:root {
  --bg: #14110e;
  --bg-2: #2a2118;
  --paper: #1f1a14;
  --ink: #efe4cf;
  --muted: #b8a78a;
  --line: rgba(239, 228, 207, 0.14);
  --accent: #c47a3a;
  --shadow: 0 24px 60px rgba(0, 0, 0, 0.45);
  --page-w: min(720px, calc(100vw - 48px));
  --page-h: min(78vh, 820px);
}

[data-theme="coal"] {
  --bg: #14110e;
  --bg-2: #2c2218;
  --paper: #1f1a14;
  --ink: #efe4cf;
  --muted: #b8a78a;
  --accent: #c47a3a;
}

[data-theme="paper"] {
  --bg: #cbb48a;
  --bg-2: #a8895c;
  --paper: #f6edd6;
  --ink: #2c2416;
  --muted: #6d5c3f;
  --accent: #8a4b1f;
  --line: rgba(44, 36, 22, 0.12);
}

[data-theme="snow"] {
  --bg: #c5d3de;
  --bg-2: #8ea3b5;
  --paper: #f7fafc;
  --ink: #1b2733;
  --muted: #5b6d7c;
  --accent: #35587a;
  --line: rgba(27, 39, 51, 0.1);
}

[data-theme="lamp"] {
  --bg: #3a2208;
  --bg-2: #6a3d10;
  --paper: #f0c56a;
  --ink: #2a1604;
  --muted: #6a4314;
  --accent: #8a2e0b;
  --line: rgba(42, 22, 4, 0.14);
}

[data-theme="ink"] {
  --bg: #050505;
  --bg-2: #222;
  --paper: #111;
  --ink: #d8d8d8;
  --muted: #8a8a8a;
  --accent: #b04a3a;
  --line: rgba(255, 255, 255, 0.08);
}

[data-theme="moss"] {
  --bg: #8ea37c;
  --bg-2: #5d704d;
  --paper: #e7eedc;
  --ink: #24301c;
  --muted: #546246;
  --accent: #3f5a2c;
  --line: rgba(36, 48, 28, 0.12);
}

* { box-sizing: border-box; }
html, body { margin: 0; min-height: 100%; }
body {
  font-family: "Songti SC", "Noto Serif SC", "Source Han Serif SC", "STSong", serif;
  color: var(--ink);
  background:
    radial-gradient(1200px 600px at 50% -10%, var(--bg-2), transparent 60%),
    linear-gradient(180deg, var(--bg), #0b0907 130%);
  overflow: hidden;
}

.stage {
  min-height: 100vh;
  display: grid;
  grid-template-rows: auto 1fr auto;
}

.topbar, .bottombar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 16px 28px;
}

.brand { display: flex; align-items: baseline; gap: 12px; min-width: 0; }
.brand-mark {
  border: 1px solid var(--line);
  padding: 2px 8px;
  font-size: 12px;
  letter-spacing: 0.3em;
  color: var(--muted);
}
.brand h1 {
  margin: 0;
  font-size: 28px;
  font-weight: 700;
  letter-spacing: 0.4em;
}
.brand p {
  margin: 0;
  color: var(--muted);
  font-size: 13px;
  white-space: nowrap;
}

.tools { display: flex; gap: 8px; flex-wrap: wrap; }
.tool, .bottombar button, .close-panel, .swatch, .marks button, .catalog button {
  font: inherit;
  cursor: pointer;
  border: 1px solid var(--line);
  background: rgba(255,255,255,0.04);
  color: inherit;
  border-radius: 999px;
  padding: 8px 14px;
}
.tool.accent, .bottombar button:hover, .tool:hover {
  background: var(--accent);
  color: #fff;
  border-color: transparent;
}

.reader {
  position: relative;
  display: grid;
  place-items: center;
  padding: 0 64px 12px;
}

.book {
  width: var(--page-w);
  position: relative;
}

.page-stack {
  height: var(--page-h);
  perspective: 1800px;
  position: relative;
}

.page {
  position: absolute;
  inset: 0;
  background:
    linear-gradient(90deg, rgba(0,0,0,0.08), transparent 18px),
    var(--paper);
  color: var(--ink);
  box-shadow: var(--shadow);
  border-radius: 2px 10px 10px 2px;
  padding: 42px 48px 36px;
  overflow: hidden;
  transform-origin: left center;
}

.page.cover {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  background:
    linear-gradient(180deg, rgba(0,0,0,0.18), rgba(0,0,0,0.55)),
    radial-gradient(circle at 30% 20%, #6a4a28, transparent 40%),
    linear-gradient(160deg, #2a1c12, #0c0a08);
  color: #f3e6cf;
}

.cover-kicker { letter-spacing: 0.5em; color: #d7b48a; font-size: 13px; }
.cover h2 {
  margin: 24px 0 8px;
  font-size: 64px;
  letter-spacing: 0.55em;
  text-indent: 0.55em;
}
.cover .sub { font-size: 18px; letter-spacing: 0.18em; color: #d8c4a4; }
.cover .meta { color: #cbb79a; line-height: 1.8; }

.chapter-title {
  margin: 0 0 22px;
  font-size: 22px;
  letter-spacing: 0.35em;
  text-align: center;
}
.page p {
  margin: 0 0 1.05em;
  font-size: 18px;
  line-height: 1.95;
  text-indent: 2em;
  text-align: justify;
}
.page p.no-indent { text-indent: 0; text-align: center; letter-spacing: 0.2em; }

.toc h3 { margin: 0 0 18px; letter-spacing: 0.4em; text-align: center; }
.toc ol { list-style: none; margin: 0; padding: 0; columns: 1; }
.toc li { break-inside: avoid; }
.toc button {
  width: 100%;
  text-align: left;
  background: transparent;
  border: 0;
  border-bottom: 1px dashed var(--line);
  border-radius: 0;
  padding: 10px 0;
  color: inherit;
}

.flip-layer { z-index: 2; }
.page.turning-next {
  animation: turnNext 420ms ease forwards;
}
.page.turning-prev {
  animation: turnPrev 420ms ease forwards;
}

@keyframes turnNext {
  from { transform: rotateY(0); }
  to { transform: rotateY(-90deg); opacity: 0.2; }
}
@keyframes turnPrev {
  from { transform: rotateY(-90deg); opacity: 0.2; }
  to { transform: rotateY(0); }
}

.page-meta {
  display: flex;
  justify-content: space-between;
  margin-top: 10px;
  color: var(--muted);
  font-size: 13px;
  letter-spacing: 0.12em;
}

.nav-hit {
  position: absolute;
  top: 0;
  bottom: 0;
  width: 18%;
  border: 0;
  background: transparent;
  cursor: pointer;
  z-index: 3;
}
.nav-hit.left { left: 0; }
.nav-hit.right { right: 0; }
.nav-hit:hover { background: linear-gradient(90deg, transparent, rgba(255,255,255,0.03)); }
.nav-hit.left:hover { background: linear-gradient(270deg, transparent, rgba(255,255,255,0.03)); }

.bottombar input[type="range"] { flex: 1; accent-color: var(--accent); }

.panel {
  position: fixed;
  top: 0;
  right: 0;
  width: min(360px, 92vw);
  height: 100vh;
  background: color-mix(in srgb, var(--paper) 92%, black);
  color: var(--ink);
  box-shadow: -16px 0 40px rgba(0,0,0,0.3);
  z-index: 8;
  padding: 22px;
  overflow: auto;
}
.panel-head { display: flex; justify-content: space-between; align-items: center; }
.panel h2 { margin: 0; letter-spacing: 0.3em; }
.catalog, .marks { list-style: none; padding: 0; margin: 18px 0 0; }
.catalog button, .marks .row { width: 100%; text-align: left; border-radius: 10px; }
.marks li { margin-bottom: 10px; }
.marks .row {
  display: flex;
  justify-content: space-between;
  gap: 8px;
  align-items: center;
  padding: 10px 12px;
  border: 1px solid var(--line);
}
.marks .go { flex: 1; background: transparent; border: 0; color: inherit; text-align: left; cursor: pointer; }
.marks .del { border: 0; background: transparent; color: var(--muted); cursor: pointer; }

.theme-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  margin: 18px 0;
}
.swatch { display: flex; align-items: center; gap: 8px; border-radius: 12px; }
.swatch i {
  width: 18px;
  height: 18px;
  border-radius: 50%;
  display: inline-block;
  border: 1px solid rgba(0,0,0,0.2);
}
.custom-color {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 12px;
  color: var(--muted);
}
.custom-color input { width: 54px; height: 32px; border: 0; background: transparent; }

.toast {
  position: fixed;
  left: 50%;
  bottom: 28px;
  transform: translateX(-50%);
  background: rgba(20,16,12,0.92);
  color: #f3e6cf;
  padding: 10px 16px;
  border-radius: 999px;
  z-index: 9;
}

.measure {
  position: absolute;
  left: -9999px;
  top: 0;
  visibility: hidden;
  pointer-events: none;
  padding: 42px 48px 36px;
  font: inherit;
}

@media (max-width: 760px) {
  .brand p { display: none; }
  .brand h1 { font-size: 22px; letter-spacing: 0.3em; }
  .reader { padding: 0 8px 8px; }
  .page { padding: 28px 22px 24px; }
  .cover h2 { font-size: 44px; }
  .topbar, .bottombar { padding: 12px; }
  .page p { font-size: 16px; }
}