:root {
  --gray-50: #f9fafb;
  --gray-100: #f3f4f6;
  --gray-200: #e5e7eb;
  --gray-300: #d1d5db;
  --gray-400: #9ca3af;
  --gray-500: #6b7280;
  --gray-600: #4b5563;
  --gray-700: #374151;
  --gray-800: #1f2937;
  --gray-900: #111827;
  --accent: #6366f1;
}

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

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  color: var(--gray-900);
  background: white;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

.container {
  max-width: 800px;
  margin: 0 auto;
  padding: 4rem 2rem;
}

/* Home Page */
.book-header {
  text-align: center;
  margin-bottom: 4rem;
  padding-bottom: 3rem;
  border-bottom: 2px solid var(--gray-200);
}

.book-title {
  font-size: 5rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 0.5rem;
  color: var(--gray-900);
}

.book-subtitle {
  font-size: 1.5rem;
  color: var(--gray-600);
  font-weight: 500;
  margin-bottom: 0.5rem;
}

.book-tagline {
  font-size: 1.125rem;
  color: var(--gray-500);
  font-weight: 400;
}

.book-description {
  margin-bottom: 4rem;
}

.book-description p {
  font-size: 1.125rem;
  line-height: 1.8;
  margin-bottom: 1.5rem;
  color: var(--gray-700);
}

.book-description strong {
  color: var(--gray-900);
  font-weight: 600;
}

.book-description ul {
  list-style: none;
  padding: 0;
  margin: 1.5rem 0 2rem;
}

.book-description li {
  padding-left: 2rem;
  margin-bottom: 0.75rem;
  position: relative;
  color: var(--gray-700);
}

.book-description li::before {
  content: "→";
  position: absolute;
  left: 0;
  color: var(--accent);
  font-weight: 600;
}

.stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2rem;
  margin: 3rem 0;
  padding: 2rem;
  background: var(--gray-50);
  border-radius: 12px;
  border: 1px solid var(--gray-200);
}

.stat {
  text-align: center;
}

.stat-value {
  display: block;
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--accent);
  margin-bottom: 0.5rem;
}

.stat-label {
  display: block;
  font-size: 0.875rem;
  color: var(--gray-600);
  font-weight: 500;
}

.cta-section {
  margin: 4rem 0;
  padding: 3rem 0;
  border-top: 2px solid var(--gray-200);
  border-bottom: 2px solid var(--gray-200);
  text-align: center;
}

.cta-section h2 {
  font-size: 2rem;
  margin-bottom: 2rem;
  font-weight: 700;
}

.cta-options {
  display: flex;
  gap: 1.5rem;
  justify-content: center;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
}

.btn-primary, .btn-secondary {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 1.25rem 2rem;
  border-radius: 8px;
  text-decoration: none;
  transition: all 0.2s;
  min-width: 200px;
}

.btn-primary {
  background: var(--gray-900);
  color: white;
}

.btn-primary:hover {
  background: var(--gray-800);
  transform: translateY(-2px);
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.15);
}

.btn-secondary {
  background: white;
  border: 2px solid var(--gray-300);
  color: var(--gray-900);
}

.btn-secondary:hover {
  border-color: var(--gray-900);
  transform: translateY(-2px);
}

.btn-label {
  font-size: 1.125rem;
  font-weight: 600;
}

.btn-meta {
  font-size: 0.875rem;
  color: var(--gray-500);
  margin-top: 0.25rem;
}

.btn-secondary .btn-meta {
  color: var(--gray-500);
}

.license-note {
  font-size: 0.875rem;
  color: var(--gray-600);
}

.license-note a {
  color: var(--accent);
  text-decoration: none;
}

.license-note a:hover {
  text-decoration: underline;
}

.author-section {
  margin: 4rem 0;
}

.author-section h2 {
  font-size: 1.5rem;
  margin-bottom: 1.5rem;
  font-weight: 700;
}

.author-section p {
  font-size: 1.125rem;
  line-height: 1.8;
  color: var(--gray-700);
  margin-bottom: 1rem;
}

.author-section a {
  color: var(--accent);
  text-decoration: none;
}

.author-section a:hover {
  text-decoration: underline;
}

.author-links {
  display: flex;
  gap: 2rem;
  margin-top: 1rem;
}

.author-links a {
  font-weight: 500;
}

.related-section {
  margin: 4rem 0;
}

.related-section h2 {
  font-size: 1.5rem;
  margin-bottom: 2rem;
  font-weight: 700;
}

.related-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1.5rem;
}

.related-card {
  padding: 1.5rem;
  background: var(--gray-50);
  border: 1px solid var(--gray-200);
  border-radius: 8px;
  text-decoration: none;
  color: inherit;
  transition: all 0.2s;
}

.related-card:hover {
  border-color: var(--gray-900);
  transform: translateY(-2px);
  box-shadow: 0 5px 20px rgba(0, 0, 0, 0.08);
}

.related-card h3 {
  font-size: 1.125rem;
  margin-bottom: 0.5rem;
  font-weight: 600;
  color: var(--gray-900);
}

.related-card p {
  font-size: 0.875rem;
  color: var(--gray-600);
  line-height: 1.6;
}

.book-footer {
  margin-top: 4rem;
  padding-top: 2rem;
  border-top: 1px solid var(--gray-200);
  text-align: center;
  color: var(--gray-600);
  font-size: 0.875rem;
}

.book-footer p {
  margin: 0.5rem 0;
}

.book-footer a {
  color: var(--accent);
  text-decoration: none;
}

.book-footer a:hover {
  text-decoration: underline;
}

/* Responsive */
@media (max-width: 640px) {
  .container {
    padding: 2rem 1.5rem;
  }

  .book-title {
    font-size: 3rem;
  }

  .book-subtitle {
    font-size: 1.25rem;
  }

  .stats {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }

  .cta-options {
    flex-direction: column;
    align-items: stretch;
  }

  .btn-primary, .btn-secondary {
    width: 100%;
  }

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

  .author-links {
    flex-direction: column;
    gap: 0.5rem;
  }
}