/* ==========================================================================
   OPS GLOBAL EEL AQUACULTURE HANDBOOK — MARKETING LANDING PAGE STYLES
   PT Ocean Pearl Seafood · Commercial Operations & Technology Series
   ========================================================================== */

:root {
  --navy-950: #040e15;
  --navy-900: #061622;
  --navy-850: #0a2131;
  --navy-800: #0f2c40;
  --navy-700: #17425f;
  --teal-600: #0d9488;
  --teal-500: #14b8a6;
  --teal-400: #2dd4bf;
  --teal-glow: rgba(20, 184, 166, 0.25);
  --cyan-400: #38bdf8;
  --gold-500: #f59e0b;
  --gold-600: #d97706;
  --gold-glow: rgba(245, 158, 11, 0.28);
  
  --surface-white: #ffffff;
  --surface-subtle: #f8fafc;
  --surface-card: #f1f5f9;
  --surface-border: #e2e8f0;
  
  --text-dark: #0f172a;
  --text-body: #334155;
  --text-muted: #64748b;
  --text-white: #ffffff;
  --text-light: #cbd5e1;
  
  --font-sans: 'Plus Jakarta Sans', system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-serif: 'Newsreader', 'Fraunces', Georgia, serif;
  
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.06);
  --shadow-md: 0 8px 24px -4px rgba(6, 22, 34, 0.08);
  --shadow-lg: 0 20px 35px -8px rgba(6, 22, 34, 0.16);
  --shadow-glow: 0 0 35px var(--teal-glow);
  --shadow-book: 0 25px 50px -12px rgba(0, 0, 0, 0.65), 0 0 0 1px rgba(255,255,255,0.15);
  
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 18px;
  --radius-full: 9999px;
}

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

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

body {
  font-family: var(--font-sans);
  color: var(--text-dark);
  background: var(--surface-subtle);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

img, svg {
  max-width: 100%;
  height: auto;
  display: block;
}

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

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
}

.container {
  width: 100%;
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 clamp(1.25rem, 4vw, 2.5rem);
}

/* ==========================================================================
   NAVIGATION / TOPBAR
   ========================================================================== */
.hb-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(6, 22, 34, 0.88);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
  height: 72px;
  display: flex;
  align-items: center;
  transition: all 0.3s ease;
}

.hb-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
}

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

.hb-brand img {
  height: 42px;
  width: auto;
  object-fit: contain;
}

.hb-brand-badge {
  font-size: 0.68rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  padding: 4px 8px;
  background: rgba(20, 184, 166, 0.15);
  color: var(--teal-400);
  border: 1px solid rgba(20, 184, 166, 0.3);
  border-radius: var(--radius-sm);
}

.hb-links {
  display: flex;
  align-items: center;
  gap: 2rem;
}

.hb-links a {
  color: var(--text-light);
  font-size: 0.88rem;
  font-weight: 500;
  transition: color 0.2s;
}

.hb-links a:hover {
  color: var(--surface-white);
}

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

.lang-switch {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--teal-400);
  padding: 6px 12px;
  border: 1px solid rgba(20, 184, 166, 0.35);
  border-radius: var(--radius-sm);
  transition: all 0.2s;
}

.lang-switch:hover {
  background: rgba(20, 184, 166, 0.15);
  color: var(--surface-white);
}

.btn-header-buy {
  background: linear-gradient(135deg, var(--gold-500), var(--gold-600));
  color: var(--navy-950);
  font-size: 0.85rem;
  font-weight: 700;
  padding: 8px 18px;
  border-radius: var(--radius-sm);
  box-shadow: 0 4px 12px var(--gold-glow);
  transition: all 0.2s ease;
  white-space: nowrap;
}

.btn-header-buy:hover {
  transform: translateY(-1px);
  filter: brightness(1.08);
}

/* ==========================================================================
   HERO SECTION
   ========================================================================== */
.hb-hero {
  position: relative;
  background: radial-gradient(circle at 75% 20%, #10384f 0%, var(--navy-900) 55%, var(--navy-950) 100%);
  color: var(--text-white);
  padding: clamp(3.5rem, 7vw, 6rem) 0 clamp(4rem, 8vw, 6.5rem);
  overflow: hidden;
}

.hb-hero::before {
  content: "";
  position: absolute;
  top: -150px;
  right: -100px;
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, rgba(20, 184, 166, 0.18) 0%, transparent 70%);
  pointer-events: none;
}

.hb-hero::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100%;
  height: 60px;
  background: linear-gradient(to top, var(--surface-subtle), transparent);
  pointer-events: none;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: clamp(2rem, 5vw, 4.5rem);
  align-items: center;
  position: relative;
  z-index: 2;
}

.hero-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--teal-400);
  background: rgba(20, 184, 166, 0.12);
  border: 1px solid rgba(20, 184, 166, 0.25);
  padding: 6px 14px;
  border-radius: var(--radius-full);
  margin-bottom: 1.5rem;
}

.hero-title {
  font-family: var(--font-serif);
  font-size: clamp(2rem, 3.4vw, 2.65rem);
  font-weight: 600;
  line-height: 1.12;
  letter-spacing: -0.025em;
  margin-bottom: 1.25rem;
  color: var(--surface-white);
}

.hero-title em {
  font-style: italic;
  font-weight: 400;
  color: var(--teal-400);
  background: linear-gradient(120deg, #5eead4, #38bdf8);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-lead {
  font-size: clamp(1rem, 1.2vw, 1.18rem);
  line-height: 1.65;
  color: var(--text-light);
  margin-bottom: 2rem;
  max-width: 620px;
}

.hero-pills {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 2.25rem;
}

.hero-pill {
  font-size: 0.75rem;
  font-weight: 600;
  padding: 5px 12px;
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(255, 255, 255, 0.12);
  border-radius: var(--radius-full);
  color: #e2e8f0;
  display: flex;
  align-items: center;
  gap: 6px;
}

.hero-pill svg {
  color: var(--teal-400);
}

/* Hero Buy Box */
.hero-buy-box {
  background: rgba(10, 33, 49, 0.85);
  border: 1px solid rgba(255, 255, 255, 0.15);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  box-shadow: 0 15px 35px -5px rgba(0, 0, 0, 0.4);
  backdrop-filter: blur(12px);
  max-width: 540px;
}

.buy-box-header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  margin-bottom: 1.25rem;
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
  padding-bottom: 1rem;
}

.price-display {
  display: flex;
  flex-direction: column;
}

.price-currency {
  font-size: 0.8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--teal-400);
}

.price-amount {
  font-family: var(--font-serif);
  font-size: 2.25rem;
  font-weight: 700;
  color: var(--surface-white);
  line-height: 1.1;
}

.price-usd-sub {
  font-size: 0.8rem;
  color: var(--text-muted);
}

.stock-badge {
  font-size: 0.75rem;
  font-weight: 700;
  color: #22c55e;
  background: rgba(34, 197, 94, 0.15);
  border: 1px solid rgba(34, 197, 94, 0.3);
  padding: 4px 10px;
  border-radius: var(--radius-sm);
  display: inline-flex;
  align-items: center;
  gap: 5px;
}

.btn-primary-buy {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  width: 100%;
  background: linear-gradient(135deg, var(--gold-500), var(--gold-600));
  color: var(--navy-950);
  font-size: 1.05rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  padding: 1.1rem 1.75rem;
  border-radius: var(--radius-md);
  box-shadow: 0 10px 25px -4px var(--gold-glow);
  transition: all 0.25s ease;
  margin-bottom: 0.85rem;
}

.btn-primary-buy:hover {
  transform: translateY(-2px);
  box-shadow: 0 14px 30px -4px var(--gold-glow);
  filter: brightness(1.08);
}

.buy-guarantee {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  font-size: 0.75rem;
  color: var(--text-light);
  text-align: center;
}

.buy-guarantee span {
  display: inline-flex;
  align-items: center;
  gap: 4px;
}

/* 3D Book Showcase */
.hero-visual {
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  perspective: 1200px;
}

.book-card-3d {
  position: relative;
  width: 100%;
  max-width: 420px;
  transform: rotateY(-8deg) rotateX(4deg);
  transform-style: preserve-3d;
  transition: transform 0.5s cubic-bezier(0.2, 0.8, 0.2, 1);
}

.book-card-3d:hover {
  transform: rotateY(-2deg) rotateX(0deg) translateY(-8px);
}

.book-cover-img {
  width: 100%;
  border-radius: 8px 16px 16px 8px;
  box-shadow: var(--shadow-book);
  border: 1px solid rgba(255, 255, 255, 0.12);
}

.book-badge-floating {
  position: absolute;
  top: 20px;
  right: -15px;
  background: var(--navy-900);
  border: 1px solid var(--teal-400);
  color: var(--teal-400);
  font-size: 0.72rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  padding: 8px 14px;
  border-radius: var(--radius-md);
  box-shadow: 0 10px 20px rgba(0,0,0,0.5);
  backdrop-filter: blur(8px);
}

.book-preview-trigger {
  margin-top: 1.5rem;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--teal-400);
  background: rgba(20, 184, 166, 0.1);
  border: 1px solid rgba(20, 184, 166, 0.3);
  padding: 10px 20px;
  border-radius: var(--radius-full);
  transition: all 0.2s ease;
}

.book-preview-trigger:hover {
  background: rgba(20, 184, 166, 0.25);
  color: var(--surface-white);
  transform: translateY(-2px);
}

/* ==========================================================================
   METRICS / PROOF STRIP
   ========================================================================== */
.proof-strip {
  background: var(--surface-white);
  border-bottom: 1px solid var(--surface-border);
  box-shadow: var(--shadow-sm);
}

.proof-strip-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
}

.proof-item {
  padding: 2rem 1.5rem;
  text-align: center;
  border-right: 1px solid var(--surface-border);
}

.proof-item:last-child {
  border-right: none;
}

.proof-value {
  font-family: var(--font-serif);
  font-size: clamp(2rem, 3vw, 2.75rem);
  font-weight: 700;
  color: var(--navy-900);
  line-height: 1;
  margin-bottom: 0.35rem;
}

.proof-label {
  font-size: 0.8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--teal-600);
  margin-bottom: 0.25rem;
}

.proof-sub {
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* ==========================================================================
   PROBLEM VS SOLUTION SECTION
   ========================================================================== */
.section-contrast {
  padding: clamp(4rem, 8vw, 7rem) 0;
  background: var(--surface-subtle);
}

.section-head-center {
  text-align: center;
  max-width: 820px;
  margin: 0 auto clamp(2.5rem, 5vw, 4rem);
}

.section-eyebrow {
  font-size: 0.72rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.16em;
  color: var(--teal-600);
  margin-bottom: 0.75rem;
  display: block;
}

.section-title {
  font-family: var(--font-serif);
  font-size: clamp(2rem, 3.5vw, 3rem);
  font-weight: 600;
  color: var(--navy-900);
  line-height: 1.18;
  letter-spacing: -0.02em;
  margin-bottom: 1rem;
}

.section-subtitle {
  font-size: 1.05rem;
  color: var(--text-muted);
  line-height: 1.6;
}

.contrast-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.75rem;
}

.contrast-card {
  background: var(--surface-white);
  border: 1px solid var(--surface-border);
  border-radius: var(--radius-lg);
  padding: 2rem 1.75rem;
  box-shadow: var(--shadow-sm);
  transition: transform 0.25s, box-shadow 0.25s;
}

.contrast-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
}

.contrast-tag {
  font-size: 0.7rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  padding: 4px 10px;
  border-radius: var(--radius-sm);
  display: inline-block;
  margin-bottom: 1.25rem;
}

.tag-red {
  background: #fef2f2;
  color: #dc2626;
  border: 1px solid #fecaca;
}

.contrast-problem {
  margin-bottom: 1.5rem;
  padding-bottom: 1.25rem;
  border-bottom: 1px dashed var(--surface-border);
}

.contrast-problem h4 {
  font-size: 1.05rem;
  color: var(--navy-900);
  margin-bottom: 0.5rem;
  font-weight: 700;
}

.contrast-problem p {
  font-size: 0.88rem;
  color: var(--text-muted);
}

.contrast-solution h5 {
  font-size: 0.75rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--teal-600);
  margin-bottom: 0.35rem;
}

.contrast-solution p {
  font-size: 0.92rem;
  font-weight: 600;
  color: var(--text-dark);
}

/* ==========================================================================
   INTERACTIVE CURRICULUM (24 CHAPTERS)
   ========================================================================== */
.section-curriculum {
  padding: clamp(2.8rem, 4.8vw, 4.2rem) 0;
  background: var(--surface-white);
  border-top: 1px solid var(--surface-border);
  border-bottom: 1px solid var(--surface-border);
}

.module-tabs {
  display: flex;
  gap: 8px;
  margin-bottom: 2.5rem;
  overflow-x: auto;
  padding-bottom: 8px;
  scrollbar-width: thin;
}

.module-tab {
  padding: 12px 20px;
  background: var(--surface-subtle);
  border: 1px solid var(--surface-border);
  border-radius: var(--radius-md);
  font-size: 0.88rem;
  font-weight: 700;
  color: var(--text-muted);
  white-space: nowrap;
  transition: all 0.2s ease;
}

.module-tab:hover {
  background: #e2e8f0;
  color: var(--navy-900);
}

.module-tab.active {
  background: var(--navy-900);
  border-color: var(--navy-900);
  color: var(--surface-white);
  box-shadow: 0 4px 12px rgba(6, 22, 34, 0.2);
}

.module-panel {
  display: none;
}

.module-panel.active {
  display: block;
}

.chapters-accordion-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.25rem;
}

.chapter-card {
  background: var(--surface-subtle);
  border: 1px solid var(--surface-border);
  border-radius: var(--radius-md);
  padding: 1.5rem;
  transition: all 0.2s ease;
}

.chapter-card:hover {
  border-color: var(--teal-500);
  background: #fcfdfd;
  box-shadow: 0 4px 14px rgba(13, 148, 136, 0.08);
}

.chapter-num {
  font-size: 0.72rem;
  font-weight: 800;
  color: var(--teal-600);
  text-transform: uppercase;
  letter-spacing: 0.12em;
  margin-bottom: 0.4rem;
}

.chapter-title {
  font-size: 1.12rem;
  font-weight: 700;
  color: var(--navy-900);
  line-height: 1.35;
  margin-bottom: 0.65rem;
}

.chapter-desc {
  font-size: 0.88rem;
  color: var(--text-muted);
  margin-bottom: 1rem;
}

.chapter-meta-tag {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--navy-700);
  background: #e0f2fe;
  padding: 3px 8px;
  border-radius: 4px;
}

/* ==========================================================================
   TECHNICAL BLUEPRINT & DIAGRAM SHOWCASE
   ========================================================================== */
.section-diagrams {
  padding: clamp(2.8rem, 4.8vw, 4.2rem) 0;
  background: var(--navy-950);
  color: var(--surface-white);
  position: relative;
}

.section-diagrams .section-title {
  color: var(--surface-white);
}

.diagram-gallery-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.75rem;
  margin-top: 2.5rem;
}

.diagram-item {
  background: var(--navy-900);
  border: 1px solid rgba(255, 255, 255, 0.12);
  border-radius: var(--radius-md);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: transform 0.25s, border-color 0.25s;
}

.diagram-item:hover {
  transform: translateY(-4px);
  border-color: var(--teal-400);
  box-shadow: 0 12px 30px rgba(0,0,0,0.5);
}

.diagram-frame {
  height: 220px;
  background: #0f172a;
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 12px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}

.diagram-frame img {
  width: 100%;
  height: 100%;
  object-fit: contain;
}

.diagram-caption {
  padding: 1.25rem;
  display: flex;
  flex-direction: column;
  flex-grow: 1;
}

.diagram-id {
  font-size: 0.7rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--teal-400);
  margin-bottom: 0.35rem;
}

.diagram-caption h4 {
  font-size: 1rem;
  font-weight: 700;
  color: var(--surface-white);
  margin-bottom: 0.5rem;
  line-height: 1.35;
}

.diagram-caption p {
  font-size: 0.82rem;
  color: var(--text-light);
  line-height: 1.5;
}

/* ==========================================================================
   PACKAGE BREAKDOWN (WHAT'S INSIDE)
   ========================================================================== */
.section-package {
  padding: clamp(2.8rem, 4.8vw, 4.2rem) 0;
  background: var(--surface-subtle);
}

.package-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1.5rem;
}

.package-item {
  background: var(--surface-white);
  border: 1px solid var(--surface-border);
  border-radius: var(--radius-lg);
  padding: 2rem 1.5rem;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
}

.package-icon {
  width: 52px;
  height: 52px;
  background: rgba(20, 184, 166, 0.1);
  color: var(--teal-600);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 1.25rem;
}

.package-item h3 {
  font-size: 1.2rem;
  color: var(--navy-900);
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.package-item p {
  font-size: 0.88rem;
  color: var(--text-muted);
  line-height: 1.55;
  margin-bottom: 1.25rem;
  flex-grow: 1;
}

.package-tag {
  font-size: 0.72rem;
  font-weight: 700;
  padding: 4px 8px;
  background: var(--surface-card);
  color: var(--navy-800);
  border-radius: 4px;
  align-self: flex-start;
}

/* ==========================================================================
   FAQ SECTION
   ========================================================================== */
.section-faq {
  padding: clamp(4.5rem, 8vw, 7rem) 0;
  background: var(--surface-white);
  border-top: 1px solid var(--surface-border);
}

.faq-wrapper {
  max-width: 860px;
  margin: 0 auto;
}

.faq-item {
  border-bottom: 1px solid var(--surface-border);
  padding: 1.5rem 0;
}

.faq-question {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  text-align: left;
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--navy-900);
  gap: 1rem;
}

.faq-icon {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: var(--surface-subtle);
  border: 1px solid var(--surface-border);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: transform 0.25s ease;
  color: var(--teal-600);
}

.faq-item.open .faq-icon {
  transform: rotate(45deg);
  background: var(--teal-600);
  color: var(--surface-white);
  border-color: var(--teal-600);
}

.faq-answer {
  display: none;
  padding-top: 1rem;
  font-size: 0.95rem;
  color: var(--text-body);
  line-height: 1.65;
}

.faq-item.open .faq-answer {
  display: block;
}

/* ==========================================================================
   FINAL CONVERSION CTA
   ========================================================================== */
.section-final-cta {
  padding: clamp(3rem, 5vw, 4.5rem) 0;
  background: radial-gradient(circle at 50% 30%, #0d384c 0%, var(--navy-900) 60%, var(--navy-950) 100%);
  color: var(--surface-white);
  text-align: center;
  position: relative;
}

.final-cta-content {
  max-width: 820px;
  margin: 0 auto;
}

.final-cta-content h2 {
  font-family: var(--font-serif);
  font-size: clamp(1.85rem, 3.2vw, 2.45rem);
  font-weight: 600;
  line-height: 1.12;
  margin-bottom: 1.25rem;
  letter-spacing: -0.02em;
}

.final-cta-content p {
  font-size: 1.12rem;
  color: var(--text-light);
  line-height: 1.6;
  margin-bottom: 2.25rem;
}

.final-cta-box {
  background: rgba(10, 33, 49, 0.8);
  border: 1px solid rgba(255, 255, 255, 0.15);
  border-radius: var(--radius-lg);
  padding: 2.5rem clamp(1.5rem, 4vw, 3rem);
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.4);
  backdrop-filter: blur(14px);
  margin: 0 auto 2rem;
  max-width: 580px;
}

/* Sticky Buy Bar */
.sticky-buy-bar {
  position: fixed;
  bottom: 0;
  left: 0;
  width: 100%;
  background: rgba(6, 22, 34, 0.94);
  backdrop-filter: blur(12px);
  border-top: 1px solid rgba(255, 255, 255, 0.12);
  padding: 12px clamp(1rem, 4vw, 2.5rem);
  z-index: 99;
  display: flex;
  align-items: center;
  justify-content: space-between;
  transform: translateY(100%);
  opacity: 0;
  pointer-events: none;
  transition: transform 0.3s cubic-bezier(0.2, 0.8, 0.2, 1), opacity 0.3s ease;
  box-shadow: 0 -10px 25px rgba(0,0,0,0.3);
}

.sticky-buy-bar.visible {
  transform: translateY(0);
  opacity: 1;
  pointer-events: auto;
}

.sticky-bar-left {
  display: flex;
  align-items: center;
  gap: 14px;
}

.sticky-bar-thumb {
  width: 42px;
  height: 54px;
  object-fit: cover;
  border-radius: 4px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.4);
}

.sticky-bar-info strong {
  display: block;
  font-size: 0.92rem;
  color: var(--surface-white);
  line-height: 1.2;
}

.sticky-bar-info span {
  font-size: 0.75rem;
  color: var(--teal-400);
}

.sticky-bar-right {
  display: flex;
  align-items: center;
  gap: 16px;
}

.sticky-price {
  font-family: var(--font-serif);
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--surface-white);
}

/* Lightbox Modal */
.preview-modal {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(4, 14, 21, 0.92);
  backdrop-filter: blur(8px);
  z-index: 1000;
  align-items: center;
  justify-content: center;
  padding: 20px;
}

.preview-modal.active {
  display: flex;
}

.preview-modal-inner {
  position: relative;
  background: var(--navy-900);
  border: 1px solid rgba(255, 255, 255, 0.15);
  border-radius: var(--radius-lg);
  max-width: 900px;
  width: 100%;
  max-height: 90vh;
  overflow-y: auto;
  padding: 2rem;
  color: var(--surface-white);
}

.preview-modal-close {
  position: absolute;
  top: 1.25rem;
  right: 1.25rem;
  width: 36px;
  height: 36px;
  background: rgba(255, 255, 255, 0.1);
  color: #ffffff;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
}

/* Footer & Legal */
.hb-footer {
  background: var(--navy-950);
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  padding: 3rem 0;
  color: var(--text-muted);
  font-size: 0.8rem;
}

.footer-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.5rem;
  text-align: center;
}

.footer-legal-notice {
  max-width: 800px;
  font-size: 0.75rem;
  color: #64748b;
  line-height: 1.6;
}

/* ==========================================================================
   RESPONSIVENESS (MOBILE / TABLET)
   ========================================================================== */
@media (max-width: 1024px) {
  .hero-grid {
    grid-template-columns: 1fr;
    text-align: center;
  }
  
  .hero-eyebrow, .hero-lead {
    margin-left: auto;
    margin-right: auto;
  }
  
  .hero-pills {
    justify-content: center;
  }
  
  .hero-buy-box {
    margin: 0 auto;
  }
  
  .hero-visual {
    margin-top: 2rem;
  }
  
  .contrast-grid, .diagram-gallery-grid, .package-grid, .photo-plates-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .chapters-accordion-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 768px) {
  html, body { max-width: 100%; overflow-x: hidden; }

  .hb-links {
    display: none;
  }

  .hb-header-inner { padding-inline: 12px; }

  .hb-nav-actions { gap: 8px; min-width: 0; }

  .hb-nav-actions .lang-switch { display: none; }

  .btn-header-buy {
    max-width: 180px;
    padding-inline: 10px;
    font-size: .72rem;
    white-space: normal;
    text-align: center;
    line-height: 1.2;
  }
  
  .proof-strip-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .proof-item {
    border-bottom: 1px solid var(--surface-border);
  }
  
  .proof-item:nth-child(2n) {
    border-right: none;
  }
  
  .contrast-grid, .diagram-gallery-grid, .package-grid, .photo-plates-grid {
    grid-template-columns: 1fr;
  }
  
  .sticky-bar-thumb, .sticky-bar-info {
    display: none;
  }
}

/* ==========================================================================
   PHOTO PLATES GALLERY & CHAPTER FIGURE TAGS
   ========================================================================== */
.photo-plates-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1.5rem;
  margin-top: 2rem;
}

.photo-plate-card {
  background: var(--surface-white);
  border: 1px solid var(--surface-border);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  transition: transform 0.25s cubic-bezier(0.16, 1, 0.3, 1), box-shadow 0.25s, border-color 0.25s;
  cursor: pointer;
}

.photo-plate-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-lg);
  border-color: var(--teal-500);
}

.photo-plate-thumb {
  position: relative;
  height: 190px;
  background: #0b1523;
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
}

.photo-plate-thumb img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.4s ease;
}

.photo-plate-card:hover .photo-plate-thumb img {
  transform: scale(1.06);
}

.photo-plate-zoom-badge {
  position: absolute;
  bottom: 8px;
  right: 8px;
  background: rgba(11, 21, 35, 0.85);
  backdrop-filter: blur(4px);
  color: var(--teal-300);
  font-size: 0.68rem;
  font-weight: 700;
  padding: 3px 8px;
  border-radius: 4px;
  display: inline-flex;
  align-items: center;
  gap: 4px;
  border: 1px solid rgba(255,255,255,0.1);
  transition: opacity 0.2s, background 0.2s;
}

.photo-plate-card:hover .photo-plate-zoom-badge {
  background: var(--teal-600);
  color: #fff;
}

.photo-plate-body {
  padding: 1.15rem;
  display: flex;
  flex-direction: column;
  flex-grow: 1;
}

.photo-plate-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.4rem;
}

.photo-plate-id {
  font-size: 0.68rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--teal-600);
}

.photo-plate-ch {
  font-size: 0.68rem;
  font-weight: 600;
  color: var(--text-muted);
}

.photo-plate-title {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--navy-900);
  line-height: 1.35;
  margin-bottom: 0.5rem;
}

.photo-plate-desc {
  font-size: 0.82rem;
  color: var(--text-muted);
  line-height: 1.5;
  margin-bottom: 0;
  flex-grow: 1;
}

/* Chapter Figure Pills in Syllabus */
.ch-figure-tag {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--teal-700);
  background: rgba(15, 118, 110, 0.08);
  border: 1px solid rgba(15, 118, 110, 0.2);
  border-radius: 4px;
  padding: 2px 7px;
  margin-top: 0.6rem;
  cursor: pointer;
  transition: background 0.15s, color 0.15s;
}

.ch-figure-tag:hover {
  background: var(--teal-600);
  color: #fff;
}

/* Module Visual Banner */
.module-visual-banner {
  background: var(--surface-subtle);
  border: 1px solid var(--surface-border);
  border-radius: var(--radius-md);
  padding: 1.25rem 1.5rem;
  margin-bottom: 1.75rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
  flex-wrap: wrap;
}

.module-visual-banner-info {
  flex: 1;
  min-width: 260px;
}

.module-visual-banner-title {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--navy-900);
  margin-bottom: 0.25rem;
}

.module-visual-banner-sub {
  font-size: 0.82rem;
  color: var(--text-muted);
  line-height: 1.45;
  margin: 0;
}

.module-visual-banner-thumbs {
  display: flex;
  gap: 0.75rem;
}

.module-visual-thumb {
  width: 76px;
  height: 52px;
  border-radius: 4px;
  overflow: hidden;
  border: 1px solid var(--surface-border);
  box-shadow: 0 2px 6px rgba(0,0,0,0.06);
  cursor: pointer;
  transition: transform 0.2s, box-shadow 0.2s;
}

.module-visual-thumb:hover {
  transform: translateY(-2px) scale(1.05);
  box-shadow: 0 4px 12px rgba(0,0,0,0.15);
  border-color: var(--teal-500);
}

.module-visual-thumb img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

/* Modal 6-Batch Switcher Grid */
.modal-batch-grid {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: 8px;
  margin-bottom: 1.25rem;
}

@media (max-width: 900px) {
  .modal-batch-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

@media (max-width: 500px) {
  .modal-batch-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

.modal-batch-btn {
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(255, 255, 255, 0.15);
  color: #94a3b8;
  padding: 8px 10px;
  border-radius: var(--radius-sm);
  font-size: 0.76rem;
  font-weight: 700;
  text-align: center;
  cursor: pointer;
  transition: all 0.2s;
  line-height: 1.3;
}

.modal-batch-btn:hover {
  background: rgba(255, 255, 255, 0.12);
  color: #fff;
  border-color: var(--teal-400);
}

.modal-batch-btn.active {
  background: var(--teal-600);
  border-color: var(--teal-400);
  color: #fff;
  box-shadow: 0 4px 12px rgba(13, 148, 136, 0.35);
}

/* WCAG AA contrast for controls, light solution panels, and legal copy. */
.book-preview-trigger { color: #075f58 !important; border-color: #08746b !important; }
.contrast-solution h5 { color: #075f58 !important; }
.hb-footer p { color: #94aeb8 !important; }