/* ==========================================================================
 * 7. STAGE 3: FULL-SCREEN IMMERSIVE 2-PAGE OPEN-BOOK SPREAD READER
 * ========================================================================== */
.immersive-reader-overlay {
  position: fixed;
  inset: 0;
  z-index: 2000;
  background: var(--bg-canvas);
  background-image: var(--bg-canvas-gradient);
  display: flex;
  flex-direction: column;
  color: var(--fg-primary);
}

.immersive-reader-overlay .btn-nav {
  background: var(--nav-bg-elevated);
  color: var(--nav-fg);
  border-color: var(--nav-border);
}

:root[data-ui-theme="candlelight"] .immersive-reader-overlay .btn-nav {
  background: #272522;
  color: #edeae4;
  border-color: #3d3a35;
}

.reader-top-bar,
.reader-top-actionbar {
  height: 58px;
  background: var(--nav-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  color: var(--nav-fg);
  border-bottom: 1px solid var(--nav-border);
  padding: 0 1.35rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  flex-shrink: 0;
}

.reader-top-title,
.reader-top-center {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  min-width: 0;
  font-size: 0.88rem;
  color: var(--fg-primary);
}

.reader-top-right {
  display: flex;
  align-items: center;
  gap: 0.45rem;
}

.reader-workspace,
.reader-desk-stage {
  flex: 1;
  display: flex;
  position: relative;
  overflow: hidden;
  align-items: stretch;
  justify-content: center;
  padding: 1.25rem 1.5rem;
}

.reader-open-book {
  width: 100%;
  max-width: 1240px;
  height: 100%;
  border-radius: 12px;
  border: 1px solid var(--border);
  box-shadow:
    0 20px 48px -12px rgba(28, 25, 23, 0.22),
    0 4px 12px rgba(28, 25, 23, 0.08);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  position: relative;
  transition:
    background 0.2s ease,
    color 0.2s ease;
}

.theme-paper {
  color-scheme: light;
  background: #faf6ee;
  color: #241e18;
}
.theme-sepia {
  color-scheme: light;
  background: #f4ecd8;
  color: #36281b;
}
.theme-white {
  color-scheme: light;
  background: #ffffff;
  color: #18181b;
}
.theme-dark {
  color-scheme: dark;
  background: #18181b;
  color: #e4e4e7;
}

.reader-book-header,
.reader-page-header {
  padding: 0.65rem 2rem;
  border-bottom: 1px solid rgba(120, 113, 108, 0.16);
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.75rem;
  opacity: 0.72;
  flex-shrink: 0;
}

.reader-book-viewport,
.reader-page-content {
  flex: 1;
  overflow-y: auto;
  padding: 2.25rem 3rem;
  position: relative;
}

.reader-page-content h1,
.reader-page-content h2,
.reader-page-content h3 {
  font-family:
    "Merriweather", "Noto Serif KR", "Noto Serif SC", "Noto Serif TC", Georgia,
    serif;
  font-size: 1.32em;
  line-height: 1.38;
  margin: 0 0 0.85em;
  font-weight: 700;
}

.reader-page-content p {
  margin: 0 0 0.95em;
}

.reader-page-content blockquote {
  margin: 0.85em 0 1em 1.25em;
  padding-left: 1em;
  border-left: 2px solid rgba(120, 113, 108, 0.35);
  font-style: italic;
}

@media (min-width: 1024px) {
  .reader-open-book.spread-2col .reader-book-viewport {
    column-count: 2;
    column-gap: 4.5rem;
    column-rule: 1px solid rgba(120, 113, 108, 0.18);
    padding: 2.5rem 3.5rem;
  }

  .reader-open-book.spread-2col
    .reader-paginated-spread
    > .reader-page-sheet:first-child {
    padding-right: 2.1rem;
    border-right: 1px solid rgba(120, 113, 108, 0.18);
  }

  .reader-open-book.spread-2col::after {
    content: "";
    position: absolute;
    top: 0;
    bottom: 0;
    left: 50%;
    width: 32px;
    transform: translateX(-50%);
    background: linear-gradient(
      90deg,
      transparent 0%,
      rgba(0, 0, 0, 0.04) 38%,
      rgba(0, 0, 0, 0.1) 50%,
      rgba(0, 0, 0, 0.04) 62%,
      transparent 100%
    );
    pointer-events: none;
  }
}

.reader-open-book.spread-1col {
  max-width: 840px;
}

.reader-slide-drawer {
  width: 360px;
  max-width: 90vw;
  background: var(--bg-surface);
  color: var(--fg-primary);
  border-left: 1px solid var(--border);
  box-shadow: -8px 0 28px rgba(0, 0, 0, 0.08);
  padding: 1.25rem;
  overflow-y: auto;
  flex-shrink: 0;
}

.reader-bottom-scrubber,
.reader-bottom-bar {
  height: 52px;
  background: var(--nav-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  color: var(--nav-fg);
  border-top: 1px solid var(--nav-border);
  padding: 0 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  font-size: 0.8rem;
  flex-shrink: 0;
}

.scrubber-track,
.progress-track {
  flex: 1;
  max-width: 480px;
  height: 6px;
  background: var(--border-strong);
  border-radius: 999px;
  overflow: hidden;
}

.scrubber-fill,
.progress-fill {
  height: 100%;
  background: var(--primary);
  transition: width 0.25s ease;
}

.reader-paginated-spread {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 4.25rem;
  min-height: 100%;
  align-items: start;
}

.reader-open-book.spread-1col .reader-paginated-spread {
  grid-template-columns: 1fr;
  gap: 0;
}

@media (max-width: 1023px) {
  .reader-paginated-spread {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }
}

.reader-page-sheet {
  min-width: 0;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  min-height: 420px;
}

.reader-page-folio-num {
  margin-top: 1.5rem;
  padding-top: 0.65rem;
  border-top: 1px solid rgba(120, 113, 108, 0.16);
  font-size: 0.74rem;
  opacity: 0.68;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.reader-page-click-zone-prev,
.reader-page-click-zone-next {
  position: absolute;
  top: 52px;
  bottom: 48px;
  width: 44px;
  z-index: 15;
  background: transparent;
  border: none;
  cursor: pointer;
  opacity: 0;
  transition:
    opacity 0.15s ease,
    background 0.15s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  color: inherit;
  font-size: 1.15rem;
}

.reader-page-click-zone-prev {
  left: 0;
}

.reader-page-click-zone-next {
  right: 0;
}

.reader-open-book:hover .reader-page-click-zone-prev:not(:disabled),
.reader-open-book:hover .reader-page-click-zone-next:not(:disabled) {
  opacity: 0.55;
}

.reader-page-click-zone-prev:hover:not(:disabled),
.reader-page-click-zone-next:hover:not(:disabled) {
  opacity: 0.95 !important;
  background: rgba(120, 113, 108, 0.08);
}

.reader-scrubber-range {
  width: 100%;
  max-width: 360px;
  accent-color: var(--primary);
  cursor: pointer;
  height: 6px;
}

mark.ebook-inline-highlight {
  color: #18181b;
  padding: 0.06em 0.18em;
  border-radius: 3px;
  cursor: pointer;
  box-decoration-break: clone;
  -webkit-box-decoration-break: clone;
  border-bottom: 2px solid rgba(28, 25, 23, 0.25);
  transition:
    box-shadow 0.2s ease,
    filter 0.15s ease;
}

mark.ebook-inline-highlight:hover {
  filter: brightness(0.95);
}

@keyframes ebookHighlightPulse {
  0% {
    box-shadow: 0 0 0 0 rgba(200, 169, 126, 0.85);
  }
  50% {
    box-shadow: 0 0 0 8px rgba(200, 169, 126, 0);
  }
  100% {
    box-shadow: 0 0 0 0 rgba(200, 169, 126, 0);
  }
}

.ebook-highlight-pulse {
  animation: ebookHighlightPulse 1.1s ease-out 2;
}

.reader-selection-popover {
  position: sticky;
  top: 0.5rem;
  z-index: 40;
  margin: 0 auto 1rem;
  max-width: 620px;
  background: var(--bg-surface);
  color: var(--fg-primary);
  border: 1px solid var(--border-strong);
  border-radius: 10px;
  padding: 0.6rem 0.85rem;
  box-shadow: var(--card-shadow);
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.6rem;
}

.selection-color-swatch {
  width: 22px;
  height: 22px;
  border-radius: 999px;
  border: 2px solid var(--border-strong);
  cursor: pointer;
  padding: 0;
  transition: transform 0.12s ease;
}

.selection-color-swatch:hover {
  transform: scale(1.16);
}

.reader-ink-canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  z-index: 25;
  pointer-events: none;
  touch-action: none;
}

.reader-ink-canvas.ink-active {
  pointer-events: auto;
  cursor: crosshair;
}

.reader-ink-toolbar {
  background: var(--bg-elevated);
  color: var(--fg-primary);
  border-bottom: 1px solid var(--border);
  padding: 0.45rem 1.25rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  font-size: 0.78rem;
  z-index: 30;
}

.reader-search-hit-card {
  background: var(--bg-canvas);
  color: var(--fg-primary);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.65rem 0.75rem;
  margin-bottom: 0.55rem;
  cursor: pointer;
  transition: border-color 0.15s ease;
}

.reader-search-hit-card:hover {
  border-color: var(--primary);
}

.reader-search-snippet mark {
  background: #fde047;
  color: #18181b;
  padding: 0 0.2em;
  border-radius: 2px;
  font-weight: 700;
}

.pdf-folio-sheet {
  margin: 0 auto;
  background: #ffffff;
  color: #18181b;
  border: 1px solid rgba(120, 113, 108, 0.3);
  border-radius: 6px;
  box-shadow: 0 12px 32px rgba(0, 0, 0, 0.28);
  padding: 2.5rem 3rem;
  transform-origin: top center;
  transition: transform 0.18s ease;
}

.theme-dark .pdf-folio-sheet {
  background: #222225;
  color: #e4e4e7;
  border-color: #3f3f46;
}

.pdf-zoom-toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  margin-bottom: 1rem;
  padding: 0.45rem 0.75rem;
  background: var(--bg-surface);
  color: var(--fg-primary);
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 0.78rem;
}

.reader-shortcuts-modal {
  position: fixed;
  inset: 0;
  z-index: 2500;
  background: rgba(12, 12, 11, 0.72);
  backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1.5rem;
}

.reader-shortcuts-card {
  background: var(--bg-surface);
  color: var(--fg-primary);
  border: 1px solid var(--border);
  border-radius: 12px;
  max-width: 520px;
  width: 100%;
  padding: 1.35rem 1.5rem;
  box-shadow: var(--card-shadow);
}

/* ==========================================================================
 * MOBILE & TABLET RESPONSIVE RULES (D3, D8, WCAG 2.2 AA)
 * ========================================================================== */
@media (max-width: 768px) {
  .reader-top-bar,
  .reader-top-actionbar {
    height: auto;
    min-height: 52px;
    padding: 0.5rem 0.75rem;
    flex-wrap: wrap;
    gap: 0.45rem;
  }
  .reader-top-title,
  .reader-top-center {
    order: 3;
    width: 100%;
    justify-content: center;
    font-size: 0.8rem;
    padding-top: 0.2rem;
    border-top: 1px solid rgba(120, 113, 108, 0.12);
  }
  .reader-top-right {
    margin-left: auto;
    gap: 0.3rem;
  }
  .reader-top-right .btn-sm {
    padding: 0.25rem 0.5rem;
    font-size: 0.74rem;
  }
  .reader-workspace,
  .reader-desk-stage {
    padding: 0.5rem 0.35rem;
  }
  .reader-slide-drawer {
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    width: 100%;
    max-width: 380px;
    z-index: 50;
    box-shadow: -8px 0 32px rgba(0, 0, 0, 0.28);
  }
  .reader-bottom-scrubber,
  .reader-bottom-bar {
    height: auto;
    min-height: 52px;
    padding: 0.5rem 0.75rem;
    flex-wrap: wrap;
    gap: 0.4rem;
    justify-content: center;
  }
  .reader-bottom-bar > div:nth-child(2) {
    order: 3;
    width: 100%;
    max-width: 100% !important;
    justify-content: space-between;
  }
}

@media (max-width: 480px) {
  .reader-open-book {
    border-radius: 6px;
  }
  .reader-page-click-zone-prev,
  .reader-page-click-zone-next {
    width: 32px;
    font-size: 1rem;
  }
}