:root {
  --bg-color: #f5f7fb;
  --card-bg: #ffffff;
  --text-color: #1f2d3d;
  --text-muted: #5f6b7a;
  --accent: #4caf50;
  --accent-dark: #388e3c;
  --border-color: rgba(31, 45, 61, 0.08);
  --shadow: 0 20px 45px rgba(15, 23, 42, 0.12);
  --radius-lg: 24px;
  --radius-md: 18px;
  --radius-sm: 12px;
  --transition: all 0.3s ease;
}

body.dark {
  --bg-color: #0f172a;
  --card-bg: #111c34;
  --text-color: #e2e8f0;
  --text-muted: #94a3b8;
  --accent: #22d3a6;
  --accent-dark: #14b89c;
  --border-color: rgba(148, 163, 184, 0.12);
  --shadow: 0 20px 45px rgba(2, 6, 23, 0.65);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: 'Inter', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  background: var(--bg-color);
  color: var(--text-color);
  transition: background-color 0.4s ease, color 0.4s ease;
  font-size: 16px;
  line-height: 1.7;
}

.layout {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

.header {
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(12px);
  background: rgba(255, 255, 255, 0.9);
  border-bottom: 1px solid var(--border-color);
  transition: background 0.4s ease, border-color 0.3s ease;
}

body.dark .header {
  background: rgba(15, 23, 42, 0.9);
}

.header-content {
  max-width: 1200px;
  margin: 0 auto;
  padding: 18px 32px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 12px;
}

.logo h1 {
  font-size: 20px;
  font-weight: 700;
  margin: 0;
}

.header-nav {
  display: flex;
  gap: 8px;
}

.nav-btn {
  border: none;
  background: transparent;
  padding: 8px 16px;
  border-radius: var(--radius-sm);
  font-weight: 600;
  color: var(--text-muted);
  cursor: pointer;
  transition: var(--transition);
}

.nav-btn.active,
.nav-btn:hover {
  background: rgba(76, 175, 80, 0.12);
  color: var(--accent);
}

body.dark .nav-btn.active,
body.dark .nav-btn:hover {
  background: rgba(34, 211, 166, 0.16);
  color: var(--accent);
}

.nav-btn-featured {
  background: var(--accent);
  color: #ffffff;
  box-shadow: 0 12px 30px rgba(76, 175, 80, 0.28);
  padding: 10px 20px;
}

.nav-btn-featured:hover,
.nav-btn-featured.active {
  background: var(--accent-dark);
  color: #ffffff;
  transform: translateY(-1px);
}

body.dark .nav-btn-featured {
  color: #0f172a;
  box-shadow: 0 12px 30px rgba(34, 211, 166, 0.32);
}

body.dark .nav-btn-featured:hover,
body.dark .nav-btn-featured.active {
  color: #0f172a;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 16px;
}

.theme-toggle {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  border: 1px solid var(--border-color);
  background: transparent;
  display: grid;
  place-items: center;
  cursor: pointer;
  position: relative;
  transition: var(--transition);
  color: var(--text-muted);
}

.theme-toggle:hover {
  transform: translateY(-2px);
  color: var(--accent);
}

.theme-toggle .moon-icon {
  opacity: 0;
  position: absolute;
}

body.dark .theme-toggle .sun-icon {
  opacity: 0;
}

body.dark .theme-toggle .moon-icon {
  opacity: 1;
}

.search-box {
  position: relative;
  display: flex;
  align-items: center;
  background: rgba(79, 94, 113, 0.05);
  border-radius: 999px;
  padding: 8px 16px;
  gap: 10px;
  min-width: 220px;
  transition: var(--transition);
}

body.dark .search-box {
  background: rgba(148, 163, 184, 0.12);
}

.search-box input {
  border: none;
  outline: none;
  background: transparent;
  color: var(--text-color);
  font-size: 14px;
  width: 100%;
}

.main-content {
  flex: 1;
  max-width: 1200px;
  width: 100%;
  margin: 32px auto;
  padding: 0 32px 64px;
}

.view {
  display: none;
  animation: fadeUp 0.45s ease;
}

.view.active {
  display: block;
}

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

.hero {
  background: linear-gradient(135deg, rgba(76, 175, 80, 0.12), rgba(76, 175, 80, 0.06));
  padding: 48px;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
  position: relative;
  overflow: hidden;
}

body.dark .hero {
  background: linear-gradient(135deg, rgba(34, 211, 166, 0.18), rgba(34, 211, 166, 0.05));
}

.hero::after {
  content: '';
  position: absolute;
  width: 280px;
  height: 280px;
  background: rgba(76, 175, 80, 0.16);
  filter: blur(80px);
  border-radius: 50%;
  top: -120px;
  right: -80px;
  z-index: 0;
}

.hero h2 {
  font-size: 36px;
  margin-bottom: 12px;
  position: relative;
  z-index: 1;
}

.hero-subtitle {
  font-size: 18px;
  color: var(--text-muted);
  max-width: 560px;
  position: relative;
  z-index: 1;
}

.hero-stats {
  display: flex;
  gap: 24px;
  margin: 36px 0;
  position: relative;
  z-index: 1;
}

.hero-actions {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
  align-items: center;
  position: relative;
  z-index: 1;
}

.hero-actions .cta-btn {
  min-width: 180px;
}

.stat-card {
  background: rgba(255, 255, 255, 0.65);
  padding: 24px;
  border-radius: var(--radius-md);
  min-width: 140px;
  text-align: center;
  backdrop-filter: blur(6px);
  border: 1px solid rgba(76, 175, 80, 0.15);
}

body.dark .stat-card {
  background: rgba(15, 23, 42, 0.55);
  border-color: rgba(34, 211, 166, 0.22);
}

.stat-number {
  font-size: 32px;
  font-weight: 700;
  color: var(--accent);
}

.cta-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 14px 32px;
  border-radius: 999px;
  border: none;
  background: var(--accent);
  color: white;
  font-weight: 600;
  letter-spacing: 0.5px;
  cursor: pointer;
  transition: var(--transition);
  position: relative;
  z-index: 1;
}

.cta-btn:hover {
  transform: translateY(-2px);
  background: var(--accent-dark);
}

.secondary-btn {
  border: 1px solid var(--border-color);
  background: transparent;
  padding: 12px 18px;
  border-radius: var(--radius-sm);
  color: var(--text-muted);
  cursor: pointer;
  transition: var(--transition);
}

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

.categories-grid {
  margin-top: 48px;
}

.categories-grid h3 {
  margin-bottom: 24px;
}

#categoriesContainer {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
}

.category-card {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  padding: 28px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  gap: 14px;
  position: relative;
}

.category-card::before {
  content: '';
  position: absolute;
  inset: 0;
  border-radius: var(--radius-md);
  border: 1px solid transparent;
  background: linear-gradient(135deg, rgba(76, 175, 80, 0.26), rgba(76, 175, 80, 0)) border-box;
  -webkit-mask: linear-gradient(#fff 0 0) padding-box, linear-gradient(#fff 0 0);
  -webkit-mask-composite: xor;
  mask-composite: exclude;
  opacity: 0;
  transition: var(--transition);
}

.category-card:hover::before {
  opacity: 1;
}

.category-card h4 {
  margin: 0;
  font-size: 18px;
}

.category-meta {
  display: flex;
  gap: 16px;
  color: var(--text-muted);
  font-size: 13px;
}

.learn-layout {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 24px;
}

.sidebar {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  padding: 24px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
  position: sticky;
  top: 110px;
  max-height: calc(100vh - 150px);
  overflow: auto;
}

.sidebar h3 {
  margin-top: 0;
  margin-bottom: 18px;
}

.sidebar button {
  width: 100%;
  padding: 12px 14px;
  border-radius: var(--radius-sm);
  border: none;
  background: transparent;
  text-align: left;
  cursor: pointer;
  color: var(--text-muted);
  font-weight: 600;
  transition: var(--transition);
}

.sidebar button.active,
.sidebar button:hover {
  background: rgba(76, 175, 80, 0.12);
  color: var(--accent);
}

body.dark .sidebar button.active,
body.dark .sidebar button:hover {
  background: rgba(34, 211, 166, 0.15);
  color: var(--accent);
}

.learn-content {
  background: transparent;
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.module-card {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
  padding: 32px;
}

.module-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 20px;
  margin-bottom: 24px;
}

.module-body {
  line-height: 1.8;
  color: var(--text-muted);
}

.learning-points {
  margin-top: 32px;
  display: grid;
  gap: 14px;
}

.learning-point {
  background: rgba(76, 175, 80, 0.12);
  border-radius: var(--radius-sm);
  padding: 14px 18px;
  border: 1px solid rgba(76, 175, 80, 0.18);
  color: var(--text-color);
}

body.dark .learning-point {
  background: rgba(34, 211, 166, 0.12);
  border-color: rgba(34, 211, 166, 0.22);
}

.practice-header {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-bottom: 24px;
}

.practice-filters {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.practice-filters select {
  padding: 12px 16px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  background: var(--card-bg);
  min-width: 160px;
  color: var(--text-color);
}

.practice-card {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
  padding: 24px;
  margin-bottom: 20px;
}

.practice-card h4 {
  margin: 0 0 16px;
}

.option-item {
  padding: 12px 16px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  margin-bottom: 12px;
  cursor: pointer;
  display: flex;
  gap: 12px;
  align-items: flex-start;
  transition: var(--transition);
}

.option-item input {
  margin-top: 4px;
}

.option-item.correct {
  border-color: rgba(76, 175, 80, 0.65);
  background: rgba(76, 175, 80, 0.08);
}

.option-item.incorrect {
  border-color: rgba(220, 38, 38, 0.65);
  background: rgba(220, 38, 38, 0.08);
}

.feedback {
  margin-top: 16px;
  padding: 16px;
  border-radius: var(--radius-sm);
  background: rgba(76, 175, 80, 0.08);
  border: 1px solid rgba(76, 175, 80, 0.2);
  display: none;
}

.feedback.show {
  display: block;
}

body.dark .feedback {
  background: rgba(34, 211, 166, 0.12);
  border-color: rgba(34, 211, 166, 0.22);
}

.exam-container {
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
  padding: 32px;
}

.exam-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 16px;
  margin-bottom: 24px;
}

.exam-timer {
  font-size: 18px;
  font-weight: 600;
  color: var(--accent);
}

.exam-question {
  margin-bottom: 24px;
  padding: 24px;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
  background: rgba(76, 175, 80, 0.05);
}

body.dark .exam-question {
  background: rgba(34, 211, 166, 0.12);
}

.footer {
  text-align: center;
  padding: 24px;
  color: var(--text-muted);
  border-top: 1px solid var(--border-color);
  margin-top: auto;
}

.modal {
  position: fixed;
  inset: 0;
  background: rgba(15, 23, 42, 0.45);
  display: none;
  align-items: center;
  justify-content: center;
  padding: 24px;
  z-index: 200;
}

.modal.show {
  display: flex;
}

.modal-content {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  width: min(640px, 100%);
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
  max-height: 90vh;
  display: flex;
  flex-direction: column;
}

.modal-header,
.modal-footer {
  padding: 18px 24px;
  border-bottom: 1px solid var(--border-color);
}

.modal-footer {
  border-top: 1px solid var(--border-color);
  border-bottom: none;
  display: flex;
  justify-content: flex-end;
  gap: 12px;
}

.modal-body {
  padding: 24px;
  overflow: auto;
}

.modal-close {
  background: transparent;
  border: none;
  font-size: 26px;
  cursor: pointer;
  color: var(--text-muted);
}

.progress-container {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.progress-summary {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 20px;
}

.progress-card {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  padding: 24px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
}

.progress-bar {
  width: 100%;
  height: 8px;
  background: rgba(76, 175, 80, 0.12);
  border-radius: 999px;
  overflow: hidden;
  margin: 12px 0;
}

.progress-fill {
  height: 100%;
  width: 0;
  background: var(--accent);
  border-radius: 999px;
  transition: width 0.6s ease;
}

.accuracy-display {
  font-size: 32px;
  font-weight: 700;
  color: var(--accent);
}

.category-progress {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  padding: 28px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
}

.category-progress-item {
  margin-bottom: 16px;
}

.category-progress-item:last-child {
  margin-bottom: 0;
}

.category-progress-item h4 {
  margin: 0 0 8px;
}

.progress-line {
  height: 6px;
  background: rgba(148, 163, 184, 0.16);
  border-radius: 999px;
  overflow: hidden;
}

.progress-line-fill {
  height: 100%;
  width: 0;
  background: var(--accent);
  border-radius: 999px;
  transition: width 0.6s ease;
}

.recent-activity {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  padding: 24px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
}

.activity-item {
  padding: 12px 0;
  border-bottom: 1px solid rgba(148, 163, 184, 0.2);
}

.activity-item:last-child {
  border-bottom: none;
}

@media (max-width: 1024px) {
  .header-content {
    flex-wrap: wrap;
  }

  .learn-layout {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
    max-height: unset;
  }
}

@media (max-width: 768px) {
  .header-content {
    padding: 16px;
  }

  .header-nav {
    width: 100%;
    justify-content: space-between;
  }

  .search-box {
    min-width: 0;
    flex: 1;
  }

  .hero {
    padding: 32px 24px;
  }

  .hero h2 {
    font-size: 28px;
  }

  .main-content {
    padding: 0 20px 40px;
    margin: 24px auto;
  }

  #categoriesContainer {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 1024px) {
  .tutorial-layout {
    grid-template-columns: 1fr;
  }

  .tutorial-content {
    padding: 40px 28px;
  }
}

@media (max-width: 480px) {
  .header-actions {
    width: 100%;
    justify-content: space-between;
  }

  .hero-stats {
    flex-direction: column;
  }

  .practice-filters {
    flex-direction: column;
  }

  .modal-content {
    width: 100%;
  }
}

/* Tutorial System Styles */
.tutorial-layout {
  display: grid;
  grid-template-columns: 300px 1fr;
  gap: 24px;
  min-height: 600px;
  align-items: start;
}

.tutorial-content {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  padding: 32px 36px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  gap: 28px;
  overflow: visible;
  max-height: none;
}

.tutorial-module {
  margin-bottom: 16px;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
  background: var(--card-bg);
  overflow: hidden;
  transition: var(--transition);
  box-shadow: 0 12px 24px rgba(15, 23, 42, 0.08);
}

body.dark .tutorial-module {
  background: var(--card-bg);
  box-shadow: 0 12px 28px rgba(2, 6, 23, 0.5);
}

.tutorial-module:hover,
.tutorial-module.active {
  border-color: var(--accent);
  box-shadow: 0 18px 36px rgba(76, 175, 80, 0.18);
}

.tutorial-module-header {
  width: 100%;
  padding: 18px 22px;
  border: none;
  background: transparent;
  text-align: left;
  cursor: pointer;
  color: var(--text-color);
  font-weight: 700;
  font-size: 15px;
  transition: var(--transition);
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
}

.tutorial-module-header:hover {
  color: var(--accent);
}

.module-progress-badge {
  font-size: 12px;
  padding: 6px 12px;
  background: rgba(76, 175, 80, 0.16);
  color: var(--accent);
  border-radius: 999px;
  font-weight: 600;
}

.tutorial-module.active .module-progress-badge {
  background: var(--accent);
  color: white;
}

.tutorial-lesson-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding: 12px 20px 20px;
}

.tutorial-lesson-item {
  width: 100%;
  padding: 12px 16px;
  border: 1px solid var(--border-color);
  background: var(--card-bg);
  text-align: left;
  cursor: pointer;
  color: var(--text-muted);
  font-size: 14px;
  transition: var(--transition);
  border-radius: var(--radius-sm);
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
  position: relative;
}

body.dark .tutorial-lesson-item {
  background: var(--card-bg);
}

.tutorial-lesson-item:hover {
  color: var(--accent);
  transform: translateX(4px);
  border-color: var(--accent);
  box-shadow: 0 10px 22px rgba(76, 175, 80, 0.18);
}

.tutorial-lesson-item.active {
  color: var(--accent);
  font-weight: 600;
  border-color: var(--accent);
  background: rgba(76, 175, 80, 0.12);
}

body.dark .tutorial-lesson-item.active {
  background: rgba(34, 211, 166, 0.16);
}

.tutorial-lesson-item.completed {
  opacity: 0.9;
}

.tutorial-lesson-item.completed .lesson-title::before {
  content: "✓ ";
  color: var(--accent);
}

.lesson-status {
  font-size: 12px;
  padding: 4px 10px;
  background: rgba(79, 94, 113, 0.12);
  border-radius: 999px;
  white-space: nowrap;
}

.tutorial-lesson-item.completed .lesson-status,
.tutorial-lesson-item.active .lesson-status {
  background: var(--accent);
  color: white;
}

.lesson-header {
  border-bottom: 2px solid var(--border-color);
  padding-bottom: 24px;
  margin-bottom: 32px;
}

.lesson-breadcrumb {
  color: var(--text-muted);
  font-size: 13px;
  margin-bottom: 12px;
  font-weight: 500;
}

.lesson-title {
  font-size: 28px;
  margin: 0 0 12px;
  color: var(--text-color);
  line-height: 1.4;
  font-weight: 700;
}

.lesson-description {
  color: var(--text-muted);
  font-size: 16px;
  margin: 0;
  line-height: 1.6;
}

.lesson-actions {
  display: flex;
  gap: 12px;
  align-items: center;
  justify-content: flex-start;
  margin-top: 20px;
}

.lesson-status-badge {
  padding: 6px 14px;
  background: rgba(76, 175, 80, 0.1);
  color: var(--accent);
  border-radius: 999px;
  font-size: 13px;
  font-weight: 600;
  border: 1px solid rgba(76, 175, 80, 0.2);
}

.lesson-body {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.lesson-block {
  padding: 24px;
  background: var(--card-bg);
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
  box-shadow: 0 10px 24px rgba(15, 23, 42, 0.08);
  position: relative;
  overflow: hidden;
}

body.dark .lesson-block {
  background: var(--card-bg);
  border-color: rgba(148, 163, 184, 0.18);
  box-shadow: 0 14px 30px rgba(2, 6, 23, 0.55);
}

.lesson-block::after {
  display: none;
}

.lesson-block > * {
  position: relative;
  z-index: 1;
}

.lesson-block-title {
  margin: 0 0 12px;
  font-size: 20px;
  color: var(--text-color);
  font-weight: 700;
}

.lesson-block-text p {
  margin: 12px 0;
  line-height: 1.7;
  color: var(--text-color);
  font-size: 15px;
}

.lesson-block-text ul, .lesson-block-text ol {
  margin: 16px 0;
  padding-left: 24px;
  line-height: 1.7;
}

.lesson-block-text li {
  margin: 8px 0;
  font-size: 15px;
}

.lesson-block-text strong {
  color: var(--accent);
  font-weight: 700;
}

.lesson-block-text code {
  background: rgba(76, 175, 80, 0.14);
  padding: 2px 8px;
  border-radius: 4px;
  font-family: 'Courier New', monospace;
  font-size: 14px;
  font-weight: 500;
}

body.dark .lesson-block-text code {
  background: rgba(34, 211, 166, 0.18);
}

.lesson-inline-code {
  background: rgba(79, 94, 113, 0.08);
  padding: 16px;
  border-radius: var(--radius-sm);
  overflow-x: auto;
  font-family: 'Courier New', monospace;
  font-size: 13px;
  line-height: 1.6;
  margin: 12px 0;
}

body.dark .lesson-inline-code {
  background: rgba(148, 163, 184, 0.1);
}

.block-code {
  background: #1e293b;
  padding: 0;
  overflow: hidden;
  border-radius: var(--radius-sm);
}

body.dark .block-code {
  background: #0f172a;
}

.code-toolbar {
  background: rgba(79, 94, 113, 0.1);
  padding: 8px 14px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid var(--border-color);
}

.code-language {
  font-size: 11px;
  font-weight: 700;
  color: var(--accent);
  letter-spacing: 0.5px;
}

.code-copy-btn {
  font-size: 12px;
  padding: 5px 10px;
}

.block-code pre {
  margin: 0;
  padding: 16px;
  background: #1e293b;
  color: #e2e8f0;
  overflow-x: auto;
  font-family: 'Courier New', monospace;
  font-size: 13px;
  line-height: 1.6;
}

body.dark .block-code pre {
  background: #0f172a;
}

.block-code code {
  color: #e2e8f0;
  background: transparent;
}

.code-explanation {
  padding: 14px;
  background: rgba(76, 175, 80, 0.08);
  border-top: 1px solid var(--accent);
  color: var(--text-color);
  line-height: 1.6;
  font-size: 14px;
}

.interactive-block {
  border: 1px solid var(--accent);
  background: var(--card-bg);
  box-shadow: 0 14px 28px rgba(15, 23, 42, 0.1);
}

body.dark .interactive-block {
  background: var(--card-bg);
  box-shadow: 0 16px 34px rgba(2, 6, 23, 0.55);
}

.interactive-task {
  font-size: 16px;
  font-weight: 600;
  color: var(--text-color);
  margin-bottom: 16px;
  line-height: 1.6;
  padding-bottom: 12px;
  border-bottom: 1px solid rgba(76, 175, 80, 0.25);
}

.interactive-actions {
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
  margin-top: 20px;
}

.interactive-hint,
.interactive-solution {
  margin-top: 16px;
  padding: 16px;
  background: rgba(255, 193, 7, 0.1);
  border-left: 4px solid #ffc107;
  border-radius: var(--radius-sm);
  line-height: 1.6;
  font-size: 15px;
}

.interactive-solution {
  background: rgba(76, 175, 80, 0.1);
  border-left-color: var(--accent);
  border-left-width: 4px;
}

.interactive-hint.hidden,
.interactive-solution.hidden {
  display: none;
}

.interactive-exercise {
  margin-top: 20px;
  padding: 20px;
  background: var(--card-bg);
  border-radius: var(--radius-md);
  border: 1px solid rgba(76, 175, 80, 0.2);
  box-shadow: 0 12px 24px rgba(15, 23, 42, 0.1);
}

body.dark .interactive-exercise {
  background: var(--card-bg);
  border-color: rgba(34, 211, 166, 0.25);
}

.exercise-title {
  font-weight: 600;
  margin-bottom: 12px;
  color: var(--text-color);
  font-size: 16px;
}

.exercise-input {
  display: flex;
  gap: 12px;
  margin-top: 12px;
}

.exercise-input input {
  flex: 1;
  padding: 12px 14px;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  background: var(--card-bg);
  color: var(--text-color);
  font-size: 15px;
  outline: none;
  transition: var(--transition);
}

.exercise-input input:focus {
  border-color: var(--accent);
  box-shadow: 0 6px 16px rgba(76, 175, 80, 0.18);
}

.exercise-feedback {
  margin-top: 12px;
  padding: 12px 14px;
  border-radius: var(--radius-sm);
  font-size: 14px;
  line-height: 1.6;
  font-weight: 500;
}

.exercise-feedback.success {
  background: rgba(76, 175, 80, 0.12);
  color: var(--accent);
  border: 1px solid var(--accent);
}

.exercise-feedback.danger {
  background: rgba(220, 38, 38, 0.12);
  color: #dc2626;
  border: 1px solid #dc2626;
}

.exercise-feedback.warning {
  background: rgba(255, 193, 7, 0.12);
  color: #f59e0b;
  border: 1px solid #f59e0b;
}

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

.lesson-keypoints li {
  padding: 10px 14px;
  margin: 8px 0;
  background: rgba(76, 175, 80, 0.08);
  border-left: 3px solid var(--accent);
  border-radius: var(--radius-sm);
  line-height: 1.6;
  font-size: 15px;
}

body.dark .lesson-keypoints li {
  background: rgba(34, 211, 166, 0.1);
}

.lesson-navigation {
  margin-top: 32px;
  padding-top: 20px;
  border-top: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  gap: 16px;
}

.nav-side {
  flex: 1;
  display: flex;
  justify-content: center;
}

.nav-side button {
  max-width: 280px;
}

.nav-placeholder {
  color: var(--text-muted);
  font-size: 14px;
  padding: 12px;
}

.tutorial-empty,
.practice-empty,
.progress-empty {
  text-align: center;
  padding: 48px 24px;
  color: var(--text-muted);
  font-size: 16px;
}

/* Enhanced Category Cards */
.category-description {
  color: var(--text-muted);
  margin: 8px 0;
  font-size: 14px;
  line-height: 1.6;
}

.category-lessons {
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px solid var(--border-color);
  font-size: 13px;
  color: var(--text-muted);
}

.category-actions {
  display: flex;
  gap: 10px;
  margin-top: 16px;
}

.category-actions .category-btn {
  flex: 1;
  font-size: 13px;
  padding: 10px 16px;
}

.module-description {
  color: var(--text-muted);
  margin: 8px 0 0;
}

.module-stats {
  display: flex;
  gap: 24px;
  text-align: right;
}

.module-stat {
  min-width: 100px;
}

.module-actions {
  margin-top: 32px;
  display: flex;
  gap: 12px;
  justify-content: flex-end;
}

.module-roadmap {
  margin-top: 32px;
  padding-top: 32px;
  border-top: 2px solid var(--border-color);
}

.module-roadmap h3 {
  margin-bottom: 20px;
}

.module-roadmap-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.roadmap-item {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 16px;
  background: var(--card-bg);
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  transition: var(--transition);
}

.roadmap-item.completed {
  border-color: var(--accent);
  background: rgba(76, 175, 80, 0.05);
}

body.dark .roadmap-item.completed {
  background: rgba(34, 211, 166, 0.08);
}

.roadmap-item:hover {
  border-color: var(--accent);
  transform: translateY(-2px);
  box-shadow: var(--shadow);
}

.roadmap-index {
  font-size: 24px;
  font-weight: 700;
  color: var(--accent);
  min-width: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.roadmap-item.completed .roadmap-index::before {
  content: "✓ ";
  color: var(--accent);
  font-size: 18px;
  margin-right: 4px;
}

.roadmap-body {
  flex: 1;
}

.roadmap-title {
  font-weight: 600;
  font-size: 15px;
  color: var(--text-color);
  margin-bottom: 4px;
}

.roadmap-description {
  font-size: 13px;
  color: var(--text-muted);
}

.roadmap-btn {
  padding: 8px 20px;
  font-size: 13px;
  white-space: nowrap;
}

.learning-point-empty {
  color: var(--text-muted);
  font-style: italic;
  text-align: center;
  padding: 20px;
}

.progress-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
}

.lesson-progress {
  font-size: 12px;
  color: var(--text-muted);
  padding: 4px 10px;
  background: rgba(76, 175, 80, 0.08);
  border-radius: 999px;
}

.activity-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.activity-time {
  color: var(--text-muted);
  font-size: 13px;
  white-space: nowrap;
  margin-left: 12px;
}

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

.exam-score {
  font-size: 72px;
  font-weight: 700;
  color: var(--accent);
  margin: 24px 0;
}

.exam-result {
  text-align: center;
  padding: 48px;
}

.exam-submit {
  margin-top: 32px;
}

@media (max-width: 768px) {
  .tutorial-layout,
  .learn-layout {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
    max-height: none;
  }

  .tutorial-content {
    max-height: none;
  }

  .lesson-navigation {
    flex-direction: column;
  }

  .nav-side button {
    max-width: none;
    width: 100%;
  }

  .module-stats {
    flex-direction: column;
    gap: 12px;
    text-align: left;
  }

  .category-actions {
    flex-direction: column;
  }

  .roadmap-item {
    flex-direction: column;
    text-align: center;
  }

  .roadmap-index {
    margin-bottom: 8px;
  }

  .lesson-actions {
    flex-direction: column;
  }

  .lesson-status-badge {
    margin-right: 0;
    margin-bottom: 12px;
  }
}

.data-actions {
  display: flex;
  gap: 8px;
  align-items: center;
}

.data-actions .secondary-btn {
  font-size: 14px;
  padding: 8px 14px;
}

.analytics-container,
.review-container {
  max-width: 1000px;
  margin: 0 auto;
}

.analytics-summary {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 20px;
  margin: 28px 0;
}

.analytics-card {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  padding: 24px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
  text-align: center;
}

.analytics-card h4 {
  margin: 0 0 12px;
  font-size: 14px;
  color: var(--text-muted);
}

.analytics-number {
  font-size: 42px;
  font-weight: 700;
  color: var(--accent);
  margin: 8px 0;
}

.analytics-card p {
  margin: 4px 0 0;
  color: var(--text-muted);
  font-size: 13px;
}

.analytics-charts {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
  gap: 24px;
  margin-top: 32px;
}

.chart-section {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  padding: 24px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
}

.chart-section h3 {
  margin-top: 0;
  margin-bottom: 20px;
}

.chart-empty {
  text-align: center;
  color: var(--text-muted);
  padding: 32px;
}

.trend-chart {
  display: flex;
  align-items: flex-end;
  justify-content: space-around;
  gap: 8px;
  height: 200px;
  padding: 12px 0;
}

.trend-bar-container {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  height: 100%;
  justify-content: flex-end;
}

.trend-bar {
  width: 100%;
  max-width: 40px;
  background: linear-gradient(180deg, var(--accent), var(--accent-dark));
  border-radius: 4px 4px 0 0;
  min-height: 4px;
  transition: var(--transition);
}

.trend-bar-container:hover .trend-bar {
  opacity: 0.8;
}

.trend-label {
  font-size: 11px;
  color: var(--text-muted);
  margin-top: 8px;
  white-space: nowrap;
}

.knowledge-chart {
  display: flex;
  flex-direction: column;
  gap: 18px;
}

.knowledge-item {
  padding: 14px;
  background: rgba(76, 175, 80, 0.04);
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
}

.knowledge-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 8px;
}

.knowledge-name {
  font-weight: 600;
  font-size: 14px;
}

.knowledge-progress {
  font-weight: 700;
  color: var(--accent);
}

.knowledge-bar {
  width: 100%;
  height: 8px;
  background: rgba(79, 94, 113, 0.08);
  border-radius: 999px;
  overflow: hidden;
  margin-bottom: 8px;
}

body.dark .knowledge-bar {
  background: rgba(148, 163, 184, 0.12);
}

.knowledge-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--accent-dark));
  border-radius: 999px;
  transition: width 0.5s ease;
}

.knowledge-stats {
  display: flex;
  justify-content: space-between;
  font-size: 12px;
  color: var(--text-muted);
}

.review-tabs {
  display: flex;
  gap: 12px;
  margin: 24px 0;
  border-bottom: 2px solid var(--border-color);
}

.tab-btn {
  padding: 12px 20px;
  border: none;
  background: transparent;
  color: var(--text-muted);
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  border-bottom: 2px solid transparent;
  margin-bottom: -2px;
}

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

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

.review-content {
  margin-top: 24px;
}

.review-tab-content {
  display: none;
}

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

.review-empty {
  text-align: center;
  color: var(--text-muted);
  padding: 48px 24px;
  font-size: 16px;
}

.review-card,
.note-card,
.mistake-card {
  background: var(--card-bg);
  border-radius: var(--radius-md);
  padding: 24px;
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
  margin-bottom: 16px;
}

.review-header,
.mistake-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
}

.review-type,
.mistake-type {
  padding: 4px 12px;
  background: rgba(76, 175, 80, 0.12);
  color: var(--accent);
  border-radius: 999px;
  font-size: 12px;
  font-weight: 600;
}

body.dark .review-type,
body.dark .mistake-type {
  background: rgba(34, 211, 166, 0.16);
}

.review-interval,
.mistake-attempts {
  font-size: 12px;
  color: var(--text-muted);
}

.review-card h4,
.note-card h4,
.mistake-card h4 {
  margin: 12px 0;
  font-size: 16px;
}

.review-meta,
.note-meta {
  font-size: 12px;
  color: var(--text-muted);
  margin: 12px 0;
}

.note-content {
  padding: 14px;
  background: rgba(79, 94, 113, 0.05);
  border-radius: var(--radius-sm);
  font-size: 14px;
  line-height: 1.6;
  margin: 12px 0;
  white-space: pre-wrap;
  word-break: break-word;
}

body.dark .note-content {
  background: rgba(148, 163, 184, 0.08);
}

.review-btn,
.note-delete,
.mistake-retry {
  margin-top: 12px;
}

.note-editor {
  margin-top: 18px;
  border-top: 1px solid var(--border-color);
  padding-top: 16px;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.note-editor textarea {
  width: 100%;
  min-height: 120px;
  padding: 14px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  font-family: inherit;
  font-size: 14px;
  line-height: 1.6;
  resize: vertical;
  background: rgba(79, 94, 113, 0.05);
  color: var(--text-color);
}

body.dark .note-editor textarea {
  background: rgba(148, 163, 184, 0.12);
}

.note-editor-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 12px;
  color: var(--text-muted);
  flex-wrap: wrap;
  gap: 12px;
}

.note-buttons {
  display: flex;
  gap: 10px;
}

.note-timestamp {
  display: flex;
  align-items: center;
  gap: 6px;
}

.practice-card.review-due {
  border-color: var(--accent);
  box-shadow: 0 12px 30px rgba(76, 175, 80, 0.18);
}

.review-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  border-radius: 999px;
  background: rgba(76, 175, 80, 0.12);
  color: var(--accent);
  font-size: 12px;
  font-weight: 600;
}

body.dark .review-badge {
  background: rgba(34, 211, 166, 0.16);
}

.practice-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
}

.review-toggle {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 14px;
  color: var(--text-muted);
}

.review-toggle input {
  width: 18px;
  height: 18px;
  accent-color: var(--accent);
}

@media (max-width: 768px) {
  .data-actions {
    flex-direction: column;
    gap: 6px;
  }

  .data-actions .secondary-btn {
    width: 100%;
  }

  .analytics-summary {
    grid-template-columns: repeat(2, 1fr);
  }

  .analytics-charts {
    grid-template-columns: 1fr;
  }

  .trend-label {
    font-size: 9px;
  }

  .review-tabs {
    overflow-x: auto;
    overflow-y: hidden;
    flex-wrap: nowrap;
  }

  .tab-btn {
    white-space: nowrap;
    padding: 10px 16px;
  }
}

/* Document Center */
.documents-container {
  display: flex;
  flex-direction: column;
  gap: 32px;
  padding: 24px;
}

.documents-header h2 {
  margin: 0 0 8px;
  font-size: 28px;
}

.documents-subtitle {
  margin: 0;
  color: var(--text-muted);
}

.upload-section {
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  padding: 32px;
  border: 1px solid var(--border-color);
  transition: var(--transition);
}

.upload-area {
   border: 2px dashed rgba(76, 175, 80, 0.25);
   border-radius: var(--radius-lg);
   padding: 48px 24px;
   text-align: center;
   background: rgba(76, 175, 80, 0.05);
   color: var(--text-muted);
   transition: var(--transition);
   position: relative;
   cursor: pointer;
   user-select: none;
 }

 .upload-area:hover {
   border-color: var(--accent);
   background: rgba(76, 175, 80, 0.08);
   transform: translateY(-1px);
 }

 .upload-area svg {
   color: var(--accent);
   margin-bottom: 16px;
   transition: var(--transition);
 }

 .upload-area .upload-text {
   font-size: 18px;
   margin: 0 0 8px;
   color: var(--text-color);
   font-weight: 600;
 }

 .upload-area .upload-hint {
   margin: 0 0 24px;
   color: var(--text-muted);
   font-size: 14px;
 }

 .upload-area.drag-over {
   border-color: var(--accent);
   background: rgba(76, 175, 80, 0.15);
   transform: translateY(-2px);
   box-shadow: 0 8px 24px rgba(76, 175, 80, 0.15);
 }

 .upload-area.drag-over svg {
   transform: scale(1.1);
 }

 .upload-area.uploading {
   opacity: 0.6;
   pointer-events: none;
 }

 .upload-area.uploading::after {
   content: '';
   position: absolute;
   inset: 16px;
   border: 2px solid rgba(76, 175, 80, 0.2);
   border-radius: var(--radius-md);
   border-top-color: var(--accent);
   animation: rotate 1.2s linear infinite;
   pointer-events: none;
 }

.documents-layout {
  display: grid;
  grid-template-columns: 0.95fr 1.05fr;
  gap: 24px;
}

.documents-list,
.document-preview-panel {
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 18px;
}

.documents-list-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.documents-list-header h3 {
  margin: 0;
}

.documents-filters {
  display: flex;
  align-items: center;
  gap: 12px;
}

.documents-search {
  position: relative;
  display: flex;
  align-items: center;
  background: rgba(79, 94, 113, 0.05);
  border-radius: var(--radius-sm);
  padding: 6px 12px;
  gap: 8px;
}

body.dark .documents-search {
  background: rgba(148, 163, 184, 0.12);
}

.documents-search input {
  border: none;
  outline: none;
  background: transparent;
  font-size: 14px;
  color: var(--text-color);
  min-width: 140px;
}

#documentsGrid {
  display: grid;
  gap: 12px;
}

.document-card {
  display: grid;
  grid-template-columns: 48px 1fr;
  gap: 16px;
  padding: 16px;
  border-radius: var(--radius-md);
  border: 1px solid transparent;
  background: rgba(79, 94, 113, 0.04);
  cursor: pointer;
  transition: var(--transition);
}

body.dark .document-card {
  background: rgba(15, 23, 42, 0.45);
}

.document-card:hover,
.document-card.selected {
  border-color: var(--accent);
  background: rgba(76, 175, 80, 0.12);
}

.document-icon {
  font-size: 28px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
  background: rgba(76, 175, 80, 0.12);
  color: var(--accent);
}

.document-name {
  font-weight: 600;
  font-size: 15px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.document-meta {
  display: flex;
  gap: 12px;
  color: var(--text-muted);
  font-size: 13px;
  flex-wrap: wrap;
}

.document-info {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.document-footer {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  font-size: 12px;
  color: var(--text-muted);
}

.document-chip {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 2px 8px;
  border-radius: 999px;
  background: rgba(79, 94, 113, 0.12);
  color: var(--text-muted);
  font-weight: 500;
}

body.dark .document-chip {
  background: rgba(148, 163, 184, 0.18);
  color: var(--text-muted);
}

.document-status {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 2px 10px;
  border-radius: 999px;
  font-weight: 600;
  font-size: 12px;
  letter-spacing: 0.02em;
}

.document-status::before {
  content: '';
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: currentColor;
}

.document-status-processing {
  background: rgba(245, 158, 11, 0.16);
  color: #b45309;
}

body.dark .document-status-processing {
  background: rgba(245, 158, 11, 0.22);
  color: #fbbf24;
}

.document-status-ready {
  background: rgba(76, 175, 80, 0.16);
  color: var(--accent);
}

body.dark .document-status-ready {
  background: rgba(34, 211, 166, 0.18);
  color: var(--accent);
}

.document-status-error {
  background: rgba(244, 67, 54, 0.16);
  color: #d32f2f;
}

body.dark .document-status-error {
  background: rgba(244, 67, 54, 0.28);
  color: #f87171;
}

.document-status-pending {
  background: rgba(79, 94, 113, 0.12);
  color: var(--text-muted);
}

.document-snippet {
  font-size: 13px;
  color: var(--text-muted);
  line-height: 1.5;
  max-height: 48px;
  overflow: hidden;
  text-overflow: ellipsis;
}

.document-badge {
  display: inline-block;
  margin-top: 8px;
  padding: 2px 10px;
  border-radius: 999px;
  background: rgba(76, 175, 80, 0.15);
  color: var(--accent);
  font-size: 12px;
}

.document-preview-panel {
  min-height: 420px;
}

.document-preview-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.document-preview-header h3 {
  margin: 0;
}

.preview-meta {
  margin: 4px 0 0;
  color: var(--text-muted);
  font-size: 13px;
}

.preview-actions {
  display: flex;
  gap: 10px;
}

.document-preview {
  flex: 1;
  border-radius: var(--radius-md);
  border: 1px dashed rgba(79, 94, 113, 0.15);
  background: rgba(79, 94, 113, 0.05);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
  min-height: 260px;
}

.preview-placeholder {
  text-align: center;
  color: var(--text-muted);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.preview-placeholder svg {
  color: var(--accent);
}

.preview-placeholder .spinner {
  width: 32px;
  height: 32px;
  border: 3px solid rgba(79, 94, 113, 0.2);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: rotate 0.9s linear infinite;
}

.preview-summary {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 12px;
}

.preview-pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(79, 94, 113, 0.08);
  color: var(--text-muted);
  font-size: 12px;
  font-weight: 500;
}

body.dark .preview-pill {
  background: rgba(148, 163, 184, 0.18);
}

.preview-pill strong {
  color: var(--text-color);
  font-weight: 600;
}

.preview-text-container {
  width: 100%;
  max-height: 320px;
  overflow: auto;
  background: rgba(79, 94, 113, 0.05);
  border-radius: var(--radius-sm);
  padding: 16px;
}

body.dark .preview-text-container {
  background: rgba(148, 163, 184, 0.12);
}

.preview-text {
  margin: 0;
  font-size: 13px;
  line-height: 1.6;
  font-family: 'Menlo', 'Monaco', 'Fira Code', 'Consolas', monospace;
  white-space: pre-wrap;
  word-break: break-word;
}

.ocr-summary {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 12px;
  font-size: 12px;
  color: var(--text-muted);
}

.ocr-summary span {
  padding: 2px 8px;
  border-radius: 999px;
  background: rgba(79, 94, 113, 0.08);
}

body.dark .ocr-summary span {
  background: rgba(148, 163, 184, 0.18);
}

.ocr-error {
  color: #d32f2f;
  text-align: center;
  line-height: 1.6;
}

body.dark .ocr-error {
  color: #f87171;
}

.ocr-warning {
  color: #b45309;
  margin-top: 8px;
  font-size: 13px;
  line-height: 1.6;
}

body.dark .ocr-warning {
  color: #fbbf24;
}

.preview-image-container {
  width: 100%;
  max-height: 400px;
  overflow: auto;
  display: flex;
  align-items: center;
  justify-content: center;
}

.preview-image {
  max-width: 100%;
  border-radius: var(--radius-sm);
  box-shadow: 0 20px 45px rgba(15, 23, 42, 0.2);
}

.preview-pdf-container {
  width: 100%;
  height: 100%;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.preview-pdf {
  width: 100%;
  height: 380px;
  border: none;
  border-radius: var(--radius-sm);
}

.preview-hint {
  text-align: center;
  font-size: 13px;
  color: var(--text-muted);
  margin: 0;
}

.preview-download-link {
  color: var(--accent);
  text-decoration: none;
}

.ocr-panel {
  border-top: 1px solid var(--border-color);
  padding-top: 12px;
}

.ocr-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 12px;
}

.ocr-header h4 {
  margin: 0;
}

.ocr-content {
  min-height: 120px;
  max-height: 200px;
  overflow: auto;
  padding: 12px;
  border-radius: var(--radius-sm);
  background: rgba(79, 94, 113, 0.04);
}

.ocr-text {
  white-space: pre-wrap;
  line-height: 1.6;
}

.ocr-empty {
  color: var(--text-muted);
  text-align: center;
  margin: 0;
}

.ocr-loading {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  color: var(--text-muted);
}

.ocr-loading .spinner {
  width: 28px;
  height: 28px;
  border: 3px solid rgba(76, 175, 80, 0.2);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: rotate 0.9s linear infinite;
}

.documents-empty,
.documents-error {
  text-align: center;
  padding: 60px 20px;
  border-radius: var(--radius-md);
  border: 1px dashed var(--border-color);
  color: var(--text-muted);
}

.documents-empty svg {
  color: var(--accent);
  margin-bottom: 12px;
}

/* Mobile Navigation */
.mobile-menu-btn {
  display: none;
  border: none;
  background: transparent;
  color: var(--text-color);
  cursor: pointer;
  padding: 8px;
}

.mobile-nav {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(255, 255, 255, 0.92);
  border-top: 1px solid var(--border-color);
  display: none;
  justify-content: space-around;
  padding: 12px 8px calc(env(safe-area-inset-bottom) + 12px);
  z-index: 120;
  backdrop-filter: blur(12px);
}

body.dark .mobile-nav {
  background: rgba(15, 23, 42, 0.92);
}

.mobile-nav-item {
  border: none;
  background: none;
  color: var(--text-muted);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
  font-size: 12px;
  cursor: pointer;
  transition: var(--transition);
  padding: 8px;
}

.mobile-nav-item.active,
.mobile-nav-item:hover {
  color: var(--accent);
}

.mobile-nav-item svg {
  width: 24px;
  height: 24px;
}

@keyframes rotate {
  from {
    transform: rotate(0deg);
  }
  to {
    transform: rotate(360deg);
  }
}

/* Responsive adjustments - Documents */
@media (max-width: 1024px) {
  .documents-layout {
    grid-template-columns: 1fr;
  }

  .document-preview-panel {
    order: -1;
  }
}

@media (max-width: 768px) {
  .header-nav {
    display: none;
  }

  .header-actions {
    gap: 12px;
  }

  .header-actions .search-box {
    display: none;
  }

  .header-actions .data-actions {
    order: 2;
  }

  .header-actions .theme-toggle {
    order: 1;
  }

  .mobile-menu-btn {
    display: none;
  }

  .documents-container {
    padding: 16px;
  }

  .upload-section {
    padding: 20px;
  }

  .upload-area {
    padding: 36px 16px;
  }

  .upload-area .upload-text {
    font-size: 16px;
  }

  .documents-list,
  .document-preview-panel {
    padding: 20px;
  }

  .documents-filters {
    flex-wrap: wrap;
  }

  .documents-search input {
    min-width: 120px;
  }

  .document-preview {
    min-height: 200px;
  }

  .mobile-nav {
    display: flex;
  }

  .main-content {
    padding-bottom: 80px;
  }
}

@media (max-width: 480px) {
  .documents-container {
    padding: 12px;
  }

  .upload-section {
    padding: 16px;
  }

  .documents-list,
  .document-preview-panel {
    padding: 16px;
  }

  .documents-list-header {
    flex-direction: column;
    align-items: flex-start;
  }

  .preview-actions {
    flex-wrap: wrap;
  }

  .preview-actions .secondary-btn {
    flex: 1;
  }

  .document-card {
    grid-template-columns: 40px 1fr;
  }

  .document-icon {
    font-size: 24px;
  }
}

/* Question Generation Styles */
.ocr-actions {
  display: flex;
  gap: 10px;
  align-items: center;
  flex-wrap: wrap;
}

.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(15, 23, 42, 0.75);
  backdrop-filter: blur(8px);
  z-index: 9999;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
  animation: fadeIn 0.2s ease;
}

@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

.generate-modal {
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  box-shadow: 0 30px 60px rgba(15, 23, 42, 0.3);
  max-width: 580px;
  width: 100%;
  max-height: 90vh;
  overflow: auto;
  animation: slideUp 0.3s ease;
}

@keyframes slideUp {
  from {
    transform: translateY(30px);
    opacity: 0;
  }
  to {
    transform: translateY(0);
    opacity: 1;
  }
}

.generate-modal .modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 24px 28px;
  border-bottom: 1px solid var(--border-color);
}

.generate-modal .modal-header h2 {
  margin: 0;
  font-size: 22px;
}

.generate-modal .modal-close {
  background: none;
  border: none;
  font-size: 28px;
  color: var(--text-muted);
  cursor: pointer;
  padding: 0;
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 6px;
  transition: var(--transition);
}

.generate-modal .modal-close:hover {
  background: rgba(79, 94, 113, 0.1);
  color: var(--text-color);
}

.generate-modal .modal-body {
  padding: 28px;
}

.generate-modal .modal-footer {
  display: flex;
  gap: 12px;
  justify-content: flex-end;
  padding: 20px 28px;
  border-top: 1px solid var(--border-color);
}

.generate-form {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.generate-modal .form-group {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.generate-modal .form-group label {
   font-weight: 600;
   font-size: 14px;
   color: var(--text-color);
 }

 .input-group {
   display: flex;
   align-items: center;
   gap: 12px;
 }

 .input-group input {
   flex: 1;
   padding: 10px 14px;
   border: 1px solid var(--border-color);
   border-radius: var(--radius-sm);
   background: var(--card-bg);
   color: var(--text-color);
   font-size: 14px;
   transition: var(--transition);
 }

 .input-hint {
   font-size: 12px;
   color: var(--text-muted);
   white-space: nowrap;
 }

 .generate-modal .form-group input[type="number"],
 .generate-modal .form-group select {
   padding: 10px 14px;
   border: 1px solid var(--border-color);
   border-radius: var(--radius-sm);
   background: var(--card-bg);
   color: var(--text-color);
   font-size: 14px;
   transition: var(--transition);
 }

 .generate-modal .form-group input[type="number"]:focus,
 .generate-modal .form-group select:focus {
   outline: none;
   border-color: var(--accent);
   box-shadow: 0 0 0 3px rgba(76, 175, 80, 0.1);
 }

.generate-modal .checkbox-group {
  display: flex;
  flex-direction: column;
  gap: 10px;
  padding: 12px 0;
}

.generate-modal .checkbox-group label {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 400;
  cursor: pointer;
}

.generate-modal .checkbox-group input[type="checkbox"] {
  width: 18px;
  height: 18px;
  accent-color: var(--accent);
  cursor: pointer;
}

.generate-info {
  padding: 16px;
  background: rgba(76, 175, 80, 0.08);
  border-radius: var(--radius-sm);
  border: 1px solid rgba(76, 175, 80, 0.15);
}

.generate-info p {
  margin: 8px 0;
  font-size: 14px;
  color: var(--text-color);
}

.generate-info p:first-child {
  margin-top: 0;
}

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

.generate-progress {
  display: flex;
  flex-direction: column;
  gap: 16px;
  align-items: center;
  padding: 40px 20px;
}

.generate-progress .progress-bar {
  width: 100%;
  height: 10px;
  background: rgba(79, 94, 113, 0.12);
  border-radius: 999px;
  overflow: hidden;
  position: relative;
}

.generate-progress .progress-fill {
  height: 100%;
  width: 0%;
  background: linear-gradient(90deg, var(--accent), var(--accent-dark));
  border-radius: 999px;
  transition: width 0.3s ease;
}

.generate-progress .progress-text {
  font-size: 15px;
  color: var(--text-muted);
  text-align: center;
  margin: 0;
}

.generate-result {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 24px;
  padding: 20px;
  text-align: center;
}

.result-icon {
  font-size: 64px;
  animation: bounceIn 0.5s ease;
}

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

.generate-result h3 {
  margin: 0;
  font-size: 24px;
  color: var(--text-color);
}

.result-stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
  width: 100%;
}

.stat-item {
  padding: 16px;
  background: rgba(76, 175, 80, 0.08);
  border-radius: var(--radius-sm);
  border: 1px solid rgba(76, 175, 80, 0.15);
}

.stat-number {
  font-size: 28px;
  font-weight: 700;
  color: var(--accent);
  margin-bottom: 6px;
}

.stat-label {
   font-size: 13px;
   color: var(--text-muted);
 }

 .result-note {
   padding: 12px 16px;
   background: rgba(76, 175, 80, 0.1);
   border-left: 3px solid var(--accent);
   border-radius: var(--radius-sm);
   width: 100%;
   text-align: left;
 }

 .result-note p {
   margin: 0;
   font-size: 14px;
   color: var(--text-color);
 }

 .result-actions {
   display: flex;
   flex-direction: column;
   gap: 12px;
   width: 100%;
 }

@media (max-width: 600px) {
  .result-stats {
    grid-template-columns: repeat(2, 1fr);
  }

  .generate-modal {
    max-height: 95vh;
  }

  .generate-modal .modal-header,
  .generate-modal .modal-body,
  .generate-modal .modal-footer {
    padding-left: 20px;
    padding-right: 20px;
  }

  .ocr-actions {
    flex-direction: column;
    align-items: stretch;
  }

  .ocr-actions button {
    width: 100%;
  }
}