/* ==========================================================================
   BO2K — Book Detail & In-Depth Chapter Reader Experience
   ========================================================================== */

/* ==========================================================================
   1. BOOK DETAIL PAGE (OVERVIEW)
   ========================================================================== */
.book-detail-header-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 2rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border-subtle);
}

.book-detail-grid {
  display: flex;
  flex-direction: column;
  gap: 2.5rem;
}

@media (min-width: 860px) {
  .book-detail-grid {
    display: grid;
    grid-template-columns: 320px 1fr;
    gap: 4rem;
    align-items: start;
  }
}

.book-cover-stage-large {
  max-width: 280px;
  margin: 0 auto;
  position: sticky;
  top: calc(var(--header-height) + 2rem);
}

@media (min-width: 860px) {
  .book-cover-stage-large {
    max-width: 100%;
    margin: 0;
  }
}

.book-info-column {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.book-meta-strip {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--text-muted);
}

.book-detail-title {
  font-size: clamp(2rem, 5vw, 3rem);
  font-weight: 500;
  line-height: 1.12;
  color: var(--text-primary);
}

.book-detail-subtitle {
  font-size: 1rem;
  color: var(--text-muted);
  font-family: var(--font-serif);
  font-style: italic;
}

.book-detail-author {
  font-family: var(--font-sans);
  font-size: 0.875rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-secondary);
  font-weight: 600;
}

.book-detail-intro {
  font-size: 1rem;
  line-height: 1.75;
  color: var(--text-secondary);
  padding: 1.25rem 0;
  border-top: 1px solid var(--border-subtle);
  border-bottom: 1px solid var(--border-subtle);
}

.book-detail-actions {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-top: 0.5rem;
}

/* Bookmark Icon Button */
.btn-bookmark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 46px;
  height: 46px;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  transition: all var(--transition-fast);
}

.btn-bookmark:hover {
  border-color: var(--text-primary);
  color: var(--text-primary);
}

.btn-bookmark.saved {
  background-color: var(--text-primary);
  color: var(--bg-primary);
  border-color: var(--text-primary);
}

/* Chapter Index List */
.chapter-index-section {
  margin-top: 2.5rem;
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.chapter-index-heading {
  font-family: var(--font-sans);
  font-size: 0.75rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--text-muted);
  font-weight: 600;
}

.chapter-index-list {
  display: flex;
  flex-direction: column;
  border-top: 1px solid var(--border-subtle);
}

.chapter-index-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1.125rem 0.5rem;
  border-bottom: 1px solid var(--border-subtle);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.chapter-index-row:hover {
  background-color: rgba(52, 51, 47, 0.03);
  padding-left: 0.875rem;
}

.chapter-index-left {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.chapter-num {
  font-family: var(--font-sans);
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--text-faint);
}

.chapter-row-title {
  font-family: var(--font-serif);
  font-size: 1.0625rem;
  color: var(--text-primary);
}

.chapter-row-duration {
  font-size: 0.75rem;
  color: var(--text-muted);
}

/* ==========================================================================
   2. IMMERSIVE CHAPTER READER
   ========================================================================== */
.reader-wrapper {
  max-width: var(--max-reading-width);
  margin: 0 auto;
  padding: 1rem 0 5rem;
}

/* Sticky Minimal Reading Progress Indicator */
.reading-progress-bar-container {
  position: fixed;
  top: var(--header-height);
  left: 0;
  right: 0;
  height: 2px;
  background-color: rgba(216, 211, 200, 0.4);
  z-index: 85;
}

.reading-progress-fill {
  height: 100%;
  background-color: var(--text-primary);
  width: 0%;
  transition: width 150ms ease-out;
}

/* Reader Top Bar Controls */
.reader-top-controls {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 2.5rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border-subtle);
}

.reader-book-reference {
  display: flex;
  flex-direction: column;
}

.reader-book-title-sub {
  font-size: 0.6875rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text-muted);
}

.reader-chapter-tracker {
  font-family: var(--font-serif);
  font-size: 0.9375rem;
  color: var(--text-secondary);
}

/* Chapter Title Masthead */
.reader-chapter-head {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  margin-bottom: 3.5rem;
}

.reader-chapter-num-badge {
  font-family: var(--font-sans);
  font-size: 0.75rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--accent-leather);
  font-weight: 600;
}

.reader-chapter-headline {
  font-size: clamp(2.15rem, 5.5vw, 3.25rem);
  font-weight: 400;
  line-height: 1.15;
  color: var(--text-primary);
}

/* ==========================================================================
   THE 4 PILLARS OF CHAPTER COMPREHENSION
   1. The Idea
   2. Why It Matters
   3. Key Takeaway
   4. Remember This
   ========================================================================== */
.pillar-section {
  margin-bottom: 3rem;
  display: flex;
  flex-direction: column;
  gap: 0.875rem;
}

.pillar-header {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.pillar-label {
  font-family: var(--font-sans);
  font-size: 0.6875rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  font-weight: 700;
  color: var(--text-secondary);
}

.pillar-line {
  flex: 1;
  height: 1px;
  background-color: var(--border-subtle);
}

.pillar-content-text {
  font-size: 1.0625rem;
  line-height: 1.8;
  color: var(--text-secondary);
}

/* Pillar 4: Remember This (Callout / Pullquote Treatment) */
.remember-this-card {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-left: 3px solid var(--text-primary);
  padding: 1.75rem 1.5rem;
  border-radius: var(--radius-sm);
  margin: 3.5rem 0;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.remember-this-label {
  font-family: var(--font-sans);
  font-size: 0.625rem;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  font-weight: 700;
  color: var(--text-muted);
}

.remember-this-quote {
  font-family: var(--font-serif);
  font-style: italic;
  font-size: 1.25rem;
  line-height: 1.55;
  color: var(--text-primary);
}

/* Chapter Bottom Navigation (Prev / Next) */
.reader-nav-footer {
  margin-top: 4rem;
  padding-top: 2rem;
  border-top: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.reader-nav-btn {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.8125rem;
  font-weight: 500;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--text-secondary);
  padding: 0.625rem 1rem;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}

.reader-nav-btn:hover:not(:disabled) {
  border-color: var(--text-primary);
  color: var(--text-primary);
  background-color: var(--bg-surface);
}

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