/* =============================================
   TURING SIMULATOR CSS
   ============================================= */

/* === VARIABLES === */
:root {
  --bg-dark: #0a0e14;
  --bg-card: #0d1117;
  --bg-elevated: #161b22;
  --border: #21262d;
  --text: #e6edf3;
  --text-dim: #8b949e;
  --text-muted: #484f58;
  --cyan: #00ffff;
  --green: #00ff95;
  --purple: #bd93f9;
  --orange: #ffb86c;
  --red: #ff5555;
  --font: 'JetBrains Mono', 'Fira Code', monospace;
}

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

/* === BASE === */
html, body {
  height: 100%;
}

body {
  font-family: var(--font);
  background: var(--bg-dark);
  color: var(--text);
  line-height: 1.6;
  display: flex;
  flex-direction: column;
}

a {
  color: inherit;
  text-decoration: none;
}

.hidden {
  display: none !important;
}

/* ===========================================
   SIMULATOR PAGE STYLES
   =========================================== */

.simulator-page {
  max-width: 900px;
  margin: 0 auto;
  padding: 40px 20px;
}

/* Input Row */
.simulator-page .input-row {
  display: flex;
  justify-content: flex-end;
  gap: 12px;
  margin-bottom: 30px;
}

.simulator-page .tape-input {
  width: 120px;
  padding: 10px 16px;
  font-family: var(--font);
  font-size: 1.1rem;
  text-align: center;
  background: var(--bg-elevated);
  border: 2px solid var(--border);
  border-radius: 6px;
  color: var(--text);
  transition: border-color 0.2s;
}

.simulator-page .tape-input:focus {
  outline: none;
  border-color: var(--cyan);
}

/* Card Base */
.simulator-page .card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  margin-bottom: 20px;
  overflow: hidden;
}

.simulator-page .card-header {
  padding: 12px 20px;
  background: var(--bg-elevated);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.15em;
  color: var(--cyan);
  border-bottom: 1px solid var(--border);
}

/* Tape Section */
.simulator-page .tape-container {
  padding: 30px 20px;
  display: flex;
  justify-content: center;
}

.simulator-page .tape {
  display: flex;
  gap: 4px;
}

.simulator-page .tape-cell {
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
  font-weight: 700;
  background: var(--bg-elevated);
  border: 2px solid var(--border);
  border-radius: 6px;
  color: var(--text);
  transition: all 0.2s ease;
}

.simulator-page .tape-cell.blank {
  color: var(--text-muted);
}

.simulator-page .tape-cell.head {
  background: var(--green);
  border-color: var(--green);
  color: var(--bg-dark);
  box-shadow: 0 0 20px rgba(0, 255, 149, 0.4);
  animation: pulse-head 1.5s ease-in-out infinite;
}

@keyframes pulse-head {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.05); }
}

/* Animation when value is written/changed */
.simulator-page .tape-cell.just-written {
  animation: flash-write 0.5s ease-out;
}

@keyframes flash-write {
  0% {
    transform: scale(1.2);
    box-shadow: 0 0 30px rgba(0, 255, 149, 0.8);
  }
  100% {
    transform: scale(1);
  }
}

.simulator-page .head-label {
  font-size: 0.65rem;
  font-weight: 500;
  letter-spacing: 0.15em;
  color: var(--text-dim);
  text-align: center;
  margin-top: 8px;
}

/* State Section */
.simulator-page .state-section {
  padding: 16px 24px;
}

.simulator-page .state-display {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
}

.simulator-page .state-indicator {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--green);
  box-shadow: 0 0 10px var(--green);
  animation: pulse-glow 1.5s ease-in-out infinite;
}

.simulator-page .state-indicator.add {
  background: var(--cyan);
  box-shadow: 0 0 10px var(--cyan);
}

.simulator-page .state-indicator.done {
  background: #ffff00;
  box-shadow: 0 0 10px #ffff00;
  animation: none;
}

@keyframes pulse-glow {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.6; }
}

.simulator-page .state-label {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-dim);
}

.simulator-page .state-value {
  font-size: 0.9rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  color: var(--green);
}

.simulator-page .state-emoji {
  font-size: 1rem;
}

.simulator-page .state-description {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-left: auto;
}

.simulator-page .status-badge {
  padding: 4px 10px;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  border-radius: 4px;
  background: rgba(0, 255, 149, 0.1);
  color: var(--green);
}

.simulator-page .status-badge.running {
  background: rgba(0, 255, 255, 0.1);
  color: var(--cyan);
}

.simulator-page .status-badge.done {
  background: rgba(255, 255, 0, 0.1);
  color: #ffff00;
}

/* Controls Section */
.simulator-page .controls-section {
  padding: 20px 24px;
}

.simulator-page .controls-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 16px;
}

.simulator-page .controls-group {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

/* Buttons */
.simulator-page .btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 18px;
  font-family: var(--font);
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  border: 2px solid;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.2s ease;
}

.simulator-page .btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.simulator-page .btn-icon {
  font-size: 0.9rem;
}

.simulator-page .btn-primary {
  background: var(--green);
  border-color: var(--green);
  color: var(--bg-dark);
}

.simulator-page .btn-primary:hover:not(:disabled) {
  box-shadow: 0 0 20px rgba(0, 255, 149, 0.4);
  transform: translateY(-1px);
}

.simulator-page .btn-secondary {
  background: transparent;
  border-color: var(--cyan);
  color: var(--cyan);
}

.simulator-page .btn-secondary:hover:not(:disabled) {
  box-shadow: 0 0 20px rgba(0, 255, 255, 0.3);
  transform: translateY(-1px);
}

.simulator-page .btn-outline {
  background: transparent;
  border-color: var(--orange);
  color: var(--orange);
}

.simulator-page .btn-outline:hover:not(:disabled) {
  box-shadow: 0 0 20px rgba(255, 184, 108, 0.3);
}

.simulator-page .btn-danger {
  background: transparent;
  border-color: var(--red);
  color: var(--red);
}

.simulator-page .btn-danger:hover:not(:disabled) {
  box-shadow: 0 0 20px rgba(255, 85, 85, 0.3);
  transform: translateY(-1px);
}

.simulator-page .btn-set {
  background: transparent;
  border-color: var(--green);
  color: var(--green);
}

.simulator-page .btn-set:hover:not(:disabled) {
  box-shadow: 0 0 20px rgba(0, 255, 149, 0.3);
  transform: translateY(-1px);
}

/* Speed Control */
.simulator-page .speed-control {
  display: flex;
  align-items: center;
  gap: 12px;
}

.simulator-page .speed-label {
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  color: var(--text-dim);
}

.simulator-page .speed-slider {
  width: 100px;
  height: 6px;
  -webkit-appearance: none;
  appearance: none;
  background: linear-gradient(to right, var(--cyan) 50%, var(--border) 50%);
  border-radius: 3px;
  cursor: pointer;
}

.simulator-page .speed-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 14px;
  height: 14px;
  background: var(--cyan);
  border-radius: 50%;
  cursor: pointer;
  box-shadow: 0 0 10px rgba(0, 255, 255, 0.5);
}

.simulator-page .speed-value {
  font-size: 0.75rem;
  font-family: var(--font);
  color: var(--text-muted);
  min-width: 30px;
}

/* Rules Section - 2 columns side by side like original */
.simulator-page .rules-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
  padding: 0;
}

@media (max-width: 768px) {
  .simulator-page .rules-grid {
    grid-template-columns: 1fr;
  }
}

.simulator-page .state-card {
  background: var(--bg-elevated);
  border-radius: 8px;
  overflow: hidden;
}

.simulator-page .state-card-header {
  padding: 12px 16px;
  background: var(--bg-dark);
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.15em;
  color: var(--green);
  text-align: center;
  border-bottom: 1px solid var(--border);
}

/* Rules Table - like original React design */
.simulator-page .rules-table {
  width: 100%;
  border-collapse: collapse;
  font-family: var(--font);
  font-size: 0.85rem;
}

.simulator-page .rules-table thead th {
  padding: 8px 12px;
  text-align: left;
  font-size: 0.65rem;
  font-weight: 700;
  letter-spacing: 0.15em;
  color: var(--text-muted);
  border-bottom: 1px solid var(--border);
  background: var(--bg-dark);
}

.simulator-page .rules-table tbody tr {
  transition: all 0.2s;
}

.simulator-page .rules-table tbody tr:hover {
  background: rgba(255, 255, 255, 0.03);
}

.simulator-page .rules-table tbody tr.active {
  background: rgba(0, 255, 149, 0.15);
  box-shadow: inset 3px 0 0 var(--green);
}

.simulator-page .rules-table tbody td {
  padding: 10px 12px;
  border-bottom: 1px solid var(--border);
  color: var(--text);
}

.simulator-page .rules-table tbody td.see {
  font-weight: 700;
  color: var(--cyan);
}

.simulator-page .rules-table tbody td.write {
  color: var(--text);
}

.simulator-page .rules-table tbody td.move {
  font-weight: 600;
  color: var(--orange);
}

.simulator-page .rules-table tbody td.goto {
  font-weight: 600;
  color: var(--green);
}

.simulator-page .rules-table tbody tr:last-child td {
  border-bottom: none;
}

/* Algorithm Footer */
.simulator-page .algo-footer {
  text-align: center;
  padding: 30px 0;
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.2em;
  color: var(--text-muted);
}

/* Challenge Prompt */
.simulator-page .challenge-prompt .card {
  text-align: center;
  padding: 40px;
}

.simulator-page .text-green {
  color: var(--green);
}

.simulator-page .text-muted {
  color: var(--text-muted);
}

.simulator-page .mt-2 {
  margin-top: 8px;
}

.simulator-page .mt-3 {
  margin-top: 12px;
}

/* END SIMULATOR PAGE STYLES */

/* === OVERLAYS (scanlines, grid) === */
.scanlines {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  pointer-events: none;
  z-index: 1000;
  background: repeating-linear-gradient(
    0deg,
    rgba(0, 0, 0, 0.1) 0px,
    rgba(0, 0, 0, 0.1) 1px,
    transparent 1px,
    transparent 3px
  );
  opacity: 0.3;
}

.grid-bg {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  pointer-events: none;
  z-index: -1;
  background-image:
    linear-gradient(rgba(0, 255, 149, 0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(0, 255, 149, 0.03) 1px, transparent 1px);
  background-size: 50px 50px;
}

/* === NAVIGATION === */
.nav {
  background: rgba(10, 14, 20, 0.95);
  border-bottom: 1px solid var(--border);
  padding: 0 24px;
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-inner {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 60px;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: 12px;
}

.brand-logo {
  font-size: 1.1rem;
  font-weight: 700;
}

.logo-bracket {
  color: var(--text-muted);
}

.logo-symbol {
  color: var(--cyan);
}

.brand-text {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-dim);
  letter-spacing: 1px;
}

.brand-dot {
  color: var(--green);
}

.nav-links {
  display: flex;
  gap: 8px;
}

.nav-link {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  border-radius: 6px;
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text-dim);
  transition: all 0.15s ease;
}

.nav-link:hover {
  background: var(--bg-elevated);
  color: var(--text);
}

.nav-link.active {
  background: var(--bg-elevated);
  color: var(--cyan);
}

.link-icon {
  font-size: 0.7rem;
  color: var(--text-muted);
}

.link-text {
  letter-spacing: 1px;
}

.nav-status {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.75rem;
  color: var(--text-muted);
}

.status-indicator {
  width: 8px;
  height: 8px;
  background: var(--green);
  border-radius: 50%;
  box-shadow: 0 0 8px var(--green);
}

.status-text {
  letter-spacing: 1px;
}

/* === NAVIGATION MOBILE === */
@media (max-width: 600px) {
  .nav {
    padding: 0 12px;
  }

  .nav-inner {
    height: 48px;
  }

  .nav-brand {
    gap: 6px;
  }

  .logo-bracket {
    display: none;
  }

  .brand-text {
    display: none;
  }

  .nav-links {
    gap: 4px;
  }

  .nav-link {
    padding: 6px 10px;
    font-size: 0.7rem;
  }

  .link-icon {
    display: none;
  }

  .nav-status {
    display: none;
  }
}

/* === MAIN CONTENT === */
.main {
  flex: 1;
  padding: 20px 24px;
}

/* === LESSON PAGE === */
.lesson-page {
  max-width: 700px;
  margin: 0 auto;
}

/* === PROGRESS BAR === */
.lesson-progress {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-bottom: 16px;
}

.progress-bar {
  flex: 1;
  height: 4px;
  background: var(--bg-elevated);
  border-radius: 2px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--green), var(--cyan));
  transition: width 0.3s ease;
}

.progress-text {
  font-size: 0.8rem;
  color: var(--text-muted);
  white-space: nowrap;
}

/* === LESSON CONTAINER === */
.lesson-container {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 24px 32px;
}

.lesson-title {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 20px;
}

.lesson-content {
  margin-bottom: 20px;
}

/* === LESSON NAVIGATION === */
.lesson-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-top: 16px;
  border-top: 1px solid var(--border);
  margin-top: 20px;
}

/* === BUTTONS === */
button,
.btn-primary,
.btn-secondary,
.btn-success {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font);
  font-size: 0.85rem;
  font-weight: 600;
  padding: 12px 24px;
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.15s ease;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  text-decoration: none;
  border: 2px solid;
}

.btn-primary {
  background: var(--cyan);
  border-color: var(--cyan);
  color: var(--bg-dark);
}

.btn-primary:hover {
  box-shadow: 0 0 20px rgba(0, 255, 255, 0.4);
  transform: translateY(-1px);
}

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

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

.btn-success {
  background: var(--green);
  border-color: var(--green);
  color: var(--bg-dark);
}

.btn-success:hover {
  box-shadow: 0 0 20px rgba(0, 255, 149, 0.4);
}

.btn-large {
  padding: 14px 32px;
  font-size: 0.9rem;
}

button:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

/* === FOOTER === */
.footer {
  background: var(--bg-card);
  border-top: 1px solid var(--border);
  padding: 16px 24px;
}

.footer-inner {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 0.75rem;
  color: var(--text-muted);
}

.footer-left {
  display: flex;
  align-items: center;
  gap: 8px;
}

.terminal-prompt {
  color: var(--green);
}

.footer-text {
  color: var(--text-dim);
}

.ascii-art {
  color: var(--text-muted);
  font-style: italic;
}

.copyright {
  color: var(--text-muted);
  font-size: 0.75rem;
}

.cursor-blink {
  animation: blink 1s infinite;
}

@keyframes blink {
  0%, 50% { opacity: 1; }
  51%, 100% { opacity: 0; }
}

/* =============================================
   LESSON 1: The Magic Trick
   ============================================= */

/* Hook intro */
.hook-intro {
  text-align: center;
  padding: 32px 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

.hook-line {
  font-size: 3rem;
  color: var(--cyan);
  font-weight: 700;
  margin: 0;
  text-shadow: 0 0 30px rgba(0, 255, 255, 0.5);
  animation: pulseGlow 2s ease-in-out infinite;
}

@keyframes pulseGlow {
  0%, 100% { text-shadow: 0 0 30px rgba(0, 255, 255, 0.5); }
  50% { text-shadow: 0 0 50px rgba(0, 255, 255, 0.8), 0 0 80px rgba(0, 255, 255, 0.4); }
}

/* Practice section */
.practice-section {
  margin-top: 20px;
}

.practice-exercise {
  background: var(--bg-elevated);
  border-radius: 8px;
  padding: 32px;
}

/* Magic demo */
.magic-demo-container {
  text-align: center;
}

.demo-intro {
  padding: 20px 0;
}

.demo-prompt {
  font-size: 1rem;
  color: var(--text-dim);
  margin-bottom: 12px;
}

.demo-prompt strong {
  color: var(--cyan);
}

.demo-context {
  margin: 24px 0;
  padding: 16px;
  background: var(--bg-dark);
  border-radius: 6px;
  font-size: 0.9rem;
  color: var(--text-dim);
}

.binary {
  color: var(--green);
  font-weight: 600;
}

/* Magic simulator */
.magic-simulator {
  padding: 24px 0;
}

.sim-state {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  margin-bottom: 24px;
}

.state-emoji {
  font-size: 1.5rem;
}

.state-label {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--green);
  letter-spacing: 2px;
}

/* Tape */
.tape-wrapper {
  margin: 24px 0;
  position: relative;
}

.tape {
  display: flex;
  justify-content: center;
  gap: 4px;
}

.tape-cell {
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-dark);
  border: 2px solid var(--border);
  border-radius: 6px;
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--text);
  transition: all 0.2s ease;
}

.tape-cell.blank {
  color: var(--text-muted);
}

.tape-cell.head {
  background: var(--green);
  border-color: var(--green);
  color: var(--bg-dark);
  box-shadow: 0 0 15px rgba(0, 255, 149, 0.5);
  transform: scale(1.1);
}

.head-indicator {
  text-align: center;
  margin-top: 8px;
  font-size: 0.7rem;
  font-weight: 700;
  color: var(--green);
  letter-spacing: 2px;
}

.sim-explanation {
  margin: 20px 0;
  padding: 12px;
  background: var(--bg-dark);
  border-radius: 6px;
  font-size: 0.9rem;
  color: var(--text-dim);
}

.step-counter {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.step-counter strong {
  color: var(--cyan);
}

/* Magic result */
.magic-result {
  padding: 24px 0;
}

.result-success {
  margin-bottom: 24px;
}

.result-math {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 8px;
}

.result-decimal {
  font-size: 1rem;
  color: var(--text-dim);
}

.result-reveal {
  margin: 32px 0;
}

.result-reveal p {
  font-size: 1.1rem;
  color: var(--text-dim);
  margin-bottom: 12px;
}

.result-reveal strong {
  color: var(--cyan);
}

.reveal-punchline {
  font-size: 1.3rem !important;
  color: var(--green) !important;
  font-weight: 700;
}

/* =============================================
   LESSON 2: The Tape
   ============================================= */

/* Concept intro */
.concept-intro {
  margin-bottom: 20px;
}

.concept-intro .lead {
  font-size: 1.1rem;
  color: var(--text);
  margin-bottom: 8px;
}

.concept-intro p {
  color: var(--text-dim);
  margin-bottom: 8px;
}

.concept-intro strong {
  color: var(--cyan);
}

/* Tape visual demo - HORIZONTAL */
.tape-visual-demo {
  display: flex;
  justify-content: center;
  gap: 4px;
  margin: 20px 0;
}

.tape-visual-demo.horizontal {
  flex-direction: row;
}

.tape-visual-demo .tape-cell {
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-dark);
  border: 2px solid var(--border);
  border-radius: 6px;
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--text);
}

.tape-visual-demo .tape-cell.blank {
  color: var(--text-muted);
}

.tape-visual-demo .tape-cell.head {
  background: var(--green);
  border-color: var(--green);
  color: var(--bg-dark);
  box-shadow: 0 0 15px rgba(0, 255, 149, 0.5);
  transform: scale(1.1);
}

/* Insight box */
.insight-box {
  background: var(--bg-elevated);
  border-left: 3px solid var(--cyan);
  padding: 16px 20px;
  margin: 20px 0;
  border-radius: 0 8px 8px 0;
}

.insight-box p {
  color: var(--text-dim);
  margin-bottom: 8px;
}

.insight-box strong {
  color: var(--cyan);
}

.insight-box ul {
  list-style: none;
  margin: 12px 0 0 0;
}

.insight-box li {
  color: var(--text-dim);
  margin-bottom: 4px;
  padding-left: 16px;
  position: relative;
}

.insight-box li::before {
  content: '>';
  position: absolute;
  left: 0;
  color: var(--green);
}

.insight-box li strong {
  color: var(--green);
}

/* Wow connection */
.wow-connection {
  margin: 20px 0;
  padding: 16px;
  background: rgba(0, 255, 255, 0.05);
  border-radius: 8px;
}

.wow-connection p {
  color: var(--text-dim);
  margin-bottom: 8px;
}

.wow-connection p:last-child {
  margin-bottom: 0;
}

.wow-connection strong {
  color: var(--orange);
}

/* Practice prompt */
.practice-prompt {
  color: var(--text-dim);
  margin-bottom: 16px;
  font-size: 0.9rem;
}

/* Interactive tape */
.practice-tape {
  margin: 16px 0;
}

.practice-tape .tape {
  display: flex;
  justify-content: center;
  gap: 4px;
}

.practice-tape .tape-cell {
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-dark);
  border: 2px solid var(--border);
  border-radius: 6px;
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--text);
  cursor: pointer;
  transition: all 0.15s ease;
}

.practice-tape .tape-cell:hover {
  border-color: var(--cyan);
}

.practice-tape .tape-cell.selected {
  background: var(--cyan);
  border-color: var(--cyan);
  color: var(--bg-dark);
  box-shadow: 0 0 15px rgba(0, 255, 255, 0.5);
}

.practice-tape .tape-cell.head {
  background: var(--green);
  border-color: var(--green);
  color: var(--bg-dark);
  box-shadow: 0 0 15px rgba(0, 255, 149, 0.5);
  transform: scale(1.1);
}

.practice-tape .tape-cell.blank {
  color: var(--text-muted);
}

.practice-tape .tape-cell.head.blank {
  color: var(--bg-dark);
}

/* Cell inspector */
.cell-inspector {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 20px;
  margin: 16px 0;
  padding: 12px;
  background: var(--bg-dark);
  border-radius: 8px;
}

.inspector-content {
  display: flex;
  align-items: center;
  gap: 8px;
}

.inspector-label {
  color: var(--text-muted);
  font-size: 0.85rem;
}

.inspector-value {
  color: var(--cyan);
  font-weight: 700;
  font-size: 1.1rem;
}

.inspector-edit {
  display: flex;
  gap: 8px;
}

.edit-btn {
  width: 36px;
  height: 36px;
  padding: 0;
  font-size: 1rem;
  background: var(--bg-elevated);
  border: 2px solid var(--border);
  color: var(--text);
}

.edit-btn:hover {
  border-color: var(--green);
  color: var(--green);
}

/* Tape stats */
.tape-stats {
  display: flex;
  justify-content: center;
  gap: 24px;
  margin-top: 16px;
  font-size: 0.9rem;
}

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

.tape-stats strong {
  color: var(--green);
}

/* =============================================
   LESSON 3-8: Common Lesson Styles
   ============================================= */

/* Lead text */
.lead {
  font-size: 1.1rem;
  color: var(--text);
  margin-bottom: 8px;
}

/* Solution/transition intro */
.solution-intro,
.transition-text {
  margin: 16px 0;
}

.solution-intro p,
.transition-text p {
  color: var(--text-dim);
  margin-bottom: 8px;
}

.solution-intro strong,
.transition-text strong {
  color: var(--cyan);
}

/* ============================================
   LOCK PUZZLE - Puzzle Styles
   ============================================ */
.puzzle-intro {
  margin-bottom: 24px;
  text-align: center;
}

.puzzle-intro .lead {
  color: var(--text);
  font-size: 1.2rem;
  margin-bottom: 8px;
}

.puzzle-intro p {
  color: var(--text-dim);
}

.puzzle-intro strong {
  color: var(--cyan);
  font-family: var(--font);
}

.puzzle-question {
  margin: 20px 0;
  padding: 16px;
  background: rgba(255, 107, 53, 0.1);
  border-left: 3px solid var(--orange);
  border-radius: 0 8px 8px 0;
}

.puzzle-question p {
  color: var(--text);
  margin: 0 0 8px 0;
}

.puzzle-question p:last-child {
  margin-bottom: 0;
}

.puzzle-question p.dim {
  color: var(--text-muted);
  font-size: 0.9rem;
  font-family: var(--font);
}

.puzzle-question strong {
  color: var(--orange);
}

.puzzle-insight {
  margin: 20px 0;
  padding: 16px;
  background: var(--bg-elevated);
  border-radius: 8px;
}

.puzzle-insight p {
  color: var(--text);
  margin: 0 0 8px 0;
}

.puzzle-insight p:last-child {
  margin-bottom: 0;
}

.puzzle-insight p.dim {
  color: var(--text-muted);
  font-size: 0.9rem;
}

.puzzle-insight strong {
  color: var(--cyan);
}

.puzzle-reveal {
  margin: 24px 0;
  padding: 20px;
  background: linear-gradient(135deg, rgba(0, 255, 255, 0.1), rgba(0, 255, 149, 0.1));
  border: 2px solid var(--cyan);
  border-radius: 12px;
  text-align: center;
}

.puzzle-reveal p {
  color: var(--text);
  font-size: 1.1rem;
  margin: 0;
}

.puzzle-reveal em {
  color: var(--text-dim);
  font-style: normal;
}

.puzzle-reveal strong {
  color: var(--green);
  font-size: 1.3rem;
}

/* ============================================
   STATES LESSON - Lock Timeline
   ============================================ */
.lock-timeline {
  margin: 24px 0;
  padding: 20px;
  background: var(--bg-elevated);
  border-radius: 12px;
}

.lock-timeline-title {
  text-align: center;
  color: var(--text-dim);
  font-size: 0.85rem;
  margin-bottom: 16px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.lock-timeline-flow {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0;
  flex-wrap: wrap;
}

.lock-step {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
  padding: 12px 16px;
  min-width: 70px;
}

.lock-step-label {
  padding: 8px 12px;
  background: var(--bg-dark);
  border: 2px solid var(--cyan);
  border-radius: 6px;
  font-weight: 700;
  font-size: 0.75rem;
  font-family: var(--font-mono);
  color: var(--cyan);
  letter-spacing: 0.03em;
}

.lock-step.open .lock-step-label {
  border-color: var(--green);
  background: rgba(0, 255, 149, 0.15);
  color: var(--green);
}

.lock-step-meaning {
  font-size: 0.65rem;
  color: var(--text-muted);
  text-align: center;
  line-height: 1.3;
  margin-top: 4px;
}

.lock-step.open .lock-step-meaning {
  color: var(--green);
}

.lock-step-arrow {
  width: 24px;
  height: 2px;
  background: var(--border);
  position: relative;
}

.lock-step-arrow::after {
  content: '';
  position: absolute;
  right: 0;
  top: 50%;
  transform: translateY(-50%);
  border: 4px solid transparent;
  border-left-color: var(--border);
}

/* Key Insight Box */
.key-insight {
  margin: 24px 0;
  border-radius: 12px;
  overflow: hidden;
  border: 2px solid var(--cyan);
  background: rgba(0, 255, 255, 0.05);
}

.key-insight-header {
  background: var(--cyan);
  color: var(--bg-dark);
  padding: 8px 16px;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-align: center;
}

.key-insight-content {
  padding: 16px 20px;
  text-align: center;
}

.key-insight-content p {
  margin: 0;
  color: var(--text);
  font-size: 1.05rem;
}

.key-insight-content p.dim {
  color: var(--text-muted);
  font-size: 0.85rem;
  margin-top: 6px;
}

.key-insight-content strong {
  color: var(--cyan);
}

/* Transition Box */
.transition-box {
  margin: 24px 0;
  padding: 16px 20px;
  background: var(--bg-elevated);
  border-left: 3px solid var(--orange);
  border-radius: 0 8px 8px 0;
  text-align: center;
}

.transition-box p {
  margin: 0;
  color: var(--text);
}

.transition-box p.dim {
  color: var(--text-muted);
  font-size: 0.85rem;
  margin-top: 4px;
}

/* TM States Showcase */
.tm-states-showcase {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0;
  margin: 24px 0;
  flex-wrap: wrap;
}

.tm-state-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  padding: 20px 24px;
  background: var(--bg-elevated);
  border: 2px solid var(--border);
  border-radius: 12px;
  min-width: 110px;
  transition: all 0.2s ease;
}

.tm-state-card.cyan {
  border-color: var(--cyan);
}

.tm-state-card.orange {
  border-color: var(--orange);
}

.tm-state-card.green {
  border-color: var(--green);
}

.tm-state-icon {
  font-size: 1.8rem;
}

.tm-state-name {
  font-weight: 700;
  font-size: 1rem;
  color: var(--text);
}

.tm-state-card.cyan .tm-state-name {
  color: var(--cyan);
}

.tm-state-card.orange .tm-state-name {
  color: var(--orange);
}

.tm-state-card.green .tm-state-name {
  color: var(--green);
}

.tm-state-desc {
  font-size: 0.75rem;
  color: var(--text-muted);
  text-align: center;
}

.tm-states-arrow {
  width: 32px;
  height: 2px;
  background: var(--border);
  position: relative;
  margin: 0 4px;
}

.tm-states-arrow::after {
  content: '';
  position: absolute;
  right: 0;
  top: 50%;
  transform: translateY(-50%);
  border: 5px solid transparent;
  border-left-color: var(--border);
}

/* Conclusion Box */
.conclusion-box {
  margin: 24px 0;
  padding: 20px;
  background: var(--bg-elevated);
  border-radius: 12px;
  text-align: center;
}

.conclusion-box p {
  margin: 0 0 8px 0;
  color: var(--text);
}

.conclusion-box p:last-child {
  margin-bottom: 0;
}

.conclusion-box p.highlight {
  font-family: var(--font-mono);
  font-size: 0.9rem;
  padding: 8px 12px;
  background: var(--bg-dark);
  border-radius: 6px;
  margin: 8px 0;
  display: inline-block;
}

.conclusion-box p.highlight strong {
  color: var(--cyan);
}

.conclusion-box p.dim {
  color: var(--text-muted);
  font-size: 0.85rem;
  margin-top: 12px;
}

/* Legacy lock styles kept for compatibility */
.lock-arrow {
  color: var(--text-muted);
  font-size: 1.2rem;
}

/* ===========================================
   LESSON 6 LOCK PUZZLE - Scoped styles
   These styles ONLY apply to the lock in lesson 6
   =========================================== */

#practice-lock .lock-simulator {
  display: flex;
  flex-direction: column;
  align-items: center;
  margin: 30px auto;
  position: relative;
  width: fit-content;
}

/* Lock Shackle (the U-shaped part) */
#practice-lock .lock-shackle {
  position: relative;
  width: 100px;
  height: 60px;
  margin-bottom: -10px;
  transition: transform 0.5s ease;
}

#practice-lock .lock-shackle.open {
  transform: translateY(-20px) rotate(-30deg);
  transform-origin: right bottom;
}

#practice-lock .shackle-left,
#practice-lock .shackle-right {
  position: absolute;
  width: 12px;
  height: 50px;
  background: linear-gradient(90deg, #888, #aaa, #888);
  border-radius: 6px 6px 0 0;
  bottom: 0;
}

#practice-lock .shackle-left {
  left: 15px;
}

#practice-lock .shackle-right {
  right: 15px;
}

#practice-lock .shackle-top {
  position: absolute;
  top: 0;
  left: 15px;
  right: 15px;
  height: 25px;
  border: 12px solid #999;
  border-bottom: none;
  border-radius: 35px 35px 0 0;
  background: transparent;
}

/* Lock Body */
#practice-lock .lock-body {
  background: linear-gradient(145deg, #444, #2a2a2a);
  border-radius: 12px;
  padding: 20px;
  box-shadow:
    0 8px 25px rgba(0,0,0,0.4),
    inset 0 1px 0 rgba(255,255,255,0.1);
  border: 2px solid #555;
  min-width: 200px;
}

/* Lock Display */
#practice-lock .lock-display {
  display: flex;
  justify-content: center;
  gap: 8px;
  margin-bottom: 12px;
  padding: 12px;
  background: #111;
  border-radius: 6px;
  border: 2px solid #333;
}

#practice-lock .lock-digit {
  font-family: 'Courier New', monospace;
  font-size: 1.8rem;
  font-weight: bold;
  color: #00ff95;
  text-shadow: 0 0 10px rgba(0, 255, 149, 0.5);
  width: 30px;
  text-align: center;
}

/* Lock Status */
#practice-lock .lock-status {
  text-align: center;
  padding: 8px;
  font-size: 0.85rem;
  color: #aaa;
  margin-bottom: 12px;
  border-radius: 4px;
  background: rgba(0,0,0,0.3);
}

#practice-lock .lock-status.success {
  color: #00ff95;
  background: rgba(0, 255, 149, 0.1);
  font-weight: bold;
  animation: pulse-success 0.5s ease;
}

#practice-lock .lock-status.error {
  color: #ff4444;
  background: rgba(255, 68, 68, 0.1);
}

@keyframes pulse-success {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.05); }
}

/* Lock Keypad */
#practice-lock .lock-keypad {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
}

#practice-lock .lock-keypad .key {
  width: 50px;
  height: 50px;
  border: none;
  border-radius: 8px;
  font-size: 1.2rem;
  font-weight: bold;
  cursor: pointer;
  background: linear-gradient(145deg, #555, #3a3a3a);
  color: #fff;
  box-shadow:
    0 3px 6px rgba(0,0,0,0.3),
    inset 0 1px 0 rgba(255,255,255,0.1);
  transition: all 0.1s ease;
}

#practice-lock .lock-keypad .key:hover {
  background: linear-gradient(145deg, #666, #444);
  transform: translateY(-1px);
}

#practice-lock .lock-keypad .key:active {
  transform: translateY(2px);
  box-shadow: 0 1px 2px rgba(0,0,0,0.3);
}

#practice-lock .lock-keypad .key-clear {
  background: linear-gradient(145deg, #664444, #443333);
  color: #ff8888;
}

#practice-lock .lock-keypad .key-clear:hover {
  background: linear-gradient(145deg, #774444, #553333);
}

#practice-lock .lock-keypad .key-enter {
  background: linear-gradient(145deg, #446644, #334433);
  color: #88ff88;
}

#practice-lock .lock-keypad .key-enter:hover {
  background: linear-gradient(145deg, #447744, #335533);
}

/* Lock intro text */
#practice-lock .lock-intro {
  text-align: center;
  margin-bottom: 10px;
}

#practice-lock .lock-intro p {
  color: var(--text-dim);
}

#practice-lock .lock-intro strong {
  color: var(--cyan);
  font-family: monospace;
  letter-spacing: 2px;
}

/* END LESSON 6 LOCK STYLES */

/* States visual */
.states-visual {
  display: flex;
  justify-content: center;
  gap: 16px;
  margin: 20px 0;
  flex-wrap: wrap;
}

.state-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
  padding: 16px 24px;
  background: var(--bg-elevated);
  border: 2px solid var(--border);
  border-radius: 8px;
  min-width: 100px;
}

.state-card.scan {
  border-color: var(--cyan);
}

.state-card.add {
  border-color: var(--orange);
}

.state-card.done {
  border-color: var(--green);
}

.state-emoji {
  font-size: 1.5rem;
}

.state-desc {
  font-size: 0.75rem;
  color: var(--text-muted);
}

/* Rules with states */
.rules-with-states {
  margin: 20px 0;
  padding: 16px;
  background: var(--bg-elevated);
  border-radius: 8px;
}

.rules-with-states h3 {
  color: var(--text);
  margin-bottom: 12px;
  font-size: 1rem;
}

.rules-with-states > p {
  color: var(--text-dim);
  margin-bottom: 16px;
  font-size: 0.9rem;
}

.rules-group {
  margin-bottom: 16px;
}

.rules-group:last-child {
  margin-bottom: 0;
}

.rules-group h4 {
  color: var(--text);
  margin-bottom: 8px;
  font-size: 0.9rem;
}

/* Rules display - table style like simulator */
.rules-display {
  margin: 20px 0;
  background: var(--bg-elevated);
  border-radius: 8px;
  overflow: hidden;
}

.rules-display .rule,
.rules-display .rule-item {
  display: flex;
  align-items: center;
  padding: 12px 16px;
  border-bottom: 1px solid var(--border);
  font-size: 0.9rem;
  color: var(--text-dim);
  font-family: var(--font);
}

.rules-display .rule:last-child,
.rules-display .rule-item:last-child {
  border-bottom: none;
}

.rules-display .rule strong,
.rules-display .rule-item strong {
  color: var(--cyan);
  margin: 0 4px;
}

.rules-display .rule-item.active {
  background: rgba(0, 255, 149, 0.1);
  color: var(--text);
}

.rules-display .rule-item.active strong {
  color: var(--green);
}

/* Legacy rule style for rules-group */
.rule {
  color: var(--text-dim);
  font-size: 0.85rem;
  padding: 4px 0;
  padding-left: 16px;
  position: relative;
}

.rules-group .rule::before {
  content: '>';
  position: absolute;
  left: 0;
  color: var(--green);
}

.rules-group .rule strong {
  color: var(--orange);
}

/* State display */
.state-display {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  padding: 16px;
  background: var(--bg-dark);
  border-radius: 8px;
  margin-bottom: 16px;
}

.state-label {
  font-weight: 700;
  color: var(--green);
  font-size: 1.1rem;
  letter-spacing: 2px;
}

/* Rules reference columns */
.rules-reference {
  display: flex;
  justify-content: center;
  gap: 24px;
  margin: 16px 0;
}

.rules-col {
  padding: 12px 16px;
  background: var(--bg-dark);
  border: 2px solid var(--border);
  border-radius: 8px;
  min-width: 140px;
}

.rules-col.active-col {
  border-color: var(--cyan);
  background: rgba(0, 255, 255, 0.05);
}

.rules-col h4 {
  color: var(--text);
  margin-bottom: 8px;
  font-size: 0.85rem;
}

.rule-item {
  font-size: 0.8rem;
  color: var(--text-muted);
  padding: 4px 0;
}

.rule-item.active {
  color: var(--green);
  font-weight: 700;
}

/* Sim status/action */
.sim-status {
  display: flex;
  justify-content: center;
  gap: 24px;
  margin: 12px 0;
  font-size: 0.9rem;
  color: var(--text-muted);
}

.sim-status strong {
  color: var(--cyan);
}

.sim-action {
  text-align: center;
  color: var(--text-dim);
  font-size: 0.85rem;
  font-style: italic;
  margin-bottom: 16px;
}

/* Practice controls */
.practice-controls {
  display: flex;
  justify-content: center;
  gap: 12px;
  margin: 16px 0;
}

.practice-controls button {
  padding: 10px 20px;
}

/* Step counter */
.step-counter {
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-top: 12px;
}

.step-counter strong {
  color: var(--cyan);
}

/* States result */
.states-result,
.simple-result,
.quiz-result {
  margin-top: 16px;
  padding: 16px;
  background: rgba(0, 255, 149, 0.1);
  border: 2px solid var(--green);
  border-radius: 8px;
  text-align: center;
}

.states-result .success,
.quiz-result .success {
  color: var(--green);
  font-size: 1rem;
  margin-bottom: 8px;
}

.states-result p,
.quiz-result p {
  color: var(--text-dim);
  font-size: 0.9rem;
}

/* =============================================
   LESSON 3: The Head
   ============================================= */

/* Head display */
.head-display {
  display: flex;
  flex-direction: column;
  align-items: center;
  margin: 20px 0;
}

.head-pointer {
  font-size: 2rem;
  color: var(--green);
}

.head-insight {
  margin-top: 8px;
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* Actions box */
.actions-box {
  margin: 20px 0;
}

.action-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.action-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 16px;
  background: var(--bg-elevated);
  border-radius: 8px;
}

.action-icon {
  font-size: 1.2rem;
}

.action-text {
  color: var(--text-dim);
}

.action-text strong {
  color: var(--cyan);
}

/* Constraint box */
.constraint-box {
  margin: 20px 0;
  padding: 16px;
  background: var(--bg-elevated);
  border-left: 3px solid var(--orange);
  border-radius: 0 8px 8px 0;
}

.constraint-title {
  color: var(--orange);
  font-weight: 700;
  margin-bottom: 8px;
}

.constraint-box p {
  color: var(--text-dim);
}

/* Analogy */
.analogy {
  margin: 20px 0;
  padding: 16px;
  background: var(--bg-elevated);
  border-radius: 8px;
}

.analogy p {
  color: var(--text-dim);
}

.analogy strong {
  color: var(--cyan);
}

/* =============================================
   LESSON 8: Quiz/Summary
   ============================================= */

/* Quiz input */
.quiz-input {
  display: flex;
  align-items: center;
  gap: 12px;
  margin: 12px 0;
}

.quiz-input label {
  color: var(--text-dim);
  font-size: 0.9rem;
}

.quiz-input input[type="text"] {
  width: 100px;
  padding: 8px 12px;
  font-family: var(--font);
  font-size: 1rem;
  background: var(--bg-dark);
  border: 2px solid var(--border);
  border-radius: 6px;
  color: var(--text);
}

.quiz-input input[type="text"]:focus {
  outline: none;
  border-color: var(--cyan);
}

/* Number pad */
.number-pad {
  display: flex;
  justify-content: center;
  gap: 8px;
  margin: 16px 0;
}

.number-pad button {
  width: 44px;
  height: 44px;
  padding: 0;
  font-size: 1.1rem;
}

/* Summary list */
.summary-list {
  margin: 16px 0;
}

.summary-item {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 12px 0;
  border-bottom: 1px solid var(--border);
}

.summary-item:last-child {
  border-bottom: none;
}

.summary-num {
  color: var(--cyan);
  font-weight: 700;
  min-width: 20px;
}

.summary-text {
  color: var(--text-dim);
}

.summary-text strong {
  color: var(--text);
}

/* ===========================================
   CHALLENGE PAGE STYLES
   =========================================== */

.challenge-page {
  max-width: 900px;
  margin: 0 auto;
  padding: 40px 20px;
}

.challenge-page h1 {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 24px;
  color: var(--text);
}

.challenge-page h2 {
  font-size: 1.2rem;
  font-weight: 600;
  margin-bottom: 16px;
  color: var(--cyan);
}

.challenge-page h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 12px;
  color: var(--text);
}

.challenge-container {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

/* Challenge Card */
.challenge-page .challenge-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 24px;
}

.challenge-page .challenge-task h2 {
  color: var(--text);
  margin-bottom: 12px;
}

.challenge-page .task-detail {
  color: var(--text-dim);
  margin-bottom: 16px;
}

/* Output Spec Box */
.challenge-page .output-spec,
.challenge-page .spec-box {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 16px;
  margin: 16px 0;
}

.challenge-page .spec-box ul {
  list-style: none;
  margin: 12px 0;
}

.challenge-page .spec-box li {
  padding: 6px 0;
  color: var(--text-dim);
}

.challenge-page .spec-box code {
  background: var(--bg-dark);
  padding: 2px 8px;
  border-radius: 4px;
  color: var(--cyan);
  font-family: var(--font);
}

/* Test Table */
.challenge-page .test-table {
  width: 100%;
  border-collapse: collapse;
  margin: 16px 0;
}

.challenge-page .test-table th,
.challenge-page .test-table td {
  padding: 12px 16px;
  text-align: left;
  border-bottom: 1px solid var(--border);
}

.challenge-page .test-table th {
  background: var(--bg-elevated);
  color: var(--text-dim);
  font-weight: 600;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.challenge-page .test-table td {
  color: var(--text);
}

.challenge-page .test-table code {
  background: var(--bg-dark);
  padding: 4px 10px;
  border-radius: 4px;
  color: var(--green);
  font-family: var(--font);
}

/* System Info Grid */
.challenge-page .system-info {
  margin: 20px 0;
}

.challenge-page .info-grid {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.challenge-page .info-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px;
  background: var(--bg-elevated);
  border-radius: 8px;
}

.challenge-page .badge {
  padding: 4px 12px;
  border-radius: 4px;
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.challenge-page .badge.start {
  background: var(--cyan);
  color: var(--bg-dark);
}

.challenge-page .badge.done {
  background: var(--green);
  color: var(--bg-dark);
}

.challenge-page .badge.user {
  background: var(--purple);
  color: var(--bg-dark);
}

/* Hint Section */
.challenge-page .hint-section {
  margin-top: 20px;
}

.challenge-page .hint-toggle {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-dim);
  padding: 10px 20px;
  border-radius: 6px;
  cursor: pointer;
  font-family: var(--font);
  transition: all 0.2s;
}

.challenge-page .hint-toggle:hover {
  border-color: var(--cyan);
  color: var(--cyan);
}

.challenge-page .hint-content {
  margin-top: 12px;
  padding: 16px;
  background: var(--bg-elevated);
  border-radius: 8px;
  border-left: 3px solid var(--orange);
  color: var(--text-dim);
}

/* Challenge Actions */
.challenge-page .challenge-actions {
  display: flex;
  justify-content: center;
  margin-top: 24px;
}

/* Challenge Reminder */
.challenge-page .challenge-reminder {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 16px;
  border-left: 3px solid var(--cyan);
}

.challenge-page .challenge-reminder p {
  margin: 4px 0;
  color: var(--text-dim);
}

.challenge-page .challenge-reminder strong {
  color: var(--text);
}

/* Explanation Box */
.challenge-page .explanation-box {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 24px;
}

.challenge-page .example-box {
  margin-top: 16px;
  padding: 16px;
  background: var(--bg-elevated);
  border-radius: 8px;
}

.challenge-page .example-box ul {
  margin: 12px 0 0 20px;
}

.challenge-page .example-box li {
  padding: 4px 0;
  color: var(--text-dim);
}

.challenge-page .example-box code {
  background: var(--bg-dark);
  padding: 2px 8px;
  border-radius: 4px;
  color: var(--cyan);
}

/* System States */
.challenge-page .system-states {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 24px;
}

.challenge-page .state-row {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 12px 0;
  border-bottom: 1px solid var(--border);
}

.challenge-page .state-row:last-child {
  border-bottom: none;
}

.challenge-page .state-badge {
  padding: 6px 14px;
  border-radius: 6px;
  font-size: 0.85rem;
  font-weight: 700;
  min-width: 80px;
  text-align: center;
}

.challenge-page .state-badge.start {
  background: var(--cyan);
  color: var(--bg-dark);
}

.challenge-page .state-badge.done {
  background: var(--green);
  color: var(--bg-dark);
}

.challenge-page .state-desc {
  color: var(--text-dim);
}

/* States Builder */
.challenge-page .states-builder {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 24px;
}

.challenge-page .states-builder .hint {
  color: var(--text-dim);
  font-size: 0.9rem;
  margin-bottom: 16px;
}

.challenge-page .user-states-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-bottom: 16px;
}

.challenge-page .user-state-row {
  display: flex;
  gap: 12px;
  align-items: center;
}

.challenge-page .state-name-input {
  flex: 1;
  padding: 12px 16px;
  font-family: var(--font);
  font-size: 1rem;
  background: var(--bg-elevated);
  border: 2px solid var(--border);
  border-radius: 6px;
  color: var(--text);
  text-transform: uppercase;
}

.challenge-page .state-name-input:focus {
  outline: none;
  border-color: var(--cyan);
}

.challenge-page .btn-remove {
  width: 40px;
  height: 40px;
  padding: 0;
  background: transparent;
  border: 1px solid var(--red);
  border-radius: 6px;
  color: var(--red);
  font-size: 1.5rem;
  cursor: pointer;
  transition: all 0.2s;
}

.challenge-page .btn-remove:hover {
  background: var(--red);
  color: var(--bg-dark);
}

/* Suggested States */
.challenge-page .suggested-states {
  margin-bottom: 20px;
  padding: 16px;
  background: var(--bg-elevated);
  border-radius: 8px;
}

.challenge-page .suggested-state-btn {
  padding: 8px 16px;
  margin: 4px;
  background: transparent;
  border: 1px solid var(--purple);
  border-radius: 6px;
  color: var(--purple);
  font-family: var(--font);
  cursor: pointer;
  transition: all 0.2s;
}

.challenge-page .suggested-state-btn:hover {
  background: var(--purple);
  color: var(--bg-dark);
}

.challenge-page .suggested-state-btn.used {
  opacity: 0.4;
  cursor: not-allowed;
}

/* Validation Section */
.challenge-page .validation-section {
  text-align: center;
  margin-top: 24px;
}

.challenge-page .validation-section .note {
  color: var(--text-dim);
  font-size: 0.85rem;
  margin-top: 12px;
}

/* Progress Bar (Steps) */
.challenge-page .progress-bar {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 24px;
}

.challenge-page .progress-step {
  padding: 8px 16px;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--text-dim);
  font-size: 0.8rem;
  font-weight: 600;
}

.challenge-page .progress-step.active {
  background: var(--cyan);
  border-color: var(--cyan);
  color: var(--bg-dark);
}

.challenge-page .progress-step.done {
  background: var(--green);
  border-color: var(--green);
  color: var(--bg-dark);
}

/* State Explanation */
.challenge-page .state-explanation {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 24px;
}

.challenge-page .rule-template {
  margin-top: 16px;
  padding: 16px;
  background: var(--bg-elevated);
  border-radius: 8px;
  color: var(--text-dim);
}

/* Rules Form Section */
.challenge-page .rules-form-section {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 24px;
}

.challenge-page .rule-cards {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.challenge-page .rule-card-input {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 8px;
  overflow: hidden;
}

.challenge-page .rule-card-header {
  padding: 12px 16px;
  background: var(--bg-dark);
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 0.9rem;
}

.challenge-page .rule-card-header .symbol {
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--cyan);
  color: var(--bg-dark);
  border-radius: 6px;
  font-weight: 700;
}

.challenge-page .rule-card-header .symbol.blank {
  background: var(--text-dim);
}

.challenge-page .rule-card-body {
  padding: 16px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
}

.challenge-page .rule-field {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.challenge-page .rule-field label {
  font-size: 0.75rem;
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.challenge-page .rule-field select {
  padding: 10px 12px;
  font-family: var(--font);
  font-size: 0.9rem;
  background: var(--bg-dark);
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--text);
  cursor: pointer;
}

.challenge-page .rule-field select:focus {
  outline: none;
  border-color: var(--cyan);
}

/* Rules Summary */
.challenge-page .rules-summary {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 24px;
}

.challenge-page .summary-rule {
  padding: 8px 12px;
  margin: 8px 0;
  background: var(--bg-elevated);
  border-radius: 6px;
  color: var(--text-dim);
  font-size: 0.9rem;
}

/* Nav Buttons */
.challenge-page .nav-buttons {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 24px;
  gap: 16px;
}

/* Help Section */
.challenge-page .help-section {
  margin-top: 24px;
  text-align: center;
}

.challenge-page .help-toggle {
  background: transparent;
  border: 1px solid var(--orange);
  color: var(--orange);
  padding: 10px 24px;
  border-radius: 6px;
  font-family: var(--font);
  cursor: pointer;
  transition: all 0.2s;
}

.challenge-page .help-toggle:hover {
  background: var(--orange);
  color: var(--bg-dark);
}

.challenge-page .help-content {
  margin-top: 16px;
  padding: 20px;
  background: var(--bg-elevated);
  border-radius: 8px;
  border-left: 3px solid var(--orange);
  text-align: left;
}

.challenge-page .help-content ul {
  margin: 12px 0 12px 20px;
}

.challenge-page .help-content li {
  padding: 4px 0;
  color: var(--text-dim);
}

/* Test Results Summary */
.challenge-page .test-results-summary {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px 24px;
}

.challenge-page .results-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.challenge-page .results-header .status {
  padding: 6px 16px;
  border-radius: 6px;
  font-weight: 700;
  font-size: 0.85rem;
}

.challenge-page .results-header .status.pass {
  background: var(--green);
  color: var(--bg-dark);
}

.challenge-page .results-header .status.fail {
  background: var(--red);
  color: var(--text);
}

/* Test Cases Grid */
.challenge-page .test-cases-grid {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.challenge-page .test-case-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 8px;
  overflow: hidden;
}

.challenge-page .test-case-card.pass {
  border-color: var(--green);
}

.challenge-page .test-case-card.fail {
  border-color: var(--red);
}

.challenge-page .test-case-header {
  padding: 12px 16px;
  background: var(--bg-elevated);
  display: flex;
  justify-content: space-between;
  align-items: center;
  cursor: pointer;
}

.challenge-page .test-case-header:hover {
  background: var(--bg-dark);
}

.challenge-page .test-input code {
  background: var(--bg-dark);
  padding: 4px 10px;
  border-radius: 4px;
  color: var(--cyan);
}

.challenge-page .test-status {
  font-weight: 700;
}

.challenge-page .test-case-card.pass .test-status {
  color: var(--green);
}

.challenge-page .test-case-card.fail .test-status {
  color: var(--red);
}

.challenge-page .test-case-body {
  display: none;
  padding: 16px;
}

.challenge-page .test-case-card.expanded .test-case-body {
  display: block;
}

.challenge-page .test-details {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-bottom: 12px;
}

.challenge-page .detail-box {
  padding: 12px;
  background: var(--bg-elevated);
  border-radius: 6px;
}

.challenge-page .detail-label {
  font-size: 0.75rem;
  color: var(--text-dim);
  text-transform: uppercase;
  margin-bottom: 6px;
}

.challenge-page .detail-value {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--text);
}

.challenge-page .detail-box.correct .detail-value {
  color: var(--green);
}

.challenge-page .test-reason {
  color: var(--text-dim);
  font-size: 0.9rem;
}

/* Visualization Section */
.challenge-page .visualization-section {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 24px;
}

.challenge-page .visualization-section .tape-wrapper {
  position: relative;
  margin: 20px 0;
  padding-bottom: 30px;
}

.challenge-page .visualization-section .tape {
  display: flex;
  justify-content: center;
  gap: 4px;
}

.challenge-page .visualization-section .tape-cell {
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-elevated);
  border: 2px solid var(--border);
  border-radius: 6px;
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--text);
}

.challenge-page .visualization-section .tape-cell.head {
  border-color: var(--cyan);
  box-shadow: 0 0 10px var(--cyan);
}

.challenge-page .visualization-section .tape-cell.blank {
  color: var(--text-dim);
}

.challenge-page .visualization-section .head-indicator {
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  color: var(--cyan);
  font-size: 0.7rem;
  font-weight: 700;
}

.challenge-page .machine-state {
  display: flex;
  justify-content: center;
  gap: 24px;
  margin: 16px 0;
  color: var(--text-dim);
}

.challenge-page .machine-state strong {
  color: var(--cyan);
}

.challenge-page .visual-controls {
  display: flex;
  justify-content: center;
  gap: 12px;
  margin-top: 16px;
}

/* Final Result */
.challenge-page .final-result {
  margin-top: 24px;
}

.challenge-page .result-box {
  text-align: center;
  padding: 32px;
  border-radius: 12px;
}

.challenge-page .result-box.success {
  background: rgba(0, 255, 149, 0.1);
  border: 2px solid var(--green);
}

.challenge-page .result-box.success h2 {
  color: var(--green);
}

.challenge-page .result-box.failure {
  background: rgba(255, 85, 85, 0.1);
  border: 2px solid var(--red);
}

.challenge-page .result-box.failure h2 {
  color: var(--red);
}

.challenge-page .result-box p {
  color: var(--text-dim);
  margin: 12px 0 20px;
}

/* Loading Overlay */
.challenge-page .loading-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(10, 14, 20, 0.9);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  z-index: 1000;
}

.challenge-page .spinner {
  width: 48px;
  height: 48px;
  border: 4px solid var(--border);
  border-top-color: var(--cyan);
  border-radius: 50%;
  animation: spin 1s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.challenge-page .loading-overlay p {
  margin-top: 16px;
  color: var(--text-dim);
}

/* Challenge Page Buttons */
.challenge-page .btn-primary,
.challenge-page .btn-secondary,
.challenge-page .btn-large,
.challenge-page .btn-small {
  display: inline-block;
  padding: 12px 24px;
  font-family: var(--font);
  font-size: 0.9rem;
  font-weight: 600;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.2s;
  text-decoration: none;
  border: none;
}

.challenge-page .btn-primary {
  background: var(--cyan);
  color: var(--bg-dark);
}

.challenge-page .btn-primary:hover {
  background: #00cccc;
  transform: translateY(-2px);
}

.challenge-page .btn-secondary {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text);
}

.challenge-page .btn-secondary:hover {
  border-color: var(--cyan);
  color: var(--cyan);
}

.challenge-page .btn-large {
  padding: 16px 32px;
  font-size: 1rem;
}

.challenge-page .btn-small {
  padding: 8px 16px;
  font-size: 0.8rem;
}

/* Current State Highlight */
.challenge-page .current-state {
  color: var(--cyan);
}

/* Loading Text */
.challenge-page .loading {
  color: var(--text-dim);
  font-style: italic;
}

/* Error Text */
.challenge-page .error {
  color: var(--red);
}

/* Responsive */
@media (max-width: 768px) {
  .challenge-page {
    padding: 20px 16px;
  }

  .challenge-page .rule-card-body {
    grid-template-columns: 1fr;
  }

  .challenge-page .test-details {
    grid-template-columns: 1fr;
  }

  .challenge-page .nav-buttons {
    flex-direction: column;
  }

  .challenge-page .visual-controls {
    flex-wrap: wrap;
  }
}

/* ============================================
   SIMULATOR & CHALLENGE HEADER STYLES
   ============================================ */
.simulator header,
.challenge-mode header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
  padding: 16px 20px;
  background: var(--bg-card);
  border-bottom: 1px solid var(--border);
  margin-bottom: 20px;
}

.simulator header h1,
.challenge-mode header h1 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text);
  margin: 0;
  letter-spacing: 0.5px;
}

.tutorial-btn {
  padding: 8px 16px;
  font-size: 0.8rem;
  background: transparent;
  border: 1px solid var(--cyan);
  color: var(--cyan);
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.2s;
  white-space: nowrap;
}

.tutorial-btn:hover {
  background: var(--cyan);
  color: var(--bg-dark);
}

/* Mobile responsive header */
@media (max-width: 480px) {
  .simulator header,
  .challenge-mode header {
    flex-direction: column;
    align-items: stretch;
    text-align: center;
    padding: 12px 16px;
    gap: 10px;
  }

  .simulator header h1,
  .challenge-mode header h1 {
    font-size: 1.1rem;
    line-height: 1.3;
  }

  .tutorial-btn {
    width: 100%;
    padding: 10px 16px;
  }
}

@media (max-width: 360px) {
  .simulator header h1,
  .challenge-mode header h1 {
    font-size: 1rem;
  }
}

/* ============================================
   MOBILE RESPONSIVE - Lessons
   ============================================ */
@media (max-width: 600px) {
  /* Lesson page base */
  .lesson-page {
    padding: 16px 12px;
  }

  .lesson-title {
    font-size: 1.3rem;
  }

  .lesson-content {
    font-size: 0.9rem;
  }

  /* Lock Timeline - stack vertically on mobile */
  .lock-timeline {
    padding: 16px 12px;
  }

  .lock-timeline-flow {
    flex-direction: column;
    gap: 8px;
  }

  .lock-step {
    flex-direction: row;
    gap: 12px;
    align-items: center;
  }

  .lock-step-arrow {
    width: 20px;
    height: 2px;
    transform: rotate(90deg);
  }

  .lock-step-arrow::after {
    right: -4px;
    top: -3px;
    border-width: 4px 0 4px 6px;
  }

  /* TM States showcase - stack vertically */
  .tm-states-showcase {
    flex-direction: column;
    gap: 12px;
  }

  .tm-state-card {
    padding: 12px 16px;
    min-width: auto;
    width: 100%;
  }

  .tm-states-arrow {
    width: 20px;
    height: 2px;
    transform: rotate(90deg);
  }

  .tm-states-arrow::after {
    right: -4px;
    top: -3px;
    border-width: 4px 0 4px 6px;
  }

  /* Key insight box */
  .key-insight {
    padding: 16px;
  }

  .key-insight-header {
    font-size: 0.7rem;
  }

  /* Puzzle styles */
  .puzzle-intro .lead {
    font-size: 1rem;
  }

  .puzzle-reveal {
    padding: 16px;
  }

  .puzzle-reveal strong {
    font-size: 1.1rem;
  }

  /* Lock simulator */
  .lock-simulator {
    transform: scale(0.85);
    transform-origin: top center;
  }

  /* Conclusion box */
  .conclusion-box {
    padding: 16px;
  }

  .conclusion-box .highlight {
    font-size: 0.85rem;
  }

  /* Lesson navigation */
  .lesson-nav {
    flex-direction: column;
    gap: 10px;
  }

  .lesson-nav button {
    width: 100%;
  }

  /* Tape visual demo */
  .tape-visual-demo.horizontal {
    gap: 4px;
    flex-wrap: wrap;
    justify-content: center;
  }

  .tape-visual-demo .tape-cell {
    width: 36px;
    height: 36px;
    font-size: 1rem;
  }

  /* Actions box */
  .actions-box .action-list {
    gap: 8px;
  }

  .action-item {
    padding: 10px;
  }

  /* Rules display */
  .rules-display .rule {
    padding: 10px 12px;
    font-size: 0.85rem;
  }

  /* Recap box in finale */
  .recap-box .recap-item {
    padding: 12px;
    font-size: 0.9rem;
  }

  /* Wow box */
  .wow-box {
    padding: 16px;
  }

  /* Final revelation */
  .final-revelation .revelation-answer {
    font-size: 2rem;
  }
}