.book-reader {
  --book-accent: #ff5e10;
  width: 100%;
  max-width: none;
  margin: 0 auto 7rem;
  padding: 0;
}

.book-reader__shell {
  display: grid;
  grid-template-columns: 6rem minmax(0, 1fr) 6rem;
  align-items: center;
  gap: 1.8rem;
  width: 100%;
}

.book-reader__stage {
  position: relative;
  width: 100%;
  max-width: none;
  aspect-ratio: 0.72;
  perspective: 2200px;
  border-radius: 3px 10px 10px 3px;
  background: #f4f2ed;
  box-shadow: -10px 14px 28px rgba(0, 0, 0, 0.3), 10px 20px 50px rgba(0, 0, 0, 0.38);
  outline: 0;
  isolation: isolate;
}

.book-reader__stage::after {
  content: "";
  position: absolute;
  z-index: 5;
  top: 1%;
  bottom: 1%;
  left: 0;
  width: 2.2%;
  border-radius: 3px 0 0 3px;
  background: linear-gradient(90deg, rgba(0, 0, 0, 0.24), rgba(0, 0, 0, 0.03), transparent);
  pointer-events: none;
}

.book-reader__paper {
  position: absolute;
  inset: 0;
  overflow: hidden;
  border-radius: inherit;
  background: #fff;
  backface-visibility: hidden;
  transform-style: preserve-3d;
  will-change: transform;
}

.book-reader__paper::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(90deg, rgba(0, 0, 0, 0.08), transparent 8%, transparent 78%, rgba(0, 0, 0, 0.04));
  pointer-events: none;
}

.book-reader__paper canvas {
  display: block;
  width: 100%;
  height: 100%;
  background: #fff;
}

.book-reader__paper--front { z-index: 2; }
.book-reader__paper--back { z-index: 1; }

.book-reader__stage.is-next .book-reader__paper--front {
  transform-origin: left center;
  animation: book-page-next 620ms cubic-bezier(0.55, 0.02, 0.2, 1) both;
}

.book-reader__stage.is-prev .book-reader__paper--back {
  z-index: 3;
  transform-origin: left center;
  animation: book-page-prev 620ms cubic-bezier(0.22, 0.7, 0.2, 1) both;
}

@keyframes book-page-next {
  0% { transform: rotateY(0deg); filter: brightness(1); }
  45% { filter: brightness(0.7); }
  100% { transform: rotateY(-102deg); filter: brightness(0.52); }
}

@keyframes book-page-prev {
  0% { transform: rotateY(-102deg); filter: brightness(0.55); }
  55% { filter: brightness(0.82); }
  100% { transform: rotateY(0deg); filter: brightness(1); }
}

.book-reader__arrow {
  display: grid;
  place-items: center;
  width: 5.4rem;
  height: 5.4rem;
  border: 1px solid rgba(255, 255, 255, 0.16);
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.07);
  color: #fff;
  cursor: pointer;
  transition: transform 0.2s ease, background 0.2s ease, opacity 0.2s ease;
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
}

.book-reader__arrow:hover:not(:disabled) {
  transform: scale(1.07);
  background: var(--book-accent);
}

.book-reader__arrow:disabled {
  opacity: 0.22;
  cursor: default;
}

.book-reader__arrow svg {
  width: 2.5rem;
  height: 2.5rem;
}

.book-reader__arrow--prev { justify-self: start; }
.book-reader__arrow--next { justify-self: end; }

.book-reader__loading,
.book-reader__error {
  position: absolute;
  z-index: 8;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 1.4rem;
  padding: 3rem;
  background: #f4f2ed;
  color: #222;
  text-align: center;
  font-family: "Pretendard", sans-serif;
}

.book-reader__loading span {
  width: 3rem;
  height: 3rem;
  border: 3px solid rgba(0, 0, 0, 0.12);
  border-top-color: var(--book-accent);
  border-radius: 50%;
  animation: book-loading 0.8s linear infinite;
}

.book-reader__loading b,
.book-reader__error b {
  font-size: 1.4rem;
  font-weight: 600;
}

.book-reader__error a {
  padding: 1rem 1.5rem;
  border-radius: 999px;
  background: var(--book-accent);
  color: #fff;
  font-size: 1.3rem;
}

.book-reader__error[hidden],
.book-reader__loading[hidden] { display: none; }

@keyframes book-loading { to { transform: rotate(360deg); } }

@media (max-width: 768px) {
  .book-reader {
    margin-bottom: 4.5rem;
    padding: 0;
  }

  .book-reader__shell {
    grid-template-columns: 3.8rem minmax(0, 1fr) 3.8rem;
    gap: 0.8rem;
  }
  .book-reader__arrow { width: 3.8rem; height: 3.8rem; }
  .book-reader__arrow svg { width: 2rem; height: 2rem; }
}

@media (max-width: 480px) {
  .book-reader__shell {
    grid-template-columns: 3.4rem minmax(0, 1fr) 3.4rem;
    gap: 0.45rem;
  }
  .book-reader__arrow { width: 3.4rem; height: 3.4rem; }
}

@media (prefers-reduced-motion: reduce) {
  .book-reader__stage.is-next .book-reader__paper--front,
  .book-reader__stage.is-prev .book-reader__paper--back { animation-duration: 1ms; }
}