  cursor: pointer;
  padding: var(--spacing-xs);
  z-index: 102;
  position: relative;
  pointer-events: auto;
  touch-action: manipulation;
}

.mobile-menu-toggle .menu-icon {
  display: block;
  font-size: 1.8rem;
  line-height: 1;
}

/* Backdrop overlay for mobile menu */
.nav-overlay {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.5);
  z-index: 99;
  opacity: 0;
  transition: opacity 0.3s ease;
}

.nav-overlay.active {
  display: block;
  opacity: 1;
}

/* Dark Mode Toggle */
.dark-mode-toggle {
  background: var(--bg-tertiary);
  border: none;
  color: var(--text-primary);
  font-size: 1.5rem;
  cursor: pointer;
  padding: var(--spacing-xs) var(--spacing-sm);
  border-radius: var(--radius-md);
  transition: all var(--transition-base);
  margin-left: var(--spacing-sm);
  position: relative;
  z-index: 101;
}

.dark-mode-toggle:hover {
  background: var(--accent);
  transform: scale(1.1);
}

/* Audio Button */
.audio-btn {
  background: var(--accent);
  border: none;
  color: white;
  cursor: pointer;
  padding: 0.5rem;
  border-radius: 50%;
  width: 36px;
  height: 36px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  margin-left: var(--spacing-sm);
  transition: all var(--transition-base);
  font-size: 1.1rem;
}

.audio-btn:hover {
  background: var(--accent-hover);
  transform: scale(1.1);
}

/* Timer Display */
.timer-display {
  background: var(--bg-tertiary);
  padding: var(--spacing-sm) var(--spacing-md);
  border-radius: var(--radius-lg);
  font-weight: 600;
  font-size: 1.2rem;
  color: var(--accent);
  display: inline-block;
  margin-bottom: var(--spacing-md);
}

/* Progress Bar */
.progress-bar {
  width: 100%;
  height: 8px;
  background: var(--bg-tertiary);
  border-radius: var(--radius-lg);
  overflow: hidden;
  margin: var(--spacing-sm) 0;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--accent-light));
  transition: width var(--transition-base);
}

/* Share Button */
.share-btn {
  background: #1DA1F2;
  color: white;
  border: none;
  padding: var(--spacing-sm) var(--spacing-md);
  border-radius: var(--radius-md);
  cursor: pointer;
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  transition: all var(--transition-base);
  margin-top: var(--spacing-md);
}

.share-btn:hover {
  background: #1a8cd8;
  transform: translateY(-2px);
}

/* Certificate Styles */
.certificate {
  background: linear-gradient(135deg, #fff 0%, #f8fafc 100%);
  border: 3px solid var(--accent);
  border-radius: var(--radius-xl);
  padding: var(--spacing-2xl);
  text-align: center;
  box-shadow: var(--shadow-xl);
  max-width: 600px;
  margin: var(--spacing-xl) auto;
  position: relative;
}

.certificate::before {
  content: '🏆';
  font-size: 4rem;
  display: block;
  margin-bottom: var(--spacing-md);
}

.certificate h2 {
  color: var(--accent);
  margin-bottom: var(--spacing-md);
  font-size: 2rem;
}

.certificate .cert-name {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
  margin: var(--spacing-lg) 0;
}

.certificate .cert-details {
  color: var(--text-secondary);
  margin-top: var(--spacing-md);
}

/* Streak Counter */
.streak-display {
  background: linear-gradient(135deg, var(--accent) 0%, var(--accent-light) 100%);
  color: white;
  padding: var(--spacing-md);
  border-radius: var(--radius-lg);
  display: inline-block;
  font-weight: 700;
  box-shadow: var(--shadow-md);
  margin-bottom: var(--spacing-md);
}

.streak-display .streak-icon {
  font-size: 2rem;
  display: block;
}

.streak-display .streak-count {
  font-size: 2rem;
  display: block;
}

/* Flashcard Styles */
.flashcard-container {
  perspective: 1000px;
  max-width: 500px;
  margin: var(--spacing-xl) auto;
}

.flashcard {
  width: 100%;
  height: 300px;
  position: relative;
  transform-style: preserve-3d;
  transition: transform 0.6s;
  cursor: pointer;
}

.flashcard.flipped {
  transform: rotateY(180deg);
}

.flashcard-face {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background: var(--bg-card);
  border: 2px solid var(--accent);
  border-radius: var(--radius-xl);
  padding: var(--spacing-xl);
  box-shadow: var(--shadow-lg);
}

.flashcard-front {
  background: linear-gradient(135deg, var(--bg-card) 0%, rgba(59, 130, 246, 0.05) 100%);
}

.flashcard-back {
  transform: rotateY(180deg);
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.1) 0%, var(--bg-card) 100%);
}

.flashcard-text {
  font-size: 3rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: var(--spacing-md);
}

.flashcard-pinyin {
  font-size: 1.5rem;
  color: var(--accent);
  margin-bottom: var(--spacing-sm);
}

.flashcard-meaning {
  font-size: 1.2rem;
  color: var(--text-secondary);
}

/* Canvas for writing practice */
.writing-canvas {
  border: 2px solid var(--accent);
  border-radius: var(--radius-lg);
  background: white;
  cursor: crosshair;
  touch-action: none;
  box-shadow: var(--shadow-md);
}

/* Container for consistent max-width */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
}

/* ========================================
   TYPOGRAPHY
   ======================================== */
h1 {
  font-size: 3.5rem;
  font-weight: 800;
  line-height: 1.1;
  margin-bottom: var(--spacing-md);
  color: var(--text-primary);
}

h2 {
  font-size: 2.5rem;
  font-weight: 700;
  margin-bottom: var(--spacing-md);
  color: var(--text-primary);
}

h3 {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: var(--spacing-sm);
  color: var(--text-primary);
}

p {
  color: var(--text-secondary);
  line-height: 1.8;
}

h1, h2 {
  letter-spacing: -0.5px;
}

h2 {
  margin-bottom: var(--spacing-lg);
}

h3 {
  font-size: 1.125rem;
  letter-spacing: -0.3px;
}

p {
  font-size: 1rem;
}

/* ========================================
   BUTTONS (Consistent Design System)
   ======================================== */
.btn {
  display: inline-block;
  padding: 0.875rem 2rem;
  border: 2px solid transparent;
  border-radius: var(--radius-lg);
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  font-weight: 600;
  line-height: 1.5;
  text-align: center;
  text-decoration: none;
  cursor: pointer;
  transition: all var(--transition-base);
  user-select: none;
  min-height: 48px;
  min-width: 48px;
  touch-action: manipulation;
  -webkit-tap-highlight-color: transparent;
}

.btn:active:not(:disabled) {
  transform: scale(0.97);
}

/* Primary Button */
.btn-primary {
  background: var(--accent);
  color: white;
  border-color: var(--accent);
}

.btn-primary:hover:not(:disabled) {
  background: var(--accent-hover);
  border-color: var(--accent-hover);
  transform: translateY(-2px);
  box-shadow: var(--shadow-accent);
}

.btn-primary:active:not(:disabled) {
  transform: translateY(0);
}

/* Secondary Button */
.btn-secondary {
  background: var(--bg-tertiary);
  color: var(--text-primary);
  border-color: var(--bg-tertiary);
}

.btn-secondary:hover:not(:disabled) {
  background: var(--accent);
  color: white;
  border-color: var(--accent);
}

/* Outline Button */
.btn-outline {
  background: transparent;
  color: var(--accent);
  border-color: var(--accent);
}

.btn-outline:hover:not(:disabled) {
  background: var(--accent);
  color: white;
}

/* Large Button */
.btn-large {
  padding: var(--spacing-md) var(--spacing-xl);
  font-size: 1.1rem;
  min-width: 200px;
}

/* Disabled State */
.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

.option-btn {
  width: 100%;
  padding: 0.75rem 1rem;
  margin-bottom: var(--spacing-sm);
  background: var(--bg-tertiary);
  color: var(--text-primary);
  border: 2px solid transparent;
  border-radius: var(--radius-md);
  font-weight: 500;
  cursor: pointer;
  transition: all 0.3s ease;
  position: relative;
  z-index: 1;
  pointer-events: auto;
}

.option-btn:hover {
  border-color: var(--accent);
  background: var(--bg-secondary);
}

.option-btn:active {
  background: var(--accent);
  color: #ffffff;
}

/* Locked/Disabled Level Buttons */
.selector-btn.locked,
.level-btn.locked,
.btn.locked {
  opacity: 0.5;
  cursor: not-allowed;
  position: relative;
  background: var(--bg-tertiary);
  color: var(--text-tertiary);
  border-color: var(--text-tertiary);
  pointer-events: auto;
}

.selector-btn.locked::after,
.level-btn.locked::after,
.btn.locked::after {
  content: " 🔒";
  margin-left: 0.25rem;
}

.selector-btn.locked:hover,
.level-btn.locked:hover,
.btn.locked:hover {
  background: var(--bg-tertiary);
  color: var(--text-tertiary);
  transform: none;
  box-shadow: none;
  border-color: var(--text-tertiary);
}

/* Category Separator */
.category-separator {
  margin: 40px 0 20px 0;
  padding-top: 20px;
  border-top: 2px dashed var(--text-tertiary);
}

.category-note {
  color: var(--text-secondary);
  font-size: 0.9em;
  font-style: italic;
  margin-top: 10px;
  margin-bottom: 15px;
}

/* ========================================
   HERO SECTION
   ======================================== */
.hero {
  padding-top: 8rem;
  padding-bottom: var(--spacing-xl);
  text-align: center;
}

.hero-content {
  max-width: 800px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

/* Hero Title */
.hero-title {
  color: var(--text-primary);
  font-size: 2.75rem;
  line-height: 1.2;
  margin-bottom: var(--spacing-lg);
  font-weight: 700;
  max-width: 700px;
  margin-left: auto;
  margin-right: auto;
}

/* Hero Subtitle */
.hero-subtitle {
  font-size: 1.15rem;
  color: var(--text-secondary);
  margin-bottom: var(--spacing-xl);
  line-height: 1.7;
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

/* Hero Action Buttons */
.hero-actions {
  display: flex;
  gap: var(--spacing-md);
  justify-content: center;
  flex-wrap: wrap;
  margin-top: var(--spacing-xl);
}

/* ========================================
   LEARNING PATH SECTION
   ======================================== */
.learning-path {
  background: var(--bg-secondary);
  padding: var(--spacing-2xl) 0;
}

.path-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--spacing-lg);
  margin-top: var(--spacing-xl);
  max-width: 1200px;
  margin-left: auto;
  margin-right: auto;
}

/* Level Cards */
.level-card {
  background: var(--bg-card);
  padding: var(--spacing-xl);
  border-radius: var(--radius-lg);
  border: 3px solid var(--bg-tertiary);
  text-align: center;
  transition: all var(--transition-base);
  box-shadow: var(--shadow-sm);
  position: relative;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.level-card:hover {
  transform: translateY(-8px);
  box-shadow: var(--shadow-lg);
}

/* Level Badge */
.level-badge {
  width: 60px;
  height: 60px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), var(--accent-light));
  color: white;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.75rem;
  font-weight: 700;
  margin: 0 auto var(--spacing-md);
  box-shadow: var(--shadow-md);
}

.level-number {
  display: block;
}

/* Level specific colors */
.level-newbie:hover {
  border-color: #4a9d6f;
}

.level-beginner:hover {
  border-color: #5ba3d0;
}

.level-intermediate:hover {
  border-color: #f5a623;
}

.level-advanced {
  opacity: 0.6;
}

.level-advanced .level-badge {
  background: var(--bg-tertiary);
  color: var(--text-tertiary);
}

/* Level Content */
.level-title {
  font-size: 1.5rem;
  color: var(--text-primary);
  margin-bottom: var(--spacing-sm);
  font-weight: 600;
}

.level-description {
  color: var(--text-secondary);
  line-height: 1.6;
  font-size: 0.95rem;
  flex-grow: 1;
}

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

.stat {
  background: var(--bg-tertiary);
  padding: var(--spacing-xs) var(--spacing-md);
  border-radius: var(--radius-lg);
  font-size: 0.85rem;
  color: var(--text-secondary);
  font-weight: 500;
}

.stat-locked {
  color: var(--text-tertiary);
  font-size: 0.9rem;
}

.level-link {
  color: var(--accent);
  font-weight: 600;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  transition: all var(--transition-base);
  margin-top: var(--spacing-sm);
}

.level-link:hover {
  color: var(--accent-hover);
  transform: translateX(5px);
}

/* ========================================
   TOOLS SECTION
   ======================================== */
.tools-section {
  padding: var(--spacing-2xl) 0;
  background: var(--bg-primary);
}

.tools-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--spacing-xl);
  margin-top: var(--spacing-xl);
  max-width: 1000px;
  margin-left: auto;
  margin-right: auto;
}

.tool-card {
  background: var(--bg-card);
  padding: var(--spacing-xl);
  border-radius: var(--radius-lg);
  border: 2px solid var(--bg-tertiary);
  text-align: center;
  transition: all var(--transition-base);
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.tool-card:hover {
  border-color: var(--accent);
  transform: translateY(-5px);
  box-shadow: var(--shadow-lg);
}

.tool-icon {
  font-size: 3.5rem;
  display: block;
  margin-bottom: var(--spacing-sm);
}

.tool-card h3 {
  font-size: 1.5rem;
  color: var(--text-primary);
  margin-bottom: var(--spacing-sm);
  font-weight: 600;
}

.tool-card p {
  color: var(--text-secondary);
  line-height: 1.6;
  font-size: 0.95rem;
  flex-grow: 1;
}

.tool-link {
  color: var(--accent);
  font-weight: 600;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  justify-content: center;
  transition: all var(--transition-base);
  margin-top: var(--spacing-sm);
}

.tool-link:hover {
  color: var(--accent-hover);
  transform: translateX(5px);
}

/* ========================================
   SELECTION CARDS (Quiz/Flashcard Select)
   ======================================== */
.selection-container {
  max-width: 900px;
  margin: 0 auto;
}

.selection-step {
  margin-bottom: var(--spacing-2xl);
}

.step-title {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  font-size: 1.75rem;
  color: var(--text-primary);
  margin-bottom: var(--spacing-xl);
  font-weight: 600;
}

.step-number {
  width: 45px;
  height: 45px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), var(--accent-light));
  color: white;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
  font-weight: 700;
  box-shadow: var(--shadow-md);
}

/* Selection Grids */
.level-selection-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: var(--spacing-lg);
}

.category-selection-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: var(--spacing-lg);
  max-width: 600px;
}

/* Selection Cards */
.selection-card {
  background: var(--bg-card);
  padding: var(--spacing-xl);
  border-radius: var(--radius-lg);
  border: 3px solid var(--bg-tertiary);
  text-align: center;
  transition: all var(--transition-base);
  box-shadow: var(--shadow-sm);
  cursor: pointer;
  position: relative;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-sm);
  min-height: 180px;
  touch-action: manipulation;
  -webkit-tap-highlight-color: transparent;
}

.selection-card:not(.locked):hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-lg);
  border-color: var(--accent);
}

.selection-card:not(.locked):active {
  transform: translateY(-2px) scale(0.98);
  transition: transform var(--transition-fast);
}

.selection-card.selected {
  border-color: var(--accent);
  background: linear-gradient(135deg, rgba(74, 157, 111, 0.05), rgba(74, 157, 111, 0.1));
  box-shadow: var(--shadow-accent);
}

.selection-card.selected::after {
  content: '✓';
  position: absolute;
  top: 10px;
  right: 10px;
  width: 30px;
  height: 30px;
  background: var(--accent);
  color: white;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: bold;
  font-size: 1rem;
  box-shadow: var(--shadow-md);
}

/* Locked State */
.selection-card.locked {
  opacity: 0.6;
  cursor: not-allowed;
  position: relative;
}

.selection-card.locked:hover {
  transform: none;
  box-shadow: var(--shadow-sm);
  border-color: var(--bg-tertiary);
}

.lock-overlay {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(255, 255, 255, 0.7);
  border-radius: var(--radius-lg);
  z-index: 1;
}

.lock-icon {
  font-size: 3rem;
  opacity: 0.8;
}

/* Card Content */
.card-icon {
  font-size: 3rem;
  display: block;
  margin-bottom: var(--spacing-sm);
}

.card-title {
  font-size: 1.25rem;
  color: var(--text-primary);
  font-weight: 600;
  margin-bottom: var(--spacing-xs);
}

.card-description {
  color: var(--text-secondary);
  font-size: 0.9rem;
  line-height: 1.4;
  margin-bottom: var(--spacing-sm);
}

.card-stats {
  display: flex;
  gap: var(--spacing-xs);
  justify-content: center;
  flex-wrap: wrap;
  margin-top: auto;
}

.stat-badge {
  background: var(--accent);
  color: white;
  padding: 0.4rem 0.9rem;
  border-radius: var(--radius-lg);
  font-size: 0.8rem;
  font-weight: 600;
  box-shadow: var(--shadow-sm);
}

/* Special Card (SJKC) */
.selection-card.special {
  border-color: var(--accent-light);
}

.selection-card.special:hover {
  border-color: var(--accent);
}

/* Category Cards (smaller) */
.category-card {
  min-height: 140px;
}

.category-card .card-icon {
  font-size: 2.5rem;
}

/* Selection Status */
.selection-status {
  text-align: center;
  padding: var(--spacing-md);
  margin: var(--spacing-xl) 0;
  border-radius: var(--radius-md);
  font-size: 1.1rem;
  font-weight: 500;
  min-height: 50px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  transition: all var(--transition-base);
}

.selection-status.active {
  background: linear-gradient(135deg, rgba(74, 157, 111, 0.1), rgba(74, 157, 111, 0.15));
  color: var(--accent);
  border: 2px solid var(--accent);
}

.selection-status.locked-message {
  background: linear-gradient(135deg, rgba(245, 166, 35, 0.1), rgba(245, 166, 35, 0.15));
  color: var(--warning);
  border: 2px solid var(--warning);
  animation: fadeIn 0.3s ease;
}

.status-icon {
  font-size: 1.3rem;
}

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(-10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Selection Actions */
.selection-actions {
  text-align: center;
  margin-top: var(--spacing-xl);
}

/* ========================================
   QUIZ UI (Professional Educational Design)
   ======================================== */
.quiz-list {
  max-width: 800px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-2xl);
}

.quiz-card {
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  border: 2px solid var(--bg-tertiary);
  padding: var(--spacing-2xl);
  box-shadow: var(--shadow-md);
  transition: all var(--transition-base), opacity var(--transition-base), transform var(--transition-slow);
  animation: questionSlideIn var(--transition-slow) ease;
}

@keyframes questionSlideIn {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.quiz-card.answered-correct {
  border-color: var(--success);
  background: linear-gradient(135deg, rgba(74, 157, 111, 0.03), rgba(74, 157, 111, 0.05));
}

.quiz-card.answered-incorrect {
  border-color: var(--error);
  background: linear-gradient(135deg, rgba(214, 69, 80, 0.03), rgba(214, 69, 80, 0.05));
}

/* Quiz Header with Progress */
.quiz-header {
  margin-bottom: var(--spacing-xl);
}

.quiz-progress-label {
  color: var(--text-secondary);
  font-size: 0.95rem;
  font-weight: 600;
  margin-bottom: var(--spacing-sm);
  text-align: center;
}

.quiz-progress-bar {
  width: 100%;
  height: 8px;
  background: var(--bg-tertiary);
  border-radius: 10px;
  overflow: hidden;
}

.quiz-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--accent-light));
  border-radius: 10px;
  transition: width 0.3s ease;
  box-shadow: 0 0 10px rgba(74, 157, 111, 0.3);
}

/* Quiz Question Area */
.quiz-question-area {
  text-align: center;
  margin-bottom: var(--spacing-2xl);
  padding: var(--spacing-xl) 0;
  border-bottom: 2px solid var(--bg-tertiary);
}

.quiz-pinyin {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--accent);
  margin-bottom: var(--spacing-sm);
  letter-spacing: 0.5px;
  line-height: 1.2;
}

.quiz-chinese {
  font-size: 1.5rem;
  color: var(--text-secondary);
  margin-bottom: var(--spacing-lg);
  font-weight: 400;
}

.quiz-prompt {
  font-size: 1rem;
  color: var(--text-tertiary);
  margin: 0;
  font-style: italic;
}

/* Quiz Options */
.quiz-options {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-lg);
}

.quiz-option-btn {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  padding: var(--spacing-md) var(--spacing-lg);
  background: var(--bg-secondary);
  border: 2px solid var(--bg-tertiary);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: 1.1rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-base), transform var(--transition-fast);
  text-align: left;
  min-height: 60px;
  touch-action: manipulation;
  -webkit-tap-highlight-color: transparent;
}

.quiz-option-btn:hover:not(:disabled) {
  border-color: var(--accent);
  background: linear-gradient(135deg, rgba(74, 157, 111, 0.05), rgba(74, 157, 111, 0.08));
  transform: translateX(5px);
}

.quiz-option-btn:active:not(:disabled) {
  transform: scale(0.98);
  transition: transform var(--transition-fast);
}

.quiz-option-btn:focus {
  outline: 3px solid var(--accent);
  outline-offset: 2px;
  border-color: var(--accent);
}

.quiz-option-btn:focus:not(:focus-visible) {
  outline: none;
}

.quiz-option-btn:disabled {
  cursor: not-allowed;
  opacity: 0.7;
}

.quiz-option-btn.correct {
  border-color: var(--success);
  background: linear-gradient(135deg, rgba(74, 157, 111, 0.1), rgba(74, 157, 111, 0.15));
  color: var(--success);
  font-weight: 600;
}

.quiz-option-btn.incorrect {
  border-color: var(--error);
  background: linear-gradient(135deg, rgba(214, 69, 80, 0.1), rgba(214, 69, 80, 0.15));
  color: var(--error);
  opacity: 0.8;
}

.option-letter {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: var(--accent);
  color: white;
  font-weight: 700;
  font-size: 1rem;
  flex-shrink: 0;
  transition: all var(--transition-fast);
}

.quiz-option-btn:hover:not(:disabled) .option-letter {
  background: var(--accent-hover);
  transform: scale(1.1);
}

.quiz-option-btn.correct .option-letter {
  background: var(--success);
}

.quiz-option-btn.incorrect .option-letter {
  background: var(--error);
}

.option-text {
  flex-grow: 1;
}

/* Quiz Feedback */
.quiz-feedback {
  display: none;
  padding: var(--spacing-lg);
  border-radius: var(--radius-md);
  font-size: 1.1rem;
  font-weight: 600;
  margin-top: var(--spacing-lg);
  animation: feedbackSlideIn var(--transition-base) ease;
  text-align: left;
}

@keyframes feedbackSlideIn {
  from {
    opacity: 0;
    transform: translateY(-10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.quiz-feedback.success {
  background: linear-gradient(135deg, rgba(74, 157, 111, 0.1), rgba(74, 157, 111, 0.15));
  color: var(--success);
  border: 2px solid var(--success);
  text-align: center;
}

.quiz-feedback.error {
  background: linear-gradient(135deg, rgba(214, 69, 80, 0.1), rgba(214, 69, 80, 0.15));
  color: var(--error);
  border: 2px solid var(--error);
}

.feedback-icon {
  font-size: 1.3rem;
  margin-right: var(--spacing-xs);
}

.feedback-text {
  display: inline-block;
  margin-right: var(--spacing-sm);
}

/* Correct Answer Display */
.correct-answer-display {
  display: block;
  margin-top: var(--spacing-md);
  padding-top: var(--spacing-md);
  border-top: 2px solid rgba(214, 69, 80, 0.2);
  color: var(--text-primary);
  font-size: 1rem;
  font-weight: 500;
}

.correct-answer-label {
  color: var(--text-secondary);
  font-weight: 400;
  font-size: 0.95rem;
  margin-right: var(--spacing-xs);
}

.correct-answer-display strong {
  color: var(--success);
  font-size: 1.1rem;
  font-weight: 700;
}

@keyframes slideIn {
  from {
    opacity: 0;
    transform: translateY(-10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Quiz Submit Container */
.quiz-submit-container {
  text-align: center;
  margin-top: var(--spacing-2xl);
  padding-top: var(--spacing-xl);
  border-top: 2px dashed var(--bg-tertiary);
}

/* ========================================
   QUIZ RESULTS SCREEN
   ======================================== */
.quiz-results {
  max-width: 700px;
  margin: 0 auto;
  background: var(--bg-card);
  border-radius: var(--radius-xl);
  padding: var(--spacing-2xl);
  box-shadow: var(--shadow-lg);
  animation: fadeIn 0.5s ease;
}

.results-header {
  text-align: center;
  margin-bottom: var(--spacing-2xl);
  padding-bottom: var(--spacing-xl);
  border-bottom: 2px solid var(--bg-tertiary);
}

.results-emoji {
  font-size: 4rem;
  margin-bottom: var(--spacing-md);
  animation: bounceIn 0.6s ease;
}

@keyframes bounceIn {
  0% {
    transform: scale(0);
    opacity: 0;
  }
  50% {
    transform: scale(1.1);
  }
  100% {
    transform: scale(1);
    opacity: 1;
  }
}

.results-title {
  font-size: 2rem;
  color: var(--text-primary);
  margin-bottom: var(--spacing-sm);
  font-weight: 700;
}

.results-note {
  color: var(--warning);
  font-size: 0.95rem;
  margin-top: var(--spacing-sm);
  font-style: italic;
}

/* Results Stats Cards */
.results-stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-2xl);
}

.stat-card {
  background: var(--bg-secondary);
  border: 2px solid var(--bg-tertiary);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
  text-align: center;
  transition: all var(--transition-base);
}

.stat-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
}

.stat-card.stat-primary {
  border-color: var(--accent);
  background: linear-gradient(135deg, rgba(74, 157, 111, 0.05), rgba(74, 157, 111, 0.1));
}

.stat-value {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--accent);
  margin-bottom: var(--spacing-xs);
  line-height: 1;
}

.stat-label {
  font-size: 0.95rem;
  color: var(--text-secondary);
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

/* Results Actions */
.results-actions {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
  padding-top: var(--spacing-xl);
  border-top: 2px solid var(--bg-tertiary);
}

.results-actions .btn {
  width: 100%;
  justify-content: center;
  font-size: 1.1rem;
  font-weight: 600;
}

/* Responsive Results */
@media (max-width: 768px) {
  .quiz-results {
    padding: var(--spacing-xl);
  }
  
  .results-emoji {
    font-size: 3rem;
  }
  
  .results-title {
    font-size: 1.5rem;
  }
  
  .results-stats {
    grid-template-columns: 1fr;
  }
  
  .stat-value {
    font-size: 2rem;
  }
}

/* ========================================
   PROGRESS DASHBOARD
   ======================================== */
.progress-header {
  text-align: center;
  margin-bottom: var(--spacing-2xl);
}

/* Summary Stats */
.progress-summary {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-2xl);
}

.summary-card {
  background: var(--bg-card);
  border: 2px solid var(--bg-tertiary);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  transition: all var(--transition-base);
}

.summary-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
  border-color: var(--accent);
}

.summary-icon {
  font-size: 2.5rem;
  flex-shrink: 0;
}

.summary-content {
  flex-grow: 1;
}

.summary-value {
  font-size: 2rem;
  font-weight: 700;
  color: var(--accent);
  line-height: 1;
  margin-bottom: var(--spacing-xs);
}

.summary-label {
  font-size: 0.9rem;
  color: var(--text-secondary);
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

/* Level Groups */
.progress-levels {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-2xl);
}

.level-group {
  background: var(--bg-secondary);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
}

.level-group-title {
  font-size: 1.5rem;
  color: var(--accent);
  margin-bottom: var(--spacing-lg);
  padding-bottom: var(--spacing-md);
  border-bottom: 2px solid var(--bg-tertiary);
}

/* Category Grid */
.category-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--spacing-lg);
}

/* Category Cards */
.category-card {
  background: var(--bg-card);
  border: 2px solid var(--bg-tertiary);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  transition: all var(--transition-base);
  display: flex;
  flex-direction: column;
  touch-action: manipulation;
  -webkit-tap-highlight-color: transparent;
}

.category-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
}

.category-card:active {
  transform: translateY(-1px) scale(0.99);
  transition: transform var(--transition-fast);
}

/* Performance-based styling */
.category-card.strong {
  border-color: var(--success);
  background: linear-gradient(135deg, rgba(74, 157, 111, 0.03), rgba(74, 157, 111, 0.05));
}

.category-card.average {
  border-color: var(--warning);
  background: linear-gradient(135deg, rgba(245, 166, 35, 0.03), rgba(245, 166, 35, 0.05));
}

.category-card.weak {
  border-color: var(--error);
  background: linear-gradient(135deg, rgba(214, 69, 80, 0.03), rgba(214, 69, 80, 0.05));
}

.category-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--spacing-md);
  padding-bottom: var(--spacing-sm);
  border-bottom: 1px solid var(--bg-tertiary);
}

.category-title {
  font-size: 1.1rem;
  color: var(--text-primary);
  font-weight: 600;
  margin: 0;
}

.performance-badge {
  padding: 0.3rem 0.7rem;
  border-radius: var(--radius-md);
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

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

.performance-badge.average {
  background: var(--warning);
  color: white;
}

.performance-badge.weak {
  background: var(--error);
  color: white;
}

/* Category Stats */
.category-stats {
  margin-bottom: var(--spacing-md);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-xs);
}

.stat-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--spacing-xs) 0;
}

.stat-label {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

.stat-value {
  color: var(--text-primary);
  font-weight: 600;
}

.stat-highlight {
  font-size: 1.1rem;
  color: var(--accent);
}

.stat-date {
  font-size: 0.85rem;
  font-style: italic;
}

/* Practice Again Button */
.practice-again-btn {
  display: block;
  text-align: center;
  padding: var(--spacing-sm) var(--spacing-md);
  background: var(--accent);
  color: white;
  border-radius: var(--radius-md);
  text-decoration: none;
  font-weight: 600;
  transition: all var(--transition-base);
  margin-top: auto;
}

.practice-again-btn:hover {
  background: var(--accent-hover);
  transform: translateY(-2px);
  box-shadow: var(--shadow-sm);
}

/* Empty State */
.empty-state {
  text-align: center;
  padding: var(--spacing-2xl);
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  border: 2px dashed var(--bg-tertiary);
}

.empty-icon {
  font-size: 4rem;
  margin-bottom: var(--spacing-md);
}

.empty-state h3 {
  color: var(--text-primary);
  margin-bottom: var(--spacing-sm);
}

.empty-state p {
  color: var(--text-secondary);
  margin-bottom: var(--spacing-lg);
}

/* Responsive Progress Dashboard */
@media (max-width: 768px) {
  .progress-summary {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .summary-card {
    flex-direction: column;
    text-align: center;
    padding: var(--spacing-md);
  }
  
  .summary-value {
    font-size: 1.5rem;
  }
  
  .category-grid {
    grid-template-columns: 1fr;
  }
  
  .level-group {
    padding: var(--spacing-md);
  }
}

@media (max-width: 480px) {
  .progress-summary {
    grid-template-columns: 1fr;
  }
}

/* Detailed Student Progress View (similar to tutor dashboard) */
.student-detail {
  background: var(--bg-secondary);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
  margin-bottom: var(--spacing-2xl);
  border: 2px solid var(--bg-tertiary);
}

.student-detail h3 {
  margin-top: 0;
  color: var(--accent);
}

.progress-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: var(--spacing-md);
  margin: var(--spacing-lg) 0;
}

.progress-item {
  background: var(--bg-card);
  padding: var(--spacing-lg);
  border-radius: var(--radius-md);
  text-align: center;
  border: 1px solid var(--bg-tertiary);
}

.progress-item h4 {
  margin: 0 0 var(--spacing-sm) 0;
  font-size: 0.9rem;
  color: var(--text-secondary);
  font-weight: 600;
}

.progress-item .value {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--accent);
}

.activity-list {
  max-height: 400px;
  overflow-y: auto;
  margin-top: var(--spacing-lg);
}

.activity-item {
  background: var(--bg-card);
  padding: var(--spacing-md);
  border-radius: var(--radius-md);
  margin-bottom: var(--spacing-sm);
  display: flex;
  justify-content: space-between;
  align-items: center;
  border: 1px solid var(--bg-tertiary);
}

/* Responsive Quiz Design */
@media (max-width: 768px) {
  .quiz-card {
    padding: var(--spacing-lg);
  }
  
  .quiz-pinyin {
    font-size: 2rem;
  }
  
  .quiz-chinese {
    font-size: 1.2rem;
  }
  
  .quiz-option-btn {
    font-size: 1rem;
    min-height: 54px;
    padding: var(--spacing-sm) var(--spacing-md);
  }
  
  .option-letter {
    width: 32px;
    height: 32px;
    font-size: 0.9rem;
  }
}

/* Section Header (reusable) */
.section-header {
  text-align: center;
  margin-bottom: var(--spacing-xl);
}

.section-title {
  color: var(--text-primary);
  font-size: 2.5rem;
  margin-bottom: var(--spacing-sm);
  font-weight: 700;
}

.section-subtitle {
  font-size: 1.15rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto;
  line-height: 1.6;
}

/* Practice Grid */
.practice-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--spacing-lg);
  margin-top: var(--spacing-xl);
}

/* Practice Cards */
.practice-card {
  background: var(--bg-card);
  padding: var(--spacing-xl);
  border-radius: var(--radius-lg);
  border: 2px solid var(--bg-tertiary);
  text-align: center;
  transition: all var(--transition-base);
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
  min-height: 160px;
  touch-action: manipulation;
  -webkit-tap-highlight-color: transparent;
}

.practice-card:hover {
  border-color: var(--accent);
  transform: translateY(-5px);
  box-shadow: var(--shadow-lg);
}

.practice-card:active {
  transform: translateY(-2px) scale(0.98);
  transition: transform var(--transition-fast);
}

.practice-icon {
  font-size: 3rem;
  margin-bottom: var(--spacing-sm);
  display: block;
}

.card-title {
  font-size: 1.5rem;
  color: var(--text-primary);
  margin-bottom: var(--spacing-sm);
  font-weight: 600;
}

.card-description {
  color: var(--text-secondary);
  line-height: 1.6;
  font-size: 0.95rem;
  flex-grow: 1;
}

/* Card Action Link */
.card-link {
  color: var(--accent);
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  touch-action: manipulation;
  font-weight: 600;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  transition: all var(--transition-base);
  margin-top: var(--spacing-sm);
}

.card-link:hover {
  color: var(--accent-hover);
  transform: translateX(5px);
}

.practice-card h3 {
  color: var(--accent);
  margin-bottom: var(--spacing-sm);
  font-size: 1.3rem;
}

.practice-card p {
  font-size: 1rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.practice-note {
  background: linear-gradient(135deg, var(--bg-tertiary) 0%, rgba(74, 157, 111, 0.1) 100%);
  padding: var(--spacing-xl);
  border-radius: var(--radius-lg);
  margin-top: var(--spacing-xl);
  text-align: center;
  border-left: 4px solid var(--accent);
}

.practice-note p {
  font-size: 1.1rem;
  color: var(--text-primary);
  line-height: 1.8;
  max-width: 800px;
  margin: 0 auto;
}

.practice-note strong {
  color: var(--accent);
  font-size: 1.2rem;
}

/* ========================================
   LANGUAGES SECTION
   ======================================== */
.languages {
  background: linear-gradient(180deg, transparent 0%, rgba(74, 157, 111, 0.05) 100%);
  padding: var(--spacing-2xl) 0;
}

.languages-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
  gap: var(--spacing-lg);
  max-width: 800px;
  margin: 0 auto;
}

.language-card {
  background: var(--bg-card);
  padding: var(--spacing-xl);
  border-radius: var(--radius-lg);
  border: 2px solid var(--bg-tertiary);
  text-align: center;
  transition: all 0.3s ease;
  box-shadow: var(--shadow-sm);
}

.language-card:hover {
  border-color: var(--accent);
  transform: translateY(-5px);
  box-shadow: var(--shadow-lg);
}

.language-emoji {
  font-size: 4rem;
  margin-bottom: var(--spacing-md);
  display: block;
}

.language-card h3 {
  color: var(--accent);
  margin-bottom: var(--spacing-md);
  font-size: 1.5rem;
  font-weight: 600;
}

.language-description {
  font-size: 0.95rem;
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: var(--spacing-md);
}

/* Language Level List */
.language-levels {
  list-style: none;
  padding: 0;
  margin-top: var(--spacing-md);
  text-align: left;
}

.language-levels li {
  padding: var(--spacing-xs) var(--spacing-md);
  background: var(--bg-tertiary);
  margin-bottom: var(--spacing-xs);
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  color: var(--text-secondary);
}

/* ========================================
   PRACTICE SECTION
   ======================================== */
.tabs {
  display: flex;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-xl);
  border-bottom: 2px solid var(--bg-tertiary);
}

.tab-btn {
  padding: var(--spacing-md) var(--spacing-lg);
  background: none;
  border: none;
  color: var(--text-secondary);
  font-weight: 600;
  cursor: pointer;
  border-bottom: 2px solid transparent;
  transition: all 0.3s ease;
  margin-bottom: -2px;
}

.tab-btn.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

.tab-btn:hover {
  color: var(--text-primary);
}

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

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

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeInDown {
  from {
    opacity: 0;
    transform: translateY(-20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

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

.card {
  background: var(--bg-secondary);
  padding: var(--spacing-lg);
  border-radius: var(--radius-lg);
  border: 1px solid var(--bg-tertiary);
  transition: all 0.3s ease;
}

.card:hover {
  border-color: var(--accent);
  box-shadow: 0 10px 30px rgba(59, 130, 246, 0.1);
}

.question {
  font-size: 1.1rem;
  margin-bottom: var(--spacing-md);
  color: var(--text-primary);
}

.hint {
  font-size: 0.9rem;
  color: var(--accent);
  font-style: italic;
  margin-bottom: var(--spacing-md);
}

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

.exercise-input {
  width: 100%;
  padding: 0.75rem 1rem;
  background: var(--bg-primary);
  border: 2px solid var(--bg-tertiary);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-family: var(--font-family);
  font-size: 1rem; /* Prevent iOS zoom on focus */
  margin-bottom: var(--spacing-md);
  transition: border-color 0.3s ease;
  /* Touch-friendly height */
  min-height: 48px;
  /* Improve appearance on iOS */
  -webkit-appearance: none;
  appearance: none;
}

.exercise-input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.feedback {
  margin-top: var(--spacing-md);
  padding: var(--spacing-sm);
  border-radius: var(--radius-md);
  font-weight: 500;
  min-height: 24px;
}

.feedback.success {
  color: var(--success);
  background: rgba(16, 185, 129, 0.1);
}

.feedback.error {
  color: var(--error);
  background: rgba(239, 68, 68, 0.1);
}

.feedback.warning {
  color: var(--warning);
  background: rgba(245, 158, 11, 0.1);
}

/* ========================================
   CONTACT SECTION
   ======================================== */
.contact {
  background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-tertiary) 100%);
  border-radius: var(--radius-lg);
}

.contact-content {
  text-align: center;
  padding: var(--spacing-xl);
}

.contact h2 {
  margin-bottom: var(--spacing-md);
}

.contact p {
  font-size: 1.1rem;
  margin-bottom: var(--spacing-lg);
}

/* ========================================
   FOOTER
   ======================================== */
.footer {
  background: var(--bg-secondary);
  border-top: 2px solid var(--bg-tertiary);
  padding: var(--spacing-xl) 0;
  text-align: center;
}

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

.footer-text {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-bottom: var(--spacing-sm);
}

.footer-copyright {
  color: var(--text-tertiary);
  font-size: 0.85rem;
}

/* ========================================
   TABS & CARDS
   ======================================== */
.tab-btn {
  padding: var(--spacing-md) var(--spacing-lg);
  color: var(--text-tertiary);
  font-weight: 600;
  letter-spacing: 0.5px;
  font-size: 0.95rem;
  transition: all var(--transition-base);
  border-bottom: 3px solid transparent;
  margin-bottom: -3px;
  cursor: pointer;
  position: relative;
}

.tab-btn:hover {
  color: var(--text-primary);
}

.tab-btn.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

.quiz-grid,
.exercise-grid {
  gap: var(--spacing-lg);
}

.card {
  background: var(--bg-card);
  padding: var(--spacing-lg);
  border-radius: var(--radius-xl);
  border: 1px solid rgba(59, 130, 246, 0.1);
  transition: all var(--transition-base);
  position: relative;
}

.contact {
  margin: var(--spacing-2xl) 0;
  padding: var(--spacing-2xl) var(--spacing-lg);
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.1) 0%, rgba(59, 130, 246, 0.05) 100%);
  border: 1px solid rgba(59, 130, 246, 0.2);
  border-radius: var(--radius-xl);
  position: relative;
  overflow: hidden;
}

.contact::before {
  content: '';
  position: absolute;
  top: 0;
  right: -50%;
  width: 100%;
  height: 100%;
  background: radial-gradient(circle, rgba(59, 130, 246, 0.1) 0%, transparent 70%);
  pointer-events: none;
}

.card::after {
  content: '';
  position: absolute;
  inset: 0;
  letter-spacing: 0.3px;
  border-radius: var(--radius-xl);
  padding: 1px;
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.2) 0%, transparent 100%);
  -webkit-mask: linear-gradient(#fff 0 0) content-box, linear-gradient(#fff 0 0);
  mask: linear-gradient(#fff 0 0) content-box, linear-gradient(#fff 0 0);
  -webkit-mask-composite: xor;
  mask-composite: exclude;
  opacity: 0;
  transition: opacity var(--transition-base);
}

.card:hover::after {
  opacity: 1;
}

.card:hover {
  border-color: var(--accent);
  background: linear-gradient(135deg, var(--bg-card) 0%, rgba(74, 157, 111, 0.03) 100%);
  box-shadow: var(--shadow-lg);
  transform: translateY(-4px);
}

.question {
  font-size: 1.05rem;
  margin-bottom: var(--spacing-md);
  color: var(--text-primary);
  font-weight: 500;
}

.hint {
  font-size: 0.85rem;
  color: var(--accent-light);
  font-style: italic;
  margin-bottom: var(--spacing-md);
  padding: 0.5rem 0.75rem;
  background: rgba(74, 157, 111, 0.08);
  border-radius: var(--radius-md);
  border-left: 2px solid var(--accent-light);
}

/* ========================================
   RESPONSIVE - MOBILE FIRST
   ======================================== */

/* Tablet and smaller devices */
@media (max-width: 1024px) {
  .container {
    padding: 0 var(--spacing-lg);
  }
  
  /* 2-column grid for medium devices */
  .languages-grid,
  .practice-grid,
  .quiz-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-md);
  }
}

@media (max-width: 768px) {
  /* Typography adjustments */
  h1 {
    font-size: 2.5rem;
    line-height: 1.2;
  }

  h2 {
    font-size: 1.875rem;
  }

  h3 {
    font-size: 1.125rem;
  }

  /* Mobile menu toggle */
  .mobile-menu-toggle {
    display: flex;
    align-items: center;
    justify-content: center;
    /* Touch-friendly size */
    min-width: 44px;
    min-height: 44px;
  }

  /* Navigation - Mobile menu */
  .nav-wrapper {
    position: relative;
    padding: var(--spacing-sm) 0;
  }

  .nav-links {
    position: fixed;
    top: 0;
    right: -100%;
    height: 100vh;
    width: 80%;
    max-width: 320px;
    background: var(--bg-secondary);
    flex-direction: column;
    justify-content: flex-start;
    padding: 5rem var(--spacing-lg) var(--spacing-lg);
    gap: var(--spacing-md);
    transition: right 0.3s ease;
    box-shadow: -5px 0 15px rgba(0, 0, 0, 0.3);
    overflow-y: auto;
    z-index: 100;
    /* Smooth scrolling on iOS */
    -webkit-overflow-scrolling: touch;
  }

  .nav-links.active {
    right: 0;
  }

  .nav-link {
    width: 100%;
    padding: var(--spacing-md);
    justify-content: center;
    font-size: 1.125rem;
    /* Touch-friendly */
    min-height: 48px;
    display: flex;
    align-items: center;
  }

  .logo {
    font-size: 1.25rem;
  }

  /* Container padding */
  .container {
    padding: 0 var(--spacing-md);
    max-width: 100%;
  }

  /* Hero section */
  .hero {
    padding-top: 3rem;
    padding-bottom: var(--spacing-lg);
    text-align: center;
  }

  .hero h1 {
    font-size: 2.25rem;
  }

  .hero-subtitle {
    font-size: 1rem;
    margin-bottom: var(--spacing-md);
  }

  /* Section spacing */
  section {
    padding: var(--spacing-lg) 0;
  }

  .section-subtitle {
    font-size: 1rem;
    margin-bottom: var(--spacing-lg);
  }

  /* Grid layouts - Single column */
  .languages-grid,
  .practice-grid,
  .quiz-grid,
  .exercise-grid {
    grid-template-columns: 1fr;
    gap: var(--spacing-md);
  }

  /* Practice section */
  .practice-section h2 {
    font-size: 2rem;
  }

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

  .practice-icon {
    font-size: 2.5rem;
  }

  .practice-note {
    padding: var(--spacing-lg);
  }

  .practice-note p {
    font-size: 1rem;
  }

  .practice-note strong {
    font-size: 1.1rem;
  }

  /* Hero tagline */
  .hero-tagline {
    font-size: 1.1rem;
  }

  /* Cards */
  .language-card,
  .card {
    padding: var(--spacing-md);
  }

  .language-emoji {
    font-size: 2.5rem;
    margin-bottom: var(--spacing-sm);
  }

  /* Buttons - Full width on mobile */
  .btn {
    padding: 0.875rem 1.5rem;
    font-size: 0.9375rem;
    width: 100%;
    min-height: 48px;
  }

  .btn-group {
    flex-direction: column;
    width: 100%;
    gap: var(--spacing-sm);
  }

  .btn-group .btn {
    width: 100%;
  }

  /* Tabs */
  .tabs {
    flex-direction: column;
    gap: var(--spacing-sm);
  }

  .tab-btn,
  .level-btn,
  .lang-btn {
    width: 100%;
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: 0.9375rem;
    min-height: 48px;
  }

  /* Question and option buttons */
  .question {
    font-size: 1.125rem;
    margin-bottom: var(--spacing-md);
    line-height: 1.5;
  }

  .option-btn {
    padding: 1rem;
    font-size: 1rem;
    min-height: 52px;
    text-align: left;
  }

  /* Input fields */
  .exercise-input,
  input[type="text"],
  input[type="email"],
  input[type="password"],
  textarea,
  select {
    padding: 0.875rem;
    font-size: 16px; /* Prevent iOS zoom */
    min-height: 48px;
    width: 100%;
  }

  /* Auth forms */
  .auth-card {
    padding: var(--spacing-lg);
    margin: var(--spacing-md);
    width: calc(100% - 2rem);
  }

  .form-group {
    margin-bottom: var(--spacing-md);
  }

  /* Contact section */
  .contact {
    padding: var(--spacing-xl) var(--spacing-md);
  }

  .contact h2 {
    font-size: 1.75rem;
  }

  .contact p {
    font-size: 1rem;
  }

  /* Language filter */
  .language-filter {
    flex-direction: column;
    align-items: stretch;
  }

  .language-filter label {
    text-align: center;
    margin-bottom: var(--spacing-sm);
  }

  /* Level tabs */
  .level-tabs {
    flex-direction: column;
    gap: var(--spacing-sm);
  }

  /* Timer and progress */
  .timer-display {
    font-size: 1.125rem;
    padding: var(--spacing-sm) var(--spacing-md);
  }

  /* Certificate */
  .certificate {
    padding: var(--spacing-lg);
    margin: var(--spacing-md);
  }

  .certificate h2 {
    font-size: 1.5rem;
  }

  .certificate .cert-name {
    font-size: 1.25rem;
  }

  /* Tables - Make scrollable */
  .table-wrapper {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    margin: 0 calc(-1 * var(--spacing-md));
    padding: 0 var(--spacing-md);
  }

  table {
    min-width: 500px;
  }

  /* Dark mode toggle */
  .dark-mode-toggle {
    font-size: 1.25rem;
    padding: var(--spacing-xs);
    min-width: 44px;
    min-height: 44px;
  }

  /* Audio button */
  .audio-btn {
    min-width: 44px;
    min-height: 44px;
  }
}

@media (max-width: 480px) {
  /* Ultra-compact mobile view */
  :root {
    --spacing-xs: 0.375rem;
    --spacing-sm: 0.75rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
  }

  h1 {
    font-size: 1.875rem;
    line-height: 1.15;
  }

  h2 {
    font-size: 1.5rem;
  }

  h3 {
    font-size: 1rem;
  }

  /* Navigation - Compact */
  .nav-wrapper {
    padding: var(--spacing-xs) 0;
  }

  .nav-links {
    gap: var(--spacing-xs);
    font-size: 1rem;
    width: 85%;
    max-width: 280px;
  }

  .nav-link {
    font-size: 1rem;
    padding: var(--spacing-md);
  }

  .logo {
    font-size: 1.125rem;
  }

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

  section {
    padding: var(--spacing-md) 0;
  }

  /* Hero compact */
  .hero {
    padding-top: 2rem;
    padding-bottom: var(--spacing-md);
  }

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

  .hero-subtitle {
    font-size: 0.9375rem;
    margin-bottom: var(--spacing-md);
  }

  .hero-tagline {
    font-size: 1rem;
  }

  /* Buttons - Touch-friendly */
  .btn {
    padding: 1rem 1.25rem;
    font-size: 0.9375rem;
    min-height: 48px;
    width: 100%;
  }

  .option-btn {
    padding: 1rem;
    font-size: 0.9375rem;
    min-height: 52px;
  }

  /* Cards */
  .language-card,
  .card,
  .practice-card {
    padding: var(--spacing-md);
  }

  .language-emoji {
    font-size: 2rem;
  }

  .practice-icon {
    font-size: 2rem;
  }

  /* Tab buttons - Touch-friendly */
  .tab-btn,
  .level-btn,
  .lang-btn {
    padding: var(--spacing-md);
    font-size: 0.9375rem;
    min-height: 48px;
  }

  /* Input fields - Touch-friendly */
  .exercise-input,
  input[type="text"],
  input[type="email"],
  input[type="password"],
  textarea,
  select {
    padding: 1rem;
    font-size: 16px; /* Prevent iOS zoom on focus */
    min-height: 48px;
  }

  /* Auth forms */
  .auth-card {
    padding: var(--spacing-md);
    margin: var(--spacing-sm);
    width: calc(100% - 1rem);
  }

  .auth-header h1 {
    font-size: 1.75rem;
  }

  /* Feedback text */
  .feedback {
    font-size: 0.875rem;
    padding: var(--spacing-sm);
  }

  /* Questions */
  .question {
    font-size: 1rem;
    line-height: 1.4;
  }

  /* Tighter grids */
  .languages-grid,
  .quiz-grid,
  .exercise-grid,
  .practice-grid {
    gap: var(--spacing-sm);
  }

  /* Contact section */
  .contact {
    padding: var(--spacing-lg) var(--spacing-sm);
  }

  .contact h2 {
    font-size: 1.5rem;
  }

  .contact p {
    font-size: 0.9375rem;
  }

  /* Footer */
  .footer {
    font-size: 0.875rem;
    padding: var(--spacing-md) var(--spacing-sm);
  }

  /* Timer */
  .timer-display {
    font-size: 1rem;
    padding: var(--spacing-sm);
  }

  /* Certificate */
  .certificate {
    padding: var(--spacing-md);
    margin: var(--spacing-sm);
  }

  .certificate::before {
    font-size: 3rem;
    margin-bottom: var(--spacing-sm);
  }

  .certificate h2 {
    font-size: 1.25rem;
  }

  .certificate .cert-name {
    font-size: 1.125rem;
    margin: var(--spacing-md) 0;
  }

  /* Practice note */
  .practice-note {
    padding: var(--spacing-md);
  }

  .practice-note strong {
    font-size: 1rem;
  }

  .practice-note p {
    font-size: 0.875rem;
  }

  /* Mobile menu overlay when open */
  .nav-links.active::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    z-index: -1;
  }
}

/* Landscape mode optimization for phones */
@media (max-height: 600px) and (orientation: landscape) {
  .hero {
    padding-top: 2rem;
    padding-bottom: var(--spacing-md);
  }

  section {
    padding: var(--spacing-md) 0;
  }

  h1 {
    font-size: 1.75rem;
  }

  h2 {
    font-size: 1.5rem;
  }
}

/* Touch device optimizations */
@media (hover: none) and (pointer: coarse) {
  /* Larger touch targets */
  .nav-link,
  .btn,
  .option-btn,
  .tab-btn,
  .level-btn,
  .lang-btn,
  .mobile-menu-toggle,
  .dark-mode-toggle,
  .audio-btn {
    min-height: 44px;
    min-width: 44px;
  }

  /* Remove hover effects on touch devices */
  .language-card:hover,
  .card:hover,
  .practice-card:hover {
    transform: none;
  }

  /* Active states instead of hover */
  .btn:active,
  .option-btn:active,
  .tab-btn:active,
  .level-btn:active,
  .lang-btn:active {
    transform: scale(0.98);
    opacity: 0.9;
  }

  .language-card:active,
  .card:active {
    transform: scale(0.98);
  }

  /* Better tap feedback */
  * {
    -webkit-tap-highlight-color: rgba(74, 157, 111, 0.3);
  }

  /* Disable touch callouts */
  a, button {
    -webkit-touch-callout: none;
  }
}

/* High DPI / Retina screens */
@media (-webkit-min-device-pixel-ratio: 2), (min-resolution: 192dpi) {
  /* Sharper borders and shadows */
  .card,
  .language-card,
  .practice-card,
  .btn {
    border-width: 0.5px;
  }
}

/* Accessibility - Reduced motion */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
    transform: none !important;
  }
  
  /* Keep only essential transitions for feedback */
  .btn:active,
  .quiz-option-btn:active,
  .selection-card:active {
    opacity: 0.7 !important;
  }
}

/* Print styles */
@media print {
  .navbar,
  .mobile-menu-toggle,
  .dark-mode-toggle,
  .btn,
  .footer {
    display: none !important;
  }

  body {
    background: white;
    color: black;
  }

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

/* iOS safe area insets for notched devices */
@supports (padding: env(safe-area-inset-top)) {
  body {
    padding-top: env(safe-area-inset-top);
    padding-bottom: env(safe-area-inset-bottom);
    padding-left: env(safe-area-inset-left);
    padding-right: env(safe-area-inset-right);
  }

  .navbar {
    padding-top: env(safe-area-inset-top);
  }

  .nav-links {
    padding-left: calc(var(--spacing-lg) + env(safe-area-inset-left));
    padding-right: calc(var(--spacing-lg) + env(safe-area-inset-right));
  }
}

/* Small height devices (e.g., iPhone SE in landscape) */
@media (max-height: 500px) {
  .hero {
    padding-top: 1rem;
    padding-bottom: 1rem;
  }

  h1 {
    font-size: 1.5rem;
  }

  h2 {
    font-size: 1.25rem;
  }

  section {
    padding: 1rem 0;
  }

  .nav-wrapper {
    padding: 0.5rem 0;
  }
}