/**
 * DevFluentia — Section 3.1: Types of Collocations
 * THE ACADEMIC WORD UNIVERSE
 * Dark atmospheric design — midnight navy, indigo, electric cyan, ivory.
 * Scoped under .collocations-academic-page to avoid leaking styles.
 */

/* ═══════════════════════════════════════════════════
   CANVAS BACKGROUND & PAGE SHELL
   ═══════════════════════════════════════════════════ */

.col-bg {
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  overflow: hidden;
}

.col-bg-gradient {
  position: absolute;
  inset: 0;
  background: radial-gradient(ellipse 90% 70% at 20% 25%, #0d2238 0%, #071526 45%, #030a12 100%);
}

.col-canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  opacity: 0.9;
}

/* Atmospheric oceanic glow orbs (deep teal, bioluminescent cyan, marine blue) */
.col-orb {
  position: absolute;
  border-radius: 50%;
  filter: blur(95px);
  pointer-events: none;
}
.col-orb-1 {
  width: 560px; height: 560px;
  background: radial-gradient(circle, rgba(27, 107, 122, 0.28) 0%, transparent 70%);
  top: -120px; left: -80px;
  animation: colOrbDrift1 18s ease-in-out infinite alternate;
}
.col-orb-2 {
  width: 440px; height: 440px;
  background: radial-gradient(circle, rgba(42, 155, 181, 0.22) 0%, transparent 70%);
  bottom: -80px; right: 5%;
  animation: colOrbDrift2 22s ease-in-out infinite alternate;
}
.col-orb-3 {
  width: 320px; height: 320px;
  background: radial-gradient(circle, rgba(77, 196, 221, 0.16) 0%, transparent 70%);
  top: 35%; left: 55%;
  animation: colOrbDrift3 16s ease-in-out infinite alternate;
}

@keyframes colOrbDrift1 {
  from { transform: translate(0, 0) scale(1); }
  to   { transform: translate(40px, 30px) scale(1.08); }
}
@keyframes colOrbDrift2 {
  from { transform: translate(0, 0) scale(1); }
  to   { transform: translate(-30px, -40px) scale(1.1); }
}
@keyframes colOrbDrift3 {
  from { transform: translate(0, 0); }
  to   { transform: translate(20px, -25px); }
}

@media (prefers-reduced-motion: reduce) {
  .col-orb { animation: none !important; }
}

/* ═══════════════════════════════════════════════════
   MAIN PAGE WRAPPER
   ═══════════════════════════════════════════════════ */

.collocations-academic-page {
  position: relative;
  z-index: 1;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 0;
  font-family: 'Inter', system-ui, sans-serif;
  color: #e8eef8;
}

/* ═══════════════════════════════════════════════════
   HERO SECTION
   ═══════════════════════════════════════════════════ */

.col-hero {
  width: 100%;
  max-width: 900px;
  padding: clamp(80px, 12vw, 130px) 24px clamp(40px, 6vw, 60px);
  text-align: center;
  position: relative;
}

.col-breadcrumb-row {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  margin-bottom: 32px;
  flex-wrap: wrap;
}

.col-breadcrumb-item {
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: rgba(130, 165, 230, 0.7);
  cursor: pointer;
  transition: color 0.2s ease;
}
.col-breadcrumb-item:hover {
  color: rgba(130, 165, 230, 1);
}
.col-breadcrumb-sep {
  color: rgba(130, 165, 230, 0.35);
  font-size: 0.85rem;
}
.col-breadcrumb-item.active {
  color: rgba(130, 165, 230, 0.9);
  cursor: default;
}

.col-chapter-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: rgba(56, 99, 209, 0.15);
  border: 1px solid rgba(56, 99, 209, 0.35);
  color: #7ba8f0;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  padding: 6px 16px;
  border-radius: 100px;
  margin-bottom: 24px;
}

.col-hero-title {
  font-family: 'Playfair Display', Georgia, serif;
  font-size: clamp(2.4rem, 5.5vw, 4rem);
  font-weight: 800;
  line-height: 1.1;
  color: #f0f4ff;
  margin: 0 0 20px;
  letter-spacing: -0.01em;
}

.col-hero-title .col-title-highlight {
  color: transparent;
  background: linear-gradient(135deg, #63b3fa 0%, #a78bfa 50%, #34d5c8 100%);
  -webkit-background-clip: text;
  background-clip: text;
}

.col-hero-subtitle {
  font-size: clamp(1rem, 2vw, 1.2rem);
  color: rgba(180, 205, 240, 0.78);
  line-height: 1.7;
  max-width: 640px;
  margin: 0 auto 36px;
}

/* Animated Collocation Demo */
.col-demo-strip {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  margin: 0 auto 40px;
  flex-wrap: wrap;
}

.col-demo-word {
  display: inline-block;
  padding: 10px 20px;
  border: 1.5px solid rgba(99, 179, 250, 0.4);
  border-radius: 8px;
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  color: #a8ccf5;
  background: rgba(99, 179, 250, 0.07);
  animation: colWordPulse 3s ease-in-out infinite;
}
.col-demo-word:nth-child(3) {
  animation-delay: 0.4s;
}

.col-demo-plus {
  font-size: 1.4rem;
  color: rgba(130, 165, 230, 0.5);
  font-weight: 300;
}

.col-demo-arrow {
  font-size: 1.5rem;
  color: rgba(99, 179, 250, 0.5);
  animation: colArrowPulse 3s ease-in-out infinite;
}

.col-demo-result {
  display: inline-flex;
  align-items: center;
  padding: 10px 24px;
  background: linear-gradient(135deg, rgba(56, 99, 209, 0.25), rgba(99, 58, 195, 0.2));
  border: 1.5px solid rgba(120, 160, 255, 0.45);
  border-radius: 8px;
  font-size: 1.05rem;
  font-weight: 800;
  letter-spacing: 0.06em;
  color: #c4d8ff;
  animation: colResultGlow 3s ease-in-out infinite;
}

@keyframes colWordPulse {
  0%, 100% { opacity: 0.7; transform: translateY(0); }
  50%       { opacity: 1; transform: translateY(-2px); }
}
@keyframes colArrowPulse {
  0%, 100% { opacity: 0.4; transform: translateX(0); }
  50%       { opacity: 0.8; transform: translateX(4px); }
}
@keyframes colResultGlow {
  0%, 100% { box-shadow: 0 0 0 rgba(99, 179, 250, 0); }
  50%       { box-shadow: 0 0 24px rgba(99, 179, 250, 0.2); }
}

@media (prefers-reduced-motion: reduce) {
  .col-demo-word,
  .col-demo-arrow,
  .col-demo-result { animation: none; }
}

/* Start button */
.col-start-btn {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 16px 40px;
  background: linear-gradient(135deg, #2a5fd4, #6b3fc2);
  border: none;
  border-radius: 12px;
  font-family: 'Manrope', 'Inter', sans-serif;
  font-size: 1rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  color: #ffffff;
  cursor: pointer;
  box-shadow: 0 6px 28px rgba(56, 99, 209, 0.45), 0 2px 8px rgba(0,0,0,0.3);
  transition: transform 0.2s ease, box-shadow 0.2s ease, background 0.2s ease;
}
.col-start-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 10px 36px rgba(56, 99, 209, 0.6), 0 4px 12px rgba(0,0,0,0.4);
  background: linear-gradient(135deg, #3469e8, #7d50db);
}
.col-start-btn:active { transform: translateY(0); }

.col-start-btn .col-btn-arrow {
  width: 18px; height: 18px;
  transition: transform 0.2s ease;
}
.col-start-btn:hover .col-btn-arrow {
  transform: translateX(3px);
}

/* ═══════════════════════════════════════════════════
   LEARNING STAGE AREA
   ═══════════════════════════════════════════════════ */

.col-stage-area {
  width: 100%;
  max-width: 900px;
  padding: 0 24px 100px;
}

/* Progress dots at top */
.col-progress-strip {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0;
  margin-bottom: 44px;
}

.col-prog-dot-wrap {
  display: flex;
  align-items: center;
}

.col-prog-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: rgba(130, 165, 230, 0.2);
  border: 1.5px solid rgba(130, 165, 230, 0.3);
  transition: all 0.3s ease;
  cursor: pointer;
  position: relative;
}
.col-prog-dot.done {
  background: rgba(56, 99, 209, 0.6);
  border-color: rgba(99, 179, 250, 0.6);
}
.col-prog-dot.current {
  width: 14px; height: 14px;
  background: #63b3fa;
  border-color: #63b3fa;
  box-shadow: 0 0 12px rgba(99, 179, 250, 0.6);
}

.col-prog-connector {
  width: 36px; height: 1.5px;
  background: rgba(130, 165, 230, 0.2);
  transition: background 0.4s ease;
}
.col-prog-connector.done {
  background: rgba(56, 99, 209, 0.5);
}

/* Stage label above card */
.col-stage-label-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 20px;
  flex-wrap: wrap;
  gap: 12px;
}

.col-stage-tag {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: #63b3fa;
}

.col-stage-count {
  font-size: 0.75rem;
  color: rgba(130, 165, 230, 0.55);
  font-weight: 600;
  font-family: 'Manrope', sans-serif;
}

/* ═══════════════════════════════════════════════════
   CONTENT SCREENS (SLIDES)
   ═══════════════════════════════════════════════════ */

.col-screen {
  display: none;
  animation: colScreenIn 0.45s cubic-bezier(0.22, 0.61, 0.36, 1) both;
}
.col-screen.active {
  display: block;
}

@keyframes colScreenIn {
  from { opacity: 0; transform: translateY(18px); }
  to   { opacity: 1; transform: translateY(0); }
}

@media (prefers-reduced-motion: reduce) {
  .col-screen { animation: none; }
}

/* ── TYPE CARD (large feature card for each collocation type) ── */
.col-type-card {
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid rgba(130, 165, 230, 0.14);
  border-radius: 20px;
  padding: clamp(28px, 4vw, 44px);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  margin-bottom: 20px;
  position: relative;
  overflow: hidden;
}

.col-type-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 3px;
  border-radius: 20px 20px 0 0;
}

.col-type-card.verb-noun::before   { background: linear-gradient(90deg, #3b82f6, #60a5fa); }
.col-type-card.adj-noun::before    { background: linear-gradient(90deg, #7c3aed, #a78bfa); }
.col-type-card.noun-noun::before   { background: linear-gradient(90deg, #0891b2, #34d5c8); }
.col-type-card.adv-adj::before     { background: linear-gradient(90deg, #b45309, #fbbf24); }

/* Type header */
.col-type-header {
  display: flex;
  align-items: flex-start;
  gap: 20px;
  margin-bottom: 28px;
  flex-wrap: wrap;
}

.col-type-icon-bubble {
  flex-shrink: 0;
  width: 52px; height: 52px;
  border-radius: 14px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
}
.verb-noun  .col-type-icon-bubble { background: rgba(59, 130, 246, 0.18); }
.adj-noun   .col-type-icon-bubble { background: rgba(124, 58, 237, 0.18); }
.noun-noun  .col-type-icon-bubble { background: rgba(8, 145, 178, 0.18); }
.adv-adj    .col-type-icon-bubble { background: rgba(180, 83, 9, 0.18); }

.col-type-title-block {
  flex: 1;
}

.col-type-formula {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  padding: 4px 12px;
  border-radius: 100px;
  margin-bottom: 8px;
}
.verb-noun  .col-type-formula { background: rgba(59, 130, 246, 0.18); color: #93c5fd; border: 1px solid rgba(59,130,246,0.3); }
.adj-noun   .col-type-formula { background: rgba(124, 58, 237, 0.18); color: #c4b5fd; border: 1px solid rgba(124,58,237,0.3); }
.noun-noun  .col-type-formula { background: rgba(8, 145, 178, 0.18);  color: #67e8f9; border: 1px solid rgba(8,145,178,0.3); }
.adv-adj    .col-type-formula { background: rgba(180, 83, 9, 0.18);   color: #fcd34d; border: 1px solid rgba(180,83,9,0.3); }

.col-type-title {
  font-family: 'Playfair Display', Georgia, serif;
  font-size: clamp(1.4rem, 3vw, 1.9rem);
  font-weight: 700;
  color: #e8f0ff;
  line-height: 1.2;
  margin: 0 0 6px;
}

/* ── 2. PROMINENT EXPLANATORY PARAGRAPH (EDITORIAL READING AREA) ── */
.col-explanatory-card {
  background: rgba(14, 25, 48, 0.75);
  border: 1px solid rgba(130, 165, 230, 0.22);
  border-left: 4px solid #63b3fa;
  border-radius: 14px;
  padding: clamp(20px, 3.5vw, 28px);
  margin-bottom: 28px;
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.25);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
}
.verb-noun .col-explanatory-card { border-left-color: #60a5fa; }
.adj-noun  .col-explanatory-card { border-left-color: #a78bfa; }
.noun-noun .col-explanatory-card { border-left-color: #34d5c8; }
.adv-adj   .col-explanatory-card { border-left-color: #fbbf24; }

.col-explanatory-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: #7ba8f0;
  margin-bottom: 12px;
}
.col-explanatory-badge svg {
  flex-shrink: 0;
  color: #63b3fa;
}

.col-explanatory-text {
  font-family: 'Inter', system-ui, sans-serif;
  font-size: clamp(1.05rem, 1.8vw, 1.22rem);
  line-height: 1.8;
  color: #e2ecfc;
  margin: 0;
  letter-spacing: -0.005em;
  font-weight: 400;
}

/* ── 3. INTERACTIVE COLLOCATIONS SECTION ── */
.col-section-block {
  margin-bottom: 24px;
}

.col-block-heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 14px;
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: rgba(180, 205, 240, 0.75);
}
.col-block-sub {
  font-size: 0.72rem;
  font-weight: 500;
  color: rgba(130, 165, 230, 0.5);
  text-transform: none;
  letter-spacing: 0;
}

.col-groups-container {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.col-subgroup {
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid rgba(130, 165, 230, 0.1);
  border-radius: 14px;
  padding: 16px 18px;
}

.col-subgroup-label {
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: #fbbf24;
  margin-bottom: 12px;
}

/* Collocation examples grid */
.col-examples-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(210px, 1fr));
  gap: 12px;
}

.col-example-pill {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 14px 18px;
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid rgba(130, 165, 230, 0.12);
  border-radius: 12px;
  cursor: pointer;
  transition: all 0.22s ease;
  position: relative;
  overflow: hidden;
}
.col-example-pill:hover {
  background: rgba(255, 255, 255, 0.08);
  border-color: rgba(130, 165, 230, 0.28);
  transform: translateY(-1px);
}
.col-example-pill.selected {
  background: rgba(56, 99, 209, 0.18);
  border-color: rgba(99, 179, 250, 0.5);
}

.col-pill-dot {
  width: 8px; height: 8px;
  border-radius: 50%;
  flex-shrink: 0;
  transition: transform 0.2s ease;
}
.col-example-pill.selected .col-pill-dot {
  transform: scale(1.4);
}
.verb-noun  .col-pill-dot { background: #60a5fa; }
.adj-noun   .col-pill-dot { background: #a78bfa; }
.noun-noun  .col-pill-dot { background: #34d5c8; }
.adv-adj    .col-pill-dot { background: #fbbf24; }

.col-pill-text {
  font-size: 0.92rem;
  font-weight: 600;
  color: #c4d8ff;
  line-height: 1.3;
}

.col-pill-highlight {
  font-size: 0.78rem;
  font-weight: 400;
  color: rgba(180, 205, 240, 0.55);
  margin-top: 2px;
}

/* ── 4 & 5. CANONICAL EXAMPLE SENTENCE & EXPLANATION NOTE ── */
.col-sentence-demonstration {
  background: rgba(18, 30, 58, 0.6);
  border: 1px solid rgba(99, 179, 250, 0.25);
  border-radius: 14px;
  padding: clamp(20px, 3vw, 26px);
  margin-top: 24px;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.2);
}

.col-sentence-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 14px;
  flex-wrap: wrap;
  gap: 10px;
}

.col-sentence-pill {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: #7ba8f0;
  background: rgba(56, 99, 209, 0.2);
  border: 1px solid rgba(56, 99, 209, 0.35);
  padding: 4px 12px;
  border-radius: 100px;
}

.col-sentence-status {
  font-size: 0.75rem;
  font-weight: 600;
  color: rgba(180, 205, 240, 0.6);
  font-family: 'Manrope', sans-serif;
}

.col-sentence-text {
  font-family: 'Playfair Display', Georgia, serif;
  font-size: clamp(1.15rem, 2.2vw, 1.45rem);
  font-weight: 600;
  color: #ffffff;
  line-height: 1.6;
  margin-bottom: 14px;
  letter-spacing: 0.01em;
}

.col-sentence-text .col-ex-collocation {
  color: #67e8f9;
  background: rgba(6, 182, 212, 0.15);
  padding: 2px 8px;
  border-radius: 6px;
  border-bottom: 2px solid #22d3ee;
  font-weight: 700;
}

.col-explanation-note {
  font-size: 0.95rem;
  color: rgba(180, 205, 240, 0.82);
  line-height: 1.65;
  border-top: 1px solid rgba(130, 165, 230, 0.15);
  padding-top: 12px;
}
.col-explanation-note em {
  color: #93c5fd;
  font-style: italic;
  font-weight: 600;
}

/* ── TAKEAWAY SCREEN ── */
.col-takeaway-card {
  background: linear-gradient(135deg, rgba(30, 50, 120, 0.35), rgba(60, 30, 120, 0.25));
  border: 1px solid rgba(130, 165, 230, 0.22);
  border-radius: 20px;
  padding: clamp(32px, 5vw, 56px);
  text-align: center;
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  position: relative;
  overflow: hidden;
}
.col-takeaway-card::before {
  content: '';
  position: absolute;
  inset: 0;
  background: radial-gradient(ellipse 60% 50% at 50% 0%, rgba(99, 179, 250, 0.08) 0%, transparent 70%);
  pointer-events: none;
}

.col-takeaway-icon {
  font-size: 3rem;
  margin-bottom: 20px;
  display: block;
}

.col-takeaway-title {
  font-family: 'Playfair Display', Georgia, serif;
  font-size: clamp(1.6rem, 4vw, 2.4rem);
  font-weight: 800;
  color: #f0f4ff;
  margin: 0 0 16px;
}

.col-takeaway-body {
  font-size: 1.02rem;
  color: rgba(180, 205, 240, 0.82);
  line-height: 1.75;
  max-width: 640px;
  margin: 0 auto 32px;
}

.col-takeaway-summary {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 16px;
  margin-bottom: 36px;
  text-align: left;
}

.col-summary-chip {
  padding: 16px 18px;
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid rgba(130, 165, 230, 0.15);
  border-radius: 12px;
}
.col-summary-chip-formula {
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: 6px;
}
.col-summary-chip-name {
  font-family: 'Playfair Display', serif;
  font-size: 0.98rem;
  font-weight: 700;
  color: #dde8ff;
  margin-bottom: 4px;
}
.col-summary-chip-ex {
  font-size: 0.8rem;
  color: rgba(180, 205, 240, 0.6);
}

/* ═══════════════════════════════════════════════════
   NAVIGATION CONTROLS
   ═══════════════════════════════════════════════════ */

.col-nav-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-top: 32px;
  flex-wrap: wrap;
}

.col-nav-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 28px;
  border-radius: 10px;
  font-family: 'Manrope', 'Inter', sans-serif;
  font-size: 0.9rem;
  font-weight: 700;
  letter-spacing: 0.03em;
  cursor: pointer;
  transition: all 0.2s ease;
  border: none;
}

.col-nav-btn-back {
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(130, 165, 230, 0.18);
  color: rgba(180, 205, 240, 0.8);
}
.col-nav-btn-back:hover {
  background: rgba(255, 255, 255, 0.1);
  color: #c8dcf5;
}
.col-nav-btn-back:disabled {
  opacity: 0.35;
  cursor: default;
}

.col-nav-btn-next {
  background: linear-gradient(135deg, #2a5fd4, #6b3fc2);
  color: #ffffff;
  box-shadow: 0 4px 20px rgba(56, 99, 209, 0.4);
}
.col-nav-btn-next:hover {
  transform: translateY(-1px);
  box-shadow: 0 7px 28px rgba(56, 99, 209, 0.55);
  background: linear-gradient(135deg, #3469e8, #7d50db);
}
.col-nav-btn-next:active { transform: translateY(0); }

.col-nav-btn svg {
  width: 16px; height: 16px;
  flex-shrink: 0;
}

/* Keyboard hint */
.col-keyboard-hint {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-size: 0.75rem;
  color: rgba(130, 165, 230, 0.38);
  margin-top: 20px;
}
.col-key-tag {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 3px 8px;
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(130, 165, 230, 0.18);
  border-radius: 4px;
  font-family: 'Manrope', monospace;
  font-size: 0.72rem;
  color: rgba(130, 165, 230, 0.55);
}

/* ═══════════════════════════════════════════════════
   BACK-TO-CHAPTER FOOTER
   ═══════════════════════════════════════════════════ */

.col-back-chapter-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: none;
  border: 1px solid rgba(130, 165, 230, 0.2);
  border-radius: 8px;
  color: rgba(130, 165, 230, 0.6);
  font-size: 0.82rem;
  font-weight: 600;
  padding: 8px 16px;
  cursor: pointer;
  transition: all 0.2s ease;
}
.col-back-chapter-btn:hover {
  color: rgba(130, 165, 230, 0.9);
  border-color: rgba(130, 165, 230, 0.38);
  background: rgba(130, 165, 230, 0.06);
}

/* ═══════════════════════════════════════════════════
   RESPONSIVE
   ═══════════════════════════════════════════════════ */

@media (max-width: 640px) {
  .col-hero { padding: 90px 16px 36px; }
  .col-stage-area { padding: 0 16px 80px; }
  .col-demo-strip { gap: 8px; }
  .col-demo-word { font-size: 0.88rem; padding: 8px 14px; }
  .col-examples-grid { grid-template-columns: 1fr; }
  .col-nav-row { flex-direction: column-reverse; }
  .col-nav-btn { width: 100%; justify-content: center; }
  .col-takeaway-summary { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 380px) {
  .col-hero-title { font-size: 2rem; }
  .col-takeaway-summary { grid-template-columns: 1fr; }
}