:root {
  --paper: #FFFFFF;
  --ink: #16181D;
  --accent: #4C6FFF;
  --secondary: #8E97A8;
  --page-ratio: 0.773;
  --spread-ratio: 1.546;
  --reader-background: var(--ink);
  --reader-body-background: var(--ink);
  --reader-foreground: var(--paper);
  --reader-accent: var(--accent);
  --reader-muted: var(--secondary);
  --reader-line: rgba(142, 151, 168, 0.34);
  --reader-page: var(--paper);
  --reader-stage-background: transparent;
  --reader-stage-shadow: none;
  --reader-page-shadow: 0 0.75rem 1.8rem rgba(0, 0, 0, 0.28);
  --reader-control-hover: rgba(76, 111, 255, 0.12);
  --reader-heading-font: Inter, Arial, sans-serif;
  --reader-body-font: Inter, Arial, sans-serif;
  --reader-heading-weight: 700;
  --reader-heading-spacing: -0.04em;
  --reader-heading-transform: none;
}

* {
  box-sizing: border-box;
}

html {
  min-width: 320px;
  background: var(--ink);
  overflow-x: hidden;
}

body {
  margin: 0;
  overflow-x: hidden;
  min-height: 100vh;
  color: var(--paper);
  background: var(--ink);
  font-family: Inter, Arial, sans-serif;
}

button,
body {
  font-family: Inter, Arial, sans-serif;
}

.alternate-volume {
  width: min(100%, 78rem);
  min-height: 100vh;
  margin: 0 auto;
  padding: 3rem clamp(1rem, 4vw, 4rem) 2rem;
}

.alternate-intro {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 1rem;
  margin: 0 auto 1.5rem;
  max-width: 50rem;
}

.reader-home {
  align-self: start;
  color: var(--accent);
  font-size: 0.72rem;
  letter-spacing: 0.08em;
  text-decoration: none;
  text-transform: uppercase;
}

.reader-home:hover,
.reader-home:focus-visible {
  color: var(--paper);
  outline: none;
}

.alternate-intro h1,
.alternate-intro p {
  margin: 0;
}

.alternate-intro h1 {
  font-size: clamp(1.3rem, 3vw, 2rem);
  font-weight: 700;
  letter-spacing: -0.04em;
}

.alternate-label,
.alternate-note,
.reader-status,
.reader-hint {
  color: var(--secondary);
  font-size: 0.72rem;
  letter-spacing: 0.08em;
  line-height: 1.4;
  text-transform: uppercase;
}

.alternate-note {
  text-align: right;
}

.reader-shell {
  width: min(100%, 60rem);
  margin: 0 auto;
}

.page-stage {
  position: relative;
  width: min(100%, calc(82vh * var(--spread-ratio)));
  aspect-ratio: var(--spread-ratio);
  margin: 0 auto;
  perspective: 1400px;
}

.page-stage.is-cover {
  width: min(100%, calc(82vh * var(--page-ratio)));
  aspect-ratio: var(--page-ratio);
}

.page-stage::after {
  position: absolute;
  z-index: -1;
  content: "";
  pointer-events: none;
}

.page-stage::after {
  inset: 3% -4% -5% 4%;
  background: rgba(22, 24, 29, 0.7);
  filter: blur(1.2rem);
  opacity: 0.7;
  transform: translateY(1.2rem);
}

.alt-page {
  position: absolute;
  inset: 0 auto 0 0;
  width: 50%;
  overflow: hidden;
  background: var(--paper);
  box-shadow: 0 1.4rem 3rem rgba(0, 0, 0, 0.26);
  opacity: 0;
  pointer-events: none;
  transform: rotateY(8deg) translateX(1.5rem) scale(0.985);
  transform-origin: left center;
  transition: opacity 180ms ease, transform 620ms cubic-bezier(0.22, 1, 0.36, 1), visibility 0s linear 620ms;
  visibility: hidden;
}

.alt-page.is-current {
  z-index: 1;
  opacity: 1;
  pointer-events: auto;
  transform: rotateY(0) translateX(0) scale(1);
  transition-delay: 0s;
  visibility: visible;
}

.alt-page.is-current.is-backward {
  transform-origin: right center;
  animation: page-enter-backward 620ms cubic-bezier(0.22, 1, 0.36, 1);
}

.alt-page.is-reveal {
  z-index: 2;
  opacity: 1;
  pointer-events: none;
  transform: none;
  visibility: visible;
}

.alt-page.is-turn-source {
  opacity: 0;
  pointer-events: none;
}

.turning-leaf {
  position: absolute;
  top: 0;
  bottom: 0;
  z-index: 9;
  width: 50%;
  opacity: 0;
  pointer-events: none;
  transform-style: preserve-3d;
  will-change: transform;
}

.turning-leaf--forward {
  left: 50%;
  transform-origin: left center;
}

.turning-leaf--backward {
  left: 0;
  transform-origin: right center;
}

.turning-leaf.is-active {
  opacity: 1;
}

.turning-leaf--forward.is-active {
  animation: turn-page-forward 820ms cubic-bezier(0.3, 0.03, 0.2, 1) both;
}

.turning-leaf--backward.is-active {
  animation: turn-page-backward 820ms cubic-bezier(0.3, 0.03, 0.2, 1) both;
}

.leaf-face {
  position: absolute;
  inset: 0;
  overflow: hidden;
  background: var(--paper);
  box-shadow: 0 0.8rem 2rem rgba(0, 0, 0, 0.54);
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
}

.leaf-face--front {
  transform: rotateY(0deg);
}

.leaf-face--back {
  transform: rotateY(180deg);
}

.leaf-face::after {
  position: absolute;
  inset: 0;
  background: linear-gradient(90deg, transparent 68%, rgba(255, 255, 255, 0.18) 88%, rgba(22, 24, 29, 0.35));
  content: "";
}

.turning-leaf--backward .leaf-face::after {
  background: linear-gradient(270deg, transparent 68%, rgba(255, 255, 255, 0.18) 88%, rgba(22, 24, 29, 0.35));
}

.leaf-face img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.page-stage.is-turning::before {
  inset: 0 48.5% 0 48.5%;
  z-index: 8;
  background: radial-gradient(ellipse at center, rgba(22, 24, 29, 0.74), transparent 72%);
  filter: none;
  opacity: 1;
  transform: none;
  animation: gutter-shadow 820ms ease-in-out both;
}

.alt-page img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.reader-controls {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  width: min(100%, 24rem);
  margin: 1.5rem auto 0;
}

.reader-button {
  display: grid;
  width: 2.6rem;
  height: 2.6rem;
  place-items: center;
  border: 1px solid var(--secondary);
  border-radius: 50%;
  color: var(--paper);
  background: transparent;
  cursor: pointer;
  font-size: 1.2rem;
  transition: border-color 180ms ease, background 180ms ease, color 180ms ease;
}

.reader-button:hover:not(:disabled),
.reader-button:focus-visible:not(:disabled) {
  border-color: var(--accent);
  color: var(--paper);
  background: var(--accent);
}

.reader-button:disabled {
  cursor: not-allowed;
  opacity: 0.35;
}

.reader-status {
  margin: 0;
  text-align: center;
}

.reader-hint {
  margin: 0.75rem 0 0;
  text-align: center;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

@keyframes page-enter-backward {
  from {
    opacity: 0;
    transform: rotateY(-8deg) translateX(-1.5rem) scale(0.985);
  }
  to {
    opacity: 1;
    transform: rotateY(0) translateX(0) scale(1);
  }
}

@keyframes turn-page-forward {
  0% { transform: rotateY(0deg) translateZ(1px); }
  48% { transform: rotateY(-88deg) translateZ(1.4rem); }
  100% { transform: rotateY(-180deg) translateZ(1px); }
}

@keyframes turn-page-backward {
  0% { transform: rotateY(0deg) translateZ(1px); }
  48% { transform: rotateY(88deg) translateZ(1.4rem); }
  100% { transform: rotateY(180deg) translateZ(1px); }
}

@keyframes gutter-shadow {
  0%, 100% { opacity: 0.2; transform: scaleX(0.35); }
  50% { opacity: 1; transform: scaleX(1); }
}

@media (max-width: 48rem) {
  .alternate-volume {
    padding-top: 1.5rem;
  }

  .alternate-intro {
    align-items: start;
    flex-direction: column;
    margin-bottom: 1rem;
  }

  .alternate-note {
    text-align: left;
  }

  .page-stage {
    width: min(92vw, 38rem);
    aspect-ratio: var(--page-ratio);
  }

  .page-stage.is-cover {
    width: min(92vw, 38rem);
    aspect-ratio: var(--page-ratio);
  }

  .page-stage.is-mobile .alt-page,
  .page-stage.is-mobile .alt-page.is-left,
  .page-stage.is-mobile .alt-page.is-right {
    left: 0;
    width: 100%;
  }

  .page-stage.is-mobile::after,
  .page-stage.is-mobile.is-turning::before {
    display: none;
  }

  .page-stage.is-mobile .turning-leaf {
    left: 0;
    width: 100%;
  }
}

@media (prefers-reduced-motion: reduce) {
  .alt-page,
  .turning-leaf.is-active,
  .reader-button {
    transition: none;
  }

  .alt-page.is-current.is-backward {
    animation: none;
  }
}