/* ============================================================
   BOOK ADVERTISING — CATEGORY PAGES (golden template)
   Extends .book-ad-page with category-specific sections.
   ============================================================ */

.book-ad-category .hero-subline {
  font-size: 1.15rem;
  line-height: 1.55;
  color: var(--text-mid);
  max-width: 720px;
  margin: 18px auto 0;
  letter-spacing: -0.005em;
}

/* ============================================================
   AUTHORITY SIGNALS SECTION
   ============================================================ */
.book-authority-section {
  padding: 96px 0 72px;
  background: var(--bg-warm);
}

.book-authority-section .authority-header {
  text-align: center;
  max-width: 780px;
  margin: 0 auto 56px;
}

.book-authority-section .authority-eyebrow {
  display: inline-block;
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--primary);
  background: rgba(0, 113, 227, 0.08);
  padding: 6px 14px;
  border-radius: var(--radius-pill);
  margin-bottom: 18px;
}

.book-authority-section h2 {
  font-size: 2.5rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text-dark);
  margin: 0 0 14px;
  line-height: 1.15;
}

.book-authority-section .section-sub {
  font-size: 1.1rem;
  color: var(--text-mid);
  line-height: 1.55;
  margin: 0;
}

.authority-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 22px;
}

.authority-card {
  background: var(--bg-white);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 32px 28px;
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}

.authority-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  border-color: rgba(0, 113, 227, 0.25);
}

.authority-icon {
  width: 48px;
  height: 48px;
  border-radius: 12px;
  background: rgba(0, 113, 227, 0.08);
  color: var(--primary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  margin-bottom: 18px;
}

.authority-card h3 {
  font-size: 1.18rem;
  font-weight: 600;
  color: var(--text-dark);
  margin: 0 0 10px;
  letter-spacing: -0.01em;
}

.authority-card p {
  font-size: 0.98rem;
  color: var(--text-mid);
  line-height: 1.55;
  margin: 0;
}

/* ============================================================
   SIBLINGS / HUB-AND-SPOKE SECTION
   ============================================================ */
.book-siblings-section {
  padding: 88px 0 72px;
  background: var(--bg-white);
}

.book-siblings-section h2 {
  font-size: 2.25rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text-dark);
  text-align: center;
  margin: 0 0 12px;
}

.book-siblings-section .section-sub {
  font-size: 1.05rem;
  color: var(--text-mid);
  text-align: center;
  margin: 0 0 44px;
}

.siblings-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 22px;
}

.sibling-card {
  position: relative;
  display: block;
  background: var(--bg-warm);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 30px 32px 30px 32px;
  text-decoration: none;
  color: inherit;
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease, background 0.2s ease;
}

.sibling-card:hover {
  text-decoration: none;
  color: inherit;
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  border-color: rgba(0, 113, 227, 0.3);
  background: var(--bg-white);
}

.sibling-eyebrow {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-light);
  margin-bottom: 12px;
}

.sibling-card h3 {
  font-size: 1.35rem;
  font-weight: 600;
  letter-spacing: -0.015em;
  color: var(--text-dark);
  margin: 0 0 8px;
}

.sibling-card p {
  font-size: 0.98rem;
  color: var(--text-mid);
  line-height: 1.55;
  margin: 0 0 6px;
}

.sibling-arrow {
  position: absolute;
  top: 30px;
  right: 30px;
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: rgba(0, 113, 227, 0.08);
  color: var(--primary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  transition: background 0.2s ease, transform 0.2s ease;
}

.sibling-card:hover .sibling-arrow {
  background: var(--primary);
  color: #fff;
  transform: translateX(2px);
}

.sibling-card.sibling-soon {
  opacity: 0.78;
  cursor: default;
}

.sibling-card.sibling-soon:hover {
  transform: none;
  box-shadow: none;
  border-color: var(--border);
  background: var(--bg-warm);
}

.sibling-card.sibling-soon .sibling-eyebrow {
  color: var(--primary);
}

/* ============================================================
   RESPONSIVE
   ============================================================ */
@media (max-width: 991px) {
  .authority-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  .book-authority-section h2 {
    font-size: 2.1rem;
  }
}

@media (max-width: 640px) {
  .authority-grid,
  .siblings-grid {
    grid-template-columns: 1fr;
  }
  .book-authority-section {
    padding: 72px 0 56px;
  }
  .book-authority-section h2 {
    font-size: 1.75rem;
  }
  .book-authority-section .section-sub {
    font-size: 1rem;
  }
  .book-siblings-section h2 {
    font-size: 1.65rem;
  }
  .sibling-card {
    padding: 26px 24px;
  }
  .sibling-arrow {
    top: 26px;
    right: 24px;
  }
  .book-ad-category .hero-subline {
    font-size: 1.02rem;
    padding: 0 8px;
  }
}