/* === Reset & Base === */
*, *::before, *::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --bg-deep: #0a0a1a;
  --bg-surface: #111128;
  --bg-card: #1a1a3e;
  --text-primary: #e8e8f0;
  --text-secondary: #9999bb;
  --text-dim: #555577;
  --accent-electric: #00d4ff;
  --accent-amber: #ffaa00;
  --accent-violet: #aa44ff;
  --accent-green: #44ff88;
  --accent-rose: #ff4488;
  --glow-electric: 0 0 10px #00d4ff66, 0 0 30px #00d4ff33;
  --glow-amber: 0 0 10px #ffaa0066, 0 0 30px #ffaa0033;
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 20px;
  --font-heading: 'Space Grotesk', sans-serif;
  --font-body: 'Inter', sans-serif;
  --transition-fast: 0.2s ease;
  --transition-med: 0.4s ease;
  --transition-slow: 0.8s ease;
  --content-width: 720px;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-body);
  background: var(--bg-deep);
  color: var(--text-primary);
  line-height: 1.7;
  min-height: 100vh;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -webkit-text-size-adjust: 100%;
}

/* === Canvas Background === */
#bg-canvas {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 0;
  pointer-events: none;
}

/* === Header & Nav === */
#app-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: linear-gradient(180deg, var(--bg-deep) 0%, transparent 100%);
  padding: 1rem 2rem;
}

#main-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: 1200px;
  margin: 0 auto;
}

.nav-brand {
  font-family: var(--font-heading);
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--accent-electric);
  text-decoration: none;
  text-shadow: var(--glow-electric);
  letter-spacing: -0.02em;
}

.nav-links {
  display: flex;
  gap: 1.5rem;
}

.nav-link {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-secondary);
  text-decoration: none;
  transition: color var(--transition-fast);
  position: relative;
}

.nav-link:hover,
.nav-link.active {
  color: var(--accent-electric);
}

.nav-link.active::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--accent-electric);
  box-shadow: var(--glow-electric);
  border-radius: 1px;
}

/* === Progress Bar === */
#progress-bar-container {
  max-width: var(--content-width);
  margin: 0.75rem auto 0;
  height: 4px;
  background: var(--bg-card);
  border-radius: 2px;
  position: relative;
  overflow: hidden;
}

#progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--accent-electric), var(--accent-violet));
  border-radius: 2px;
  transition: width var(--transition-med);
  width: 0%;
}

#progress-text {
  position: absolute;
  right: 0;
  top: 8px;
  font-size: 0.7rem;
  color: var(--text-dim);
}

/* === Main Content === */
#app-content {
  position: relative;
  z-index: 1;
  min-height: 100vh;
  padding-top: 5rem;
}

.screen {
  max-width: var(--content-width);
  margin: 0 auto;
  padding: 2rem 1.5rem 4rem;
}

.screen[hidden] {
  display: none !important;
}

.screen-title {
  font-family: var(--font-heading);
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  color: var(--text-primary);
}

.screen-subtitle {
  color: var(--text-secondary);
  margin-bottom: 2rem;
  font-size: 0.95rem;
}

/* === Landing Screen === */
#landing-screen {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: calc(100vh - 5rem);
  text-align: center;
  max-width: 100%;
}

.landing-content {
  max-width: 600px;
}

.landing-title {
  font-family: var(--font-heading);
  font-size: 4.5rem;
  font-weight: 700;
  margin-bottom: 1rem;
  letter-spacing: -0.03em;
  line-height: 1.1;
}

.title-glow {
  background: linear-gradient(135deg, var(--accent-electric), var(--accent-violet));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.landing-subtitle {
  font-size: 1.25rem;
  color: var(--text-secondary);
  margin-bottom: 0.75rem;
}

.landing-desc {
  color: var(--text-dim);
  margin-bottom: 2.5rem;
  font-size: 0.95rem;
}

.landing-content .btn {
  display: flex;
  margin: 0.5rem auto 0;
}

.landing-content .btn-ghost {
  margin-top: 1rem;
}

/* === Buttons === */
.btn {
  font-family: var(--font-heading);
  font-weight: 600;
  border: none;
  cursor: pointer;
  border-radius: var(--radius-md);
  padding: 0.8rem 2rem;
  font-size: 1rem;
  transition: all var(--transition-fast);
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent-electric), #0088cc);
  color: #fff;
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: var(--glow-electric);
}

.btn-secondary {
  background: var(--bg-card);
  color: var(--text-primary);
  border: 1px solid #333355;
}

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

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

.btn-ghost:hover {
  color: var(--text-primary);
}

.btn-glow {
  box-shadow: var(--glow-electric);
}

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

/* === Chapter Grid (Menu) === */
.chapter-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
}

.chapter-card {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  padding: 1.25rem 1.5rem;
  background: var(--bg-surface);
  border: 1px solid #222244;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
  text-decoration: none;
  color: inherit;
}

.chapter-card:hover:not(.locked) {
  border-color: var(--accent-electric);
  transform: translateX(4px);
  box-shadow: var(--glow-electric);
}

.chapter-card.locked {
  opacity: 0.4;
  cursor: not-allowed;
}

.chapter-card.completed {
  border-color: var(--accent-green);
}

.chapter-card-num {
  font-family: var(--font-heading);
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--accent-electric);
  min-width: 2.5rem;
  text-align: center;
}

.chapter-card.locked .chapter-card-num {
  color: var(--text-dim);
}

.chapter-card.completed .chapter-card-num {
  color: var(--accent-green);
}

.chapter-card-info h3 {
  font-family: var(--font-heading);
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: 0.15rem;
}

.chapter-card-info p {
  font-size: 0.85rem;
  color: var(--text-secondary);
}

.chapter-card.locked .chapter-card-info p {
  color: var(--text-dim);
}

.chapter-card-status {
  margin-left: auto;
  font-size: 1.2rem;
}

/* === Chapter View === */
#chapter-header {
  margin-bottom: 2rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid #222244;
}

.chapter-num {
  font-family: var(--font-heading);
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--accent-electric);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  display: block;
  margin-bottom: 0.25rem;
}

.chapter-heading {
  font-family: var(--font-heading);
  font-size: 2.25rem;
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.02em;
}

/* === Narrative Blocks === */
.chapter-content {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.narrative-block {
  opacity: 0;
  transform: translateY(16px);
  animation: blockReveal 0.6s ease forwards;
}

@keyframes blockReveal {
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.block-scene {
  font-size: 1.05rem;
  color: var(--text-primary);
  line-height: 1.8;
  font-style: italic;
  padding-left: 1.25rem;
  border-left: 3px solid var(--accent-amber);
}

.block-observation {
  font-size: 1rem;
  padding: 1.25rem 1.5rem;
  background: var(--bg-surface);
  border-radius: var(--radius-md);
  border-left: 3px solid var(--accent-electric);
}

.block-question {
  font-family: var(--font-heading);
  font-size: 1.35rem;
  font-weight: 600;
  color: var(--accent-amber);
  text-shadow: var(--glow-amber);
  padding: 1rem 0;
}

.block-explanation {
  font-size: 1rem;
  line-height: 1.8;
}

.block-analogy {
  font-size: 0.95rem;
  padding: 1.25rem 1.5rem;
  background: linear-gradient(135deg, #1a1a3e, #221a3e);
  border-radius: var(--radius-md);
  border-left: 3px solid var(--accent-violet);
  color: var(--text-secondary);
}

.block-analogy::before {
  content: '💡 ';
}

.block-interactive {
  padding: 2rem;
  background: var(--bg-surface);
  border: 1px dashed #444466;
  border-radius: var(--radius-md);
  text-align: center;
}

.block-key-concept {
  padding: 1.25rem 1.5rem;
  background: linear-gradient(135deg, #0a1a2e, #0a2a3e);
  border: 1px solid #00d4ff33;
  border-radius: var(--radius-md);
  font-weight: 500;
}

.block-key-concept strong {
  color: var(--accent-electric);
}

/* === Quiz === */
.quiz-wrap {
  margin-top: 2rem;
  padding-top: 2rem;
  border-top: 1px solid #222244;
}

.quiz-question {
  font-family: var(--font-heading);
  font-size: 1.2rem;
  font-weight: 600;
  margin-bottom: 1.25rem;
}

.quiz-options {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  margin-bottom: 1.5rem;
}

.quiz-option {
  display: block;
  width: 100%;
  text-align: left;
  padding: 1rem 1.25rem;
  background: var(--bg-surface);
  border: 1px solid #333355;
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: 0.95rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: var(--font-body);
}

.quiz-option:hover:not(:disabled) {
  border-color: var(--accent-electric);
  background: var(--bg-card);
}

.quiz-option.correct {
  border-color: var(--accent-green);
  background: #44ff8815;
  color: var(--accent-green);
}

.quiz-option.incorrect {
  border-color: var(--accent-rose);
  background: #ff448815;
  color: var(--accent-rose);
}

.quiz-option:disabled {
  cursor: default;
  opacity: 0.7;
}

.quiz-feedback {
  padding: 1rem 1.25rem;
  border-radius: var(--radius-md);
  font-size: 0.95rem;
  margin-bottom: 1rem;
}

.quiz-feedback.correct {
  background: #44ff8815;
  border: 1px solid #44ff8833;
  color: var(--accent-green);
}

.quiz-feedback.incorrect {
  background: #ff448815;
  border: 1px solid #ff448833;
  color: var(--accent-rose);
}

.quiz-feedback.hint {
  background: #ffaa0015;
  border: 1px solid #ffaa0033;
  color: var(--accent-amber);
}

.quiz-progress-dots {
  display: flex;
  gap: 0.5rem;
  justify-content: center;
  margin-bottom: 1.5rem;
}

.quiz-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--bg-card);
  border: 1px solid #444466;
}

.quiz-dot.active {
  border-color: var(--accent-electric);
  background: var(--accent-electric);
  box-shadow: var(--glow-electric);
}

.quiz-dot.done {
  background: var(--accent-green);
  border-color: var(--accent-green);
}

/* === Chapter Navigation === */
.chapter-navigation {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 3rem;
  padding-top: 2rem;
  border-top: 1px solid #222244;
}

/* === Graph Screen === */
#graph-screen {
  max-width: 1200px;
}

#graph-container {
  width: 100%;
  height: 600px;
  background: var(--bg-surface);
  border-radius: var(--radius-lg);
  border: 1px solid #222244;
  overflow: hidden;
  position: relative;
}

/* === Utility === */
.hidden {
  display: none !important;
}

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

/* === Scrollbar === */
::-webkit-scrollbar {
  width: 6px;
}

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

::-webkit-scrollbar-thumb {
  background: #333355;
  border-radius: 3px;
}

::-webkit-scrollbar-thumb:hover {
  background: #444466;
}

/* === Selection === */
::selection {
  background: var(--accent-electric);
  color: var(--bg-deep);
}