:root {
  --primary-color: #4299e1;
  --primary-hover: #3182ce;
  --secondary-color: #e2e8f0;
  --secondary-hover: #cbd5e0;
  --bg-primary: #ffffff;
  --bg-secondary: #f7fafc;
  --bg-tertiary: #edf2f7;
  --text-primary: #1a202c;
  --text-secondary: #4a5568;
  --border-color: #cbd5e0;
  --success-color: #48bb78;
  --danger-color: #f56565;
  --book-shadow: 0 20px 40px rgba(0,0,0,0.15);
  --page-shadow: 0 10px 25px rgba(0,0,0,0.1);
}

body.dark-mode {
  --primary-color: #63b3ed;
  --primary-hover: #4299e1;
  --secondary-color: #2d3748;
  --secondary-hover: #4a5568;
  --bg-primary: #1a202c;
  --bg-secondary: #2d3748;
  --bg-tertiary: #4a5568;
  --text-primary: #f7fafc;
  --text-secondary: #cbd5e0;
  --border-color: #4a5568;
}

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

html, body {
  height: 100%;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  transition: background 0.3s ease, color 0.3s ease;
  line-height: 1.6;
}

/* Navbar */
.navbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0 20px;
  height: 70px;
  background: var(--bg-secondary);
  box-shadow: 0 2px 8px rgba(0,0,0,0.1);
  border-bottom: 3px solid var(--primary-color);
  position: sticky;
  top: 0;
  z-index: 100;
}

.navbar-brand h1 {
  font-size: 24px;
  color: var(--primary-color);
  font-weight: 700;
}

.navbar-menu {
  display: flex;
  gap: 20px;
  flex: 1;
  justify-content: center;
}

.nav-link {
  padding: 8px 16px;
  text-decoration: none;
  color: var(--text-secondary);
  font-weight: 500;
  border-bottom: 3px solid transparent;
  transition: all 0.3s ease;
}

.nav-link:hover {
  color: var(--text-primary);
  border-bottom-color: var(--primary-color);
}

.nav-link.active {
  color: var(--primary-color);
  border-bottom-color: var(--primary-color);
}

.btn-theme {
  padding: 8px 12px;
  border: none;
  background: transparent;
  font-size: 20px;
  cursor: pointer;
  transition: transform 0.3s ease;
}

.btn-theme:hover {
  transform: rotate(20deg);
}

/* Container */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 40px 20px;
}

/* Buttons */
.btn {
  padding: 10px 20px;
  border: none;
  border-radius: 4px;
  cursor: pointer;
  font-size: 14px;
  font-weight: 500;
  transition: all 0.3s ease;
}

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

.btn-primary:hover {
  background-color: var(--primary-hover);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0,0,0,0.15);
}

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

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

.btn-large {
  width: 100%;
  padding: 15px 20px;
  font-size: 16px;
}

.button-group {
  display: flex;
  gap: 15px;
  margin-top: 20px;
  flex-wrap: wrap;
}

/* Hero Section */
.hero {
  text-align: center;
  margin-bottom: 60px;
}

.hero h2 {
  font-size: 48px;
  margin-bottom: 20px;
  color: var(--primary-color);
}

.hero p {
  font-size: 20px;
  color: var(--text-secondary);
  margin-bottom: 40px;
}

.hero-features {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 20px;
  margin-bottom: 40px;
}

.feature-card {
  background: var(--bg-secondary);
  padding: 25px;
  border-radius: 8px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.1);
  transition: transform 0.3s ease;
}

.feature-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 16px rgba(0,0,0,0.15);
}

.feature-card h3 {
  font-size: 18px;
  margin-bottom: 10px;
  color: var(--primary-color);
}

.feature-card p {
  color: var(--text-secondary);
}

/* CTA Section */
.cta-section {
  background: var(--bg-secondary);
  padding: 40px;
  border-radius: 8px;
  text-align: center;
  margin-bottom: 60px;
}

.cta-section h3 {
  font-size: 32px;
  margin-bottom: 30px;
  color: var(--primary-color);
}

/* Features Section */
.features-section h3 {
  font-size: 32px;
  margin-bottom: 40px;
  text-align: center;
  color: var(--primary-color);
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 25px;
}

.feature {
  background: var(--bg-secondary);
  padding: 30px;
  border-radius: 8px;
  text-align: center;
  transition: transform 0.3s ease;
}

.feature:hover {
  transform: translateY(-5px);
}

.feature-icon {
  font-size: 40px;
  display: block;
  margin-bottom: 15px;
}

.feature h4 {
  font-size: 18px;
  margin-bottom: 10px;
  color: var(--primary-color);
}

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

/* Footer */
.footer {
  background: var(--bg-secondary);
  padding: 20px;
  text-align: center;
  color: var(--text-secondary);
  border-top: 1px solid var(--border-color);
  margin-top: 60px;
}

/* Reader */
.reader-container {
  display: flex;
  flex-direction: column;
  height: calc(100vh - 70px);
  padding: 20px;
  gap: 20px;
}

.reader-controls {
  background: var(--bg-secondary);
  padding: 15px;
  border-radius: 8px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.1);
  display: flex;
  gap: 20px;
  flex-wrap: wrap;
  align-items: center;
}

.control-group {
  display: flex;
  gap: 10px;
  align-items: center;
}

.status-text {
  color: var(--text-secondary);
  font-size: 14px;
}

.page-info {
  padding: 0 15px;
  border-left: 2px solid var(--border-color);
  border-right: 2px solid var(--border-color);
  color: var(--text-primary);
  font-weight: 500;
}

.zoom-display {
  min-width: 50px;
  text-align: center;
  color: var(--text-primary);
  font-weight: 500;
}

.book-viewer {
  flex: 1;
  background: linear-gradient(135deg, var(--bg-tertiary) 0%, var(--bg-secondary) 100%);
  border-radius: 8px;
  overflow: auto;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 20px;
  box-shadow: inset 0 2px 8px rgba(0,0,0,0.05);
}

.empty-state {
  text-align: center;
  color: var(--text-secondary);
  font-size: 18px;
}

.book-spread {
  display: flex;
  gap: 30px;
  perspective: 1200px;
  align-items: center;
  justify-content: center;
  padding: 20px;
}

.page {
  background: white;
  box-shadow: var(--book-shadow);
  border-radius: 2px;
  overflow: hidden;
  animation: pageFlip 0.8s cubic-bezier(0.68, -0.55, 0.265, 1.55) forwards;
  flex: 0 0 auto;
  position: relative;
  transform-style: preserve-3d;
  border: 1px solid #f0f0f0;
}

.page::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(90deg, rgba(0,0,0,0.02) 0%, transparent 50%, rgba(255,255,255,0.02) 100%);
  pointer-events: none;
}

@keyframes pageFlip {
  0% {
    transform: rotateY(90deg) rotateX(0deg);
    opacity: 0;
  }
  50% {
    transform: rotateY(45deg) rotateX(5deg);
  }
  100% {
    transform: rotateY(0deg) rotateX(0deg);
    opacity: 1;
  }
}

.page-image {
  max-width: 100%;
  height: auto;
  display: block;
  background: white;
}

/* Export */
.export-container {
  padding: 40px 20px;
}

.export-container h2 {
  margin-bottom: 30px;
  color: var(--primary-color);
}

.export-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 30px;
  margin-top: 30px;
}

.settings-panel {
  background: var(--bg-secondary);
  padding: 30px;
  border-radius: 8px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.settings-panel h3 {
  margin-bottom: 20px;
  color: var(--primary-color);
}

.form-group {
  margin-bottom: 20px;
}

.form-group label {
  display: block;
  margin-bottom: 8px;
  font-weight: 500;
  color: var(--text-primary);
}

.form-group input,
.form-group select {
  width: 100%;
  padding: 10px;
  border: 1px solid var(--border-color);
  border-radius: 4px;
  font-size: 14px;
  background: var(--bg-primary);
  color: var(--text-primary);
}

.form-group input:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(66, 153, 225, 0.1);
}

.margin-inputs {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}

.preview-panel {
  background: var(--bg-secondary);
  padding: 30px;
  border-radius: 8px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.1);
  height: fit-content;
  position: sticky;
  top: 20px;
}

.preview-panel h3 {
  margin-bottom: 20px;
  color: var(--primary-color);
}

.preview-box {
  background: var(--bg-primary);
  padding: 20px;
  border-radius: 4px;
  border-left: 4px solid var(--primary-color);
  box-shadow: inset 0 1px 3px rgba(0,0,0,0.05);
}

.preview-content h4 {
  margin-bottom: 15px;
  color: var(--primary-color);
  font-size: 16px;
}

.preview-content p {
  margin: 10px 0;
  color: var(--text-primary);
  font-size: 14px;
}

/* Responsive */
@media (max-width: 1024px) {
  .export-grid {
    grid-template-columns: 1fr;
  }
  
  .preview-panel {
    position: static;
    margin-top: 20px;
  }
}

@media (max-width: 768px) {
  .navbar {
    flex-direction: column;
    height: auto;
    gap: 10px;
    padding: 10px;
  }

  .navbar-menu {
    width: 100%;
    justify-content: space-around;
    margin: 10px 0;
  }

  .hero h2 {
    font-size: 32px;
  }

  .hero-features {
    grid-template-columns: 1fr;
  }

  .reader-controls {
    flex-direction: column;
    align-items: flex-start;
  }

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

  .btn {
    width: 100%;
  }

  .features-grid {
    grid-template-columns: 1fr;
  }
  
  .book-spread {
    flex-direction: column;
    gap: 20px;
  }
  
  .page {
    max-width: 100%;
    width: 100%;
  }
}

/* Scrollbar */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--bg-tertiary);
}

::-webkit-scrollbar-thumb {
  background: var(--primary-color);
  border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--primary-hover);
}