/* ==========================================================================
   Claude Code Cat Learning Lab - Main Styles
   ========================================================================== */

/* Google Fonts */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&family=JetBrains+Mono:wght@400;500;600&display=swap');

/* ==========================================================================
   CSS Custom Properties
   ========================================================================== */

:root {
  /* Primary - Coral / Orange */
  --primary: #e8734a;
  --primary-light: #f4a261;
  --primary-dark: #d4603a;
  --primary-glow: rgba(232, 115, 74, 0.25);

  /* Secondary - Deep Purple */
  --secondary: #6c5ce7;
  --secondary-light: #a29bfe;
  --secondary-dark: #5a4bd1;
  --secondary-glow: rgba(108, 92, 231, 0.25);

  /* Accent */
  --accent-green: #00b894;
  --accent-red: #ff6b6b;
  --accent-yellow: #ffeaa7;
  --accent-blue: #74b9ff;

  /* Dark Theme (Default) */
  --bg-primary: #0f0e17;
  --bg-secondary: #1a1a2e;
  --bg-tertiary: #16213e;
  --bg-card: rgba(26, 26, 46, 0.8);
  --bg-card-hover: rgba(26, 26, 46, 0.95);
  --bg-code: #0d0d1a;
  --bg-sidebar: #0a0a14;
  --bg-input: rgba(15, 14, 23, 0.6);

  --text-primary: #fffffe;
  --text-secondary: #b8b8d0;
  --text-muted: #6c6c8a;
  --text-code: #e8e8f0;

  --border-color: rgba(255, 255, 255, 0.06);
  --border-subtle: rgba(255, 255, 255, 0.03);
  --border-active: rgba(232, 115, 74, 0.4);

  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.5);
  --shadow-glow: 0 0 20px rgba(232, 115, 74, 0.15);

  --glass-bg: rgba(26, 26, 46, 0.6);
  --glass-border: rgba(255, 255, 255, 0.08);

  /* Sizing */
  --sidebar-width: 280px;
  --header-height: 56px;
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;

  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;

  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-base: 0.3s ease;
  --transition-slow: 0.5s ease;
}

/* Light Theme */
[data-theme="light"] {
  --bg-primary: #faf8f5;
  --bg-secondary: #fff;
  --bg-tertiary: #f0ece4;
  --bg-card: rgba(255, 255, 255, 0.9);
  --bg-card-hover: rgba(255, 255, 255, 1);
  --bg-code: #f5f2eb;
  --bg-sidebar: #f5f2ed;
  --bg-input: rgba(240, 236, 228, 0.6);

  --text-primary: #1a1a2e;
  --text-secondary: #4a4a62;
  --text-muted: #8a8a9e;
  --text-code: #2d2b55;

  --border-color: rgba(0, 0, 0, 0.08);
  --border-subtle: rgba(0, 0, 0, 0.04);
  --border-active: rgba(232, 115, 74, 0.5);

  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.12);
  --shadow-glow: 0 0 20px rgba(232, 115, 74, 0.1);

  --glass-bg: rgba(255, 255, 255, 0.7);
  --glass-border: rgba(0, 0, 0, 0.06);
}

/* ==========================================================================
   Reset & Base
   ========================================================================== */

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

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

body {
  font-family: var(--font-sans);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  overflow: hidden;
  transition: background-color var(--transition-base), color var(--transition-base);
}

a {
  color: var(--primary-light);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--primary);
  text-decoration: underline;
}

::selection {
  background: var(--primary);
  color: #fff;
}

/* ==========================================================================
   Scrollbar Styling
   ========================================================================== */

::-webkit-scrollbar {
  width: 6px;
  height: 6px;
}

::-webkit-scrollbar-track {
  background: transparent;
}

::-webkit-scrollbar-thumb {
  background: var(--text-muted);
  border-radius: 3px;
}

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

/* Firefox */
* {
  scrollbar-width: thin;
  scrollbar-color: var(--text-muted) transparent;
}

/* ==========================================================================
   App Layout
   ========================================================================== */

#app {
  display: flex;
  flex-direction: row;
  height: 100vh;
  width: 100vw;
  overflow: hidden;
}

/* ==========================================================================
   Sidebar
   ========================================================================== */

#sidebar {
  width: var(--sidebar-width);
  min-width: var(--sidebar-width);
  height: 100vh;
  background: var(--bg-sidebar);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  position: relative;
  z-index: 100;
  transition: transform var(--transition-base), background-color var(--transition-base);
}

/* Sidebar Header / Logo */
.sidebar-header {
  padding: 24px 20px 20px;
  border-bottom: 1px solid var(--border-color);
  flex-shrink: 0;
}

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

.sidebar-logo-icon {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-md);
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  box-shadow: 0 4px 12px rgba(232, 115, 74, 0.3);
}

.sidebar-logo-text {
  font-size: 17px;
  font-weight: 700;
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 50%, var(--secondary-light) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -0.3px;
  line-height: 1.2;
}

.sidebar-logo-subtitle {
  font-size: 11px;
  color: var(--text-muted);
  font-weight: 500;
  letter-spacing: 0.5px;
  text-transform: uppercase;
  margin-top: 2px;
}

/* Sidebar Navigation */
.sidebar-nav {
  flex: 1;
  overflow-y: auto;
  padding: 16px 12px;
}

.sidebar-section-title {
  font-size: 10px;
  font-weight: 700;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 1.2px;
  padding: 8px 12px 6px;
  margin-top: 8px;
}

.sidebar-section-title:first-child {
  margin-top: 0;
}

.module-nav-item {
  display: flex;
  align-items: center;
  gap: 12px;
  width: 100%;
  padding: 10px 12px;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
  border: 1px solid transparent;
  margin-bottom: 4px;
  position: relative;
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  background: transparent;
  font-family: var(--font-sans);
  text-align: left;
}

.module-nav-item:hover {
  background: var(--bg-card);
  border-color: var(--glass-border);
  box-shadow: var(--shadow-sm);
}

.module-nav-item.active {
  background: var(--bg-card-hover);
  border-color: var(--border-active);
  box-shadow: var(--shadow-sm), 0 0 0 1px var(--border-active);
}

.module-nav-item.completed .module-nav-check {
  opacity: 1;
  transform: scale(1);
}

.module-nav-icon {
  width: 36px;
  height: 36px;
  border-radius: var(--radius-sm);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 16px;
  flex-shrink: 0;
  transition: all var(--transition-fast);
}

.module-nav-item.active .module-nav-icon {
  background: linear-gradient(135deg, var(--primary), var(--primary-light));
  border-color: transparent;
  box-shadow: 0 2px 8px rgba(232, 115, 74, 0.3);
}

.module-nav-info {
  flex: 1;
  min-width: 0;
}

.module-nav-title {
  font-size: 13px;
  font-weight: 600;
  color: var(--text-primary);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  transition: color var(--transition-base);
}

.module-nav-item.active .module-nav-title {
  color: var(--primary-light);
}

.module-nav-desc {
  font-size: 11px;
  color: var(--text-muted);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* Progress Circle */
.module-nav-progress {
  width: 28px;
  height: 28px;
  flex-shrink: 0;
  position: relative;
}

.module-nav-progress svg {
  width: 28px;
  height: 28px;
  transform: rotate(-90deg);
}

.module-nav-progress .progress-track {
  fill: none;
  stroke: var(--border-color);
  stroke-width: 2.5;
}

.module-nav-progress .progress-fill {
  fill: none;
  stroke: var(--primary);
  stroke-width: 2.5;
  stroke-linecap: round;
  transition: stroke-dashoffset var(--transition-slow);
}

.module-nav-check {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: scale(0);
  margin-top: -6px;
  margin-left: -6px;
  width: 12px;
  height: 12px;
  opacity: 0;
  transition: all var(--transition-fast);
  color: var(--accent-green);
  font-size: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* Sidebar Footer */
.sidebar-footer {
  padding: 16px;
  border-top: 1px solid var(--border-color);
  flex-shrink: 0;
}

.progress-summary {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-bottom: 12px;
}

.progress-summary-text {
  font-size: 12px;
  color: var(--text-secondary);
  font-weight: 500;
}

.progress-summary-pct {
  font-size: 12px;
  color: var(--primary-light);
  font-weight: 700;
  font-family: var(--font-mono);
}

.progress-bar-container {
  width: 100%;
  height: 4px;
  background: var(--border-color);
  border-radius: 2px;
  overflow: hidden;
  margin-bottom: 16px;
}

.progress-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--primary-light));
  border-radius: 2px;
  transition: width var(--transition-slow);
  box-shadow: 0 0 8px rgba(232, 115, 74, 0.4);
}

/* Theme Toggle */
.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 8px 12px;
  border-radius: var(--radius-sm);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.theme-toggle:hover {
  border-color: var(--border-active);
}

.theme-toggle-label {
  font-size: 12px;
  color: var(--text-secondary);
  font-weight: 500;
}

.theme-toggle-switch {
  width: 40px;
  height: 22px;
  border-radius: 11px;
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  position: relative;
  transition: all var(--transition-fast);
}

.theme-toggle-switch::after {
  content: '';
  position: absolute;
  top: 2px;
  left: 2px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--primary);
  transition: transform var(--transition-fast);
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.2);
}

[data-theme="light"] .theme-toggle-switch::after {
  transform: translateX(18px);
}

/* ==========================================================================
   Main Content Area
   ========================================================================== */

#content {
  flex: 1;
  display: flex;
  flex-direction: column;
  min-width: 0;
  height: 100vh;
  overflow: hidden;
  transition: background-color var(--transition-base);
}

/* ==========================================================================
   Tutorial Panel
   ========================================================================== */

#tutorial-panel {
  flex: 1;
  overflow-y: auto;
  overflow-x: hidden;
  padding: 32px 40px;
  position: relative;
  min-height: 0;
  -webkit-overflow-scrolling: touch;
  overscroll-behavior: contain;
}

/* Background decorative gradient blobs */
#tutorial-panel::before {
  content: '';
  position: fixed;
  top: -200px;
  right: -200px;
  width: 500px;
  height: 500px;
  border-radius: 50%;
  background: radial-gradient(circle, var(--primary-glow) 0%, transparent 70%);
  pointer-events: none;
  z-index: 0;
}

#tutorial-panel::after {
  content: '';
  position: fixed;
  bottom: -150px;
  left: 200px;
  width: 400px;
  height: 400px;
  border-radius: 50%;
  background: radial-gradient(circle, var(--secondary-glow) 0%, transparent 70%);
  pointer-events: none;
  z-index: 0;
}

/* ==========================================================================
   Tutorial Content Styling (Markdown-like)
   ========================================================================== */

#tutorial-content {
  max-width: 760px;
  margin: 0 auto;
  position: relative;
  z-index: 1;
}

#tutorial-content > * {
  animation: fadeInUp 0.4s ease both;
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(12px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Staggered fade in for children */
#tutorial-content > *:nth-child(1) { animation-delay: 0s; }
#tutorial-content > *:nth-child(2) { animation-delay: 0.05s; }
#tutorial-content > *:nth-child(3) { animation-delay: 0.1s; }
#tutorial-content > *:nth-child(4) { animation-delay: 0.15s; }
#tutorial-content > *:nth-child(5) { animation-delay: 0.2s; }
#tutorial-content > *:nth-child(6) { animation-delay: 0.25s; }
#tutorial-content > *:nth-child(7) { animation-delay: 0.3s; }
#tutorial-content > *:nth-child(8) { animation-delay: 0.35s; }
#tutorial-content > *:nth-child(9) { animation-delay: 0.4s; }
#tutorial-content > *:nth-child(10) { animation-delay: 0.45s; }

/* Headings */
#tutorial-content h1 {
  font-size: 32px;
  font-weight: 800;
  letter-spacing: -0.5px;
  line-height: 1.2;
  margin-bottom: 8px;
  color: var(--text-primary);
  transition: color var(--transition-base);
}

#tutorial-content h1 .step-badge {
  display: inline-block;
  font-size: 12px;
  font-weight: 700;
  color: var(--primary);
  background: var(--primary-glow);
  padding: 4px 10px;
  border-radius: 20px;
  margin-bottom: 8px;
  letter-spacing: 0.5px;
  text-transform: uppercase;
  font-family: var(--font-mono);
}

#tutorial-content h2 {
  font-size: 22px;
  font-weight: 700;
  letter-spacing: -0.3px;
  line-height: 1.3;
  margin-top: 40px;
  margin-bottom: 16px;
  color: var(--text-primary);
  padding-bottom: 10px;
  border-bottom: 1px solid var(--border-color);
  transition: color var(--transition-base), border-color var(--transition-base);
}

#tutorial-content h3 {
  font-size: 17px;
  font-weight: 600;
  line-height: 1.4;
  margin-top: 28px;
  margin-bottom: 12px;
  color: var(--text-primary);
  transition: color var(--transition-base);
}

/* Paragraphs */
#tutorial-content p {
  font-size: 15px;
  line-height: 1.7;
  color: var(--text-secondary);
  margin-bottom: 16px;
  transition: color var(--transition-base);
}

#tutorial-content strong {
  color: var(--text-primary);
  font-weight: 600;
}

/* Inline code */
#tutorial-content code {
  font-family: var(--font-mono);
  font-size: 13px;
  background: var(--bg-code);
  color: var(--primary-light);
  padding: 2px 7px;
  border-radius: 4px;
  border: 1px solid var(--border-color);
  transition: all var(--transition-base);
}

/* Code Blocks */
#tutorial-content pre {
  position: relative;
  margin: 20px 0;
  border-radius: var(--radius-md);
  overflow: hidden;
}

#tutorial-content pre code {
  display: block;
  background: var(--bg-code);
  color: var(--text-code);
  padding: 20px 24px;
  font-size: 13.5px;
  line-height: 1.6;
  overflow-x: auto;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
}

/* Syntax-like coloring for code blocks */
#tutorial-content pre code .keyword {
  color: var(--secondary-light);
}

#tutorial-content pre code .string {
  color: var(--accent-green);
}

#tutorial-content pre code .comment {
  color: var(--text-muted);
  font-style: italic;
}

#tutorial-content pre code .function {
  color: var(--accent-blue);
}

#tutorial-content pre code .number {
  color: var(--primary-light);
}

/* Copy Button on Code Blocks */
.copy-btn {
  position: absolute;
  top: 10px;
  right: 10px;
  padding: 6px 12px;
  font-size: 11px;
  font-family: var(--font-sans);
  font-weight: 600;
  color: var(--text-muted);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  opacity: 0;
  transition: all var(--transition-fast);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  z-index: 2;
}

#tutorial-content pre:hover .copy-btn {
  opacity: 1;
}

.copy-btn:hover {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
}

.copy-btn.copied {
  background: var(--accent-green);
  color: #fff;
  border-color: var(--accent-green);
}

/* Lists */
#tutorial-content ul,
#tutorial-content ol {
  margin: 12px 0 20px;
  padding-left: 24px;
}

#tutorial-content li {
  font-size: 15px;
  line-height: 1.7;
  color: var(--text-secondary);
  margin-bottom: 6px;
  transition: color var(--transition-base);
}

#tutorial-content li::marker {
  color: var(--primary);
}

#tutorial-content ul li {
  list-style-type: none;
  position: relative;
  padding-left: 4px;
}

#tutorial-content ul li::before {
  content: '';
  position: absolute;
  left: -18px;
  top: 10px;
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: var(--primary);
}

/* ==========================================================================
   Callout Boxes
   ========================================================================== */

.info-box,
.warning-box,
.try-it-box {
  padding: 16px 20px;
  border-radius: var(--radius-md);
  margin: 20px 0;
  border-left: 4px solid;
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  transition: all var(--transition-base);
}

.info-box {
  background: rgba(108, 92, 231, 0.08);
  border-left-color: var(--secondary);
  color: var(--text-secondary);
}

.info-box .callout-title {
  color: var(--secondary-light);
  font-weight: 700;
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.warning-box {
  background: rgba(255, 107, 107, 0.08);
  border-left-color: var(--accent-red);
  color: var(--text-secondary);
}

.warning-box .callout-title {
  color: var(--accent-red);
  font-weight: 700;
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.try-it-box {
  background: rgba(232, 115, 74, 0.08);
  border-left-color: var(--primary);
  color: var(--text-secondary);
}

.try-it-box .callout-title {
  color: var(--primary-light);
  font-weight: 700;
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.callout-body {
  font-size: 14px;
  line-height: 1.6;
}

.callout-body code {
  font-family: var(--font-mono);
  font-size: 12.5px;
  background: rgba(0, 0, 0, 0.15);
  padding: 1px 6px;
  border-radius: 3px;
}

[data-theme="light"] .callout-body code {
  background: rgba(0, 0, 0, 0.06);
}

/* ==========================================================================
   Step Navigation
   ========================================================================== */

.step-navigation {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--border-color);
  gap: 16px;
}

.step-nav-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 20px;
  font-size: 14px;
  font-weight: 600;
  font-family: var(--font-sans);
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
  cursor: pointer;
  transition: all var(--transition-fast);
  background: var(--glass-bg);
  color: var(--text-secondary);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
}

.step-nav-btn:hover {
  border-color: var(--primary);
  color: var(--primary-light);
  box-shadow: var(--shadow-sm);
  transform: translateY(-1px);
}

.step-nav-btn:active {
  transform: translateY(0);
}

.step-nav-btn.primary {
  background: linear-gradient(135deg, var(--primary), var(--primary-dark));
  color: #fff;
  border-color: transparent;
  box-shadow: 0 4px 12px rgba(232, 115, 74, 0.3);
}

.step-nav-btn.primary:hover {
  box-shadow: 0 6px 20px rgba(232, 115, 74, 0.4);
  transform: translateY(-2px);
  color: #fff;
}

.step-nav-btn.primary:active {
  transform: translateY(0);
  box-shadow: 0 2px 8px rgba(232, 115, 74, 0.3);
}

.step-nav-btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
  transform: none !important;
  box-shadow: none !important;
}

.step-nav-btn .arrow-left::before {
  content: '\2190';
  font-size: 16px;
}

.step-nav-btn .arrow-right::after {
  content: '\2192';
  font-size: 16px;
}

.step-counter {
  font-size: 13px;
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-weight: 500;
}

/* ==========================================================================
   Smooth Content Transitions
   ========================================================================== */

.content-fade-enter {
  opacity: 0;
  transform: translateX(16px);
}

.content-fade-enter-active {
  opacity: 1;
  transform: translateX(0);
  transition: opacity 0.35s ease, transform 0.35s ease;
}

.content-fade-exit {
  opacity: 1;
  transform: translateX(0);
}

.content-fade-exit-active {
  opacity: 0;
  transform: translateX(-16px);
  transition: opacity 0.25s ease, transform 0.25s ease;
}

/* ==========================================================================
   Loading States
   ========================================================================== */

.loading-skeleton {
  background: linear-gradient(
    90deg,
    var(--border-color) 25%,
    var(--glass-border) 50%,
    var(--border-color) 75%
  );
  background-size: 200% 100%;
  animation: skeleton-shimmer 1.5s ease-in-out infinite;
  border-radius: var(--radius-sm);
}

@keyframes skeleton-shimmer {
  0% { background-position: -200% 0; }
  100% { background-position: 200% 0; }
}

/* ==========================================================================
   Mobile Hamburger
   ========================================================================== */

.hamburger-btn {
  display: none;
  position: fixed;
  top: 14px;
  left: 14px;
  z-index: 200;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  cursor: pointer;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 5px;
  transition: all var(--transition-fast);
}

.hamburger-btn span {
  display: block;
  width: 18px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 1px;
  transition: all var(--transition-fast);
}

.hamburger-btn.open span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.hamburger-btn.open span:nth-child(2) {
  opacity: 0;
}

.hamburger-btn.open span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* Sidebar Overlay for Mobile */
.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  z-index: 90;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-base);
}

.sidebar-overlay.visible {
  opacity: 1;
  pointer-events: auto;
}

/* ==========================================================================
   Responsive - Mobile
   ========================================================================== */

@media (max-width: 767px) {
  body {
    overflow: auto;
    overflow-x: hidden;
  }

  #app {
    height: auto;
    min-height: 100vh;
    min-height: 100dvh;
    overflow: visible;
  }

  .hamburger-btn {
    display: flex;
  }

  #sidebar {
    position: fixed;
    top: 0;
    left: 0;
    height: 100vh;
    height: 100dvh;
    transform: translateX(-100%);
    box-shadow: none;
    z-index: 150;
  }

  #sidebar.open {
    transform: translateX(0);
    box-shadow: var(--shadow-lg);
  }

  .sidebar-overlay {
    display: block;
  }

  #content {
    height: auto;
    min-height: 100vh;
    min-height: 100dvh;
    overflow: visible;
  }

  #tutorial-panel {
    padding: 24px 20px;
    padding-top: 68px;
    overflow-y: visible;
    min-height: auto;
  }

  #tutorial-content h1 {
    font-size: 26px;
  }

  #tutorial-content h2 {
    font-size: 19px;
  }

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

  .step-nav-btn {
    width: 100%;
    justify-content: center;
  }
}

@media (max-width: 480px) {
  #tutorial-panel {
    padding: 20px 16px;
    padding-top: 68px;
  }

  #tutorial-content pre code {
    font-size: 12px;
    padding: 16px;
  }
}

/* ==========================================================================
   Utility Classes
   ========================================================================== */

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border-width: 0;
}

.text-gradient {
  background: linear-gradient(135deg, var(--primary), var(--secondary-light));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.glass-card {
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-md);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  transition: all var(--transition-fast);
}

.glass-card:hover {
  border-color: var(--border-active);
  box-shadow: var(--shadow-md);
}

/* ==========================================================================
   Utility: Hidden
   ========================================================================== */

.hidden {
  display: none !important;
}

/* ==========================================================================
   Loading Screen
   ========================================================================== */

#loading-screen {
  position: fixed;
  inset: 0;
  z-index: 9999;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background: var(--bg-primary);
  gap: 20px;
  transition: opacity 0.5s ease;
}

#loading-screen .loading-cat {
  animation: idle-bounce 1.5s ease-in-out infinite;
}

@keyframes idle-bounce {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-10px); }
}

#loading-screen p {
  color: var(--text-muted);
  font-size: 14px;
}

#loading-screen.fade-out {
  opacity: 0;
  pointer-events: none;
}

/* ==========================================================================
   Content Transitions (used by app.js)
   ========================================================================== */

.content-exit {
  opacity: 0;
  transform: translateY(8px);
  transition: opacity 0.2s ease, transform 0.2s ease;
}

.content-enter {
  animation: fadeSlideIn 0.4s ease forwards;
}

@keyframes fadeSlideIn {
  from {
    opacity: 0;
    transform: translateY(12px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ==========================================================================
   Step Navigation Bar (#step-nav)
   ========================================================================== */

#step-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 20px 0;
  margin-top: 32px;
  border-top: 1px solid var(--border-color);
}

#step-counter {
  font-size: 13px;
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-weight: 500;
}

/* ==========================================================================
   Buttons (.btn system)
   ========================================================================== */

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 22px;
  font-size: 14px;
  font-weight: 600;
  font-family: var(--font-sans);
  border-radius: var(--radius-md, 10px);
  border: 1px solid var(--border-color);
  cursor: pointer;
  transition: all 0.2s ease;
  background: var(--bg-card);
  color: var(--text-secondary);
}

.btn:hover {
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}

.btn:active {
  transform: translateY(0);
}

.btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
  transform: none !important;
  box-shadow: none !important;
}

.btn-primary {
  background: linear-gradient(135deg, var(--primary), var(--primary-dark));
  color: #fff;
  border-color: transparent;
  box-shadow: 0 4px 12px rgba(232, 115, 74, 0.3);
}

.btn-primary:hover {
  box-shadow: 0 6px 20px rgba(232, 115, 74, 0.4);
  color: #fff;
}

.btn-secondary {
  background: var(--bg-card);
  color: var(--text-secondary);
  border: 1px solid var(--border-color);
}

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

.btn-try-terminal {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-top: 16px;
  padding: 10px 22px;
  font-size: 14px;
  font-weight: 600;
  font-family: var(--font-sans);
  border-radius: var(--radius-md, 10px);
  border: 1px solid var(--secondary);
  cursor: pointer;
  transition: all 0.2s ease;
  background: rgba(108, 92, 231, 0.1);
  color: var(--secondary-light);
}

.btn-try-terminal:hover {
  background: rgba(108, 92, 231, 0.2);
  transform: translateY(-1px);
  box-shadow: 0 4px 16px rgba(108, 92, 231, 0.25);
}

/* ==========================================================================
   Copy Button (inside code blocks)
   ========================================================================== */

.copy-btn {
  position: absolute;
  top: 8px;
  right: 8px;
  padding: 4px 10px;
  font-size: 11px;
  font-family: var(--font-sans);
  font-weight: 500;
  background: rgba(255, 255, 255, 0.08);
  color: var(--text-muted);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.2s ease;
  z-index: 2;
}

.copy-btn:hover {
  background: rgba(255, 255, 255, 0.15);
  color: var(--text-primary);
}

.copy-btn.copied {
  background: rgba(0, 184, 148, 0.2);
  color: var(--accent-green);
  border-color: var(--accent-green);
}

/* ==========================================================================
   Command Table (used in tutorials)
   ========================================================================== */

.command-table {
  width: 100%;
  border-collapse: collapse;
  margin: 16px 0;
  font-size: 14px;
}

.command-table th {
  text-align: left;
  padding: 10px 14px;
  background: rgba(108, 92, 231, 0.1);
  color: var(--secondary-light);
  font-weight: 600;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  border-bottom: 2px solid var(--border-color);
}

.command-table td {
  padding: 10px 14px;
  border-bottom: 1px solid var(--border-color);
  color: var(--text-secondary);
}

.command-table tr:hover td {
  background: rgba(255, 255, 255, 0.02);
}

.command-table code {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--primary-light);
  background: rgba(232, 115, 74, 0.1);
  padding: 2px 6px;
  border-radius: 4px;
}

/* ==========================================================================
   Welcome Placeholder
   ========================================================================== */

.welcome-placeholder {
  text-align: center;
  padding: 60px 20px;
}

.welcome-placeholder h2 {
  font-size: 28px;
  font-weight: 700;
  background: linear-gradient(135deg, var(--primary), var(--secondary-light));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 12px;
}

.welcome-placeholder p {
  color: var(--text-muted);
  font-size: 16px;
  margin-bottom: 40px;
}

.welcome-modules {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 16px;
  max-width: 700px;
  margin: 0 auto;
}

.welcome-module-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  padding: 24px 16px;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md, 10px);
  cursor: pointer;
  transition: all 0.2s ease;
  text-align: center;
}

.welcome-module-card:hover {
  border-color: var(--primary);
  transform: translateY(-3px);
  box-shadow: 0 8px 24px rgba(232, 115, 74, 0.15);
}

.welcome-module-card .wmc-icon {
  font-size: 32px;
}

.welcome-module-card .wmc-title {
  font-weight: 600;
  color: var(--text-primary);
  font-size: 15px;
}

.welcome-module-card .wmc-desc {
  font-size: 12px;
  color: var(--text-muted);
}

/* ==========================================================================
   Mobile Menu Toggle
   ========================================================================== */

.menu-toggle {
  display: none;
  position: fixed;
  top: 14px;
  left: 14px;
  z-index: 200;
  width: 40px;
  height: 40px;
  border-radius: 8px;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  cursor: pointer;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 5px;
  padding: 0;
}

.menu-toggle span {
  display: block;
  width: 18px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 1px;
  transition: all 0.2s ease;
}

@media (max-width: 767px) {
  .menu-toggle {
    display: flex;
  }
}

/* ==========================================================================
   Cat Area
   ========================================================================== */

#cat-area {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 20px 0 10px;
}

/* ==========================================================================
   Tutorial Content Extras
   ========================================================================== */

#tutorial-content h4 {
  font-size: 16px;
  font-weight: 600;
  color: var(--text-primary);
  margin: 20px 0 10px;
}

#tutorial-content ol {
  padding-left: 24px;
  margin: 12px 0;
  line-height: 1.8;
  color: var(--text-secondary);
}

#tutorial-content table {
  width: 100%;
  border-collapse: collapse;
  margin: 16px 0;
}

#tutorial-content table th {
  text-align: left;
  padding: 10px 14px;
  background: rgba(108, 92, 231, 0.1);
  color: var(--secondary-light);
  font-weight: 600;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  border-bottom: 2px solid var(--border-color);
}

#tutorial-content table td {
  padding: 10px 14px;
  border-bottom: 1px solid var(--border-color);
  color: var(--text-secondary);
  font-size: 14px;
}

#tutorial-content table tr:hover td {
  background: rgba(255, 255, 255, 0.02);
}

/* ==========================================================================
   Logo & Sidebar Header Elements
   ========================================================================== */

.logo {
  text-align: center;
}

.logo-icon {
  font-size: 32px;
  display: block;
  margin-bottom: 8px;
}

.logo h1 {
  font-size: 17px;
  font-weight: 700;
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 50%, var(--secondary-light) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -0.3px;
  line-height: 1.2;
}

.logo .subtitle {
  font-size: 11px;
  color: var(--text-muted);
  font-weight: 500;
  letter-spacing: 0.5px;
  margin-top: 4px;
}

/* Module navigation scrollable area */
#module-nav {
  flex: 1;
  overflow-y: auto;
  padding: 12px;
}

/* ==========================================================================
   Theme Switch (sidebar footer)
   ========================================================================== */

.theme-switch {
  margin-bottom: 12px;
}

.theme-switch label {
  display: flex;
  align-items: center;
  gap: 10px;
  cursor: pointer;
  padding: 8px 12px;
  border-radius: var(--radius-sm);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  transition: all var(--transition-fast);
}

.theme-switch label:hover {
  border-color: var(--border-active);
}

.theme-switch input[type="checkbox"] {
  display: none;
}

.switch-track {
  width: 40px;
  height: 22px;
  border-radius: 11px;
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  position: relative;
  flex-shrink: 0;
  transition: all var(--transition-fast);
}

.switch-thumb {
  position: absolute;
  top: 2px;
  left: 2px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--primary);
  transition: transform var(--transition-fast);
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.2);
}

.theme-switch input:checked + .switch-track .switch-thumb {
  transform: translateX(18px);
}

.switch-label {
  font-size: 12px;
  color: var(--text-secondary);
  font-weight: 500;
}

/* Progress bar (sidebar footer) */
.progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--primary-light));
  border-radius: 2px;
  transition: width var(--transition-slow);
  box-shadow: 0 0 8px rgba(232, 115, 74, 0.4);
}

#progress-text {
  font-size: 11px;
  color: var(--text-secondary);
  font-weight: 500;
  white-space: nowrap;
}

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

.btn-reset {
  background: none;
  border: 1px solid var(--border-color);
  color: var(--text-muted);
  font-size: 11px;
  padding: 2px 10px;
  border-radius: 6px;
  cursor: pointer;
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.btn-reset:hover {
  color: #e05545;
  border-color: #e05545;
  background: rgba(224, 85, 69, 0.08);
}

.footer-brand {
  font-size: 11px;
  color: var(--text-muted);
  text-align: center;
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px solid var(--border-color);
  letter-spacing: 0.3px;
}

/* ==========================================================================
   Diagram Containers
   ========================================================================== */

.diagram-container {
  margin: 24px 0;
  padding: 20px;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: all var(--transition-base);
}

.diagram-container:hover {
  border-color: var(--glass-border);
  box-shadow: var(--shadow-md);
}

.diagram-container svg {
  width: 100%;
  height: auto;
  display: block;
}

/* ==========================================================================
   Tip Box & Practice Box (new tutorial components)
   ========================================================================== */

.tip-box {
  padding: 16px 20px;
  border-radius: var(--radius-md);
  margin: 20px 0;
  border-left: 4px solid var(--accent-yellow);
  background: rgba(255, 234, 167, 0.08);
  color: var(--text-secondary);
  font-size: 14px;
  line-height: 1.7;
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  transition: all var(--transition-base);
}

.tip-box strong {
  color: #ffd700;
}

[data-theme="light"] .tip-box strong {
  color: #b8860b;
}

.practice-box {
  padding: 20px 24px;
  border-radius: var(--radius-md);
  margin: 24px 0;
  border-left: 4px solid var(--accent-green);
  background: rgba(0, 184, 148, 0.08);
  color: var(--text-secondary);
  font-size: 14px;
  line-height: 1.7;
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  transition: all var(--transition-base);
}

.practice-box strong {
  color: var(--accent-green);
  font-size: 15px;
}

.practice-box p {
  margin: 8px 0;
}

.practice-box pre {
  margin: 12px 0 0;
}

.practice-box pre code {
  font-size: 13px;
  background: rgba(0, 0, 0, 0.2);
  border-color: rgba(0, 184, 148, 0.2);
}

[data-theme="light"] .practice-box pre code {
  background: rgba(0, 0, 0, 0.04);
}

/* ==========================================================================
   Code Diff Display
   ========================================================================== */

.diff-container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 20px 0;
}

@media (max-width: 600px) {
  .diff-container {
    grid-template-columns: 1fr;
  }
}

.diff-panel {
  border-radius: var(--radius-md);
  overflow: hidden;
  border: 1px solid var(--border-color);
}

.diff-panel-header {
  padding: 8px 16px;
  font-size: 12px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.diff-before .diff-panel-header {
  background: rgba(255, 107, 107, 0.15);
  color: var(--accent-red);
  border-bottom: 1px solid rgba(255, 107, 107, 0.2);
}

.diff-after .diff-panel-header {
  background: rgba(0, 184, 148, 0.15);
  color: var(--accent-green);
  border-bottom: 1px solid rgba(0, 184, 148, 0.2);
}

.diff-panel-body {
  padding: 0;
  background: var(--bg-code);
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1.6;
}

.diff-line {
  padding: 2px 16px;
  white-space: pre-wrap;
  word-break: break-all;
}

.diff-line-removed {
  background: rgba(255, 107, 107, 0.1);
  color: var(--accent-red);
}

.diff-line-added {
  background: rgba(0, 184, 148, 0.1);
  color: var(--accent-green);
}

.diff-line-normal {
  color: var(--text-code);
}