:root {
  --primary-color: #0071e3;
  --bg-color: #ffffff;
  --sidebar-bg: rgba(245, 245, 247, 0.8);
  --text-color: #1d1d1f;
  --text-secondary: #6e6e73;
  --border-color: #d2d2d7;
  --code-bg: #f5f5f7;
  --accent-color: #0071e3;
  --transition-speed: 0.3s;
  --sidebar-width: 280px;
  --glass-effect: blur(20px) saturate(180%);
  --progress-height: 4px;
}

[data-theme="dark"] {
  --primary-color: #007aff;
  --bg-color: #000000;
  --sidebar-bg: rgba(28, 28, 30, 0.8);
  --text-color: #f5f5f7;
  --text-secondary: #86868b;
  --border-color: #38383a;
  --code-bg: #1c1c1e;
}

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

body {
  font-family: 'Inter', 'Noto Sans TC', -apple-system, BlinkMacSystemFont, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-color);
  line-height: 1.6;
  overflow-x: hidden;
  transition: background-color var(--transition-speed), color var(--transition-speed);
}

#app {
  display: flex;
  min-height: 100vh;
}

/* Sidebar Styling */
.sidebar {
  width: var(--sidebar-width);
  height: 100vh;
  position: sticky;
  top: 0;
  background-color: var(--sidebar-bg);
  backdrop-filter: var(--glass-effect);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  z-index: 100;
}

.sidebar-header {
  padding: 2rem 1.5rem;
  border-bottom: 1px solid var(--border-color);
}

.sidebar-header h1 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--primary-color);
}

.sidebar-header p {
  font-size: 0.8rem;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 1px;
}

.nav-menu {
  flex: 1;
  overflow-y: auto;
  padding: 1.5rem 0;
}

.nav-section {
  margin-bottom: 2rem;
}

.nav-section h3 {
  padding: 0 1.5rem 0.5rem;
  font-size: 0.75rem;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 1px;
}

.nav-menu ul {
  list-style: none;
}

.nav-menu li a {
  display: block;
  padding: 0.75rem 1.5rem;
  color: var(--text-color);
  text-decoration: none;
  font-size: 0.95rem;
  transition: all var(--transition-speed);
  border-left: 3px solid transparent;
}

.nav-menu li a:hover {
  background-color: rgba(0, 113, 227, 0.05);
  color: var(--primary-color);
}

.nav-menu li a.active {
  background-color: rgba(0, 113, 227, 0.1);
  color: var(--primary-color);
  border-left-color: var(--primary-color);
  font-weight: 600;
}

/* Content Area Styling */
.content-area {
  flex: 1;
  display: flex;
  flex-direction: column;
  max-width: 100%;
}

.content-header {
  height: 60px;
  padding: 0 2rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  background-color: rgba(255, 255, 255, 0.8);
  backdrop-filter: blur(10px);
  position: sticky;
  top: 0;
  z-index: 90;
  border-bottom: 1px solid var(--border-color);
}

.progress-container {
  position: absolute;
  bottom: -1px;
  left: 0;
  width: 100%;
  height: var(--progress-height);
  background: transparent;
}

#progress-bar {
  height: 100%;
  background: linear-gradient(to right, var(--primary-color), #00c6ff);
  width: 0%;
  transition: width 0.1s linear;
}

[data-theme="dark"] .content-header {
  background-color: rgba(0, 0, 0, 0.8);
}

#current-title {
  font-weight: 600;
  font-size: 1.1rem;
}

.markdown-body {
  flex: 1;
  padding: 3rem 4rem;
  max-width: 900px;
  margin: 0 auto;
  width: 100%;
  animation: fadeIn 0.5s ease;
}

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

/* Markdown Typography */
.markdown-body h1 { font-size: 2.5rem; margin-bottom: 1.5rem; color: var(--primary-color); }
.markdown-body h2 { font-size: 1.8rem; margin: 2rem 0 1rem; padding-bottom: 0.5rem; border-bottom: 1px solid var(--border-color); }
.markdown-body h3 { font-size: 1.4rem; margin: 1.5rem 0 1rem; }
.markdown-body p { margin-bottom: 1.2rem; line-height: 1.8; }
.markdown-body ul, .markdown-body ol { margin-bottom: 1.2rem; padding-left: 1.5rem; }
.markdown-body li { margin-bottom: 0.5rem; }

.markdown-body table {
  width: 100%;
  border-collapse: collapse;
  margin: 2rem 0;
  border-radius: 8px;
  overflow: hidden;
  box-shadow: 0 4px 12px rgba(0,0,0,0.05);
}

.markdown-body th, .markdown-body td {
  padding: 1rem;
  border: 1px solid var(--border-color);
  text-align: left;
}

.markdown-body th {
  background-color: var(--code-bg);
  font-weight: 600;
}

.markdown-body blockquote {
  border-left: 4px solid var(--primary-color);
  background-color: var(--code-bg);
  padding: 1rem 1.5rem;
  margin: 1.5rem 0;
  border-radius: 0 8px 8px 0;
  font-style: italic;
}

.markdown-body code {
  font-family: 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
  background-color: var(--code-bg);
  padding: 0.2rem 0.4rem;
  border-radius: 4px;
  font-size: 0.9em;
}

.markdown-body pre {
  background-color: var(--code-bg);
  padding: 1.5rem;
  border-radius: 12px;
  overflow-x: auto;
  margin: 1.5rem 0;
}

.markdown-body pre code {
  padding: 0;
  background-color: transparent;
}

/* Footer Styling */
.content-footer {
  padding: 3rem 4rem;
  border-top: 1px solid var(--border-color);
  max-width: 900px;
  margin: 0 auto;
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2rem;
}

.nav-buttons {
  display: flex;
  gap: 1.5rem;
  width: 100%;
  justify-content: space-between;
}

.nav-btn {
  flex: 1;
  padding: 0.8rem 1.2rem;
  border-radius: 12px;
  border: 1px solid var(--primary-color);
  background-color: transparent;
  color: var(--primary-color);
  cursor: pointer;
  font-weight: 500;
  transition: all var(--transition-speed);
  font-size: 0.95rem;
}

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

.nav-btn:disabled {
  border-color: var(--border-color);
  color: var(--text-secondary);
  cursor: not-allowed;
}

.content-footer p {
  color: var(--text-secondary);
  font-size: 0.85rem;
}

/* UI Elements */
#theme-toggle {
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  padding: 5px;
  border-radius: 50%;
  transition: background 0.3s;
}

#theme-toggle:hover {
  background: rgba(0,0,0,0.05);
}

[data-theme="dark"] #theme-toggle:hover {
  background: rgba(255,255,255,0.1);
}

/* Mobile Responsiveness */
@media (max-width: 768px) {
  .sidebar {
    position: fixed;
    left: -100%;
    transition: left 0.3s ease;
  }
  
  .sidebar.open {
    left: 0;
  }
  
  .markdown-body {
    padding: 2rem 1.5rem;
  }

  .nav-buttons {
    flex-direction: column;
    gap: 1rem;
  }
  
  .content-header {
    padding: 0 1rem;
  }
  
  .mobile-only {
    display: block !important;
  }
}

.mobile-only {
  display: none;
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
}

.loading-state {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 200px;
  color: var(--text-secondary);
  font-style: italic;
}

/* Purchase CTA Styling */
.purchase-cta {
  margin: 4rem 0;
  padding: 3rem;
  background: linear-gradient(135deg, rgba(0, 113, 227, 0.05) 0%, rgba(0, 113, 227, 0.1) 100%);
  border-radius: 24px;
  border: 1px solid var(--border-color);
  text-align: center;
}

.purchase-cta h2 {
  margin-top: 0;
  border-bottom: none;
  font-size: 1.8rem;
}

.purchase-cta p {
  color: var(--text-secondary);
  margin-bottom: 2rem;
}

.buy-button {
  display: inline-block;
  padding: 1rem 2rem;
  background-color: var(--primary-color);
  color: white !important;
  text-decoration: none;
  border-radius: 30px;
  font-weight: 600;
  font-size: 1.1rem;
  transition: transform 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275), box-shadow 0.3s;
}

.buy-button:hover {
  transform: scale(1.05);
  box-shadow: 0 10px 20px rgba(0, 113, 227, 0.2);
  text-decoration: none !important;
}

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

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

::-webkit-scrollbar-thumb {
  background: var(--border-color);
  border-radius: 10px;
}

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