:root {
  --cream: #f6eee1;
  --cream-deep: #ece0cb;
  --ink: #2c2822;
  --ink-soft: rgba(44, 40, 34, 0.58);
  --ink-faint: rgba(44, 40, 34, 0.34);
  --line: rgba(44, 40, 34, 0.13);
  --accent: #6b7a52;
  --toc-title: #55694a;
  --toc-title-active: #3d5033;
  --shadow: rgba(44, 40, 34, 0.2);
  --book-w: min(88vw, 480px, calc((100dvh - var(--safe-top) - var(--safe-bottom) - 104px) * 0.5625));
  --safe-top: env(safe-area-inset-top, 0px);
  --safe-bottom: env(safe-area-inset-bottom, 0px);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  height: 100%;
  overflow: hidden;
  background: radial-gradient(circle at 50% -10%, #fbf7ee, var(--cream) 65%);
  color: var(--ink);
  font-family: -apple-system, "PingFang TC", "Noto Sans TC", "Microsoft JhengHei", sans-serif;
  -webkit-tap-highlight-color: transparent;
  touch-action: none;
  overscroll-behavior: none;
}

body {
  display: flex;
  flex-direction: column;
  height: 100dvh;
}

/* ---------- loading ---------- */
.loading {
  position: fixed;
  inset: 0;
  z-index: 50;
  isolation: isolate;
  background: var(--cream);
  transition: opacity 1.1s ease;
}
.loading.hide { opacity: 0; pointer-events: none; }
.loading-video {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.loading-skip {
  position: absolute;
  z-index: 2;
  transform: translateZ(0);
  right: calc(34px + env(safe-area-inset-right, 0px));
  bottom: calc(32px + var(--safe-bottom));
  padding: 8px 16px;
  font-size: 11px;
  letter-spacing: 0.2em;
  color: #fff;
  background: rgba(20, 18, 14, 0.28);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border: 1px solid rgba(255, 255, 255, 0.35);
  border-radius: 999px;
  opacity: 0.9;
}
.loading-skip:active { opacity: 0.6; }

/* ---------- topbar ---------- */
.topbar {
  position: absolute;
  left: 0; right: 0;
  bottom: calc(100% + 8px);
  height: 38px;
  pointer-events: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 38px;
  height: 38px;
  border-radius: 50%;
  background: rgba(246, 238, 225, 0.55);
  backdrop-filter: blur(8px) saturate(140%);
  -webkit-backdrop-filter: blur(8px) saturate(140%);
  border: 1px solid var(--line);
  color: var(--toc-title-active);
  pointer-events: auto;
  box-shadow: 0 6px 16px rgba(44, 40, 34, 0.1);
  opacity: 0.9;
}
.icon-btn:active { transform: scale(0.92); }

.page-indicator {
  align-self: flex-end;
  padding-bottom: 4px;
  font-size: 12px;
  color: var(--ink-soft);
  letter-spacing: 0.06em;
  font-variant-numeric: tabular-nums;
}

/* ---------- stage ---------- */
.stage {
  position: relative;
  flex: 1 1 auto;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 0;
  overflow: hidden;
  padding: var(--safe-top) 0 var(--safe-bottom);
}

.book-col {
  position: relative;
  width: var(--book-w);
}

.book {
  position: relative;
  width: var(--book-w);
  aspect-ratio: 1080 / 1920;
  perspective: 2200px;
  filter: drop-shadow(0 18px 30px var(--shadow));
}

.page {
  position: absolute;
  inset: 0;
  border-radius: 10px;
  overflow: hidden;
  background: #fff;
  transform-origin: left center;
  transform: rotateY(0deg);
  backface-visibility: hidden;
  transition: transform 0.65s cubic-bezier(0.4, 0.1, 0.2, 1);
  will-change: transform;
}
.page.flipped {
  transform: rotateY(-180deg);
}
.page.no-anim {
  transition: none;
}

.page img {
  width: 100%;
  height: 100%;
  display: block;
  -webkit-user-drag: none;
  user-select: none;
  object-fit: cover;
  pointer-events: none;
  transform-origin: 0 0;
  transition: transform 0.32s cubic-bezier(0.2, 0.7, 0.3, 1);
  will-change: transform;
}
.page img.panning { transition: none; }
body.zoom-active .book { cursor: grab; }
body.zoom-active .book:active { cursor: grabbing; }

.nav-btn {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: rgba(246, 238, 225, 0.55);
  backdrop-filter: blur(8px) saturate(140%);
  -webkit-backdrop-filter: blur(8px) saturate(140%);
  color: var(--ink);
  border: 1px solid var(--line);
  box-shadow: 0 6px 16px rgba(44, 40, 34, 0.1);
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0.85;
}
.nav-btn:active { transform: translateY(-50%) scale(0.92); }
.nav-prev { left: -14px; }
.nav-next { right: -14px; }
.nav-btn:disabled { opacity: 0.2; pointer-events: none; }

body.zoom-active .nav-btn,
body.zoom-active .topbar {
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.25s ease;
}

.hint {
  position: fixed;
  left: 0; right: 0; bottom: 0;
  pointer-events: none;
  text-align: center;
  font-size: 11px;
  letter-spacing: 0.06em;
  color: var(--ink-faint);
  padding-bottom: calc(10px + var(--safe-bottom));
  transition: opacity 0.6s ease;
}
.hint.fade { opacity: 0; }

/* ---------- TOC overlay ---------- */
.toc-overlay {
  position: fixed;
  inset: 0;
  z-index: 40;
  background: rgba(20, 18, 14, 0.5);
  backdrop-filter: blur(2px);
  -webkit-backdrop-filter: blur(2px);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
}
.toc-overlay[hidden] { display: none; }

.toc-panel {
  width: 100%;
  max-width: 400px;
  height: min(56vh, 460px);
  background: var(--cream);
  border-radius: 20px;
  overflow: hidden;
  display: flex;
  flex-direction: column;
  box-shadow: 0 24px 60px rgba(20, 18, 14, 0.3);
}

.toc-header {
  flex: 0 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 24px 22px 6px;
}
.toc-logo {
  height: 15px;
  width: auto;
  display: block;
}
.close-btn {
  background: none;
  border: none;
  color: var(--ink);
  opacity: 0.55;
  padding: 4px;
  display: flex;
}
.close-btn:active { opacity: 0.9; }

.toc-caption {
  flex: 0 0 auto;
  padding: 10px 22px 14px;
  font-size: 12.5px;
  color: var(--ink-soft);
  border-bottom: 1px solid var(--line);
}
.toc-caption span {
  font-size: 10px;
  letter-spacing: 0.18em;
  color: var(--ink-faint);
}

.toc-list {
  flex: 1 1 auto;
  min-height: 0;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  touch-action: pan-y;
  padding: 4px 22px 28px;
}

.toc-item {
  display: flex;
  align-items: flex-start;
  gap: 14px;
  width: 100%;
  background: none;
  border: none;
  border-bottom: 1px solid var(--line);
  padding: 16px 4px 16px 14px;
  cursor: pointer;
  text-align: left;
  position: relative;
}
.toc-item:last-child { border-bottom: none; }
.toc-item:active { opacity: 0.55; }

.toc-item::before {
  content: "";
  position: absolute;
  left: 0;
  top: 20px;
  bottom: 20px;
  width: 2px;
  background: transparent;
}
.toc-item.active::before { background: var(--accent); }

.toc-num {
  flex: 0 0 auto;
  padding-top: 2px;
  font-size: 11px;
  letter-spacing: 0.03em;
  color: var(--ink-faint);
  font-variant-numeric: tabular-nums;
}

.toc-text {
  flex: 1 1 auto;
  min-width: 0;
}

.toc-label {
  display: block;
  font-size: 15.5px;
  font-weight: 500;
  color: var(--toc-title);
  line-height: 1.4;
}
.toc-sub {
  display: block;
  font-size: 10px;
  letter-spacing: 0.16em;
  color: var(--ink-faint);
  margin-top: 3px;
}

.toc-item.active .toc-label {
  color: var(--toc-title-active);
  font-weight: 600;
}