:root {
  --teal: #1d9ba4;
  --teal-bright: #2cc5cf;
  --bg: #14171a;
  --bg-raised: #1d2126;
  --ink: #e8ebee;
  --ink-dim: #9aa4ad;
  --bar-h: 60px;
  --top-h: 52px;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

[hidden] { display: none !important; }

html, body {
  height: 100%;
  overflow: hidden;
}

body {
  display: flex;
  flex-direction: column;
  background: radial-gradient(120% 90% at 50% 0%, #1c2126 0%, var(--bg) 60%);
  color: var(--ink);
  font-family: "Avenir Next", "Segoe UI", system-ui, -apple-system, sans-serif;
  -webkit-font-smoothing: antialiased;
  user-select: none;
}

/* ── Top bar ─────────────────────────────────────────── */

.topbar {
  height: var(--top-h);
  flex: 0 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 20px;
  background: rgba(20, 23, 26, 0.85);
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
}

.brand { display: flex; flex-direction: column; line-height: 1.2; }

.brand-mark {
  font-size: 15px;
  font-weight: 600;
  letter-spacing: 0.14em;
  color: var(--ink);
}
.brand-mark sup { font-size: 8px; letter-spacing: 0; }

.brand-sub {
  font-size: 10.5px;
  letter-spacing: 0.08em;
  color: var(--ink-dim);
}

.page-indicator {
  font-size: 13px;
  font-variant-numeric: tabular-nums;
  color: var(--ink-dim);
  letter-spacing: 0.06em;
}

/* ── Stage & book ────────────────────────────────────── */

#stage {
  position: relative;
  flex: 1 1 auto;
  min-height: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 18px 64px;
}

#bookWrap {
  width: 100%;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 0;
  min-height: 0;
}

#book {
  width: 100%;
  max-width: 1400px;
  transition: transform 0.55s cubic-bezier(0.25, 0.7, 0.3, 1);
}

/* closed book (cover only): center the single visible page */
#book.at-cover { transform: translateX(-25%); }

#book .page {
  background: #22262b;
  overflow: hidden;
}

#book .page img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
  opacity: 0;
  transition: opacity 0.25s ease;
}

#book .page img.loaded { opacity: 1; }

/* shimmer while a page image loads */
#book .page::before {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(100deg, transparent 30%, rgba(255,255,255,0.055) 50%, transparent 70%) #22262b;
  background-size: 220% 100%;
  animation: shimmer 1.3s linear infinite;
}
#book .page.ready::before { display: none; }

@keyframes shimmer {
  from { background-position: 130% 0; }
  to   { background-position: -90% 0; }
}

.page-fallback {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--ink-dim);
  font-size: 15px;
  letter-spacing: 0.08em;
  background: #22262b;
}

/* soft drop shadow under the whole book */
.stf__wrapper { filter: drop-shadow(0 24px 44px rgba(0, 0, 0, 0.55)); }

/* ── Nav arrows ──────────────────────────────────────── */

.nav-arrow {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  z-index: 30;
  width: 46px;
  height: 84px;
  border: 0;
  border-radius: 10px;
  background: rgba(255, 255, 255, 0.05);
  color: var(--ink-dim);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.2s, color 0.2s, opacity 0.2s;
}
.nav-arrow svg { width: 26px; height: 26px; }
.nav-prev { left: 10px; }
.nav-next { right: 10px; }
.nav-arrow:hover { background: rgba(29, 155, 164, 0.22); color: #fff; }
.nav-arrow:disabled { opacity: 0.25; cursor: default; background: transparent; }

/* ── Toolbar ─────────────────────────────────────────── */

.toolbar {
  height: var(--bar-h);
  flex: 0 0 auto;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 0 16px;
  background: rgba(24, 28, 32, 0.92);
  border-top: 1px solid rgba(255, 255, 255, 0.06);
}

.tool-group { display: flex; align-items: center; gap: 2px; }

.toolbar button,
.toolbar a {
  width: 40px;
  height: 40px;
  border: 0;
  border-radius: 9px;
  background: transparent;
  color: var(--ink-dim);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.18s, color 0.18s;
}
.toolbar button svg, .toolbar a svg { width: 21px; height: 21px; }
.toolbar button:hover, .toolbar a:hover { background: rgba(29, 155, 164, 0.18); color: var(--teal-bright); }
.toolbar button.active { color: var(--teal-bright); background: rgba(29, 155, 164, 0.14); }
.toolbar button:disabled { opacity: 0.3; cursor: default; background: transparent; color: var(--ink-dim); }

.tool-sep {
  width: 1px;
  height: 26px;
  background: rgba(255, 255, 255, 0.1);
  margin: 0 4px;
}

.slider-wrap {
  display: flex;
  align-items: center;
  gap: 12px;
  min-width: 0;
  flex: 0 1 340px;
}

#sliderLabel {
  font-size: 12.5px;
  font-variant-numeric: tabular-nums;
  color: var(--ink-dim);
  white-space: nowrap;
  min-width: 64px;
  text-align: center;
}

#pageSlider {
  -webkit-appearance: none;
  appearance: none;
  flex: 1;
  min-width: 90px;
  height: 4px;
  border-radius: 2px;
  background: rgba(255, 255, 255, 0.14);
  outline: none;
  cursor: pointer;
}
#pageSlider::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 15px;
  height: 15px;
  border-radius: 50%;
  background: var(--teal-bright);
  border: 0;
  box-shadow: 0 0 0 3px rgba(29, 155, 164, 0.25);
}
#pageSlider::-moz-range-thumb {
  width: 15px;
  height: 15px;
  border-radius: 50%;
  background: var(--teal-bright);
  border: 0;
  box-shadow: 0 0 0 3px rgba(29, 155, 164, 0.25);
}

/* ── Thumbnails drawer ───────────────────────────────── */

#thumbDrawer {
  flex: 0 0 auto;
  background: rgba(22, 26, 30, 0.97);
  border-top: 1px solid rgba(255, 255, 255, 0.07);
  padding: 12px 14px;
}

#thumbTrack {
  display: flex;
  gap: 10px;
  overflow-x: auto;
  scrollbar-width: thin;
  scrollbar-color: rgba(255,255,255,0.2) transparent;
  padding-bottom: 4px;
}

.thumb {
  flex: 0 0 auto;
  border: 0;
  padding: 0;
  background: none;
  cursor: pointer;
  text-align: center;
  color: var(--ink-dim);
  font-size: 10.5px;
  font-family: inherit;
}

.thumb img {
  display: block;
  width: 74px;
  height: 89px;
  object-fit: cover;
  border-radius: 4px;
  border: 2px solid transparent;
  background: #22262b;
  transition: border-color 0.15s, transform 0.15s;
}

.thumb:hover img { transform: translateY(-2px); }
.thumb.active img { border-color: var(--teal-bright); }
.thumb.active { color: var(--teal-bright); }
.thumb span { display: block; margin-top: 3px; }

/* ── Zoom overlay ────────────────────────────────────── */

#zoomOverlay {
  position: absolute;
  inset: 0;
  z-index: 50;
  background: rgba(10, 12, 14, 0.96);
}

#zoomViewport {
  position: absolute;
  inset: 0;
  overflow: hidden;
  cursor: grab;
  touch-action: none;
}
#zoomViewport.panning { cursor: grabbing; }

#zoomContent {
  position: absolute;
  top: 0;
  left: 0;
  display: flex;
  transform-origin: 0 0;
  will-change: transform;
}

#zoomContent img {
  display: block;
  width: 1500px;
  height: 1800px;
  background: #22262b;
}

.zoom-hud {
  position: absolute;
  bottom: 18px;
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  align-items: center;
  gap: 4px;
  padding: 6px 10px;
  border-radius: 12px;
  background: rgba(28, 33, 38, 0.92);
  border: 1px solid rgba(255, 255, 255, 0.09);
}

.zoom-hud button {
  width: 38px;
  height: 38px;
  border: 0;
  border-radius: 8px;
  background: transparent;
  color: var(--ink-dim);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
}
.zoom-hud button svg { width: 19px; height: 19px; }
.zoom-hud button:hover { background: rgba(29, 155, 164, 0.18); color: var(--teal-bright); }

#zoomLevel {
  min-width: 52px;
  text-align: center;
  font-size: 12.5px;
  font-variant-numeric: tabular-nums;
  color: var(--ink);
}

/* ── Responsive ──────────────────────────────────────── */

@media (max-width: 760px) {
  :root { --bar-h: 54px; --top-h: 46px; }

  #stage { padding: 10px 8px; }

  .nav-arrow {
    width: 34px;
    height: 62px;
    background: rgba(20, 23, 26, 0.45);
  }
  .nav-arrow svg { width: 20px; height: 20px; }
  .nav-prev { left: 4px; }
  .nav-next { right: 4px; }

  .topbar { padding: 0 14px; }
  .brand-mark { font-size: 12.5px; }
  .brand-sub { font-size: 9px; }

  .toolbar { gap: 4px; padding: 0 8px; }
  .toolbar button, .toolbar a { width: 36px; height: 36px; }
  .toolbar button svg, .toolbar a svg { width: 19px; height: 19px; }
  #btnFirst, #btnLast { display: none; }
  .tool-sep { margin: 0 1px; }
  .slider-wrap { flex: 1 1 auto; gap: 8px; }
  #sliderLabel { font-size: 11px; min-width: 52px; }

  .thumb img { width: 58px; height: 70px; }
}