/* ==========================================================================
   AI STUDY SYSTEM - MASTER RESPONSIVE & MOBILE-FIRST STYLESHEET
   Carefully calibrated across 320px, 375px, 390px, 430px, 768px, 1024px, 1366px, 1920px
   Accent Color: Warm Orange (#EA580C)
   Background: Clean Crisp Light (#F8FAFC)
   ========================================================================== */

:root {
  /* Brand Palette */
  --color-primary: #EA580C;         /* Vibrant Warm Orange */
  --color-primary-hover: #C2410C;   /* Deep Orange Hover */
  --color-primary-subtle: #FFF7ED;  /* Soft Orange Tint */
  --color-primary-border: #FFEDD5;  /* Light Orange Border */
  
  --color-text-main: #0F172A;       /* Deep Charcoal Heading */
  --color-text-body: #334155;       /* Muted Charcoal Body */
  --color-text-muted: #64748B;      /* Light Slate */
  
  --color-bg-page: #F8FAFC;         /* Soft Off-White */
  --color-bg-card: #FFFFFF;         /* Pure Crisp White */
  --color-border: #E2E8F0;          /* Subtle Border */
  --color-border-card: #E2E8F0;
  
  /* Modern Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -1px rgba(0, 0, 0, 0.04);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -2px rgba(0, 0, 0, 0.03);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  
  /* Border Radii */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 20px;
  --radius-full: 9999px;
  
  /* Font Family */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-size-adjust: 100%;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  color: var(--color-text-body);
  background-color: var(--color-bg-page);
  line-height: 1.6;
  overflow-x: hidden;
  position: relative;
  width: 100%;
  /* Leave space for sticky mobile bar + iOS safe-area home indicator */
  padding-bottom: max(72px, calc(64px + env(safe-area-inset-bottom)));
}

@media (min-width: 768px) {
  body {
    padding-bottom: 0;
  }
}

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

a {
  color: inherit;
  text-decoration: none;
  -webkit-tap-highlight-color: transparent;
}

button {
  -webkit-tap-highlight-color: transparent;
}

/* Container */
.container {
  width: 100%;
  max-width: 1120px;
  margin-left: auto;
  margin-right: auto;
  padding-left: 16px;
  padding-right: 16px;
}

@media (min-width: 480px) {
  .container {
    padding-left: 20px;
    padding-right: 20px;
  }
}

@media (min-width: 1024px) {
  .container {
    padding-left: 24px;
    padding-right: 24px;
  }
}

/* ==========================================================================
   TOP ANNOUNCEMENT BAR
   ========================================================================== */
.top-bar {
  background-color: #0F172A;
  color: #F8FAFC;
  font-size: 0.775rem;
  font-weight: 500;
  padding: 8px 12px;
  text-align: center;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
  line-height: 1.4;
}

@media (min-width: 480px) {
  .top-bar {
    font-size: 0.8125rem;
    padding: 9px 16px;
  }
}

.top-bar-content {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  flex-wrap: wrap;
}

.badge-pill {
  background-color: var(--color-primary);
  color: #FFFFFF;
  padding: 2px 7px;
  border-radius: var(--radius-full);
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  display: inline-block;
  line-height: 1.3;
}

/* ==========================================================================
   SECTION COMMON STYLES
   ========================================================================== */
.section {
  padding: 44px 0;
  position: relative;
}

@media (min-width: 480px) {
  .section {
    padding: 56px 0;
  }
}

@media (min-width: 768px) {
  .section {
    padding: 72px 0;
  }
}

@media (min-width: 1024px) {
  .section {
    padding: 80px 0;
  }
}

.text-center {
  text-align: center;
}

.section-header {
  margin-bottom: 32px;
}

@media (min-width: 768px) {
  .section-header {
    margin-bottom: 48px;
  }
}

.section-tag {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1.1px;
  color: var(--color-primary);
  background-color: var(--color-primary-subtle);
  border: 1px solid var(--color-primary-border);
  padding: 3px 10px;
  border-radius: var(--radius-full);
  margin-bottom: 10px;
}

@media (min-width: 480px) {
  .section-tag {
    font-size: 0.8rem;
    padding: 4px 12px;
    margin-bottom: 12px;
  }
}

.section-heading {
  font-size: clamp(1.4rem, 3.2vw + 0.6rem, 2.35rem);
  font-weight: 800;
  color: var(--color-text-main);
  line-height: 1.25;
  letter-spacing: -0.02em;
  word-break: break-word;
}

.section-subtext {
  font-size: clamp(0.9rem, 1.2vw + 0.6rem, 1.075rem);
  color: var(--color-text-muted);
  max-width: 680px;
  margin: 10px auto 0;
  line-height: 1.55;
  padding: 0 4px;
}

/* ==========================================================================
   BUTTONS (TOUCH-OPTIMIZED, MIN 48PX HEIGHT)
   ========================================================================== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-family: var(--font-sans);
  font-weight: 700;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all 0.2s ease-in-out;
  border: none;
  text-align: center;
  min-height: 48px;
  touch-action: manipulation;
  user-select: none;
  -webkit-user-select: none;
}

.btn-primary {
  background-color: var(--color-primary);
  color: #FFFFFF;
  box-shadow: 0 4px 14px 0 rgba(234, 88, 12, 0.35);
}

.btn-primary:hover {
  background-color: var(--color-primary-hover);
  transform: translateY(-2px);
  box-shadow: 0 6px 20px 0 rgba(234, 88, 12, 0.45);
}

.btn-primary:active {
  transform: translateY(0);
}

.btn-hero {
  padding: 14px 28px;
  font-size: 1.05rem;
  width: 100%;
}

@media (min-width: 480px) {
  .btn-hero {
    width: auto;
    font-size: 1.125rem;
    padding: 15px 32px;
  }
}

.btn-large {
  padding: 16px 28px;
  font-size: 1.1rem;
  width: 100%;
}

@media (min-width: 480px) {
  .btn-large {
    padding: 16px 36px;
    font-size: 1.175rem;
  }
}

.btn-block {
  width: 100%;
  padding: 14px 20px;
  font-size: 0.975rem;
}

.btn-sm {
  padding: 9px 16px;
  font-size: 0.875rem;
  min-height: 40px;
  border-radius: var(--radius-sm);
}

.btn-arrow {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
  transition: transform 0.2s ease;
}

.btn:hover .btn-arrow {
  transform: translateX(4px);
}

/* ==========================================================================
   SECTION 1: HERO SECTION
   ========================================================================== */
.hero-section {
  padding: 32px 0 48px;
  background: linear-gradient(180deg, #FFFFFF 0%, #F8FAFC 100%);
  border-bottom: 1px solid var(--color-border);
}

@media (min-width: 768px) {
  .hero-section {
    padding: 56px 0 72px;
  }
}

@media (min-width: 1024px) {
  .hero-section {
    padding: 68px 0 84px;
  }
}

.hero-container {
  display: grid;
  grid-template-columns: 1fr;
  gap: 36px;
  align-items: center;
}

@media (min-width: 860px) {
  .hero-container {
    grid-template-columns: 1.15fr 0.85fr;
    gap: 48px;
  }
}

@media (min-width: 1024px) {
  .hero-container {
    grid-template-columns: 1.25fr 0.75fr;
    gap: 60px;
  }
}

.product-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background-color: #FEF3C7;
  color: #92400E;
  border: 1px solid #FDE68A;
  padding: 5px 12px;
  border-radius: var(--radius-full);
  font-size: 0.78rem;
  font-weight: 700;
  margin-bottom: 14px;
  max-width: 100%;
}

@media (min-width: 480px) {
  .product-badge {
    font-size: 0.825rem;
    padding: 6px 14px;
    margin-bottom: 16px;
  }
}

.badge-icon {
  width: 15px;
  height: 15px;
  flex-shrink: 0;
}

.hero-title {
  font-size: clamp(1.65rem, 4.2vw + 0.5rem, 2.75rem);
  font-weight: 800;
  color: var(--color-text-main);
  line-height: 1.22;
  letter-spacing: -0.025em;
  margin-bottom: 14px;
  word-break: break-word;
}

.hero-title .highlight {
  color: var(--color-primary);
  display: inline-block;
  position: relative;
}

.hero-subtitle {
  font-size: clamp(0.95rem, 1.3vw + 0.55rem, 1.15rem);
  line-height: 1.55;
  color: var(--color-text-body);
  margin-bottom: 18px;
  max-width: 600px;
}

.reassurance-bar {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 6px 8px;
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--color-text-muted);
  margin-bottom: 22px;
}

@media (min-width: 480px) {
  .reassurance-bar {
    font-size: 0.875rem;
    gap: 8px;
    margin-bottom: 26px;
  }
}

.reassurance-bar .dot {
  color: var(--color-primary);
  font-weight: bold;
}

.hero-purchase-box {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-bottom: 16px;
}

@media (min-width: 480px) {
  .hero-purchase-box {
    flex-direction: row;
    align-items: center;
    gap: 16px;
  }
}

.price-container {
  display: flex;
  align-items: baseline;
  gap: 6px;
}

.price-label {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--color-text-muted);
}

.price-val {
  font-size: clamp(1.85rem, 3vw + 0.8rem, 2.25rem);
  font-weight: 800;
  color: var(--color-text-main);
  letter-spacing: -0.02em;
  line-height: 1;
}

.delivery-notice {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.825rem;
  font-weight: 500;
  color: #15803D;
  line-height: 1.4;
}

@media (min-width: 480px) {
  .delivery-notice {
    font-size: 0.875rem;
    gap: 8px;
  }
}

.check-icon {
  width: 17px;
  height: 17px;
  flex-shrink: 0;
}

/* 3D Realistic Ebook Mockup */
.hero-mockup-col {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  width: 100%;
}

.book-card-wrap {
  perspective: 1000px;
  position: relative;
  display: inline-block;
  padding: 6px;
  max-width: 100%;
}

.book-3d {
  position: relative;
  width: 240px;
  max-width: 75vw;
  border-radius: 4px 10px 10px 4px;
  transform: rotateY(-12deg) rotateX(3deg);
  transform-style: preserve-3d;
  box-shadow: -8px 8px 24px -3px rgba(0, 0, 0, 0.25), 
              0 16px 30px -4px rgba(234, 88, 12, 0.18);
  transition: transform 0.35s ease, box-shadow 0.35s ease;
  background: #000;
}

@media (min-width: 380px) {
  .book-3d {
    width: 270px;
    transform: rotateY(-16deg) rotateX(4deg);
  }
}

@media (min-width: 768px) {
  .book-3d {
    width: 310px;
  }
}

.book-card-wrap:hover .book-3d {
  transform: rotateY(-8deg) rotateX(2deg) translateY(-6px);
  box-shadow: -12px 12px 30px -4px rgba(0, 0, 0, 0.3), 
              0 22px 40px -4px rgba(234, 88, 12, 0.25);
}

.book-spine {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  width: 12px;
  background: linear-gradient(90deg, rgba(255,255,255,0.4) 0%, rgba(0,0,0,0.15) 60%, rgba(0,0,0,0.4) 100%);
  border-radius: 4px 0 0 4px;
  z-index: 2;
  pointer-events: none;
}

.book-cover {
  width: 100%;
  height: auto;
  border-radius: 4px 10px 10px 4px;
  display: block;
}

.book-shadow {
  position: absolute;
  bottom: 4px;
  left: 5%;
  width: 90%;
  height: 18px;
  background: radial-gradient(ellipse at center, rgba(0,0,0,0.22) 0%, rgba(0,0,0,0) 70%);
  filter: blur(5px);
  z-index: -1;
}

.book-specs-pill {
  margin-top: 18px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  background-color: var(--color-bg-card);
  border: 1px solid var(--color-border);
  padding: 6px 14px;
  border-radius: var(--radius-full);
  font-size: 0.775rem;
  font-weight: 600;
  color: var(--color-text-main);
  box-shadow: var(--shadow-sm);
  max-width: 100%;
  flex-wrap: wrap;
}

@media (min-width: 480px) {
  .book-specs-pill {
    margin-top: 22px;
    gap: 12px;
    padding: 8px 18px;
    font-size: 0.85rem;
  }
}

.spec-divider {
  color: var(--color-border);
}

/* ==========================================================================
   SECTION 2: THE STUDENT'S PROBLEM
   ========================================================================== */
.problem-section {
  background-color: #FFFFFF;
  border-bottom: 1px solid var(--color-border);
}

.problem-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
  max-width: 840px;
  margin: 0 auto;
}

@media (min-width: 600px) {
  .problem-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 16px;
  }
  .problem-grid > .problem-card:last-child {
    grid-column: span 2;
    max-width: 520px;
    margin: 0 auto;
    width: 100%;
  }
}

.problem-card {
  background-color: #F8FAFC;
  border: 1px solid #E2E8F0;
  border-radius: var(--radius-md);
  padding: 16px 18px;
  display: flex;
  align-items: flex-start;
  gap: 14px;
  transition: transform 0.2s ease, border-color 0.2s ease;
}

@media (min-width: 480px) {
  .problem-card {
    padding: 20px 22px;
    gap: 16px;
  }
}

.problem-card:hover {
  transform: translateY(-2px);
  border-color: #CBD5E1;
}

.problem-icon-wrap {
  width: 36px;
  height: 36px;
  border-radius: 8px;
  background-color: #FEE2E2;
  color: #DC2626;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.problem-icon-wrap svg {
  width: 18px;
  height: 18px;
}

.problem-text {
  font-size: 0.925rem;
  font-weight: 500;
  color: var(--color-text-main);
  line-height: 1.5;
}

@media (min-width: 480px) {
  .problem-text {
    font-size: 0.975rem;
  }
}

.transition-banner {
  margin-top: 28px;
  background-color: var(--color-primary-subtle);
  border: 1px solid var(--color-primary-border);
  border-left: 4px solid var(--color-primary);
  border-radius: var(--radius-md);
  padding: 16px 18px;
  max-width: 840px;
  margin-left: auto;
  margin-right: auto;
  text-align: center;
}

@media (min-width: 480px) {
  .transition-banner {
    margin-top: 36px;
    padding: 20px 24px;
    border-left-width: 5px;
  }
}

.transition-text {
  font-size: clamp(0.925rem, 1vw + 0.55rem, 1.05rem);
  font-weight: 600;
  color: #9A3412;
  line-height: 1.55;
}

/* ==========================================================================
   SECTION 3: WHAT YOU WILL LEARN
   ========================================================================== */
.learn-section {
  background-color: var(--color-bg-page);
  border-bottom: 1px solid var(--color-border);
}

.feature-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 16px;
}

@media (min-width: 600px) {
  .feature-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 960px) {
  .feature-grid {
    grid-template-columns: repeat(3, 1fr);
    gap: 22px;
  }
}

.feature-card {
  background-color: var(--color-bg-card);
  border: 1px solid var(--color-border-card);
  border-radius: var(--radius-lg);
  padding: 22px 18px;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

@media (min-width: 480px) {
  .feature-card {
    padding: 26px 22px;
  }
}

.feature-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
  border-color: var(--color-primary-border);
}

.feature-icon {
  width: 44px;
  height: 44px;
  border-radius: 12px;
  background-color: var(--color-primary-subtle);
  color: var(--color-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 16px;
}

.feature-icon svg {
  width: 22px;
  height: 22px;
}

.feature-title {
  font-size: clamp(1.05rem, 1.2vw + 0.5rem, 1.175rem);
  font-weight: 700;
  color: var(--color-text-main);
  margin-bottom: 8px;
  line-height: 1.35;
}

.feature-desc {
  font-size: 0.9rem;
  color: var(--color-text-body);
  line-height: 1.55;
}

@media (min-width: 480px) {
  .feature-desc {
    font-size: 0.95rem;
  }
}

/* ==========================================================================
   SECTION 4: THE 30-DAY STUDY CHALLENGE
   ========================================================================== */
.challenge-section {
  background-color: #FFFFFF;
  border-bottom: 1px solid var(--color-border);
}

.timeline-container {
  display: grid;
  grid-template-columns: 1fr;
  gap: 14px;
  max-width: 960px;
  margin: 0 auto;
}

@media (min-width: 600px) {
  .timeline-container {
    grid-template-columns: repeat(2, 1fr);
    gap: 18px;
  }
}

@media (min-width: 960px) {
  .timeline-container {
    grid-template-columns: repeat(4, 1fr);
    gap: 18px;
  }
}

.timeline-card {
  background-color: #F8FAFC;
  border: 1px solid #E2E8F0;
  border-radius: var(--radius-md);
  padding: 20px 18px;
  position: relative;
  display: flex;
  flex-direction: column;
  border-top: 4px solid var(--color-primary);
  transition: transform 0.2s ease;
}

@media (min-width: 480px) {
  .timeline-card {
    padding: 24px 20px;
  }
}

.timeline-card:hover {
  transform: translateY(-3px);
}

.timeline-badge {
  display: inline-block;
  background-color: var(--color-primary);
  color: #FFFFFF;
  font-size: 0.72rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  padding: 3px 9px;
  border-radius: var(--radius-full);
  margin-bottom: 12px;
  align-self: flex-start;
}

.timeline-title {
  font-size: 1rem;
  font-weight: 700;
  color: var(--color-text-main);
  margin-bottom: 6px;
  line-height: 1.35;
}

@media (min-width: 480px) {
  .timeline-title {
    font-size: 1.05rem;
  }
}

.timeline-desc {
  font-size: 0.875rem;
  color: var(--color-text-body);
  line-height: 1.5;
}

.challenge-footer {
  margin-top: 28px;
}

@media (min-width: 480px) {
  .challenge-footer {
    margin-top: 36px;
  }
}

.challenge-note {
  display: inline-block;
  font-size: clamp(0.85rem, 1vw + 0.5rem, 0.95rem);
  font-weight: 600;
  color: var(--color-text-muted);
  background-color: #F1F5F9;
  padding: 10px 18px;
  border-radius: var(--radius-full);
  max-width: 100%;
  line-height: 1.45;
}

/* ==========================================================================
   SECTION 5: WHAT'S INCLUDED
   ========================================================================== */
.included-section {
  background-color: var(--color-bg-page);
  border-bottom: 1px solid var(--color-border);
}

.included-card-wrapper {
  background-color: #FFFFFF;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 24px 18px;
  max-width: 960px;
  margin: 0 auto;
  box-shadow: var(--shadow-sm);
  display: grid;
  grid-template-columns: 1fr;
  gap: 28px;
}

@media (min-width: 480px) {
  .included-card-wrapper {
    padding: 32px 24px;
    border-radius: var(--radius-xl);
  }
}

@media (min-width: 800px) {
  .included-card-wrapper {
    grid-template-columns: 1.35fr 1fr;
    padding: 40px 36px;
    align-items: center;
    gap: 40px;
  }
}

.included-list {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.included-item {
  display: flex;
  align-items: flex-start;
  gap: 12px;
}

@media (min-width: 480px) {
  .included-item {
    gap: 14px;
  }
}

.inc-check {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background-color: #DCFCE7;
  color: #16A34A;
  font-weight: 800;
  font-size: 0.8rem;
  flex-shrink: 0;
  margin-top: 2px;
}

.inc-text strong {
  display: block;
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--color-text-main);
  line-height: 1.35;
}

@media (min-width: 480px) {
  .inc-text strong {
    font-size: 1rem;
  }
}

.inc-text p {
  font-size: 0.825rem;
  color: var(--color-text-muted);
  margin-top: 2px;
  line-height: 1.4;
}

@media (min-width: 480px) {
  .inc-text p {
    font-size: 0.875rem;
  }
}

.included-summary-box {
  background: linear-gradient(135deg, #FFF7ED 0%, #FFEDD5 100%);
  border: 1px solid #FED7AA;
  border-radius: var(--radius-md);
  padding: 24px 18px;
  text-align: center;
}

@media (min-width: 480px) {
  .included-summary-box {
    padding: 32px 24px;
    border-radius: var(--radius-lg);
  }
}

.summary-badge {
  display: inline-block;
  background-color: #EA580C;
  color: #FFFFFF;
  font-size: 0.72rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  padding: 3px 10px;
  border-radius: var(--radius-full);
  margin-bottom: 12px;
}

.summary-title {
  font-size: clamp(1.15rem, 1.5vw + 0.6rem, 1.3rem);
  font-weight: 800;
  color: #9A3412;
  margin-bottom: 8px;
  line-height: 1.3;
}

.summary-desc {
  font-size: 0.875rem;
  color: #7C2D12;
  margin-bottom: 20px;
  line-height: 1.5;
}

/* ==========================================================================
   SECTION 6: INSIDE THE EBOOK – PREVIEW 6 PAGES (BULLETPROOF RESPONSIVE)
   ========================================================================== */
.preview-section {
  background-color: #FFFFFF;
  border-bottom: 1px solid var(--color-border);
}

.preview-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 20px;
  max-width: 1040px;
  margin: 0 auto;
}

@media (min-width: 600px) {
  .preview-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 20px;
  }
}

@media (min-width: 960px) {
  .preview-grid {
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
  }
}

.preview-card {
  background-color: #F8FAFC;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  overflow: hidden;
  cursor: pointer;
  transition: transform 0.25s ease, box-shadow 0.25s ease, border-color 0.25s ease;
  display: flex;
  flex-direction: column;
  -webkit-tap-highlight-color: transparent;
  touch-action: manipulation;
}

.preview-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-lg);
  border-color: var(--color-primary);
}

.preview-frame {
  position: relative;
  background-color: #FFFFFF;
  border-bottom: 1px solid var(--color-border);
  overflow: hidden;
  aspect-ratio: 1 / 1.414; /* Standard A4 paper aspect ratio */
  width: 100%;
}

.preview-frame img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: top;
  transition: transform 0.3s ease;
}

.preview-card:hover .preview-frame img {
  transform: scale(1.025);
}

.preview-overlay {
  position: absolute;
  inset: 0;
  background-color: rgba(15, 23, 42, 0.45);
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  transition: opacity 0.2s ease;
}

.preview-card:hover .preview-overlay {
  opacity: 1;
}

/* On mobile / touchscreens, show the zoom badge clearly */
@media (hover: none), (max-width: 767px) {
  .preview-overlay {
    opacity: 1;
    background-color: transparent;
    align-items: flex-end;
    justify-content: flex-end;
    padding: 10px;
    pointer-events: none;
  }
  
  .zoom-btn {
    background-color: rgba(15, 23, 42, 0.75);
    color: #FFFFFF !important;
    backdrop-filter: blur(4px);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
  }
}

.zoom-btn {
  background-color: #FFFFFF;
  color: var(--color-text-main);
  padding: 6px 14px;
  border-radius: var(--radius-full);
  font-size: 0.78rem;
  font-weight: 700;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  box-shadow: var(--shadow-md);
  user-select: none;
}

.zoom-btn svg {
  width: 15px;
  height: 15px;
}

.preview-info {
  padding: 14px 16px;
  flex-grow: 1;
  display: flex;
  flex-direction: column;
}

@media (min-width: 480px) {
  .preview-info {
    padding: 16px 18px;
  }
}

.page-tag {
  display: inline-block;
  align-self: flex-start;
  font-size: 0.7rem;
  font-weight: 800;
  text-transform: uppercase;
  color: var(--color-primary);
  background-color: var(--color-primary-subtle);
  padding: 2px 7px;
  border-radius: var(--radius-full);
  margin-bottom: 6px;
}

.preview-title {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--color-text-main);
  margin-bottom: 4px;
  line-height: 1.35;
}

@media (min-width: 480px) {
  .preview-title {
    font-size: 1rem;
    margin-bottom: 6px;
  }
}

.preview-caption {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  line-height: 1.45;
}

/* ==========================================================================
   SECTION 7: WHO IS THIS EBOOK FOR?
   ========================================================================== */
.audience-section {
  background-color: var(--color-bg-page);
  border-bottom: 1px solid var(--color-border);
}

.audience-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 14px;
}

@media (min-width: 600px) {
  .audience-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 960px) {
  .audience-grid {
    grid-template-columns: repeat(3, 1fr);
    gap: 18px;
  }
}

.audience-card {
  background-color: #FFFFFF;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 20px 18px;
  transition: transform 0.2s ease, border-color 0.2s ease;
}

@media (min-width: 480px) {
  .audience-card {
    padding: 24px 20px;
    border-radius: var(--radius-lg);
  }
}

.audience-card:hover {
  transform: translateY(-3px);
  border-color: #CBD5E1;
}

.aud-icon {
  font-size: 1.6rem;
  margin-bottom: 12px;
  line-height: 1;
}

.aud-title {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--color-text-main);
  margin-bottom: 6px;
  line-height: 1.35;
}

.aud-desc {
  font-size: 0.875rem;
  color: var(--color-text-body);
  line-height: 1.5;
}

@media (min-width: 480px) {
  .aud-desc {
    font-size: 0.925rem;
  }
}

/* ==========================================================================
   SECTION 8: FINAL PURCHASE SECTION
   ========================================================================== */
.final-purchase-section {
  background-color: #FFFFFF;
  border-bottom: 1px solid var(--color-border);
}

.final-card {
  background: linear-gradient(180deg, #FFFFFF 0%, #FFFBF5 100%);
  border: 2px solid var(--color-primary-border);
  border-radius: var(--radius-lg);
  padding: 24px 16px;
  max-width: 960px;
  margin: 0 auto;
  box-shadow: 0 10px 30px -10px rgba(234, 88, 12, 0.12);
}

@media (min-width: 480px) {
  .final-card {
    border-radius: var(--radius-xl);
    padding: 32px 24px;
  }
}

@media (min-width: 768px) {
  .final-card {
    padding: 44px 36px;
  }
}

.final-card-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 28px;
  align-items: center;
}

@media (min-width: 768px) {
  .final-card-grid {
    grid-template-columns: 0.8fr 1.2fr;
    gap: 40px;
  }
}

@media (min-width: 1024px) {
  .final-card-grid {
    grid-template-columns: 0.75fr 1.25fr;
    gap: 48px;
  }
}

.final-visual-col {
  display: flex;
  justify-content: center;
  width: 100%;
}

.final-book-wrapper {
  position: relative;
  width: 220px;
  max-width: 70vw;
}

@media (min-width: 480px) {
  .final-book-wrapper {
    width: 260px;
  }
}

.final-cover-img {
  width: 100%;
  border-radius: 8px;
  box-shadow: var(--shadow-lg);
}

.final-book-badge {
  position: absolute;
  top: 10px;
  right: -8px;
  background-color: var(--color-primary);
  color: #FFFFFF;
  font-size: 0.75rem;
  font-weight: 800;
  padding: 3px 10px;
  border-radius: var(--radius-full);
  box-shadow: var(--shadow-md);
}

.final-tag {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 800;
  text-transform: uppercase;
  color: var(--color-primary);
  background-color: var(--color-primary-subtle);
  border: 1px solid var(--color-primary-border);
  padding: 3px 10px;
  border-radius: var(--radius-full);
  margin-bottom: 10px;
}

.final-title {
  font-size: clamp(1.75rem, 3.5vw + 0.5rem, 2.35rem);
  font-weight: 800;
  color: var(--color-text-main);
  line-height: 1.2;
  margin-bottom: 8px;
}

.final-subtitle {
  font-size: clamp(0.925rem, 1.2vw + 0.5rem, 1.05rem);
  color: var(--color-text-body);
  margin-bottom: 16px;
  line-height: 1.5;
}

.final-specs {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 20px;
}

.final-spec-item {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--color-text-muted);
  background-color: #F1F5F9;
  padding: 4px 10px;
  border-radius: var(--radius-sm);
}

.final-included-box {
  background-color: #FFFFFF;
  border: 1px solid #E2E8F0;
  border-radius: var(--radius-md);
  padding: 16px;
  margin-bottom: 22px;
}

@media (min-width: 480px) {
  .final-included-box {
    padding: 20px;
    margin-bottom: 24px;
  }
}

.inc-box-title {
  font-size: 0.925rem;
  font-weight: 700;
  color: var(--color-text-main);
  margin-bottom: 10px;
}

.inc-checklist {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.inc-checklist li {
  font-size: 0.85rem;
  color: var(--color-text-body);
  line-height: 1.4;
}

@media (min-width: 480px) {
  .inc-checklist li {
    font-size: 0.9rem;
  }
}

.final-price-row {
  display: flex;
  flex-direction: column;
  gap: 16px;
  background-color: var(--color-primary-subtle);
  border: 1px solid var(--color-primary-border);
  border-radius: var(--radius-md);
  padding: 18px 16px;
  margin-bottom: 20px;
}

@media (min-width: 520px) {
  .final-price-row {
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
    padding: 22px 24px;
    gap: 20px;
  }
  .final-cta-area {
    min-width: 240px;
  }
}

.price-desc {
  display: block;
  font-size: 0.78rem;
  font-weight: 600;
  color: #9A3412;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.price-number {
  font-size: clamp(2rem, 3.5vw + 0.8rem, 2.5rem);
  font-weight: 800;
  color: var(--color-text-main);
  line-height: 1;
  margin-top: 4px;
}

.final-guarantees {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.fg-item {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--color-text-muted);
}

@media (min-width: 480px) {
  .fg-item {
    font-size: 0.85rem;
  }
}

.fg-item svg {
  width: 16px;
  height: 16px;
  color: #16A34A;
  flex-shrink: 0;
}

/* ==========================================================================
   SECTION 9: FAQ (TOUCH-FRIENDLY ACCORDION)
   ========================================================================== */
.faq-section {
  background-color: var(--color-bg-page);
  border-bottom: 1px solid var(--color-border);
}

.faq-container {
  max-width: 760px;
}

.faq-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.faq-item {
  background-color: #FFFFFF;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  overflow: hidden;
  transition: border-color 0.2s ease;
}

.faq-item:hover {
  border-color: #CBD5E1;
}

.faq-question {
  width: 100%;
  padding: 16px 18px;
  background: none;
  border: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
  text-align: left;
  font-family: var(--font-sans);
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--color-text-main);
  cursor: pointer;
  gap: 12px;
  min-height: 52px;
  line-height: 1.4;
}

@media (min-width: 480px) {
  .faq-question {
    padding: 18px 22px;
    font-size: 1.05rem;
    gap: 16px;
  }
}

.faq-toggle-icon {
  font-size: 1.35rem;
  font-weight: 400;
  color: var(--color-primary);
  transition: transform 0.2s ease;
  flex-shrink: 0;
  line-height: 1;
}

.faq-answer {
  padding: 0 18px 18px 18px;
  display: none;
  font-size: 0.9rem;
  color: var(--color-text-body);
  line-height: 1.6;
}

@media (min-width: 480px) {
  .faq-answer {
    padding: 0 22px 20px 22px;
    font-size: 0.975rem;
  }
}

.faq-answer.show {
  display: block;
}

/* ==========================================================================
   FOOTER
   ========================================================================== */
.site-footer {
  background-color: #0F172A;
  color: #94A3B8;
  padding: 40px 0 24px;
}

@media (min-width: 768px) {
  .site-footer {
    padding: 50px 0 30px;
  }
}

.footer-brand strong {
  font-size: 1.2rem;
  color: #FFFFFF;
  letter-spacing: 0.5px;
}

.footer-tagline {
  font-size: 0.85rem;
  margin-top: 6px;
  color: #CBD5E1;
  max-width: 580px;
  margin-left: auto;
  margin-right: auto;
  line-height: 1.45;
}

.disclaimer-box {
  margin: 24px auto;
  max-width: 760px;
  background-color: rgba(255, 255, 255, 0.05);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: var(--radius-md);
  padding: 14px 16px;
}

@media (min-width: 480px) {
  .disclaimer-box {
    margin: 30px auto;
    padding: 16px 20px;
  }
}

.disclaimer-text {
  font-size: 0.75rem;
  line-height: 1.55;
  color: #94A3B8;
}

.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  padding-top: 20px;
  font-size: 0.775rem;
  color: #64748B;
}

/* ==========================================================================
   STICKY MOBILE CTA BAR (SMARTPHONE-ONLY, SAFE-AREA AWARE)
   ========================================================================== */
.sticky-mobile-bar {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  background-color: rgba(255, 255, 255, 0.96);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border-top: 1px solid var(--color-border);
  box-shadow: 0 -4px 16px rgba(0, 0, 0, 0.08);
  padding: 10px 16px;
  padding-bottom: max(10px, env(safe-area-inset-bottom));
  z-index: 1000;
  transform: translateY(115%);
  transition: transform 0.25s cubic-bezier(0.16, 1, 0.3, 1);
}

@media (min-width: 768px) {
  .sticky-mobile-bar {
    display: none !important;
  }
}

.sticky-mobile-bar.visible {
  transform: translateY(0);
}

.sticky-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: 500px;
  margin: 0 auto;
  gap: 12px;
}

.sticky-info {
  display: flex;
  flex-direction: column;
}

.sticky-title {
  font-size: 0.825rem;
  font-weight: 700;
  color: var(--color-text-main);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 170px;
}

@media (min-width: 360px) {
  .sticky-title {
    max-width: 210px;
  }
}

.sticky-price {
  font-size: 1.15rem;
  font-weight: 800;
  color: var(--color-primary);
  line-height: 1;
  margin-top: 2px;
}

/* ==========================================================================
   LIGHTBOX PREVIEW MODAL (RESPONSIVE & MOBILE-SCROLLABLE)
   ========================================================================== */
.modal-backdrop {
  position: fixed;
  inset: 0;
  background-color: rgba(15, 23, 42, 0.85);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  z-index: 2000;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 12px;
}

@media (min-width: 480px) {
  .modal-backdrop {
    padding: 20px;
  }
}

.modal-backdrop.show {
  display: flex;
}

.modal-dialog {
  background-color: #FFFFFF;
  border-radius: var(--radius-md);
  max-width: 760px;
  width: 100%;
  max-height: 92vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  box-shadow: var(--shadow-xl);
}

@media (min-width: 480px) {
  .modal-dialog {
    border-radius: var(--radius-lg);
  }
}

.modal-header {
  padding: 12px 16px;
  border-bottom: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  background-color: #F8FAFC;
}

@media (min-width: 480px) {
  .modal-header {
    padding: 16px 20px;
  }
}

.modal-title {
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--color-text-main);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  padding-right: 12px;
}

@media (min-width: 480px) {
  .modal-title {
    font-size: 1rem;
  }
}

.modal-close {
  background: none;
  border: none;
  font-size: 1.75rem;
  line-height: 1;
  color: var(--color-text-muted);
  cursor: pointer;
  padding: 4px;
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
  flex-shrink: 0;
}

.modal-close:hover {
  color: var(--color-text-main);
  background-color: #E2E8F0;
}

.modal-body {
  padding: 12px;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  display: flex;
  justify-content: center;
  background-color: #F1F5F9;
}

@media (min-width: 480px) {
  .modal-body {
    padding: 16px;
  }
}

.modal-body img {
  max-height: 75vh;
  width: auto;
  max-width: 100%;
  object-fit: contain;
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-md);
}