/* Agent Harness Interactive Learning Hub - Global Stylesheet */
:root {
  --bg-primary: #0b0f19;
  --bg-secondary: #111827;
  --bg-tertiary: #1f2937;
  --bg-card: rgba(31, 41, 55, 0.7);
  --bg-glass: rgba(17, 24, 39, 0.75);
  --border-color: rgba(255, 255, 255, 0.1);
  --border-accent: rgba(99, 102, 241, 0.4);
  
  --text-main: #f3f4f6;
  --text-muted: #9ca3af;
  --text-dim: #6b7280;
  
  --accent-primary: #6366f1;
  --accent-primary-hover: #4f46e5;
  --accent-cyan: #06b6d4;
  --accent-emerald: #10b981;
  --accent-amber: #f59e0b;
  --accent-rose: #f43f5e;
  --accent-purple: #a855f7;

  --code-bg: #030712;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-lg: 0 10px 25px -5px rgba(0, 0, 0, 0.5), 0 8px 10px -6px rgba(0, 0, 0, 0.5);
  --shadow-glow: 0 0 25px rgba(99, 102, 241, 0.25);
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 18px;
  --radius-full: 9999px;
}

[data-theme="light"] {
  --bg-primary: #f8fafc;
  --bg-secondary: #ffffff;
  --bg-tertiary: #f1f5f9;
  --bg-card: rgba(255, 255, 255, 0.85);
  --bg-glass: rgba(248, 250, 252, 0.85);
  --border-color: rgba(0, 0, 0, 0.08);
  --border-accent: rgba(99, 102, 241, 0.3);
  --text-main: #0f172a;
  --text-muted: #475569;
  --text-dim: #94a3b8;
  --code-bg: #1e293b;
  --shadow-lg: 0 10px 25px -5px rgba(0, 0, 0, 0.07), 0 8px 10px -6px rgba(0, 0, 0, 0.05);
  --shadow-glow: 0 0 25px rgba(99, 102, 241, 0.12);
}

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

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-main);
  line-height: 1.7;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

/* Background Gradients */
.ambient-glow {
  position: fixed;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 100vw;
  height: 100vh;
  z-index: -1;
  pointer-events: none;
  background: 
    radial-gradient(circle at 15% 15%, rgba(99, 102, 241, 0.12) 0%, transparent 40%),
    radial-gradient(circle at 85% 30%, rgba(6, 182, 212, 0.08) 0%, transparent 40%),
    radial-gradient(circle at 50% 85%, rgba(168, 85, 247, 0.08) 0%, transparent 45%);
}

/* Top Progress Bar */
#reading-progress {
  position: fixed;
  top: 0;
  left: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--accent-cyan), var(--accent-primary), var(--accent-purple));
  width: 0%;
  z-index: 1000;
  transition: width 0.1s ease;
}

/* Top Navigation Bar */
.navbar {
  position: sticky;
  top: 0;
  z-index: 900;
  background: var(--bg-glass);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-color);
  padding: 0.75rem 2rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
  color: var(--text-main);
  font-weight: 700;
  font-size: 1.15rem;
}

.brand-badge {
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-cyan));
  color: #fff;
  font-size: 0.75rem;
  padding: 0.2rem 0.55rem;
  border-radius: var(--radius-sm);
  font-weight: 600;
  letter-spacing: 0.5px;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.nav-link {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.9rem;
  padding: 0.4rem 0.75rem;
  border-radius: var(--radius-sm);
  transition: all 0.2s ease;
}

.nav-link:hover, .nav-link.active {
  color: var(--text-main);
  background: var(--bg-tertiary);
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.btn-icon {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  width: 36px;
  height: 36px;
  border-radius: var(--radius-md);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s;
}

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

/* Chapter Menu Dropdown */
.dropdown {
  position: relative;
  display: inline-block;
}

.dropdown-content {
  display: none;
  position: absolute;
  right: 0;
  top: 120%;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  min-width: 280px;
  box-shadow: var(--shadow-lg);
  border-radius: var(--radius-md);
  padding: 0.5rem;
  z-index: 950;
}

.dropdown.open .dropdown-content {
  display: block;
  animation: fadeInDown 0.2s ease;
}

.dropdown-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.65rem 0.85rem;
  color: var(--text-main);
  text-decoration: none;
  font-size: 0.88rem;
  border-radius: var(--radius-sm);
  transition: background 0.15s;
}

.dropdown-item:hover {
  background: var(--bg-tertiary);
}

.dropdown-item.active {
  background: rgba(99, 102, 241, 0.15);
  color: var(--accent-primary);
  font-weight: 600;
}

.dropdown-num {
  background: var(--bg-tertiary);
  color: var(--accent-cyan);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  padding: 0.15rem 0.4rem;
  border-radius: 4px;
}

/* Layout Container */
.container {
  max-width: 960px;
  margin: 0 auto;
  padding: 2.5rem 1.5rem 6rem;
}

/* Waterfall Header / Hero */
.chapter-hero {
  text-align: center;
  margin-bottom: 3.5rem;
  padding: 2rem 1rem;
  border-bottom: 1px solid var(--border-color);
}

.chapter-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: rgba(99, 102, 241, 0.12);
  border: 1px solid var(--border-accent);
  color: var(--accent-cyan);
  padding: 0.35rem 1rem;
  border-radius: var(--radius-full);
  font-size: 0.85rem;
  font-weight: 600;
  margin-bottom: 1.25rem;
}

.chapter-title {
  font-size: 2.3rem;
  font-weight: 800;
  line-height: 1.3;
  margin-bottom: 1rem;
  background: linear-gradient(135deg, #ffffff 30%, var(--text-muted) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

[data-theme="light"] .chapter-title {
  background: linear-gradient(135deg, #0f172a 30%, #334155 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.chapter-lead {
  font-size: 1.15rem;
  color: var(--text-muted);
  max-width: 720px;
  margin: 0 auto;
  line-height: 1.7;
}

/* Waterfall Section Cards */
.waterfall-step {
  background: var(--bg-card);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 2.25rem;
  margin-bottom: 3rem;
  box-shadow: var(--shadow-lg);
  position: relative;
  transition: transform 0.2s ease, border-color 0.2s ease;
}

.waterfall-step:hover {
  border-color: var(--border-accent);
}

.step-header {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-bottom: 1.5rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border-color);
}

.step-number {
  width: 38px;
  height: 38px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-purple));
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 1.1rem;
  flex-shrink: 0;
  box-shadow: var(--shadow-glow);
}

.step-title {
  font-size: 1.45rem;
  font-weight: 700;
  color: var(--text-main);
}

/* Content typography */
p {
  margin-bottom: 1.25rem;
  color: var(--text-main);
  font-size: 1.02rem;
}

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

h3 {
  font-size: 1.2rem;
  font-weight: 600;
  margin: 1.75rem 0 0.85rem;
  color: var(--accent-cyan);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

ul, ol {
  margin-bottom: 1.5rem;
  padding-left: 1.5rem;
}

li {
  margin-bottom: 0.5rem;
  color: var(--text-main);
}

li strong {
  color: var(--accent-cyan);
}

/* Callout & Comparison Boxes */
.callout {
  border-left: 4px solid var(--accent-primary);
  background: rgba(99, 102, 241, 0.08);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  padding: 1.25rem 1.5rem;
  margin: 1.5rem 0;
}

.callout.tip {
  border-left-color: var(--accent-emerald);
  background: rgba(16, 185, 129, 0.08);
}

.callout.warning {
  border-left-color: var(--accent-amber);
  background: rgba(245, 158, 11, 0.08);
}

.callout.danger {
  border-left-color: var(--accent-rose);
  background: rgba(244, 63, 94, 0.08);
}

.callout-title {
  font-weight: 700;
  font-size: 0.95rem;
  margin-bottom: 0.4rem;
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

/* Comparison Grid */
.comparison-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.25rem;
  margin: 1.5rem 0;
}

.comparison-card {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.25rem;
}

.comparison-card.bad {
  border-top: 3px solid var(--accent-rose);
}

.comparison-card.good {
  border-top: 3px solid var(--accent-emerald);
}

.comparison-badge {
  display: inline-block;
  padding: 0.2rem 0.6rem;
  border-radius: var(--radius-sm);
  font-size: 0.78rem;
  font-weight: 700;
  margin-bottom: 0.75rem;
}

.comparison-card.bad .comparison-badge {
  background: rgba(244, 63, 94, 0.15);
  color: var(--accent-rose);
}

.comparison-card.good .comparison-badge {
  background: rgba(16, 185, 129, 0.15);
  color: var(--accent-emerald);
}

/* Interactive Sandbox / Simulator Component */
.interactive-playground {
  background: var(--bg-secondary);
  border: 1px solid var(--border-accent);
  border-radius: var(--radius-md);
  margin: 2rem 0;
  overflow: hidden;
  box-shadow: var(--shadow-glow);
}

.playground-header {
  background: var(--bg-tertiary);
  padding: 0.85rem 1.25rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid var(--border-color);
}

.playground-title {
  font-size: 0.95rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--text-main);
}

.playground-body {
  padding: 1.5rem;
}

/* Control Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.6rem 1.25rem;
  font-size: 0.9rem;
  font-weight: 600;
  border-radius: var(--radius-sm);
  cursor: pointer;
  border: none;
  transition: all 0.2s ease;
  text-decoration: none;
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-primary-hover));
  color: #fff;
  box-shadow: 0 4px 12px rgba(99, 102, 241, 0.3);
}

.btn-primary:hover {
  transform: translateY(-1px);
  box-shadow: 0 6px 16px rgba(99, 102, 241, 0.4);
}

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

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

.btn-success {
  background: linear-gradient(135deg, #059669, #10b981);
  color: #fff;
}

/* Code Blocks */
.code-container {
  background: var(--code-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  margin: 1.5rem 0;
  overflow: hidden;
}

.code-header {
  background: rgba(255, 255, 255, 0.03);
  padding: 0.5rem 1rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid rgba(255, 255, 255, 0.05);
  font-size: 0.8rem;
  color: var(--text-dim);
  font-family: var(--font-mono);
}

.code-copy-btn {
  background: transparent;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 0.75rem;
  padding: 0.2rem 0.5rem;
  border-radius: 4px;
}

.code-copy-btn:hover {
  background: rgba(255, 255, 255, 0.1);
  color: #fff;
}

pre {
  padding: 1.25rem;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.88rem;
  line-height: 1.6;
  color: #e2e8f0;
}

code {
  font-family: var(--font-mono);
}

p code, li code {
  background: rgba(99, 102, 241, 0.15);
  color: var(--accent-cyan);
  padding: 0.15rem 0.4rem;
  border-radius: 4px;
  font-size: 0.9em;
}

/* Interactive Quiz Widget */
.quiz-box {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-accent);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  margin: 2rem 0;
}

.quiz-question {
  font-weight: 700;
  font-size: 1.05rem;
  margin-bottom: 1rem;
  color: var(--text-main);
}

.quiz-options {
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
}

.quiz-opt {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  padding: 0.8rem 1rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  text-align: left;
  color: var(--text-main);
  font-size: 0.95rem;
  transition: all 0.15s ease;
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.quiz-opt:hover {
  background: rgba(99, 102, 241, 0.1);
  border-color: var(--accent-primary);
}

.quiz-opt.correct {
  background: rgba(16, 185, 129, 0.15) !important;
  border-color: var(--accent-emerald) !important;
  color: var(--accent-emerald) !important;
}

.quiz-opt.wrong {
  background: rgba(244, 63, 94, 0.15) !important;
  border-color: var(--accent-rose) !important;
  color: var(--accent-rose) !important;
}

.quiz-feedback {
  margin-top: 1rem;
  padding: 0.85rem 1rem;
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  display: none;
}

/* Bottom Pagination */
.chapter-nav-bottom {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1.5rem;
  margin-top: 4rem;
  padding-top: 2rem;
  border-top: 1px solid var(--border-color);
}

.nav-card {
  flex: 1;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.25rem 1.5rem;
  text-decoration: none;
  color: var(--text-main);
  transition: all 0.2s ease;
  display: flex;
  flex-direction: column;
}

.nav-card:hover {
  border-color: var(--accent-primary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-glow);
}

.nav-card-label {
  font-size: 0.8rem;
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 0.25rem;
}

.nav-card-title {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--accent-cyan);
}

/* Responsive */
@media (max-width: 768px) {
  .navbar {
    padding: 0.75rem 1rem;
  }
  .nav-links {
    display: none;
  }
  .chapter-title {
    font-size: 1.75rem;
  }
  .waterfall-step {
    padding: 1.5rem 1.15rem;
  }
  .comparison-grid {
    grid-template-columns: 1fr;
  }
  .chapter-nav-bottom {
    flex-direction: column;
  }
}

@keyframes fadeInDown {
  from { opacity: 0; transform: translateY(-8px); }
  to { opacity: 1; transform: translateY(0); }
}