:root {
  --bg: #06111d;
  --text: #f8fafc;
  --muted: rgba(248, 250, 252, 0.72);
  --gold: #d8a441;
  --edge: rgba(255,255,255,.14);
  --page-ratio: .744;
  --spread-ratio: 1.488;
  --turn-duration: 620ms;
}

* { box-sizing: border-box; }
html, body { height: 100%; margin: 0; }
body {
  overflow: hidden;
  background: #02060b;
  color: var(--text);
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  -webkit-font-smoothing: antialiased;
}
button, input { font: inherit; }
button { -webkit-tap-highlight-color: transparent; }

.launch-screen {
  position: fixed;
  inset: 0;
  z-index: 1;
  display: grid;
  place-items: center;
  padding: 24px;
  background: radial-gradient(circle at top left, rgba(216,164,65,.16), transparent 34%), #07131f;
}
.launch-btn {
  cursor: pointer;
  border: 1px solid rgba(255,255,255,.18);
  border-radius: 24px;
  background: rgba(255,255,255,.08);
  color: #fff;
  padding: 22px 28px;
  min-width: min(420px, 92vw);
  box-shadow: 0 24px 70px rgba(0,0,0,.38);
}
.launch-btn span { display:block; font-size: clamp(24px, 4vw, 40px); font-weight: 800; letter-spacing: -.03em; }
.launch-btn small { display:block; margin-top: 8px; color: var(--muted); }

.tc-lightbox {
  position: fixed;
  inset: 0;
  z-index: 10;
  width: 100vw;
  height: 100svh;
  min-height: 100dvh;
  overflow: hidden;
  isolation: isolate;
  background:
    radial-gradient(circle at 20% 12%, rgba(216,164,65,.12), transparent 32%),
    radial-gradient(circle at 85% 88%, rgba(42,116,175,.16), transparent 38%),
    linear-gradient(180deg, #06111d, #03070d);
  opacity: 0;
  visibility: hidden;
  transform: scale(1.006);
  transition: opacity .18s ease, transform .18s ease, visibility .18s ease;
}
.tc-lightbox.is-open { opacity: 1; visibility: visible; transform: scale(1); }

.topbar, .bottombar {
  position: fixed;
  z-index: 35;
  left: max(14px, env(safe-area-inset-left));
  right: max(14px, env(safe-area-inset-right));
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  pointer-events: none;
}
.topbar { top: max(12px, env(safe-area-inset-top)); }
.bottombar { bottom: max(12px, env(safe-area-inset-bottom)); }
.brand-pill, .reader-controls, .hint, .range-wrap {
  pointer-events: auto;
  border: 1px solid var(--edge);
  background: rgba(3,9,15,.72);
  box-shadow: 0 12px 34px rgba(0,0,0,.18);
}
.brand-pill {
  display: flex;
  align-items: baseline;
  gap: 10px;
  border-radius: 999px;
  padding: 10px 16px;
  user-select: none;
  background: #fff;
}

.brand-pill strong { font-size: 15px; letter-spacing: .02em; }
.brand-pill span { color: var(--gold); font-size: 12px; text-transform: uppercase; letter-spacing: .14em; }
.reader-controls { display: flex; align-items: center; gap: 8px; border-radius: 999px; padding: 7px; }
.control-btn {
  display: grid;
  place-items: center;
  min-width: 38px;
  height: 38px;
  border: 0;
  border-radius: 999px;
  color: #fff;
  background: rgba(255,255,255,.10);
  cursor: pointer;
  transition: transform .14s ease, background .14s ease, opacity .14s ease;
}
.control-btn:hover { transform: translateY(-1px); background: rgba(255,255,255,.16); }
.control-btn:disabled { opacity: .34; cursor: not-allowed; transform: none; }
.control-btn.wide { width: 56px; font-size: 12px; text-transform: uppercase; letter-spacing: .08em; }
.control-btn.close { background: rgba(216,73,73,.26); font-size: 24px; line-height: 1; }
.page-label { min-width: 82px; text-align: center; color: #fff; font-size: 13px; font-weight: 700; }

.stage {
  position: absolute;
  inset: 0;
  z-index: 20;
  display: grid;
  place-items: center;
  padding: 76px 16px 68px;
  perspective: 2400px;
}

.book-shell {
  position: relative;
  width: min(97vw, calc((100svh - 154px) * var(--spread-ratio)));
  width: min(97vw, calc((100dvh - 154px) * var(--spread-ratio)));
  aspect-ratio: var(--spread-ratio) / 1;
  max-height: calc(100svh - 154px);
  max-height: calc(100dvh - 154px);
  border-radius: clamp(9px, 1.2vw, 20px);
  overflow: hidden;
  isolation: isolate;
  contain: layout paint style;
  background: #111827;
  box-shadow: 0 44px 100px rgba(0,0,0,.58), inset 0 0 0 1px rgba(255,255,255,.10);
  transform: translateZ(0);
  transform-style: preserve-3d;
  touch-action: pan-y;
}
.book-shell.single {
  width: min(94vw, calc((100svh - 154px) * var(--page-ratio)));
  width: min(94vw, calc((100dvh - 154px) * var(--page-ratio)));
  aspect-ratio: var(--page-ratio) / 1;
}
.book-shadow {
  position: absolute;
  inset: auto 5% -4% 5%;
  height: 9%;
  z-index: 0;
  pointer-events: none;
  background: radial-gradient(ellipse at center, rgba(0,0,0,.42), transparent 70%);
}
.spine {
  position: absolute;
  z-index: 25;
  top: 0;
  bottom: 0;
  left: 50%;
  width: clamp(10px, 1vw, 18px);
  transform: translateX(-50%);
  background: linear-gradient(90deg, rgba(0,0,0,.25), rgba(255,255,255,.12) 48%, rgba(0,0,0,.28));
  opacity: .72;
  pointer-events: none;
}
.book-shell.single .spine { display: none; }

.spread {
  position: absolute;
  inset: 0;
  z-index: 5;
  display: flex;
  overflow: hidden;
  backface-visibility: hidden;
  transform-style: preserve-3d;
}
.book-base { z-index: 4; }
.page-card {
  position: relative;
  flex: 1 1 50%;
  min-width: 0;
  height: 100%;
  overflow: hidden;
  background: #fff;
  box-shadow: inset 0 0 0 1px rgba(0,0,0,.06);
  transform: translateZ(0);
  backface-visibility: hidden;
}
.spread.single-spread .page-card { flex: 0 0 100%; width: 100%; max-width: 100%; }
.page-card.blank, .static-page.blank, .flip-face.blank { background: linear-gradient(135deg, #f6f1e9, #fffaf1); }
.page-card.left-page { border-right: 1px solid rgba(0,0,0,.14); }
.page-card.right-page { border-left: 1px solid rgba(255,255,255,.16); }
.page-card img, .static-page img, .flip-face img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: fill;
  user-select: none;
  -webkit-user-drag: none;
  backface-visibility: hidden;
  transform: translateZ(0);
}
.page-card::after, .static-page::after, .flip-face::after {
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
}
.page-card.left-page::after, .static-left::after { background: linear-gradient(90deg, transparent 76%, rgba(0,0,0,.15)); }
.page-card.right-page::after, .static-right::after { background: linear-gradient(90deg, rgba(0,0,0,.13), transparent 22%); }
.spread.single-spread .page-card::after { background: linear-gradient(90deg, rgba(0,0,0,.07), transparent 14%, transparent 86%, rgba(0,0,0,.10)); }

.static-page {
  position: absolute;
  top: 0;
  bottom: 0;
  width: 50%;
  z-index: 12;
  overflow: hidden;
  display: none;
  background: #fff;
  transform: translateZ(2px);
  backface-visibility: hidden;
}
.static-left { left: 0; }
.static-right { right: 0; }
.static-page.is-visible { display: block; }
.book-shell.single .static-page { width: 100%; left: 0; right: auto; }

.flip-layer {
  position: absolute;
  top: 0;
  bottom: 0;
  width: 50%;
  z-index: 18;
  display: none;
  overflow: visible;
  pointer-events: none;
  perspective: 2400px;
  transform-style: preserve-3d;
}
.flip-layer.is-visible { display: block; }
.flip-layer.turn-next { right: 0; left: auto; }
.flip-layer.turn-prev { left: 0; right: auto; }
.flip-layer.full-flip { left: 0; right: auto; width: 100%; }
.flip-paper {
  position: absolute;
  inset: 0;
  transform-style: preserve-3d;
  backface-visibility: hidden;
  background: #fff;
}
.book-shell.is-flipping .flip-paper { will-change: transform; }
.flip-layer.turn-next .flip-paper {
  transform-origin: left center;
  animation: pageTurnNext var(--turn-duration) cubic-bezier(.2,.76,.22,1) both;
}
.flip-layer.turn-prev .flip-paper {
  transform-origin: right center;
  animation: pageTurnPrev var(--turn-duration) cubic-bezier(.2,.76,.22,1) both;
}
.flip-face {
  position: absolute;
  inset: 0;
  overflow: hidden;
  background: #fff;
  backface-visibility: hidden;
  transform-style: preserve-3d;
  box-shadow: inset 0 0 0 1px rgba(0,0,0,.05);
}
.flip-front { transform: rotateY(0deg) translateZ(.5px); }
.flip-back { transform: rotateY(180deg) translateZ(.5px); }
.flip-paper::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 6;
  pointer-events: none;
  backface-visibility: hidden;
  opacity: .42;
  background: linear-gradient(90deg, rgba(255,255,255,.25), transparent 24%, transparent 70%, rgba(0,0,0,.28));
  animation: turnShadeNext var(--turn-duration) linear both;
}
.flip-layer.turn-prev .flip-paper::before {
  background: linear-gradient(270deg, rgba(255,255,255,.25), transparent 24%, transparent 70%, rgba(0,0,0,.28));
  animation-name: turnShadePrev;
}
.flip-paper::after {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  width: 18px;
  z-index: 7;
  pointer-events: none;
  opacity: .52;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,.45), transparent);
}
.flip-layer.turn-next .flip-paper::after { left: -5px; }
.flip-layer.turn-prev .flip-paper::after { right: -5px; }
.book-shell.is-flipping .book-base { z-index: 3; }
.book-shell.is-flipping .tap-zone { pointer-events: none; }

@keyframes pageTurnNext {
  0%   { transform: translate3d(0,0,4px) rotateY(0deg); }
  45%  { transform: translate3d(-2.4%,0,24px) rotateY(-88deg); }
  100% { transform: translate3d(0,0,4px) rotateY(-179.5deg); }
}
@keyframes pageTurnPrev {
  0%   { transform: translate3d(0,0,4px) rotateY(0deg); }
  45%  { transform: translate3d(2.4%,0,24px) rotateY(88deg); }
  100% { transform: translate3d(0,0,4px) rotateY(179.5deg); }
}
@keyframes turnShadeNext {
  0% { opacity: .12; }
  42% { opacity: .58; }
  100% { opacity: .10; }
}
@keyframes turnShadePrev {
  0% { opacity: .12; }
  42% { opacity: .58; }
  100% { opacity: .10; }
}

.tap-zone {
  position: absolute;
  z-index: 27;
  top: 0;
  bottom: 0;
  width: 28%;
  border: 0;
  opacity: 0;
  background: transparent;
  cursor: pointer;
}
.tap-left { left: 0; }
.tap-right { right: 0; }

.hint {
  display: inline-flex;
  align-items: center;
  min-height: 38px;
  padding: 0 14px;
  border-radius: 999px;
  color: var(--muted);
  font-size: 13px;
}
.mobile-hint { display: none; }
.range-wrap {
  width: min(460px, 48vw);
  min-height: 38px;
  display: flex;
  align-items: center;
  padding: 0 12px;
  border-radius: 999px;
}
input[type="range"] { width: 100%; accent-color: var(--gold); cursor: pointer; }

@media (max-width: 900px), (orientation: portrait) {
  :root { --turn-duration: 520ms; }
  .topbar { align-items: flex-start; }
  .brand-pill span { display: none; }
  .control-btn.wide { display: none; }
  .reader-controls { gap: 5px; padding: 6px; }
  .control-btn { min-width: 36px; height: 36px; }
  .page-label { min-width: 70px; font-size: 12px; }
  .stage { padding: 66px 8px 62px; perspective: 1600px; }
  .book-shell, .book-shell.single {
    width: min(96vw, calc((100svh - 132px) * var(--page-ratio)));
    width: min(96vw, calc((100dvh - 132px) * var(--page-ratio)));
    max-height: calc(100svh - 132px);
    max-height: calc(100dvh - 132px);
    aspect-ratio: var(--page-ratio) / 1;
  }
  .spine { display: none; }
  .spread:not(.single-spread) .page-card:not(:first-child) { display: none; }
  .static-page, .flip-layer { width: 100%; left: 0; right: auto; }
  .flip-layer.turn-next .flip-paper { transform-origin: left center; }
  .flip-layer.turn-prev .flip-paper { transform-origin: right center; }
  .hint.desktop-hint { display: none; }
  .hint.mobile-hint { display: inline-flex; }
  .range-wrap { width: 46vw; }
}

@media (max-width: 560px) {
  .topbar, .bottombar { left: 8px; right: 8px; gap: 8px; }
  .brand-pill { padding: 9px 12px; }
  .brand-pill strong { font-size: 13px; }
  .page-label { min-width: 60px; }
  .hint { display: none !important; }
  .range-wrap { width: 100%; flex: 1; }
  .bottombar { justify-content: stretch; }
  .stage { padding-left: 5px; padding-right: 5px; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: .01ms !important; animation-iteration-count: 1 !important; transition-duration: .01ms !important; }
}