/* =============================================================================
   teach-once — TP-GPT Demo Site
   W1: Site shell, hero, highlight reel
   ============================================================================= */

/* =============================================================================
   1. CSS RESET + CUSTOM PROPERTIES
   ============================================================================= */

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

:root {
  /* Colors */
  --bg-primary:     #0a0a0f;
  --bg-secondary:   #111118;
  --bg-tertiary:    #1a1a28;
  --accent:         #00d4ff;
  --accent-dim:     #00d4ff22;
  --accent-border:  #00d4ff44;
  --text-primary:   #f0f0f8;
  --text-secondary: #8888aa;
  --text-dim:       #44445a;
  --success:        #00ff88;
  --warning:        #ffaa00;
  --error:          #ff4466;

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

  /* Spacing */
  --space-xs:  4px;
  --space-sm:  8px;
  --space-md:  16px;
  --space-lg:  32px;
  --space-xl:  64px;
  --space-2xl: 128px;

  /* Border radius */
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 20px;

  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-base: 0.2s ease;
  --transition-slow: 0.4s ease;
}

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

body {
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-family: var(--font-display);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

/* =============================================================================
   2. BASE TYPOGRAPHY
   ============================================================================= */

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-display);
  color: var(--text-primary);
  line-height: 1.15;
  letter-spacing: -0.5px;
}

h1 { font-size: 4rem; font-weight: 600; letter-spacing: -1px; }
h2 { font-size: 2.5rem; font-weight: 600; }
h3 { font-size: 1.5rem; font-weight: 500; }

p {
  color: var(--text-secondary);
  line-height: 1.7;
}

a {
  color: var(--accent);
  text-decoration: none;
  transition: opacity var(--transition-fast);
}

a:hover { opacity: 0.8; }

code, .mono {
  font-family: var(--font-mono);
  font-size: 0.875em;
}

/* =============================================================================
   3. LAYOUT UTILITIES
   ============================================================================= */

.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

.container--narrow {
  max-width: 800px;
}

.section {
  padding: var(--space-2xl) 0;
}

.section-label {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 400;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--text-secondary);
  margin-bottom: var(--space-md);
}

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

/* =============================================================================
   4. NAVIGATION
   ============================================================================= */

.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  height: 48px;
  display: flex;
  align-items: center;
  background: rgba(10, 10, 15, 0.8);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--bg-tertiary);
}

.nav__inner {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--space-lg);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav__wordmark {
  font-family: var(--font-mono);
  font-size: 0.9rem;
  color: var(--accent);
  font-weight: 400;
  letter-spacing: 0.02em;
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 0.45rem;
}

.nav__logo {
  flex-shrink: 0;
  border-radius: 50%;
}

.nav__wordmark:hover { opacity: 1; }

.nav__links {
  display: flex;
  align-items: center;
  gap: var(--space-lg);
  list-style: none;
}

.nav__links a {
  font-size: 0.875rem;
  color: var(--text-secondary);
  text-decoration: none;
  transition: color var(--transition-fast);
  font-weight: 400;
}

.nav__links a:hover,
.nav__links a.active {
  color: var(--accent);
  opacity: 1;
}

/* =============================================================================
   5. HERO SECTION
   ============================================================================= */

.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  overflow: hidden;
  padding-top: 48px; /* nav height */
}

/* Animated grid background */
.hero__grid {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(68, 68, 90, 0.15) 1px, transparent 1px),
    linear-gradient(90deg, rgba(68, 68, 90, 0.15) 1px, transparent 1px);
  background-size: 48px 48px;
  animation: grid-drift 20s linear infinite;
  pointer-events: none;
}

@keyframes grid-drift {
  0%   { background-position: 0 0; }
  100% { background-position: 0 -48px; }
}

/* Radial vignette over grid */
.hero__grid::after {
  content: '';
  position: absolute;
  inset: 0;
  background: radial-gradient(
    ellipse 80% 70% at 50% 50%,
    transparent 30%,
    var(--bg-primary) 100%
  );
}

.hero__content {
  position: relative;
  z-index: 1;
  max-width: 800px;
  padding: 0 var(--space-lg);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-md);
}

/* Staggered fade-up animations — triggered by body.loaded */
.hero__badge,
.hero__line1,
.hero__line2,
.hero__sub,
.hero__ctas,
.hero__scroll-hint {
  opacity: 0;
  transform: translateY(20px);
}

body.loaded .hero__badge       { animation: fade-up 0.6s ease 0s    forwards; }
body.loaded .hero__line1       { animation: fade-up 0.6s ease 0.1s  forwards; }
body.loaded .hero__line2       { animation: fade-up 0.6s ease 0.2s  forwards; }
body.loaded .hero__sub         { animation: fade-up 0.6s ease 0.3s  forwards; }
body.loaded .hero__ctas        { animation: fade-up 0.6s ease 0.4s  forwards; }
body.loaded .hero__scroll-hint { animation: fade-up 0.6s ease 0.55s forwards; }

@keyframes fade-up {
  to { opacity: 1; transform: translateY(0); }
}

/* Algorithm badge */
.hero__badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  background: var(--accent-dim);
  border: 1px solid var(--accent-border);
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 0.8rem;
  padding: var(--space-xs) var(--space-md);
  border-radius: 100px;
  margin-bottom: var(--space-sm);
}

/* Hero headline */
.hero__headline {
  font-size: 4rem;
  font-weight: 600;
  letter-spacing: -1px;
  line-height: 1.1;
  margin: 0;
}

.hero__line1,
.hero__line2 {
  display: block;
}

.hero__line2 .accent { color: var(--accent); }

/* Sub-headline */
.hero__sub {
  font-size: 1.2rem;
  color: var(--text-secondary);
  max-width: 560px;
  line-height: 1.65;
  margin-top: var(--space-sm);
}

/* CTA buttons */
.hero__ctas {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  margin-top: var(--space-md);
  flex-wrap: wrap;
  justify-content: center;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  height: 48px;
  padding: 0 var(--space-lg);
  border-radius: var(--radius-sm);
  font-family: var(--font-display);
  font-size: 0.925rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-base);
  border: none;
  text-decoration: none;
}

.btn--primary {
  background: var(--accent);
  color: #0a0a0f;
}

.btn--primary:hover {
  background: #33ddff;
  opacity: 1;
  box-shadow: 0 0 24px rgba(0, 212, 255, 0.35);
  transform: translateY(-1px);
}

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

.btn--secondary:hover {
  background: var(--accent-dim);
  border-color: var(--accent);
  opacity: 1;
  transform: translateY(-1px);
}

/* Scroll hint */
.hero__scroll-hint {
  position: absolute;
  bottom: var(--space-xl);
  left: 50%;
  transform: translateX(-50%) translateY(20px);
  font-size: 0.8rem;
  color: var(--text-dim);
  font-family: var(--font-mono);
  letter-spacing: 0.05em;
  animation: bounce 2.5s ease-in-out infinite, fade-up 0.6s ease 0.55s forwards !important;
}

body.loaded .hero__scroll-hint {
  animation: fade-up 0.6s ease 0.55s forwards, bounce 2.5s ease-in-out 1.2s infinite !important;
}

@keyframes bounce {
  0%, 100% { transform: translateX(-50%) translateY(0); }
  50%       { transform: translateX(-50%) translateY(-6px); }
}

/* =============================================================================
   6. ALGORITHM BADGE STYLES (reusable)
   ============================================================================= */

.badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
  background: var(--accent-dim);
  border: 1px solid var(--accent-border);
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  padding: 2px 10px;
  border-radius: 100px;
}

.badge--success {
  background: rgba(0, 255, 136, 0.1);
  border-color: rgba(0, 255, 136, 0.3);
  color: var(--success);
}

.badge--warning {
  background: rgba(255, 170, 0, 0.1);
  border-color: rgba(255, 170, 0, 0.3);
  color: var(--warning);
}

/* =============================================================================
   7. HIGHLIGHT / DEMO PREVIEW SECTION
   ============================================================================= */

.highlight {
  padding: var(--space-2xl) 0;
  border-top: 1px solid var(--bg-tertiary);
}

.highlight__header {
  text-align: center;
  margin-bottom: var(--space-xl);
}

.highlight__header h2 {
  margin-bottom: var(--space-md);
}

/* Three task cards */
.task-cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
  margin-bottom: var(--space-xl);
}

.task-card {
  background: var(--bg-secondary);
  border: 1px solid var(--bg-tertiary);
  border-radius: var(--radius-md);
  padding: var(--space-md);
  cursor: pointer;
  transition: border-color var(--transition-base), transform var(--transition-base), box-shadow var(--transition-base);
  position: relative;
  overflow: hidden;
}

/* Mouse-following radial gradient */
.task-card::before {
  content: '';
  position: absolute;
  inset: 0;
  background: radial-gradient(
    300px circle at var(--mouse-x, 50%) var(--mouse-y, 50%),
    rgba(0, 212, 255, 0.04),
    transparent 60%
  );
  opacity: 0;
  transition: opacity var(--transition-base);
  pointer-events: none;
  border-radius: inherit;
}

.task-card:hover::before { opacity: 1; }

.task-card:hover {
  border-color: var(--accent-border);
  transform: scale(1.01);
  box-shadow: 0 8px 32px rgba(0, 212, 255, 0.06), 0 0 0 1px var(--accent-border);
}

.task-card__label {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 400;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: var(--space-sm);
}

.task-card__gif {
  width: 100%;
  height: auto;
  display: block;
  border-radius: var(--radius-sm);
  background: var(--bg-tertiary);
}

.task-card__desc {
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-top: var(--space-sm);
  line-height: 1.5;
}

/* Full-width highlight reel */
.highlight__reel-wrap {
  max-width: 1100px;
  margin: 0 auto;
  text-align: center;
}

.highlight__reel {
  width: 100%;
  border-radius: var(--radius-md);
  display: block;
  background: var(--bg-secondary);
  border: 1px solid var(--bg-tertiary);
}

.highlight__caption {
  margin-top: var(--space-sm);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-dim);
  letter-spacing: 0.04em;
}

/* =============================================================================
   8. DEMO SECTION (placeholder for W2/W3)
   ============================================================================= */

.demo {
  padding: var(--space-2xl) 0;
  border-top: 1px solid var(--bg-tertiary);
}

.demo__placeholder {
  height: 600px;
  background: var(--bg-secondary);
  border: 1px solid var(--bg-tertiary);
  border-radius: var(--radius-lg);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: var(--space-md);
}

.demo__placeholder-label {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--text-dim);
}

.demo__placeholder-badge {
  background: rgba(255, 170, 0, 0.1);
  border: 1px solid rgba(255, 170, 0, 0.25);
  color: var(--warning);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  padding: var(--space-xs) var(--space-md);
  border-radius: 100px;
}

/* =============================================================================
   9. HOW IT WORKS SECTION (placeholder for W5)
   ============================================================================= */

.how {
  padding: var(--space-2xl) 0;
  border-top: 1px solid var(--bg-tertiary);
}

.how__header {
  text-align: center;
  margin-bottom: var(--space-xl);
}

.how__header h2 { margin-bottom: var(--space-md); }

.step-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 24px;
}

.step-card {
  background: var(--bg-secondary);
  border: 1px solid var(--bg-tertiary);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.step-card__number {
  font-family: var(--font-mono);
  font-size: 3rem;
  font-weight: 400;
  color: var(--text-dim);
  line-height: 1;
}

.step-card__title {
  font-size: 1.1rem;
  font-weight: 500;
  color: var(--text-primary);
}

.step-card__desc {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.step-card__img-placeholder {
  width: 100%;
  height: 160px;
  background: var(--bg-tertiary);
  border-radius: var(--radius-sm);
  border: 1px solid rgba(68, 68, 90, 0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-dim);
}

/* =============================================================================
   RESULTS SECTION (placeholder for W5)
   ============================================================================= */

.results {
  padding: var(--space-2xl) 0;
  border-top: 1px solid var(--bg-tertiary);
  text-align: center;
}

.results__header { margin-bottom: var(--space-xl); }

.results__placeholder {
  background: var(--bg-secondary);
  border: 1px solid var(--bg-tertiary);
  border-radius: var(--radius-md);
  padding: var(--space-xl);
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--text-dim);
}

/* =============================================================================
   10. FOOTER
   ============================================================================= */

.footer {
  border-top: 1px solid var(--bg-tertiary);
  background: var(--bg-primary);
  padding: var(--space-xl) 0;
}

.footer__inner {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: var(--space-xl);
  align-items: start;
}

.footer__wordmark {
  font-family: var(--font-mono);
  font-size: 1rem;
  color: var(--accent);
  display: block;
  margin-bottom: var(--space-sm);
}

.footer__tagline {
  font-size: 0.85rem;
  color: var(--text-dim);
  line-height: 1.5;
}

.footer__links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  align-items: center;
}

.footer__links a {
  font-size: 0.875rem;
  color: var(--text-secondary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.footer__links a:hover { color: var(--accent); opacity: 1; }

.footer__right {
  text-align: right;
}

.footer__credit {
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.footer__credit-dim {
  font-size: 0.75rem;
  color: var(--text-dim);
  margin-top: var(--space-sm);
  font-family: var(--font-mono);
}

/* =============================================================================
   11. ANIMATIONS
   ============================================================================= */

@keyframes fadeIn {
  from { opacity: 0; }
  to   { opacity: 1; }
}

@keyframes slideUp {
  from { opacity: 0; transform: translateY(24px); }
  to   { opacity: 1; transform: translateY(0); }
}

@keyframes pulse-accent {
  0%, 100% { box-shadow: 0 0 0 0 rgba(0, 212, 255, 0.3); }
  50%       { box-shadow: 0 0 0 8px rgba(0, 212, 255, 0); }
}

.animate-pulse-accent { animation: pulse-accent 2s ease infinite; }

/* =============================================================================
   12. RESPONSIVE BREAKPOINTS
   ============================================================================= */

/* Tablet: 768px */
@media (max-width: 768px) {
  h1 { font-size: 2.8rem; }
  h2 { font-size: 1.9rem; }

  .hero__headline { font-size: 2.8rem; }
  .hero__sub      { font-size: 1.05rem; }

  .task-cards {
    grid-template-columns: 1fr;
    gap: var(--space-md);
  }

  .step-grid {
    grid-template-columns: 1fr;
  }

  .footer__inner {
    grid-template-columns: 1fr;
    gap: var(--space-lg);
    text-align: center;
  }

  .footer__links { align-items: center; }
  .footer__right { text-align: center; }

  .nav__links { gap: var(--space-md); }
}

/* Mobile: 480px */
@media (max-width: 480px) {
  h1 { font-size: 2.2rem; }
  h2 { font-size: 1.6rem; }

  .hero__headline { font-size: 2.2rem; }
  .hero__sub      { font-size: 1rem; }

  .container { padding: 0 var(--space-md); }

  .hero__ctas { flex-direction: column; width: 100%; }
  .btn        { width: 100%; justify-content: center; }

  .nav__links { display: none; }

  .step-grid  { gap: var(--space-md); }
}

/* =============================================================================
   13. REDUCED MOTION
   ============================================================================= */

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }

  .hero__grid { animation: none; }

  /* Ensure elements are visible without animation */
  .hero__badge,
  .hero__line1,
  .hero__line2,
  .hero__sub,
  .hero__ctas,
  .hero__scroll-hint {
    opacity: 1;
    transform: none;
  }
}

/* =============================================================================
   W2 — DEMO SECTION: canvas + control panel
   ============================================================================= */

#demo {
  padding: var(--space-xl) var(--space-lg);
  max-width: 1400px;
  margin: 0 auto;
  border-top: 1px solid var(--bg-tertiary);
}

.demo-container {
  display: grid;
  grid-template-columns: 3fr 2fr;
  gap: var(--space-lg);
  align-items: start;
}

/* Canvas wrapper */
.canvas-wrapper {
  position: relative;
  aspect-ratio: 16 / 9;
  border-radius: var(--radius-md);
  overflow: hidden;
  border: 1px solid var(--bg-tertiary);
  background: var(--bg-primary);
}

#robot-canvas {
  width: 100%;
  height: 100%;
  display: block;
}

.canvas-overlay {
  position: absolute;
  top: var(--space-md);
  left: var(--space-md);
  right: var(--space-md);
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  pointer-events: none;
}

.mode-badge {
  background: var(--accent-dim);
  border: 1px solid var(--accent-border);
  color: var(--accent);
  padding: 4px 12px;
  border-radius: 20px;
  font-family: var(--font-mono);
  font-size: 0.75rem;
}

.render-info {
  color: var(--text-dim);
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.03em;
}

/* Control panel */
.control-panel {
  background: var(--bg-secondary);
  border: 1px solid var(--bg-tertiary);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.panel-header h3 {
  margin: 0 0 4px 0;
  font-size: 1rem;
  font-weight: 500;
  color: var(--text-primary);
}

.panel-header p {
  margin: 0;
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

/* Mode tabs */
.mode-tabs {
  display: flex;
  gap: 3px;
  background: var(--bg-primary);
  padding: 4px;
  border-radius: var(--radius-sm);
}

.mode-tab {
  flex: 1;
  padding: 7px var(--space-sm);
  border: none;
  border-radius: calc(var(--radius-sm) - 2px);
  font-size: 0.78rem;
  font-family: var(--font-mono);
  cursor: pointer;
  transition: all var(--transition-fast);
  background: transparent;
  color: var(--text-secondary);
  white-space: nowrap;
}

.mode-tab.active {
  background: var(--accent);
  color: #0a0a0f;
  font-weight: 600;
}

.mode-tab:not(.active):hover {
  background: var(--bg-tertiary);
  color: var(--text-primary);
}

/* Panel body */
.panel-body {
  flex: 1;
  min-height: 80px;
}

.panel-placeholder {
  font-size: 0.8rem;
  color: var(--text-dim);
  font-family: var(--font-mono);
  text-align: center;
  padding: var(--space-md) 0;
}

/* Metrics panel */
.metrics-panel {
  background: var(--bg-primary);
  border-radius: var(--radius-sm);
  padding: var(--space-md);
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-sm);
}

.metric {
  display: flex;
  flex-direction: column;
  gap: 3px;
}

.metric-label {
  font-family: var(--font-mono);
  font-size: 0.63rem;
  text-transform: uppercase;
  color: var(--text-dim);
  letter-spacing: 0.06em;
}

.metric-value {
  font-family: var(--font-mono);
  font-size: 1.05rem;
  color: var(--text-primary);
}

/* Demo section buttons */
.btn-generalize {
  width: 100%;
  height: 48px;
  background: var(--accent);
  color: #0a0a0f;
  border: none;
  border-radius: var(--radius-sm);
  font-size: 0.95rem;
  font-weight: 600;
  font-family: var(--font-display);
  cursor: pointer;
  transition: all var(--transition-fast);
  letter-spacing: 0.01em;
}

.btn-generalize:hover:not(:disabled) {
  background: #33ddff;
  transform: translateY(-1px);
  box-shadow: 0 4px 20px rgba(0, 212, 255, 0.3);
}

.btn-generalize:disabled {
  opacity: 0.35;
  cursor: not-allowed;
}

.btn-reset {
  width: 100%;
  height: 40px;
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--bg-tertiary);
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  font-family: var(--font-display);
  cursor: pointer;
  transition: all var(--transition-fast);
}

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

/* Demo responsive */
@media (max-width: 900px) {
  .demo-container {
    grid-template-columns: 1fr;
  }
  #demo {
    padding: var(--space-lg) var(--space-md);
  }
}

/* Mobile: shrink canvas overlays so they don't obscure the 3D scene */
@media (max-width: 768px) {
  .mode-badge {
    font-size: 0.6rem;
    padding: 2px 8px;
  }
  /* The "Three.js · TP-GPT inference" watermark isn't useful on a phone */
  .render-info { display: none; }
  .canvas-hint { font-size: 0.55rem; }
}

/* =============================================================================
   MOBILE PRESET PANEL — shown only on mobile instead of sliders/drawing
   ============================================================================= */
.mobile-note {
  margin: 0;
  font-size: 0.78rem;
  color: var(--text-secondary);
  line-height: 1.5;
  padding: var(--space-sm) var(--space-md);
  background: var(--bg-primary);
  border: 1px solid var(--bg-tertiary);
  border-radius: var(--radius-sm);
}

.mobile-preset-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-sm);
}

.mobile-preset-btn {
  padding: 10px var(--space-sm);
  border: 1px solid var(--bg-tertiary);
  border-radius: var(--radius-sm);
  background: var(--bg-primary);
  color: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  text-align: center;
  line-height: 1.35;
}

.mobile-preset-btn:hover,
.mobile-preset-btn:active {
  background: var(--bg-tertiary);
  border-color: var(--accent-border);
}

.mobile-preset-btn.running {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-dim);
}

/* =============================================================================
   W3 — SLIDER CONTROLS + DRAG INSTRUCTIONS
   ============================================================================= */

.drag-instructions {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.drag-instructions p {
  margin: 0;
  font-size: 0.82rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

.slider-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  padding: var(--space-md);
  background: var(--bg-primary);
  border-radius: var(--radius-sm);
  border: 1px solid var(--bg-tertiary);
}

.slider-label {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.78rem;
  color: var(--text-secondary);
  font-family: var(--font-mono);
  letter-spacing: 0.02em;
}

.slider-value {
  color: var(--accent);
  font-weight: 600;
  min-width: 36px;
  text-align: right;
}

.tp-slider {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 4px;
  background: var(--bg-tertiary);
  border-radius: 2px;
  outline: none;
  cursor: pointer;
  transition: background var(--transition-fast);
}

.tp-slider:hover { background: #2a2a3a; }

.tp-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
  box-shadow: 0 0 8px rgba(0, 212, 255, 0.4);
  transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.tp-slider::-webkit-slider-thumb:hover {
  transform: scale(1.25);
  box-shadow: 0 0 14px rgba(0, 212, 255, 0.6);
}

.tp-slider::-moz-range-thumb {
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
  border: none;
  box-shadow: 0 0 8px rgba(0, 212, 255, 0.4);
}

.config-summary {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--text-dim);
  padding: var(--space-sm) 0 0;
  border-top: 1px solid var(--bg-tertiary);
}

.config-label {
  display: block;
  margin-bottom: 3px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.config-value {
  color: var(--text-secondary);
  display: block;
  line-height: 1.5;
  white-space: pre-wrap;
}

/* =============================================================================
   W4 — Mode 2 cleaning, Mode 3 armpose, GIF fallback controls
   ============================================================================= */

/* Surface type selector (cleaning mode) */
.surface-selector {
  display: flex;
  gap: 4px;
  flex-wrap: wrap;
  margin-top: var(--space-sm);
}

.surface-btn {
  padding: 6px 12px;
  border: 1px solid var(--bg-tertiary);
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--text-secondary);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  cursor: pointer;
  transition: all 0.15s;
}

.surface-btn.active {
  background: var(--accent);
  border-color: var(--accent);
  color: #0a0a0f;
  font-weight: 600;
}

.surface-btn:not(.active):hover {
  border-color: var(--accent-border);
  color: var(--accent);
}

/* Keypoint controls (armpose mode) */
.keypoint-controls {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  max-height: 280px;
  overflow-y: auto;
}

.keypoint-group {
  background: var(--bg-primary);
  border-radius: var(--radius-sm);
  padding: var(--space-sm);
}

.keypoint-header {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  margin-bottom: var(--space-sm);
}

.keypoint-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  display: inline-block;
  flex-shrink: 0;
}

.keypoint-name {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--text-primary);
  font-weight: 600;
}

/* Canvas hint bar — bottom overlay inside canvas-wrapper */
.canvas-hint-bar {
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  padding: 6px var(--space-md);
  display: flex;
  justify-content: flex-end;
  pointer-events: none;
}

.canvas-hint {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--text-dim);
}

/* =============================================================================
   W5 — HOW IT WORKS (rebuilt)
   ============================================================================= */

#how-it-works {
  padding: var(--space-2xl) var(--space-lg);
  background: var(--bg-secondary);
  border-top: 1px solid var(--bg-tertiary);
  border-bottom: 1px solid var(--bg-tertiary);
}

.section-inner {
  max-width: 1100px;
  margin: 0 auto;
}

.section-label {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.12em;
  color: var(--accent);
  text-transform: uppercase;
  margin-bottom: var(--space-sm);
}

.section-heading {
  font-size: 2.1rem;
  font-weight: 600;
  letter-spacing: -0.5px;
  margin: 0 0 var(--space-sm) 0;
  color: var(--text-primary);
}

.section-subtext {
  color: var(--text-secondary);
  font-size: 1rem;
  margin-bottom: var(--space-xl);
  max-width: 620px;
  line-height: 1.6;
}

.section-subtext a {
  color: var(--accent);
  text-decoration: none;
}

.section-subtext a:hover { text-decoration: underline; }

/* Step cards grid */
.steps-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-lg);
  margin-bottom: var(--space-xl);
}

/* Override old .step-card rule — W5 card is a row layout */
#how-it-works .step-card {
  background: var(--bg-primary);
  border: 1px solid var(--bg-tertiary);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  display: flex;
  gap: var(--space-md);
  flex-direction: row;
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.5s ease, transform 0.5s ease;
}

#how-it-works .step-card.visible {
  opacity: 1;
  transform: translateY(0);
}

#how-it-works .step-card:nth-child(2) { transition-delay: 0.10s; }
#how-it-works .step-card:nth-child(3) { transition-delay: 0.20s; }
#how-it-works .step-card:nth-child(4) { transition-delay: 0.30s; }

.step-number {
  font-family: var(--font-mono);
  font-size: 2.4rem;
  font-weight: 700;
  color: var(--text-dim);
  line-height: 1;
  min-width: 48px;
  flex-shrink: 0;
}

.step-content h3 {
  font-size: 1rem;
  font-weight: 600;
  margin: 0 0 var(--space-sm) 0;
  color: var(--text-primary);
}

.step-content p {
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.65;
  margin: 0 0 var(--space-sm) 0;
}

.step-equation {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--accent);
  background: var(--accent-dim);
  border: 1px solid var(--accent-border);
  border-radius: var(--radius-sm);
  padding: 5px 12px;
  margin-bottom: var(--space-sm);
  display: inline-block;
}

.step-figure {
  display: flex;
  flex-direction: column;
  gap: 6px;
  margin-top: var(--space-sm);
}

.step-figure img {
  width: 100%;
  border-radius: var(--radius-sm);
  border: 1px solid var(--bg-tertiary);
  background: var(--bg-secondary);
}

.fig-caption {
  font-family: var(--font-mono);
  font-size: 0.66rem;
  color: var(--text-dim);
  text-align: center;
}

/* Wide figure (Fig. 7) */
.wide-figure {
  border-top: 1px solid var(--bg-tertiary);
  padding-top: var(--space-lg);
}

.wide-figure h3 {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text-primary);
  margin: 0 0 var(--space-sm) 0;
}

.wide-figure p {
  font-size: 0.875rem;
  color: var(--text-secondary);
  max-width: 700px;
  margin-bottom: var(--space-md);
  line-height: 1.6;
}

.wide-img {
  width: 100%;
  border-radius: var(--radius-md);
  border: 1px solid var(--bg-tertiary);
  margin-bottom: 8px;
}

/* =============================================================================
   W5 — RESULTS SECTION (rebuilt)
   ============================================================================= */

#results {
  padding: var(--space-2xl) var(--space-lg);
}

.results-table-wrapper {
  margin-bottom: var(--space-xl);
}

.results-table-wrapper h3 {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text-primary);
  margin: 0 0 var(--space-sm) 0;
}

.table-caption {
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-bottom: var(--space-md);
}

.table-scroll { overflow-x: auto; }

.results-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.875rem;
  min-width: 500px;
}

.results-table th {
  text-align: left;
  padding: 10px 16px;
  font-family: var(--font-mono);
  font-size: 0.70rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-dim);
  border-bottom: 1px solid var(--bg-tertiary);
}

.results-table td {
  padding: 10px 16px;
  border-bottom: 1px solid var(--bg-tertiary);
  color: var(--text-secondary);
}

.results-table tr:last-child td { border-bottom: none; }

.highlight-row td {
  background: var(--accent-dim);
  color: var(--text-primary);
}

.highlight-row td:first-child {
  border-left: 3px solid var(--accent);
}

.type-analytical {
  color: var(--success);
  font-family: var(--font-mono);
  font-size: 0.78rem;
}

.type-estimated {
  color: var(--warning);
  font-family: var(--font-mono);
  font-size: 0.78rem;
}

.type-none {
  color: var(--text-dim);
  font-family: var(--font-mono);
  font-size: 0.78rem;
}

.results-figures {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-lg);
  margin-bottom: var(--space-xl);
}

.result-fig {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.result-fig h3 {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-primary);
  margin: 0;
}

.result-fig img {
  width: 100%;
  border-radius: var(--radius-sm);
  border: 1px solid var(--bg-tertiary);
}

.limitations-note {
  display: flex;
  gap: var(--space-md);
  align-items: flex-start;
  background: var(--bg-secondary);
  border: 1px solid var(--bg-tertiary);
  border-radius: var(--radius-md);
  padding: var(--space-md);
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.limitations-icon {
  font-size: 1.2rem;
  flex-shrink: 0;
  margin-top: 2px;
}

.limitations-note a {
  color: var(--accent);
  text-decoration: none;
}

.limitations-note a:hover { text-decoration: underline; }

/* =============================================================================
   W5 — PAPER & CITATION SECTION
   ============================================================================= */

#paper {
  padding: var(--space-2xl) var(--space-lg);
  background: var(--bg-secondary);
  border-top: 1px solid var(--bg-tertiary);
}

.paper-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-lg);
  margin-bottom: var(--space-xl);
}

.paper-card {
  background: var(--bg-primary);
  border: 1px solid var(--bg-tertiary);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.paper-card-label {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 0.10em;
  color: var(--accent);
}

.paper-card h3 {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-primary);
  margin: 0;
  line-height: 1.4;
}

.paper-authors {
  font-size: 0.82rem;
  color: var(--text-secondary);
  margin: 0;
  line-height: 1.55;
}

.btn-outline {
  display: inline-block;
  padding: 8px 16px;
  border: 1px solid var(--accent-border);
  border-radius: var(--radius-sm);
  color: var(--accent);
  font-size: 0.85rem;
  text-decoration: none;
  transition: background 0.15s, border-color 0.15s;
  align-self: flex-start;
  margin-top: auto;
}

.btn-outline:hover {
  background: var(--accent-dim);
  border-color: var(--accent);
}

.bibtex-block {
  background: var(--bg-primary);
  border: 1px solid var(--bg-tertiary);
  border-radius: var(--radius-md);
  overflow: hidden;
}

.bibtex-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 10px 16px;
  border-bottom: 1px solid var(--bg-tertiary);
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--text-secondary);
}

.btn-tertiary {
  background: none;
  border: 1px solid var(--bg-tertiary);
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  font-family: var(--font-mono);
  font-size: 0.72rem;
  padding: 4px 12px;
  cursor: pointer;
  transition: border-color 0.15s, color 0.15s;
}

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

.bibtex-code {
  margin: 0;
  padding: var(--space-md);
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--text-secondary);
  line-height: 1.6;
  overflow-x: auto;
  white-space: pre;
}

/* =============================================================================
   W5 — FOOTER (rebuilt)
   ============================================================================= */

footer {
  border-top: 1px solid var(--bg-tertiary);
  padding: var(--space-xl) var(--space-lg);
  background: var(--bg-primary);
}

.footer-inner {
  max-width: 1100px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: var(--space-xl);
  align-items: start;
}

.footer-wordmark {
  font-family: var(--font-mono);
  font-size: 1.1rem;
  color: var(--accent);
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 0.45rem;
  margin-bottom: var(--space-sm);
}

.footer-tagline {
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin: 0;
}

.footer-links-col {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.footer-links-col a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.875rem;
  transition: color 0.15s;
}

.footer-links-col a:hover { color: var(--accent); }

.footer-credits p {
  font-size: 0.8rem;
  color: var(--text-secondary);
  margin: 0 0 4px 0;
}

.footer-credits a {
  color: var(--accent);
  text-decoration: none;
}

.footer-dim {
  color: var(--text-dim) !important;
  font-family: var(--font-mono);
  font-size: 0.70rem !important;
  margin-top: var(--space-sm) !important;
}

/* =============================================================================
   W5 — GLOBAL POLISH
   ============================================================================= */

/* Scroll margin so sticky nav doesn't hide section headings */
section {
  scroll-margin-top: 60px;
}

/* Reduced motion: disable scroll-in animations */
@media (prefers-reduced-motion: reduce) {
  #how-it-works .step-card {
    opacity: 1;
    transform: none;
    transition: none;
  }
}

/* Mobile */
@media (max-width: 768px) {
  .steps-grid         { grid-template-columns: 1fr; }
  #how-it-works .step-card { flex-direction: column; }
  .results-figures    { grid-template-columns: 1fr; }
  .paper-grid         { grid-template-columns: 1fr; }
  .footer-inner       { grid-template-columns: 1fr; gap: var(--space-lg); }
  .section-heading    { font-size: 1.6rem; }
}

/* =============================================================================
   W5 QUICK FIXES — new component classes
   ============================================================================= */

/* Fix 1: Simplification disclaimer note */
.simplification-note {
  font-size: 0.82rem;
  color: var(--text-secondary);
  background: var(--bg-primary);
  border-left: 3px solid var(--accent-border);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  padding: var(--space-md);
  margin: var(--space-lg) 0;
  line-height: 1.6;
}
.simplification-note strong {
  color: var(--text-primary);
}

/* Fix 3: Paper video button variant */
.btn-video {
  border-color: #ff4444;
  color: #ff6666;
}
.btn-video:hover {
  background: rgba(255, 68, 68, 0.1);
  border-color: #ff4444;
}

/* Fix 5: Generalize button subtext */
.btn-subtext {
  font-size: 0.72rem;
  color: var(--text-dim);
  font-family: var(--font-mono);
  text-align: center;
  margin: 0;
}

/* ── Freehand drawing (cleaning mode) ─────────────────────── */
.draw-mode-group {
  background: var(--bg-primary);
  border-radius: var(--radius-sm);
  padding: var(--space-sm);
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  margin-bottom: var(--space-sm);
}
.draw-toggle-row {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  flex-wrap: wrap;
}
.draw-mode-label {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--text-secondary);
  white-space: nowrap;
}
.draw-instructions-active p {
  font-size: 0.82rem;
  color: var(--accent);
  margin: 0;
  font-style: italic;
}
.draw-status-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 2px;
}
.drawn-count {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-dim);
  transition: color 0.2s;
}
.btn-tertiary {
  background: transparent;
  border: 1px solid var(--bg-tertiary);
  color: var(--text-secondary);
  border-radius: var(--radius-sm);
  padding: 2px 8px;
  font-size: 0.75rem;
  cursor: pointer;
  transition: border-color 0.2s, color 0.2s;
}
.btn-tertiary:hover {
  border-color: var(--accent-border);
  color: var(--accent);
}