.reader-shell {
  --edge-gap: 24px;
  min-height: 100vh;
  display: grid;
  place-items: center;
  padding: var(--edge-gap);
}

.reader-stage {
  --book-width: min(92vw, 760px);
  --page-slot-width: calc(var(--book-width) * 0.5);
  position: relative;
  display: grid;
  justify-items: center;
  width: min(96vw, 860px);
  padding-top: var(--edge-gap);
  row-gap: 18px;
}

.bookmarks {
  position: absolute;
  top: 0;
  left: calc(var(--page-slot-width) + 30px);
  z-index: 1;
  display: flex;
  align-items: flex-start;
  justify-content: flex-start;
  width: auto;
  pointer-events: none;
}

.book-frame {
  position: relative;
  z-index: 2;
  width: var(--book-width);
  aspect-ratio: 1.42 / 1;
  display: grid;
  place-items: center;
  perspective: 2600px;
  margin-top: 10px;
}

.book-shadow {
  position: absolute;
  inset: auto 7% 4%;
  height: 8%;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(42, 22, 12, 0.34), transparent 72%);
  filter: blur(18px);
  transform: translateZ(-180px);
}

.book-spine {
  display: none;
}

.reader-note {
  width: min(92vw, 720px);
  margin: 0;
  min-height: var(--edge-gap);
  color: rgba(61, 39, 22, 0.74);
  font-size: 0.8rem;
  line-height: 1.5;
  text-align: center;
}

.book-scale-control {
  display: none;
}

.viewport-toggle {
  position: fixed;
  left: 50%;
  bottom: calc(env(safe-area-inset-bottom, 0px) + 10px);
  z-index: 30;
  width: 56px;
  height: 44px;
  padding: 0;
  border: 0;
  border-radius: 999px;
  background: rgba(77, 48, 27, 0.92);
  color: #f4e7d4;
  font: 600 1.35rem/1 "Georgia", "Times New Roman", serif;
  transform: translateX(-50%);
  box-shadow: 0 10px 24px rgba(32, 18, 10, 0.24);
  cursor: pointer;
}

.viewport-toggle:active {
  transform: translateX(-50%) translateY(1px);
}

@media (max-width: 640px) {
  .reader-shell {
    --edge-gap: clamp(8px, 2.4vw, 12px);
    min-height: 100dvh;
    display: block;
    padding: calc(var(--edge-gap) + 56px) 0 0;
    width: 100vw;
    min-width: 100vw;
    overflow-x: auto;
    overflow-y: visible;
  }

  .reader-stage {
    --mobile-book-scale: 0.95;
    --book-max-width: calc(100vw - (var(--edge-gap) * 2));
    --book-max-height-width: calc((100dvh - (var(--edge-gap) * 3) - 48px) * 1.3846);
    --book-width: min(
      calc(var(--book-max-width) - 1px),
      calc(var(--book-max-height-width) + 110px)
    );
    --scaled-book-width: calc(var(--book-width) * var(--mobile-book-scale));
    --scaled-book-height: calc((var(--book-width) / 1.3846) * var(--mobile-book-scale));
    --page-slot-width: calc(var(--book-width) * 0.5);
    --bookmark-width: clamp(18px, calc(var(--page-slot-width) * 0.12), 26px);
    --bookmark-height: calc(var(--bookmark-width) * 3.3);
    width: var(--scaled-book-width);
    min-width: var(--scaled-book-width);
    box-sizing: border-box;
    padding-top: 0;
    justify-items: center;
    margin-inline: 0;
  }

  .book-frame {
    width: var(--book-width);
    aspect-ratio: 1.3846 / 1;
    overflow: visible;
    margin-top: 0;
    margin-inline: calc((var(--scaled-book-width) - var(--book-width)) * 0.5);
    margin-bottom: calc(var(--scaled-book-height) - (var(--book-width) / 1.3846));
    transform: scale(var(--mobile-book-scale));
    transform-origin: top center;
  }

  .bookmarks {
    top: 0;
    left: 0;
    transform: none;
    z-index: 1;
  }

  .viewport-toggle {
    width: 60px;
    height: 46px;
    bottom: calc(env(safe-area-inset-bottom, 0px) + 14px);
    font-size: 1.45rem;
  }
}