:root {
  --shell-width: min(96vw, 1380px);
  --book-width: min(92vw, 1120px);
  --book-height: min(69vw, 780px);
  --paper: #fffdf8;
  --paper-edge: #f2e6d6;
  --ink: #2a1b0f;
  --shadow: rgba(63, 31, 0, 0.22);
  --ui-bg: rgba(255, 251, 245, 0.86);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  background:
    radial-gradient(circle at top, rgba(255, 219, 174, 0.5), transparent 34%),
    linear-gradient(135deg, #fff3df 0%, #ffd8aa 42%, #ffca84 100%);
  font-family: Arial, sans-serif;
  color: var(--ink);
}

.reader-shell {
  max-width: var(--shell-width);
  margin: 0 auto;
  padding: 24px 16px 40px;
}

.reader-card {
  background: var(--ui-bg);
  border-radius: 30px;
  padding: 22px;
  box-shadow: 0 24px 64px rgba(0, 0, 0, 0.15);
  backdrop-filter: blur(12px);
}

.reader-card:fullscreen {
  width: 100vw;
  height: 100vh;
  max-width: none;
  border-radius: 0;
  padding: 18px;
  overflow: auto;
  background:
    radial-gradient(circle at top, rgba(255, 219, 174, 0.45), transparent 28%),
    linear-gradient(135deg, #fff3df 0%, #ffd8aa 42%, #ffca84 100%);
}

.reader-card:fullscreen .book-stage {
  width: min(96vw, 1520px);
  height: min(82vh, 1000px);
}

.reader-topbar,
.reader-controls,
.reader-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-items: center;
}

.reader-topbar {
  justify-content: space-between;
  margin-bottom: 18px;
}

.reader-topbar p {
  margin: 0;
  color: rgba(42, 27, 15, 0.72);
}

.reader-controls {
  justify-content: center;
  margin-bottom: 14px;
}

.reader-controls .btn,
.reader-actions .btn,
.reader-actions .form-select {
  padding: 0.42rem 0.85rem;
  font-size: 0.92rem;
  line-height: 1.2;
}

.reader-actions .form-select {
  width: auto;
}

.reader-subcontrols {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
  gap: 12px;
  margin-bottom: 18px;
}

.reader-subcontrols .form-range {
  width: min(240px, 48vw);
}

.reader-state {
  text-align: center;
  margin-top: 18px;
  font-weight: 600;
  color: rgba(42, 27, 15, 0.8);
}

.book-stage {
  position: relative;
  width: var(--book-width);
  height: var(--book-height);
  margin: 0 auto;
  perspective: 3000px;
  transform: scale(var(--reader-zoom, 1));
  transform-origin: center top;
  transition: transform 220ms ease;
}

.book-shadow {
  position: absolute;
  left: 8%;
  right: 8%;
  bottom: -22px;
  height: 36px;
  border-radius: 50%;
  background: rgba(59, 28, 0, 0.2);
  filter: blur(20px);
}

.book-spread {
  position: absolute;
  inset: 0;
  display: grid;
  grid-template-columns: 1fr 1fr;
  overflow: hidden;
  border-radius: 28px;
  background: linear-gradient(90deg, #eadbc8 0%, #fffdf8 8%, #fffdf8 92%, #eadbc8 100%);
  box-shadow:
    inset 0 0 0 1px rgba(125, 85, 31, 0.12),
    0 18px 48px var(--shadow);
}

.book-spread::before {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  left: 50%;
  width: 28px;
  transform: translateX(-50%);
  background: linear-gradient(90deg, rgba(84, 48, 17, 0.18), rgba(255, 255, 255, 0.85), rgba(84, 48, 17, 0.1));
  z-index: 5;
  pointer-events: none;
}

.page-pane {
  position: relative;
  overflow: hidden;
  background: var(--paper);
}

.page-pane.left {
  border-right: 1px solid rgba(118, 74, 15, 0.08);
  box-shadow: inset -12px 0 20px rgba(80, 52, 18, 0.08);
}

.page-pane.right {
  box-shadow: inset 12px 0 20px rgba(80, 52, 18, 0.08);
}

.page-media {
  width: 100%;
  height: 100%;
  object-fit: contain;
  display: block;
  background: var(--paper-edge);
}

.page-placeholder {
  width: 100%;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 24px;
  color: rgba(42, 27, 15, 0.45);
  font-size: 1.1rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  background: linear-gradient(135deg, #f6edde, #fffdf8);
}

.flip-overlay {
  position: absolute;
  top: 0;
  bottom: 0;
  width: 50%;
  overflow: hidden;
  display: none;
  z-index: 9;
  backface-visibility: hidden;
  background: var(--paper);
  box-shadow: 0 14px 40px rgba(0, 0, 0, 0.18);
  will-change: transform, box-shadow, filter;
  transform-style: preserve-3d;
}

.flip-overlay img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  display: block;
  background: var(--paper-edge);
}

.flip-overlay::before,
.flip-overlay::after {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  pointer-events: none;
  opacity: 0;
}

.flip-overlay::before {
  left: 0;
  width: 100%;
  background: linear-gradient(90deg, rgba(88, 52, 18, 0.2) 0%, rgba(255, 255, 255, 0.1) 16%, rgba(255, 255, 255, 0) 36%, rgba(88, 52, 18, 0.24) 52%, rgba(255, 255, 255, 0.04) 68%, rgba(88, 52, 18, 0.12) 100%);
  mix-blend-mode: multiply;
}

.flip-overlay::after {
  right: 0;
  width: 36%;
  background: linear-gradient(90deg, rgba(255, 255, 255, 0), rgba(255, 255, 255, 0.34));
}

.flip-overlay.next {
  right: 0;
  transform-origin: left center;
  border-radius: 0 28px 28px 0;
}

.flip-overlay.prev {
  left: 0;
  transform-origin: right center;
  border-radius: 28px 0 0 28px;
}

.flip-overlay.play-next {
  display: block;
  animation: spreadFlipNext 1550ms cubic-bezier(0.42, 0.04, 0.16, 0.98) forwards;
}

.flip-overlay.play-prev {
  display: block;
  animation: spreadFlipPrev 1550ms cubic-bezier(0.42, 0.04, 0.16, 0.98) forwards;
}

.flip-overlay.play-next::before,
.flip-overlay.play-prev::before {
  animation: foldShade 1550ms ease-in-out forwards;
}

.flip-overlay.play-next::after,
.flip-overlay.play-prev::after {
  animation: foldHighlight 1550ms ease-in-out forwards;
}

.page-nav-btn {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  z-index: 12;
  width: 42px;
  height: 42px;
  border: none;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.92);
  color: #8a4e00;
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.18);
  font-size: 1.2rem;
  line-height: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
}

.page-nav-btn:hover {
  background: #ffffff;
  color: #c96a00;
}

.page-nav-btn.left { left: 12px; }
.page-nav-btn.right { right: 12px; }

.page-loader,
.empty-state {
  min-height: 50vh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 24px;
  border-radius: 22px;
}

.page-loader {
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, #fff4da, #ffe7b6);
  color: #7a4900;
  z-index: 20;
}

.empty-state {
  background: #fff3cd;
  color: #6c4b00;
}

body.reader-dark {
  --paper: #22201d;
  --paper-edge: #2a2926;
  --ink: #f6ecdc;
  --shadow: rgba(0, 0, 0, 0.4);
  --ui-bg: rgba(30, 26, 22, 0.88);
  background:
    radial-gradient(circle at top, rgba(72, 53, 22, 0.45), transparent 34%),
    linear-gradient(135deg, #21160f 0%, #3b281b 42%, #1e140d 100%);
}

body.reader-dark .page-placeholder,
body.reader-dark .page-loader {
  color: rgba(246, 236, 220, 0.74);
}

@keyframes spreadFlipNext {
  0% { transform: rotateY(0deg) skewY(0deg) scaleX(1); box-shadow: 0 14px 40px rgba(0, 0, 0, 0.18); filter: brightness(1); }
  22% { transform: rotateY(-28deg) skewY(-1.8deg) scaleX(0.985); box-shadow: -10px 18px 42px rgba(0, 0, 0, 0.16); filter: brightness(0.99); }
  48% { transform: rotateY(-92deg) skewY(-5deg) scaleX(0.93); box-shadow: -24px 22px 62px rgba(0, 0, 0, 0.25); filter: brightness(0.93); }
  76% { transform: rotateY(-146deg) skewY(-2deg) scaleX(0.975); box-shadow: -32px 18px 58px rgba(0, 0, 0, 0.15); filter: brightness(0.95); }
  100% { transform: rotateY(-180deg) skewY(0deg) scaleX(1); box-shadow: -28px 18px 60px rgba(0, 0, 0, 0.08); filter: brightness(0.94); }
}

@keyframes spreadFlipPrev {
  0% { transform: rotateY(180deg) skewY(0deg) scaleX(1); box-shadow: 28px 18px 60px rgba(0, 0, 0, 0.08); filter: brightness(0.94); }
  24% { transform: rotateY(146deg) skewY(2deg) scaleX(0.975); box-shadow: 18px 18px 52px rgba(0, 0, 0, 0.15); filter: brightness(0.95); }
  50% { transform: rotateY(92deg) skewY(5deg) scaleX(0.93); box-shadow: 24px 22px 62px rgba(0, 0, 0, 0.25); filter: brightness(0.93); }
  78% { transform: rotateY(28deg) skewY(1.8deg) scaleX(0.985); box-shadow: 10px 18px 42px rgba(0, 0, 0, 0.16); filter: brightness(0.99); }
  100% { transform: rotateY(0deg) skewY(0deg) scaleX(1); box-shadow: 0 14px 40px rgba(0, 0, 0, 0.18); filter: brightness(1); }
}

@keyframes foldShade {
  0% { opacity: 0.1; }
  35% { opacity: 0.42; }
  55% { opacity: 0.62; }
  100% { opacity: 0.12; }
}

@keyframes foldHighlight {
  0% { opacity: 0; }
  42% { opacity: 0.16; }
  58% { opacity: 0.34; }
  100% { opacity: 0.08; }
}

@media (max-width: 900px) {
  :root {
    --book-width: min(94vw, 620px);
    --book-height: min(136vw, 760px);
  }

  .book-spread { grid-template-columns: 1fr; }
  .book-spread::before,
  .page-pane.left { display: none; }

  .flip-overlay { width: 100%; }

  .flip-overlay.next,
  .flip-overlay.prev {
    left: 0;
    right: auto;
    border-radius: 28px;
    transform-origin: left center;
  }

  .reader-topbar { align-items: flex-start; }
}