:root {
  --ink: #18130e;
  --ink-soft: rgba(245, 238, 228, .74);
  --paper: #efe4d2;
  --paper-deep: #c9b99d;
  --panel: rgba(24, 19, 14, .82);
  --line: rgba(245, 238, 228, .18);
  --gold: #b99762;
  --shadow: 0 28px 80px rgba(0, 0, 0, .48);
  --sans: Inter, "Noto Sans SC", "PingFang SC", "Microsoft YaHei", Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
}

* {
  box-sizing: border-box;
}

html,
body {
  width: 100%;
  height: 100%;
  margin: 0;
  overflow: hidden;
  background:
    linear-gradient(180deg, rgba(24, 19, 14, .08), rgba(12, 16, 18, .16)),
    url("../backgrounds/matterhorn-mobile-v2.png") center / cover no-repeat,
    var(--ink);
  color: var(--ink-soft);
  font-family: var(--sans);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  touch-action: pan-y pinch-zoom;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background:
    radial-gradient(54% 46% at 50% 48%, rgba(8, 10, 11, .54), rgba(8, 10, 11, .22) 48%, transparent 74%),
    linear-gradient(180deg, rgba(8, 10, 11, .08), rgba(8, 10, 11, .22));
}

body::after {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background:
    radial-gradient(56% 48% at 50% 47%, rgba(10, 8, 6, .28), transparent 68%),
    linear-gradient(180deg, rgba(8, 7, 6, .1), rgba(8, 7, 6, .42)),
    linear-gradient(90deg, rgba(255, 255, 255, .03) 1px, transparent 1px),
    linear-gradient(0deg, rgba(255, 255, 255, .022) 1px, transparent 1px);
  background-size: 42px 42px;
  opacity: .72;
}

button {
  font: inherit;
}

.app {
  position: fixed;
  inset: 0;
  z-index: 1;
  min-height: 100dvh;
  overflow: hidden;
}

.topbar,
.bottombar {
  position: fixed;
  left: 0;
  right: 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  z-index: 30;
  pointer-events: none;
}

.topbar {
  top: 0;
  height: 58px;
  padding: max(10px, env(safe-area-inset-top)) 16px 0;
}

.brand {
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: rgba(245, 238, 228, .82);
  white-space: nowrap;
}

.icon-button,
.nav-button,
.text-button {
  pointer-events: auto;
  border: 1px solid var(--line);
  color: rgba(245, 238, 228, .86);
  background: rgba(24, 19, 14, .42);
  backdrop-filter: blur(18px);
  cursor: pointer;
}

.icon-button {
  width: 42px;
  height: 42px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  font-size: 21px;
  line-height: 1;
}

.reader {
  position: fixed;
  inset: 0;
  display: grid;
  place-items: center;
  padding: 62px 14px 88px;
  perspective: 2200px;
}

.book-stage {
  position: relative;
  width: min(91vw, calc((100dvh - 166px) * .75));
  height: min(calc(100dvh - 166px), calc(91vw / .75));
  max-width: 1080px;
  max-height: 1440px;
  isolation: isolate;
  transform-style: preserve-3d;
}

.book-stage::before {
  content: "";
  position: absolute;
  inset: -12px;
  border-radius: 12px;
  background:
    linear-gradient(90deg, rgba(255, 255, 255, .12), transparent 16%, transparent 84%, rgba(0, 0, 0, .18)),
    var(--paper);
  filter: blur(.1px);
  transform: translateZ(-30px);
  box-shadow: var(--shadow);
}

.book-stage::after {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 7;
  pointer-events: none;
  opacity: 0;
  border-radius: 4px;
  background:
    radial-gradient(120% 86% at 98% 50%, rgba(255, 255, 255, .34), transparent 18%),
    linear-gradient(90deg, transparent 0%, rgba(255, 255, 255, .26) 37%, rgba(0, 0, 0, .34) 51%, rgba(0, 0, 0, .12) 64%, transparent 78%);
  mix-blend-mode: soft-light;
  transform: translate3d(48%, 0, 34px) scaleX(.22) skewY(-4deg);
}

.turn-curl {
  position: absolute;
  inset: 0;
  z-index: 6;
  pointer-events: none;
  opacity: 0;
  border-radius: 4px;
  background:
    linear-gradient(90deg, transparent 0%, rgba(255, 255, 255, .2) 19%, rgba(255, 255, 255, .38) 35%, rgba(255, 255, 255, .1) 48%, rgba(0, 0, 0, .38) 62%, transparent 82%),
    radial-gradient(92% 125% at 86% 50%, rgba(255, 255, 255, .32), transparent 43%);
  filter: blur(.25px);
  mix-blend-mode: soft-light;
  transform: translate3d(44%, 0, 34px) scaleX(.18) skewY(-3deg);
}

.page-image {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: contain;
  border-radius: 4px;
  background: var(--paper);
  box-shadow: 0 18px 56px rgba(0, 0, 0, .38);
  user-select: none;
  -webkit-user-drag: none;
  backface-visibility: hidden;
  transform-style: preserve-3d;
  will-change: transform, opacity, filter, box-shadow;
}

.current-page {
  z-index: 2;
  opacity: 0;
}

.current-page.is-ready {
  opacity: 1;
}

.incoming-page {
  z-index: 1;
  opacity: 0;
}

.incoming-page.is-visible {
  opacity: 1;
}

.book-stage.is-dragging::after,
.book-stage.is-settling::after {
  opacity: var(--crease-opacity, 0);
  transform: var(--crease-transform);
}

.book-stage.is-dragging .turn-curl,
.book-stage.is-settling .turn-curl {
  opacity: var(--curl-opacity, 0);
  transform: var(--curl-transform);
}

.book-stage.is-settling .page-image,
.book-stage.is-settling::after,
.book-stage.is-settling .turn-curl {
  transition:
    transform var(--settle-duration, .72s) cubic-bezier(.16, .68, .12, 1),
    opacity var(--settle-duration, .72s) cubic-bezier(.16, .68, .12, 1),
    filter var(--settle-duration, .72s) cubic-bezier(.16, .68, .12, 1),
    box-shadow var(--settle-duration, .72s) cubic-bezier(.16, .68, .12, 1);
}

.book-stage.is-dragging-next .current-page,
.book-stage.is-settling-next .current-page {
  z-index: 5;
  transform-origin: left center;
  transform: var(--turning-transform);
  filter: var(--turning-filter);
  box-shadow: var(--turning-shadow);
}

.book-stage.is-dragging-next .incoming-page,
.book-stage.is-settling-next .incoming-page {
  z-index: 1;
  opacity: 1;
  transform: var(--under-transform);
  filter: var(--under-filter);
}

.book-stage.is-dragging-prev .incoming-page,
.book-stage.is-settling-prev .incoming-page {
  z-index: 5;
  opacity: 1;
  transform-origin: right center;
  transform: var(--turning-transform);
  filter: var(--turning-filter);
  box-shadow: var(--turning-shadow);
}

.book-stage.is-dragging-prev .current-page,
.book-stage.is-settling-prev .current-page {
  z-index: 1;
  transform: var(--under-transform);
  filter: var(--under-filter);
}

.page-image.flip-next-out {
  transform-origin: left center;
  animation: softFlipNextOut .92s cubic-bezier(.16, .68, .12, 1) forwards;
}

.page-image.flip-next-in {
  animation: softRevealNext .92s cubic-bezier(.16, .68, .12, 1) forwards;
}

.page-image.flip-prev-in {
  z-index: 4;
  transform-origin: left center;
  animation: softFlipPrevIn .92s cubic-bezier(.16, .68, .12, 1) forwards;
}

.page-image.flip-prev-under {
  animation: softSettleUnder .92s cubic-bezier(.16, .68, .12, 1) forwards;
}

.book-stage.is-turning-next::after {
  animation: pageCreaseNext .92s cubic-bezier(.16, .68, .12, 1) forwards;
}

.book-stage.is-turning-prev::after {
  animation: pageCreasePrev .92s cubic-bezier(.16, .68, .12, 1) forwards;
}

.book-stage.is-turning-next .turn-curl {
  animation: pageCurlNext .92s cubic-bezier(.16, .68, .12, 1) forwards;
}

.book-stage.is-turning-prev .turn-curl {
  animation: pageCurlPrev .92s cubic-bezier(.16, .68, .12, 1) forwards;
}

@keyframes softFlipNextOut {
  0% {
    transform: translate3d(0, 0, 22px) rotateY(0deg) skewY(0deg) scale(1);
    filter: brightness(1);
    box-shadow: 0 18px 56px rgba(0, 0, 0, .38);
  }
  24% {
    transform: translate3d(-.7%, 0, 40px) rotateY(-18deg) skewY(-1.8deg) scale(.999);
    filter: brightness(.98) contrast(1.01);
    box-shadow: 14px 28px 62px rgba(0, 0, 0, .46);
  }
  56% {
    transform: translate3d(-3.2%, 0, 34px) rotateY(-88deg) skewY(-.7deg) scale(.996);
    filter: brightness(.78) contrast(.98);
    box-shadow: 42px 26px 74px rgba(0, 0, 0, .42);
  }
  78% {
    transform: translate3d(-6%, 0, 8px) rotateY(-128deg) skewY(.5deg) scale(.99);
    filter: brightness(.66) contrast(.96);
    box-shadow: 48px 20px 70px rgba(0, 0, 0, .24);
  }
  100% {
    transform: translate3d(-7.8%, 0, -18px) rotateY(-154deg) skewY(0deg) scale(.986);
    filter: brightness(.58) contrast(.95);
    box-shadow: 44px 16px 62px rgba(0, 0, 0, .16);
  }
}

@keyframes softRevealNext {
  0% {
    transform: translate3d(2%, 0, -12px) scale(.99);
    filter: brightness(.76) saturate(.94);
  }
  44% {
    transform: translate3d(1%, 0, -6px) scale(.994);
    filter: brightness(.82) saturate(.96);
  }
  82% {
    transform: translate3d(.2%, 0, 0) scale(.998);
    filter: brightness(.94) saturate(.99);
  }
  100% {
    transform: translate3d(0, 0, 0) scale(1);
    filter: brightness(1) saturate(1);
  }
}

@keyframes softFlipPrevIn {
  0% {
    transform: translate3d(-7.8%, 0, -18px) rotateY(-154deg) skewY(0deg) scale(.986);
    filter: brightness(.58) contrast(.95);
    box-shadow: 44px 16px 62px rgba(0, 0, 0, .16);
  }
  24% {
    transform: translate3d(-6%, 0, 8px) rotateY(-128deg) skewY(-.3deg) scale(.99);
    filter: brightness(.66) contrast(.96);
    box-shadow: 48px 20px 70px rgba(0, 0, 0, .24);
  }
  54% {
    transform: translate3d(-3.2%, 0, 34px) rotateY(-88deg) skewY(.7deg) scale(.996);
    filter: brightness(.78) contrast(.98);
    box-shadow: 42px 26px 74px rgba(0, 0, 0, .42);
  }
  82% {
    transform: translate3d(-.5%, 0, 40px) rotateY(-18deg) skewY(1.2deg) scale(.999);
    filter: brightness(.98) contrast(1.01);
    box-shadow: 14px 28px 62px rgba(0, 0, 0, .46);
  }
  100% {
    transform: translate3d(0, 0, 22px) rotateY(0deg) skewY(0deg) scale(1);
    filter: brightness(1);
    box-shadow: 0 18px 56px rgba(0, 0, 0, .38);
  }
}

@keyframes softSettleUnder {
  0% {
    transform: translate3d(-1.4%, 0, -10px) scale(.99);
    filter: brightness(.78);
  }
  60% {
    filter: brightness(.86);
  }
  100% {
    transform: translate3d(0, 0, 0) scale(1);
    filter: brightness(1);
  }
}

@keyframes pageCurlNext {
  0% {
    opacity: 0;
    transform: translate3d(50%, 0, 34px) scaleX(.12) skewY(-5deg);
  }
  20% {
    opacity: .8;
  }
  54% {
    opacity: .92;
    transform: translate3d(-4%, 0, 46px) scaleX(.42) skewY(-.8deg);
  }
  78% {
    opacity: .64;
    transform: translate3d(-34%, 0, 24px) scaleX(.28) skewY(1.2deg);
  }
  100% {
    opacity: 0;
    transform: translate3d(-58%, 0, 8px) scaleX(.18) skewY(2deg);
  }
}

@keyframes pageCurlPrev {
  0% {
    opacity: 0;
    transform: translate3d(-58%, 0, 8px) scaleX(.18) skewY(2deg);
  }
  22% {
    opacity: .64;
  }
  58% {
    opacity: .92;
    transform: translate3d(-4%, 0, 46px) scaleX(.42) skewY(-.8deg);
  }
  82% {
    opacity: .8;
    transform: translate3d(32%, 0, 34px) scaleX(.24) skewY(-3deg);
  }
  100% {
    opacity: 0;
    transform: translate3d(50%, 0, 34px) scaleX(.12) skewY(-5deg);
  }
}

@keyframes pageCreaseNext {
  0% {
    opacity: 0;
    transform: translate3d(52%, 0, 38px) scaleX(.14) skewY(-5deg);
  }
  26% {
    opacity: .76;
  }
  62% {
    opacity: .84;
    transform: translate3d(-12%, 0, 48px) scaleX(.46) skewY(-.5deg);
  }
  82% {
    opacity: .36;
    transform: translate3d(-42%, 0, 18px) scaleX(.24) skewY(1.4deg);
  }
  100% {
    opacity: 0;
    transform: translate3d(-60%, 0, 10px) scaleX(.16) skewY(2deg);
  }
}

@keyframes pageCreasePrev {
  0% {
    opacity: 0;
    transform: translate3d(-60%, 0, 10px) scaleX(.16) skewY(2deg);
  }
  28% {
    opacity: .36;
  }
  64% {
    opacity: .84;
    transform: translate3d(-12%, 0, 48px) scaleX(.46) skewY(-.5deg);
  }
  84% {
    opacity: .76;
    transform: translate3d(32%, 0, 38px) scaleX(.24) skewY(-3deg);
  }
  100% {
    opacity: 0;
    transform: translate3d(52%, 0, 38px) scaleX(.14) skewY(-5deg);
  }
}

.loading {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  z-index: 5;
  color: rgba(24, 19, 14, .62);
  background: var(--paper);
  border-radius: 4px;
  font-size: 14px;
}

.loading.is-hidden {
  display: none;
}

.tap-zone {
  position: fixed;
  top: 58px;
  bottom: 78px;
  width: 36%;
  padding: 0;
  border: 0;
  background: transparent;
  z-index: 18;
  cursor: pointer;
  touch-action: pan-y pinch-zoom;
}

.tap-zone-left {
  left: 0;
}

.tap-zone-right {
  right: 0;
}

.bottombar {
  bottom: 0;
  min-height: 76px;
  padding: 10px 14px max(13px, env(safe-area-inset-bottom));
  gap: 12px;
}

.nav-button {
  width: 46px;
  height: 46px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  font-size: 31px;
  line-height: 1;
}

.nav-button:disabled {
  opacity: .28;
  cursor: default;
}

.page-meta {
  min-width: 0;
  text-align: center;
}

.page-title {
  max-width: 58vw;
  overflow: hidden;
  white-space: nowrap;
  text-overflow: ellipsis;
  font-size: 13px;
  color: rgba(245, 238, 228, .88);
}

.page-counter {
  margin-top: 4px;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .08em;
  color: rgba(245, 238, 228, .5);
}

.progress-track {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  height: 3px;
  background: rgba(245, 238, 228, .13);
  z-index: 35;
}

.progress-bar {
  width: 0;
  height: 100%;
  background: linear-gradient(90deg, var(--gold), #f0d9ad);
  transition: width .28s ease;
}

.toc-panel {
  position: fixed;
  inset: 0 0 0 auto;
  width: min(420px, 100vw);
  padding: max(18px, env(safe-area-inset-top)) 18px max(20px, env(safe-area-inset-bottom));
  background: var(--panel);
  border-left: 1px solid var(--line);
  backdrop-filter: blur(22px);
  z-index: 60;
  transform: translateX(100%);
  transition: transform .26s ease;
  overflow-y: auto;
}

.toc-panel.is-open {
  transform: translateX(0);
}

.toc-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 18px;
}

.toc-kicker {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .16em;
  color: rgba(245, 238, 228, .48);
  text-transform: uppercase;
}

.toc-header h1 {
  margin: 8px 0 0;
  font-size: 22px;
  font-weight: 600;
  letter-spacing: 0;
  color: rgba(245, 238, 228, .92);
}

.toc-actions {
  display: flex;
  gap: 8px;
  margin: 22px 0 14px;
}

.text-button {
  min-height: 38px;
  padding: 0 13px;
  border-radius: 999px;
  font-size: 13px;
}

.toc-list {
  display: grid;
  gap: 8px;
}

.toc-item {
  display: grid;
  grid-template-columns: 42px 1fr;
  gap: 10px;
  align-items: center;
  min-height: 46px;
  padding: 8px;
  border: 1px solid rgba(245, 238, 228, .12);
  border-radius: 8px;
  color: rgba(245, 238, 228, .84);
  background: rgba(255, 255, 255, .035);
  text-align: left;
  cursor: pointer;
}

.toc-item.is-current {
  border-color: rgba(185, 151, 98, .72);
  background: rgba(185, 151, 98, .12);
}

.toc-number {
  font-family: var(--mono);
  font-size: 11px;
  color: rgba(245, 238, 228, .48);
}

.toc-title {
  min-width: 0;
  overflow: hidden;
  white-space: nowrap;
  text-overflow: ellipsis;
  font-size: 13px;
}

@media (min-width: 820px) {
  .reader {
    padding: 68px 32px 92px;
  }

  .book-stage {
    width: min(72vw, calc((100dvh - 176px) * .75));
    height: min(calc(100dvh - 176px), calc(72vw / .75));
  }

  .page-title {
    max-width: 520px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-image.flip-next-out,
  .page-image.flip-next-in,
  .page-image.flip-prev-in,
  .page-image.flip-prev-under,
  .book-stage.is-turning-next::after,
  .book-stage.is-turning-prev::after,
  .book-stage.is-turning-next .turn-curl,
  .book-stage.is-turning-prev .turn-curl,
  .book-stage.is-dragging .page-image,
  .book-stage.is-settling .page-image,
  .book-stage.is-dragging::after,
  .book-stage.is-settling::after,
  .book-stage.is-dragging .turn-curl,
  .book-stage.is-settling .turn-curl,
  .toc-panel,
  .progress-bar {
    animation: none;
    transition: none;
  }
}