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

:root {
  --header-bg: #2c1810;
  --header-dark: #1a0e08;
  --hero-secondary: #4a2820;
  --ink: #2c1810;
  --ink-contrast: #f8f0e8;
  --accent: #8b4513;
  --accent-hover: #6b3410;
  --light: #f8f2e8;
  --white: #fffdf8;
  --text: #3a2a1a;
  --gray: #7a6a5a;
  --border: #d4c4a8;
  --success: #2d6a30;
  --shadow: 0 4px 12px rgba(44, 24, 16, 0.1);
}

[data-theme="dark"] {
  --header-bg: #1a0e08;
  --header-dark: #0d0604;
  --hero-secondary: #2a1410;
  --ink: #f0e8d8;
  --ink-contrast: #1a0e08;
  --accent: #c08040;
  --accent-hover: #a06830;
  --light: #141008;
  --white: #1e1810;
  --text: #e0d8c8;
  --gray: #9a8a78;
  --border: #3a3020;
  --success: #40a048;
  --shadow: 0 4px 12px rgba(0, 0, 0, 0.5);
  color-scheme: dark;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: 'Georgia', 'Times New Roman', serif;
  line-height: 1.6;
  color: var(--text);
  background-color: var(--light);
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  transition: background-color 0.3s ease, color 0.3s ease;
}

.card,
.info-section,
.topic-content,
.author-info,
.quiz-section,
.result-section,
.lesson,
.site-header {
  transition: background-color 0.3s ease, color 0.3s ease, border-color 0.3s ease;
}

main {
  flex: 1;
  padding: 2rem 1rem;
  max-width: 1100px;
  width: 100%;
  margin: 0 auto;
}

.site-header {
  background-color: var(--header-bg);
  box-shadow: var(--shadow);
  position: sticky;
  top: 0;
  z-index: 100;
  border-bottom: 2px solid var(--accent);
}

.navbar {
  max-width: 1100px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 1.5rem;
  flex-wrap: wrap;
}

.logo a {
  color: var(--white);
  text-decoration: none;
  font-size: 1.2rem;
  font-weight: 700;
}

.nav-menu {
  list-style: none;
  display: flex;
  gap: 1.5rem;
  align-items: center;
}

.nav-menu li a {
  color: #c0b0a0;
  text-decoration: none;
  font-weight: 500;
  padding: 0.5rem 0.75rem;
  border-radius: 6px;
  transition: color 0.3s, background-color 0.3s;
}

.nav-menu li a:hover,
.nav-menu li a.active {
  color: var(--white);
  background-color: var(--header-dark);
}

.menu-toggle {
  display: none;
  background: none;
  border: 2px solid var(--white);
  color: var(--white);
  font-size: 1.5rem;
  line-height: 1;
  cursor: pointer;
  padding: 0.25rem 0.6rem;
  border-radius: 6px;
}

.theme-toggle {
  background: none;
  border: 2px solid var(--white);
  color: var(--white);
  font-size: 1.1rem;
  line-height: 1;
  cursor: pointer;
  padding: 0.3rem 0.55rem;
  border-radius: 6px;
  margin-left: 0.5rem;
  transition: background-color 0.3s;
}

.theme-toggle:hover {
  background-color: rgba(255, 255, 255, 0.15);
}

.hero {
  text-align: center;
  padding: 3rem 1rem;
  background: linear-gradient(135deg, var(--header-bg) 0%, var(--hero-secondary) 100%);
  color: var(--white);
  border-radius: 8px;
  margin-bottom: 2rem;
  border: 2px solid var(--accent);
}

.hero h1 {
  font-size: 2.5rem;
  margin-bottom: 1rem;
}

.hero p {
  font-size: 1.1rem;
  max-width: 700px;
  margin: 0 auto 1.5rem;
}

.btn {
  display: inline-block;
  padding: 0.75rem 1.5rem;
  border: none;
  border-radius: 6px;
  font-size: 1rem;
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
  transition: background-color 0.3s, transform 0.2s;
}

.btn:hover {
  transform: translateY(-2px);
}

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

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

.btn-secondary {
  background-color: var(--white);
  color: var(--ink);
  border: 2px solid var(--ink);
}

.btn-secondary:hover {
  background-color: var(--ink);
  color: var(--ink-contrast);
}

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
  margin-bottom: 2rem;
}

.card {
  background-color: var(--white);
  border-radius: 8px;
  padding: 1.5rem;
  box-shadow: var(--shadow);
  text-align: center;
  display: flex;
  flex-direction: column;
  gap: 1rem;
  align-items: center;
  border: 2px solid var(--border);
}

.card-icon {
  font-size: 3rem;
}

.card h2,
.card h3 {
  color: var(--ink);
}

.card p {
  flex: 1;
}

.info-section {
  background-color: var(--white);
  border-radius: 8px;
  padding: 2rem;
  box-shadow: var(--shadow);
  margin-bottom: 2rem;
  text-align: center;
  border: 2px solid var(--border);
}

.info-section h2 {
  color: var(--ink);
  margin-bottom: 1rem;
}

.statistics {
  display: flex;
  justify-content: center;
  gap: 3rem;
  margin-top: 2rem;
  flex-wrap: wrap;
}

.stat {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.stat-number {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--accent);
}

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

.fact-box,
.quote-box {
  background-color: var(--light);
  border-left: 4px solid var(--accent);
  border-radius: 0 6px 6px 0;
  padding: 1.25rem;
  margin-bottom: 1rem;
  font-size: 1.05rem;
  min-height: 4.5rem;
  text-align: left;
}

.fact-box {
  font-style: italic;
}

.quote-box p {
  font-style: italic;
  margin-bottom: 0.5rem;
}

.quote-box footer {
  color: var(--gray);
  text-align: right;
}

.page-header {
  text-align: center;
  padding: 2rem 0;
  margin-bottom: 1.5rem;
}

.page-header h1 {
  font-size: 2.2rem;
  color: var(--ink);
  margin-bottom: 0.5rem;
}

.page-header p {
  color: var(--gray);
}

.topic-tabs {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  justify-content: center;
  margin-bottom: 2rem;
}

.tab-btn {
  padding: 0.6rem 1.2rem;
  border: 2px solid var(--ink);
  background-color: var(--white);
  color: var(--ink);
  border-radius: 6px;
  cursor: pointer;
  font-weight: 500;
  transition: background-color 0.3s, color 0.3s;
}

.tab-btn:hover,
.tab-btn.active {
  background-color: var(--ink);
  color: var(--ink-contrast);
}

.topic-content {
  display: none;
  background-color: var(--white);
  border-radius: 8px;
  padding: 2rem;
  box-shadow: var(--shadow);
  margin-bottom: 2rem;
  border: 2px solid var(--border);
}

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

.topic-content h2 {
  color: var(--ink);
  margin-bottom: 1rem;
  border-bottom: 3px solid var(--accent);
  padding-bottom: 0.5rem;
}

.lesson {
  margin-top: 1.5rem;
  padding: 1rem;
  background-color: var(--light);
  border-left: 4px solid var(--accent);
  border-radius: 0 6px 6px 0;
}

.lesson h3 {
  margin-bottom: 0.75rem;
  color: var(--ink);
}

.lesson ul,
.lesson ol {
  margin-left: 1.5rem;
}

.lesson li {
  margin-bottom: 0.4rem;
}

.author-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
  margin-bottom: 2rem;
}

.author-card {
  background-color: var(--white);
  border: 2px solid var(--border);
  border-radius: 8px;
  padding: 1.5rem;
  text-align: center;
  cursor: pointer;
  transition: border-color 0.3s, background-color 0.3s;
}

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

.author-card.active {
  border-color: var(--accent);
  background-color: rgba(139, 69, 19, 0.08);
}

.author-name {
  font-weight: 700;
  color: var(--ink);
  margin-bottom: 0.3rem;
}

.author-years {
  color: var(--gray);
  font-size: 0.9rem;
}

.author-info {
  display: none;
  background-color: var(--white);
  border-radius: 8px;
  padding: 2rem;
  box-shadow: var(--shadow);
  margin-bottom: 2rem;
  border: 2px solid var(--border);
}

.author-info.active {
  display: block;
}

.author-info h2 {
  color: var(--ink);
}

.author-info .years {
  color: var(--gray);
  font-style: italic;
  margin-bottom: 1rem;
}

.author-info h3 {
  margin: 1.5rem 0 0.75rem;
  color: var(--ink);
}

.author-info ul {
  margin-left: 1.5rem;
}

.author-info li {
  margin-bottom: 0.4rem;
}

.test-select {
  display: flex;
  justify-content: center;
  gap: 1rem;
  flex-wrap: wrap;
  margin-bottom: 2rem;
}

.quiz-section,
.result-section {
  background-color: var(--white);
  border-radius: 8px;
  padding: 2rem;
  box-shadow: var(--shadow);
  max-width: 700px;
  margin: 0 auto;
  border: 2px solid var(--border);
}

.quiz-header {
  text-align: center;
  margin-bottom: 1.5rem;
}

.quiz-header h2 {
  color: var(--ink);
  margin-bottom: 0.5rem;
}

.quiz-progress {
  color: var(--gray);
  margin-bottom: 0.5rem;
}

.progress-bar {
  height: 8px;
  background-color: var(--light);
  border-radius: 4px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  width: 0;
  background-color: var(--accent);
  transition: width 0.3s;
}

.question-container h3 {
  color: var(--ink);
  margin-bottom: 1rem;
}

.answer-option {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.75rem;
  border: 2px solid var(--border);
  border-radius: 6px;
  margin-bottom: 0.75rem;
  cursor: pointer;
  transition: border-color 0.3s, background-color 0.3s;
}

.answer-option:hover {
  border-color: var(--ink);
}

.answer-option.selected {
  border-color: var(--accent);
  background-color: rgba(139, 69, 19, 0.08);
}

.answer-option.correct {
  border-color: var(--success);
  background-color: rgba(45, 106, 48, 0.08);
}

.answer-option.wrong {
  border-color: var(--accent);
  background-color: rgba(139, 69, 19, 0.08);
}

.answer-option.disabled {
  pointer-events: none;
  opacity: 0.75;
}

.answer-feedback {
  margin-top: 1rem;
  padding: 0.9rem 1rem;
  border-radius: 6px;
  background-color: var(--light);
  border: 1px solid var(--border);
}

.feedback-explain {
  display: block;
  margin-top: 0.4rem;
  color: var(--gray);
  font-size: 0.95rem;
}

.quiz-navigation {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  margin-top: 1.5rem;
}

.quiz-navigation a.btn {
  text-align: center;
}

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

.result-section h2 {
  color: var(--ink);
  margin-bottom: 1rem;
}

.result-score {
  font-size: 3rem;
  font-weight: 700;
  color: var(--accent);
  margin-bottom: 1rem;
}

#resultMessage {
  margin-bottom: 1.5rem;
  font-size: 1.1rem;
}

.best-score {
  color: var(--gray);
  margin-bottom: 1.5rem;
  font-size: 1rem;
}

#backToTop {
  position: fixed;
  right: 1rem;
  bottom: 1rem;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background-color: var(--accent);
  color: var(--white);
  border: none;
  font-size: 1.4rem;
  line-height: 1;
  cursor: pointer;
  box-shadow: var(--shadow);
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.3s, visibility 0.3s, background-color 0.3s, transform 0.2s;
  z-index: 90;
}

#backToTop.show {
  opacity: 1;
  visibility: visible;
}

#backToTop:hover {
  background-color: var(--accent-hover);
  transform: translateY(-3px);
}

.js .reveal {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.js .reveal.visible {
  opacity: 1;
  transform: none;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  .js .reveal {
    opacity: 1;
    transform: none;
    transition: none;
  }
}

.site-footer {
  background-color: var(--header-dark);
  color: #b0a090;
  text-align: center;
  padding: 1.5rem;
  margin-top: 2rem;
  border-top: 2px solid var(--accent);
}

.site-footer p {
  margin: 0.25rem 0;
}

@media (max-width: 768px) {
  main {
    padding: 1rem 0.75rem;
  }

  .navbar {
    padding: 0.75rem 1rem;
  }

  .menu-toggle {
    display: block;
  }

  .nav-menu {
    display: none;
    flex-direction: column;
    width: 100%;
    gap: 0;
    margin-top: 1rem;
    padding-top: 0.5rem;
    border-top: 1px solid var(--hero-secondary);
  }

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

  .nav-menu li {
    width: 100%;
  }

  .nav-menu li a {
    display: block;
    padding: 0.8rem 0.5rem;
    border-radius: 6px;
  }

  .hero {
    padding: 2rem 1rem;
  }

  .hero h1 {
    font-size: 1.8rem;
  }

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

  .cards {
    grid-template-columns: 1fr;
    gap: 1rem;
  }

  .page-header h1 {
    font-size: 1.8rem;
  }

  .statistics {
    gap: 1.5rem;
  }

  .topic-tabs {
    gap: 0.5rem;
  }

  .tab-btn {
    padding: 0.5rem 0.9rem;
    font-size: 0.9rem;
  }

  .author-grid {
    grid-template-columns: 1fr 1fr;
    gap: 0.75rem;
  }

  .author-card {
    padding: 1rem;
  }

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

  .quiz-navigation .btn {
    width: 100%;
  }
}

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

  .statistics {
    flex-direction: column;
    gap: 0.75rem;
  }

  .topic-content,
  .author-info,
  .quiz-section,
  .result-section,
  .info-section {
    padding: 1.25rem;
  }
}

[data-theme="dark"] .author-card.active {
  background-color: #2a1a10;
}

[data-theme="dark"] .answer-option.selected {
  background-color: #2a1a10;
}

[data-theme="dark"] .answer-option.correct {
  background-color: #152a1c;
}

[data-theme="dark"] .answer-option.wrong {
  background-color: #2a1515;
}

[data-theme="dark"] .theme-toggle,
[data-theme="dark"] .menu-toggle {
  border-color: #8a7a68;
  color: #d0c0a8;
}