/* =============================================================
   READING DAO DE JING WITH DR. NON
   Design: S,M,L,XL × DETAIL × Japanese wabi-sabi graphic design
   Each chapter unfolds as five layered "panels" — origin, direct,
   reading, code, note. Mobile = vertical scroll-snap, one panel at
   a time. Laptop = composed grid, lots of breathing room.
   ============================================================ */

:root {
  /* PALETTE — rice-paper cream, sumi black, cinnabar seal, jade,
     plus the wabi-sabi greys */
  --paper:        #f4ebd5;
  --paper-deep:   #ecdfc1;
  --paper-soft:   #f8f1de;
  --paper-warm:   #e3d3ad;
  --bone:         #faf6e8;            /* lightest, for code blocks */

  --ink:          #15140f;
  --ink-soft:     #2c2820;
  --ink-fade:     #5e564a;
  --ink-mute:     #8a8170;
  --ink-silver:   #c0bcb1;            /* wabi-sabi grey */

  --seal:         #a83332;            /* cinnabar */
  --seal-deep:    #7a2222;
  --jade:         #4a6b56;
  --jade-soft:    #7a9982;
  --gold:         #b8893a;
  --code-jade:    #2a4a3a;             /* desaturated dark jade for code */

  --rule:         rgba(21, 20, 15, .14);
  --rule-soft:    rgba(21, 20, 15, .07);
  --rule-faint:   rgba(21, 20, 15, .04);

  /* TYPE — the families */
  --serif:    "Crimson Pro","Cormorant Garamond","EB Garamond",Georgia,serif;
  --display:  "Cinzel","Cormorant Garamond",Georgia,serif;
  --reader:   "Crimson Pro","EB Garamond",Georgia,serif;
  --mono:     "JetBrains Mono","IBM Plex Mono",ui-monospace,SFMono-Regular,Menlo,monospace;
  --cn-serif: "Noto Serif SC","Source Han Serif SC",serif;
  --cn-brush: "Ma Shan Zheng",cursive;
  --cn-elegant:"ZCOOL XiaoWei","Noto Serif SC",serif;
  --th:       "IBM Plex Sans Thai","Sarabun",sans-serif;

  /* SIZES — S,M,L,XL,XXL scale */
  --size-tiny:  10px;
  --size-xs:    12px;
  --size-sm:    14px;
  --size-md:    18px;
  --size-lg:    24px;
  --size-xl:    36px;
  --size-xxl:   64px;
  --size-mega:  120px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--serif);
  font-size: 18px;
  line-height: 1.6;
  font-feature-settings: "liga","kern","onum";
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* paper grain */
body::before {
  content: "";
  position: fixed; inset: 0;
  pointer-events: none; z-index: 1;
  background-image:
    radial-gradient(rgba(80,55,15,.018) 1px, transparent 1px),
    radial-gradient(rgba(80,55,15,.011) 1px, transparent 1px);
  background-size: 4px 4px, 7px 7px;
  background-position: 0 0, 2px 3px;
  mix-blend-mode: multiply;
}

::selection { background: var(--seal); color: var(--paper); }
a { color: var(--seal); text-decoration: none; border-bottom: 1px dotted var(--seal); transition: color .2s, border-color .2s; }
a:hover { color: var(--jade); border-bottom-color: var(--jade); }

/* ============================================================
   PROGRESS
   ============================================================ */
.progress {
  position: fixed; top: 0; left: 0;
  height: 2px; width: 0%;
  background: var(--seal);
  z-index: 200;
  transition: width .12s linear;
}

/* ============================================================
   TOPBAR
   ============================================================ */
.topbar {
  position: fixed; top: 0; left: 0; right: 0;
  z-index: 100;
  display: flex; justify-content: space-between; align-items: center;
  padding: 10px 18px;
  background: rgba(244,235,213,.88);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--rule-soft);
  font-family: var(--mono);
}
.topbar-brand { display: flex; align-items: center; gap: 10px; min-width: 0; }
.seal {
  width: 30px; height: 30px;
  background: var(--seal);
  color: var(--paper);
  display: grid; place-items: center;
  font-family: var(--cn-elegant);
  font-size: 16px;
  font-weight: 600;
  flex-shrink: 0;
}
.brand-text {
  font-size: 10px; letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--ink-soft);
  font-weight: 500;
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}
@media (max-width: 540px) { .brand-text { display: none; } }

.topbar-tools { display: flex; gap: 6px; flex-shrink: 0; }
.lang-toggle, .tool-btn {
  background: transparent;
  border: 1px solid var(--rule);
  color: var(--ink-soft);
  font-family: var(--mono);
  font-size: var(--size-xs);
  letter-spacing: .12em;
  cursor: pointer;
  padding: 0 10px;
  height: 38px;
  min-width: 38px;
  transition: all .2s;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 4px;
}
.tool-btn { padding: 0; font-size: var(--size-md); }
.lang-toggle:hover, .tool-btn:hover {
  background: var(--seal); color: var(--paper); border-color: var(--seal);
}
.lang-toggle .lang-on { color: var(--seal); font-weight: 600; }
.lang-toggle .lang-off { color: var(--ink-mute); }
.lang-toggle.is-th .lang-on { color: var(--ink-mute); font-weight: 400; }
.lang-toggle.is-th .lang-off { color: var(--seal); font-weight: 600; }
.lang-toggle:hover * { color: var(--paper) !important; }
.lang-sep { color: var(--ink-fade); margin: 0 2px; }

/* ============================================================
   COVER — the threshold
   ============================================================ */
.cover {
  min-height: 100vh;
  padding: 14vh 6vw 6vh;
  display: flex;
  flex-direction: column;
  position: relative;
  overflow: hidden;
}
.cover-meta {
  display: flex; justify-content: space-between; align-items: baseline;
  font-family: var(--mono);
  font-size: var(--size-tiny);
  letter-spacing: .22em;
  text-transform: uppercase;
  color: var(--ink-fade);
  border-bottom: 1px solid var(--ink);
  padding-bottom: 10px;
}

.cover-stack {
  flex: 1;
  display: grid;
  grid-template-columns: auto 1fr;
  gap: clamp(28px, 5vw, 80px);
  align-items: center;
  padding: clamp(40px, 8vh, 80px) 0;
  position: relative;
  z-index: 2;
}
.cover-cn-vertical {
  font-family: var(--cn-elegant);
  font-size: clamp(72px, 14vw, 200px);
  line-height: .95;
  color: var(--ink);
  writing-mode: vertical-rl;
  text-orientation: upright;
  letter-spacing: 12px;
  font-weight: 400;
}
.cover-text { max-width: 36ch; }
.cover-kicker {
  font-family: var(--mono);
  font-size: var(--size-xs);
  letter-spacing: .25em;
  text-transform: uppercase;
  color: var(--seal);
  margin: 0 0 14px;
}
.cover-title {
  font-family: var(--display);
  font-size: clamp(48px, 9vw, 140px);
  line-height: .9;
  letter-spacing: -.02em;
  color: var(--ink);
  margin: 0;
  font-weight: 500;
}
.cover-sub {
  font-family: var(--reader);
  font-style: italic;
  font-size: clamp(15px, 1.4vw, 18px);
  line-height: 1.55;
  color: var(--ink-soft);
  margin: 24px 0 0;
  max-width: 36ch;
}
.cover-sub em { color: var(--seal); font-style: italic; }
.cover-foot {
  border-top: 1px solid var(--rule);
  padding-top: 14px;
}
.cover-instructions {
  display: flex; flex-wrap: wrap; gap: 14px 28px;
  font-family: var(--mono);
  font-size: var(--size-tiny);
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--ink-fade);
  margin: 0;
}
.cover-instructions strong {
  color: var(--seal);
  background: var(--paper-warm);
  padding: 2px 7px;
  margin-right: 6px;
  font-weight: 500;
}

/* ============================================================
   PREFACE
   ============================================================ */
.preface {
  background: var(--paper-deep);
  padding: clamp(56px, 10vh, 120px) 6vw;
  border-top: 1px solid var(--rule);
  border-bottom: 1px solid var(--rule);
}
.preface-inner { max-width: 60ch; margin: 0 auto; }
.preface-kicker {
  font-family: var(--mono);
  font-size: var(--size-tiny);
  letter-spacing: .25em;
  text-transform: uppercase;
  color: var(--seal);
  margin: 0 0 14px;
}
.preface-title {
  font-family: var(--display);
  font-size: clamp(28px, 4vw, 44px);
  font-weight: 500;
  letter-spacing: -.012em;
  margin: 0 0 28px;
}
.preface-inner p {
  margin: 0 0 18px;
  font-family: var(--reader);
  font-size: 18px;
  line-height: 1.7;
  color: var(--ink-soft);
  text-wrap: pretty;
}
.preface-inner p:first-of-type::first-letter {
  font-family: var(--display);
  font-weight: 500;
  float: left;
  font-size: 4.4em;
  line-height: .85;
  margin: 6px 10px -6px 0;
  color: var(--seal);
}
.preface-inner em { color: var(--seal); font-style: italic; }
.preface-sig {
  font-family: var(--mono) !important;
  font-size: 11px !important;
  letter-spacing: .2em;
  color: var(--ink-fade) !important;
  text-transform: uppercase;
  margin-top: 36px !important;
}

/* ============================================================
   CHAPTER — the journey container
   Mobile: each panel is one scroll-snap screen
   Laptop: panels compose on a grid
   ============================================================ */
.chapter {
  position: relative;
  border-top: 1px solid var(--ink);
  background: var(--paper);
}
.chapter:nth-child(odd)  { background: var(--paper-soft); }

/* CHAPTER HEADER STRIP — DETAIL-magazine micro-typography */
.chapter-strip {
  position: sticky;
  top: 60px;                            /* below topbar */
  z-index: 50;
  display: grid;
  grid-template-columns: auto 1fr auto auto;
  align-items: baseline;
  gap: 16px;
  padding: 14px 6vw;
  font-family: var(--mono);
  font-size: var(--size-tiny);
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--ink-fade);
  background: rgba(244,235,213,.88);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--rule-soft);
}
.chapter-strip .cs-num {
  color: var(--seal);
  font-weight: 600;
  font-size: var(--size-xs);
}
.chapter-strip .cs-cn {
  font-family: var(--cn-elegant);
  font-size: var(--size-md);
  letter-spacing: 4px;
  color: var(--ink);
  text-transform: none;
}
.chapter-strip .cs-en {
  font-family: var(--display);
  font-style: italic;
  font-size: var(--size-sm);
  text-transform: none;
  letter-spacing: 0;
  color: var(--ink-soft);
}
.chapter-strip .cs-th {
  font-family: var(--th);
  font-size: var(--size-sm);
  text-transform: none;
  letter-spacing: 0;
  color: var(--ink-soft);
}
body.lang-en .cs-th { display: none; }
body.lang-th .cs-en { display: none; }
.chapter-strip .cs-progress {
  font-variant-numeric: tabular-nums;
  font-size: var(--size-tiny);
  color: var(--ink-mute);
}
@media (max-width: 720px) {
  .chapter-strip { gap: 10px; padding: 10px 5vw; font-size: 9px; }
  .chapter-strip .cs-cn { font-size: 14px; letter-spacing: 2px; }
  .chapter-strip .cs-en, .chapter-strip .cs-th { font-size: 12px; }
}

/* PANELS — the five layers */
.panel {
  padding: clamp(40px, 8vh, 100px) 6vw;
  position: relative;
  scroll-snap-align: start;
  border-bottom: 1px solid var(--rule-faint);
}
.panel-label {
  font-family: var(--mono);
  font-size: var(--size-tiny);
  letter-spacing: .25em;
  text-transform: uppercase;
  color: var(--seal);
  margin-bottom: 24px;
  display: flex;
  align-items: baseline;
  gap: 12px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--rule);
}
.panel-label .pl-num {
  color: var(--ink-mute);
  font-size: 9px;
  letter-spacing: .15em;
}
.panel-label .pl-cn {
  font-family: var(--cn-elegant);
  color: var(--ink-fade);
  font-size: 13px;
  text-transform: none;
  letter-spacing: 2px;
  margin-left: auto;
}

/* Panel 01 — ORIGIN */
.panel-origin {
  background: var(--paper);
}
.panel-origin .origin-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 48px;
  align-items: start;
  max-width: 1280px;
  margin: 0 auto;
}
@media (min-width: 980px) {
  .panel-origin .origin-grid { grid-template-columns: 1fr 1.4fr; gap: 80px; }
}
.origin-title-block {
  display: flex; flex-direction: column; gap: 18px;
}
.origin-num-roman {
  font-family: var(--display);
  font-size: var(--size-xl);
  font-weight: 500;
  color: var(--seal);
  letter-spacing: .04em;
  margin: 0;
  line-height: 1;
}
.origin-cn-title {
  font-family: var(--cn-elegant);
  font-size: clamp(48px, 8vw, 96px);
  line-height: 1;
  color: var(--ink);
  margin: 0;
  letter-spacing: 8px;
  font-weight: 400;
}
.origin-en-title {
  font-family: var(--display);
  font-style: italic;
  font-size: clamp(20px, 2.4vw, 28px);
  font-weight: 500;
  color: var(--ink-soft);
  margin: 0;
}
.origin-th-title {
  font-family: var(--th);
  font-size: clamp(18px, 2vw, 24px);
  font-weight: 500;
  color: var(--ink-soft);
  margin: 0;
}
body.lang-en .origin-th-title { display: none; }
body.lang-th .origin-en-title { display: none; }
.origin-divider {
  height: 1px;
  background: var(--ink);
  margin: 4px 0;
  width: 60px;
}
.origin-cn {
  font-family: var(--cn-serif);
  font-size: clamp(20px, 1.9vw, 26px);
  line-height: 2.3;
  color: var(--ink);
  letter-spacing: 4px;
  white-space: pre-line;
  text-align: justify;
  font-weight: 400;
}

/* Panel 02 — DIRECT */
.panel-direct {
  background: var(--paper-soft);
}
.direct-text {
  max-width: 60ch;
  margin: 0 auto;
  font-family: var(--reader);
  font-size: clamp(20px, 2vw, 26px);
  line-height: 1.6;
  color: var(--ink);
  white-space: pre-line;
  font-weight: 300;
}
.direct-text em { color: var(--seal); font-style: italic; }
body.lang-en .direct-text[data-lang="th"] { display: none; }
body.lang-th .direct-text[data-lang="en"] { display: none; }
body.lang-th .direct-text { font-family: var(--th); font-size: clamp(18px, 1.7vw, 22px); line-height: 1.75; }

/* Panel 03 — READING (the substantive one) */
.panel-reading {
  background: var(--paper);
}
.reading-frame {
  max-width: 1180px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1fr;
  gap: 40px;
}
@media (min-width: 980px) {
  .reading-frame { grid-template-columns: 240px 1fr; gap: 80px; }
}
.reading-aside {
  font-family: var(--mono);
  font-size: var(--size-tiny);
  letter-spacing: .15em;
  color: var(--ink-fade);
  line-height: 1.7;
  text-transform: uppercase;
}
.reading-aside .ra-q {
  font-family: var(--reader);
  font-style: italic;
  font-size: var(--size-md);
  text-transform: none;
  letter-spacing: 0;
  color: var(--ink);
  margin: 0 0 18px;
  line-height: 1.4;
}
.reading-body {
  font-family: var(--reader);
  font-size: clamp(18px, 1.5vw, 21px);
  line-height: 1.7;
  color: var(--ink-soft);
  max-width: 56ch;
  white-space: pre-line;
  text-wrap: pretty;
}
.reading-body em { color: var(--seal); font-style: italic; }
.reading-body strong { color: var(--ink); font-weight: 500; }
body.lang-en .reading-body[data-lang="th"] { display: none; }
body.lang-th .reading-body[data-lang="en"] { display: none; }
body.lang-th .reading-body { font-family: var(--th); font-size: 17px; line-height: 1.78; }

.reading-sources {
  margin-top: 32px;
  padding-top: 18px;
  border-top: 1px solid var(--rule);
  font-family: var(--mono);
  font-size: var(--size-xs);
  letter-spacing: .04em;
  color: var(--ink-fade);
  line-height: 1.65;
}
.reading-sources .rs-label {
  display: block;
  font-size: var(--size-tiny);
  letter-spacing: .25em;
  text-transform: uppercase;
  color: var(--seal);
  margin-bottom: 8px;
}
.reading-sources ul { list-style: none; padding: 0; margin: 0; }
.reading-sources li { padding: 4px 0; padding-left: 18px; position: relative; }
.reading-sources li::before {
  content: '·';
  position: absolute; left: 0;
  color: var(--seal);
}

/* Panel 04 — CODE (TypeScript-as-philosophy) */
.panel-code {
  background: var(--code-jade);
  color: var(--bone);
  padding-block: clamp(56px, 10vh, 100px);
}
.panel-code .panel-label {
  color: var(--gold-soft, #d6b372);
  border-bottom-color: rgba(244,235,213,.15);
}
.panel-code .panel-label .pl-num,
.panel-code .panel-label .pl-cn { color: rgba(244,235,213,.5); }
.code-frame {
  max-width: 880px;
  margin: 0 auto;
}
.code-block {
  font-family: var(--mono);
  font-size: clamp(13px, 1.05vw, 15px);
  line-height: 1.7;
  color: var(--bone);
  white-space: pre-wrap;
  margin: 0;
  font-weight: 400;
  letter-spacing: 0;
  font-variant-ligatures: contextual;
}
.code-block .c-key   { color: #ffaa66; }       /* keywords */
.code-block .c-com   { color: #8aa394; font-style: italic; }   /* comments */
.code-block .c-str   { color: #c8d49b; }       /* strings */
.code-block .c-num   { color: #ffd28e; }       /* numbers */
.code-block .c-type  { color: #b6e2c7; }       /* types */
.code-caption {
  font-family: var(--reader);
  font-style: italic;
  font-size: 16px;
  color: rgba(244,235,213,.6);
  margin-top: 36px;
  padding-top: 18px;
  border-top: 1px solid rgba(244,235,213,.15);
  text-align: center;
}

/* Panel 05 — NOTE */
.panel-note {
  background: var(--paper-deep);
}
.note-frame {
  max-width: 60ch;
  margin: 0 auto;
}
.note-body {
  font-family: var(--reader);
  font-size: clamp(17px, 1.4vw, 20px);
  line-height: 1.7;
  color: var(--ink-soft);
  font-style: italic;
  border-left: 3px solid var(--seal);
  padding: 4px 0 4px 22px;
  margin: 0;
}
.note-body strong { color: var(--ink); font-weight: 500; }

/* Panel image — appears between panels for some chapters */
.panel-image {
  padding: 0;
  background: var(--ink);
  position: relative;
  height: 60vh;
  min-height: 360px;
  overflow: hidden;
}
.panel-image .image-bg {
  position: absolute; inset: 0;
  background-size: cover;
  background-position: center;
  filter: contrast(1.05) saturate(.85);
}
.panel-image .image-caption {
  position: absolute;
  bottom: 0; left: 0; right: 0;
  padding: 24px 6vw;
  background: linear-gradient(to top, rgba(21,20,15,.85), transparent);
  color: var(--bone);
  font-family: var(--mono);
  font-size: var(--size-tiny);
  letter-spacing: .18em;
  text-transform: uppercase;
}
.panel-image .image-caption em {
  font-family: var(--reader);
  font-style: italic;
  font-size: 16px;
  text-transform: none;
  letter-spacing: 0;
  color: var(--paper);
  display: block;
  margin-bottom: 4px;
}

/* CHAPTER FOOT NAV */
.chapter-foot {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 24px;
  padding: 32px 6vw 48px;
  font-family: var(--mono);
  font-size: var(--size-tiny);
  letter-spacing: .2em;
  text-transform: uppercase;
  color: var(--ink-fade);
  background: var(--paper);
  border-top: 1px solid var(--rule);
}
.chapter-foot button {
  background: transparent; border: none;
  color: var(--ink-soft); font-family: inherit; font-size: inherit;
  letter-spacing: inherit; text-transform: inherit;
  cursor: pointer; padding: 8px 0;
  transition: color .2s;
  display: inline-flex; align-items: center; gap: 8px;
  text-align: left;
}
.chapter-foot button:last-child { justify-content: flex-end; text-align: right; }
.chapter-foot button:hover { color: var(--seal); }
.chapter-foot button[disabled] { opacity: .25; cursor: default; }
.chapter-foot .ch-marker {
  font-family: var(--cn-elegant);
  font-size: var(--size-md);
  letter-spacing: 4px;
  color: var(--seal);
  text-transform: none;
  font-weight: 400;
  text-align: center;
}

/* ============================================================
   CHAPTER INDEX OVERLAY  (kept from v1, minor tweaks)
   ============================================================ */
.index-scrim {
  position: fixed; inset: 0;
  background: rgba(21,20,15,.55);
  z-index: 250;
  opacity: 0; pointer-events: none;
  transition: opacity .35s;
  backdrop-filter: blur(2px);
}
.index-scrim.show { opacity: 1; pointer-events: auto; }

.index-overlay {
  position: fixed;
  top: 0; right: 0;
  height: 100vh;
  width: min(560px, 92vw);
  background: var(--paper);
  z-index: 260;
  padding: 64px 32px 32px;
  transform: translateX(100%);
  transition: transform .42s cubic-bezier(.2,.8,.25,1);
  overflow-y: auto;
  border-left: 1px solid var(--rule);
  box-shadow: -30px 0 80px rgba(21,20,15,.18);
}
.index-overlay.open { transform: translateX(0); }

.index-close {
  position: absolute; top: 16px; right: 16px;
  background: transparent; border: 1px solid var(--rule);
  color: var(--ink-fade);
  width: 38px; height: 38px;
  font-size: 20px;
  cursor: pointer; line-height: 1;
}
.index-close:hover { color: var(--seal); border-color: var(--seal); }

.index-head { margin-bottom: 36px; }
.index-kicker {
  display: block;
  font-family: var(--mono);
  font-size: var(--size-tiny);
  letter-spacing: .25em;
  text-transform: uppercase;
  color: var(--seal);
  margin-bottom: 8px;
}
.index-title {
  font-family: var(--cn-elegant);
  font-size: clamp(28px, 4vw, 40px);
  font-weight: 400;
  margin: 0 0 12px;
  line-height: 1.1;
}
.index-sub {
  font-family: var(--reader); font-style: italic;
  font-size: 15px; color: var(--ink-fade); margin: 0;
}
.index-half + .index-half { margin-top: 36px; }
.index-part {
  font-family: var(--mono);
  font-size: var(--size-tiny);
  letter-spacing: .25em; text-transform: uppercase;
  color: var(--seal);
  margin: 0 0 16px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--rule);
}
.index-list {
  list-style: none;
  padding: 0; margin: 0;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: 0;
}
.index-list a {
  display: grid;
  grid-template-columns: 36px 1fr;
  align-items: baseline;
  gap: 10px;
  padding: 7px 4px;
  text-decoration: none;
  color: var(--ink-soft);
  border: none;
  font-family: var(--reader);
  font-size: 14px;
  transition: color .2s, padding-left .2s;
  cursor: pointer;
  background: none;
}
.index-list a:hover { color: var(--seal); padding-left: 8px; }
.index-list a.current { color: var(--seal); }
.index-list a.visited { color: var(--ink); }
.index-list .ix-n {
  font-family: var(--mono);
  font-size: 11px;
  color: var(--ink-mute);
  font-weight: 500;
}
.index-list .ix-cn {
  font-family: var(--cn-elegant);
  letter-spacing: 1px;
}
.index-foot {
  margin-top: 40px;
  padding-top: 20px;
  border-top: 1px solid var(--rule);
}
.index-bookmark {
  font-family: var(--mono);
  font-size: var(--size-xs);
  letter-spacing: .12em;
  color: var(--ink-fade);
  margin: 0 0 24px;
  padding: 12px;
  background: var(--paper-warm);
  border-left: 3px solid var(--seal);
  display: none;
}
.index-bookmark.show { display: block; }
.index-bookmark.show::before {
  content: 'CONTINUE READING ';
  color: var(--seal); font-weight: 600;
}
.index-bookmark a {
  display: inline-block; margin-left: 6px;
  color: var(--ink); border: none;
  font-family: var(--reader); font-style: italic; font-size: 14px;
}
.other-books { margin-top: 12px; }
.ob-head {
  font-family: var(--mono);
  font-size: 9px;
  letter-spacing: .25em;
  text-transform: uppercase;
  color: var(--ink-mute);
  margin: 0 0 8px;
}
.other-books a {
  display: block; padding: 8px 0;
  border-bottom: 1px solid var(--rule);
  color: var(--ink-soft); text-decoration: none;
  border-left: none; border-right: none; border-top: none;
  transition: color .2s, padding-left .2s;
}
.other-books a:hover { color: var(--seal); padding-left: 4px; }
.other-books a:last-child { border-bottom: none; }
.other-books span {
  display: block; font-family: var(--reader);
  font-style: italic; font-size: 14px; color: var(--ink);
}
.other-books em {
  display: block; font-family: var(--mono); font-style: normal;
  font-size: 9px; letter-spacing: .12em; text-transform: uppercase;
  color: var(--ink-mute); margin-top: 2px;
}

/* ============================================================
   CONTINUE TOAST (minor, same pattern as other books)
   ============================================================ */
.continue-toast {
  position: fixed;
  top: 64px; left: 50%;
  z-index: 90;
  transform: translate(-50%, -200%);
  background: var(--ink); color: var(--paper);
  padding: 12px 14px;
  display: flex; align-items: center; gap: 12px;
  font-family: var(--mono); font-size: 11px;
  letter-spacing: .12em; text-transform: uppercase;
  box-shadow: 0 18px 40px rgba(0,0,0,.35);
  transition: transform .5s cubic-bezier(.2,.8,.25,1), opacity .3s;
  opacity: 0; max-width: calc(100vw - 24px);
}
.continue-toast.show { transform: translate(-50%, 0); opacity: 1; }
.continue-toast .ct-ico {
  width: 28px; height: 28px;
  background: var(--seal); color: var(--paper);
  display: grid; place-items: center;
  font-family: var(--cn-elegant); font-size: 14px;
  flex-shrink: 0;
}
.continue-toast .ct-meta { display: flex; flex-direction: column; gap: 2px; }
.continue-toast .ct-meta small { font-size: 9px; opacity: .55; }
.continue-toast .ct-meta strong {
  font-family: var(--reader); font-style: italic; font-size: 14px;
  font-weight: 500; text-transform: none; letter-spacing: 0;
}
.continue-toast button {
  background: var(--seal); color: var(--paper);
  border: none; padding: 8px 14px;
  font-family: inherit; font-size: 10px;
  letter-spacing: .14em; cursor: pointer;
  flex-shrink: 0; min-height: 38px;
}
.continue-toast .ct-x {
  background: transparent; color: rgba(255,255,255,.4);
  font-size: 16px; padding: 6px 8px;
}
@media (max-width: 560px) {
  .continue-toast { flex-wrap: wrap; left: 12px; right: 12px; transform: translate(0, -200%); }
  .continue-toast.show { transform: translate(0, 0); }
}

/* ============================================================
   COLOPHON
   ============================================================ */
.colophon {
  background: var(--ink);
  color: rgba(244,235,213,.7);
  padding: 80px 6vw;
  text-align: center;
}
.colo-inner { max-width: 60ch; margin: 0 auto; }
.colophon h3 {
  font-family: var(--mono);
  font-size: 11px; letter-spacing: .25em;
  text-transform: uppercase;
  color: var(--seal);
  margin: 0 0 24px;
}
.colophon p {
  font-family: var(--reader);
  font-size: 16px; line-height: 1.65;
  margin: 0 0 14px;
}
.colophon p em { color: var(--paper); font-style: italic; }
.colo-sig {
  font-family: var(--mono) !important;
  font-size: 10px !important;
  letter-spacing: .25em;
  text-transform: uppercase;
  color: rgba(244,235,213,.4) !important;
  margin-top: 32px !important;
}

/* ============================================================
   MOBILE-FIRST RESPONSIVE
   ============================================================ */
@media (max-width: 720px) {
  body { font-size: 17px; }
  .topbar { padding: 8px 12px; }
  .lang-toggle, .tool-btn { padding: 0 8px; height: 36px; min-width: 36px; }
  .cover { padding: 12vh 5vw 5vh; }
  .cover-stack { grid-template-columns: 1fr; padding: 24px 0; gap: 24px; }
  .cover-cn-vertical {
    writing-mode: horizontal-tb;
    font-size: clamp(56px, 16vw, 96px);
    letter-spacing: 8px;
  }
  .cover-cn-vertical br { display: none; }
  .cover-instructions { gap: 10px 18px; font-size: 9px; }
  .preface { padding: 56px 5vw; }
  .preface-inner p { font-size: 17px; }

  .chapter-strip {
    grid-template-columns: auto 1fr auto;
    top: 56px;
  }
  .chapter-strip .cs-en, .chapter-strip .cs-th { display: none; }
  .panel { padding: 56px 5vw; min-height: 80vh; }
  .panel-label { font-size: 9px; }
  .origin-cn-title { font-size: clamp(40px, 12vw, 64px); letter-spacing: 4px; }
  .origin-cn { font-size: 18px; line-height: 2.1; letter-spacing: 2px; }
  .direct-text { font-size: 19px; }
  .reading-body { font-size: 17px; }
  .reading-frame { gap: 24px; }
  .code-block { font-size: 12.5px; line-height: 1.65; }
  .panel-image { height: 50vh; min-height: 280px; }
  .index-overlay { padding: 56px 22px 22px; }
  .index-list { grid-template-columns: 1fr; }
  .colophon { padding: 56px 5vw; }
  .chapter-foot { padding: 24px 5vw 32px; gap: 12px; font-size: 9px; }
  .chapter-foot button:first-child, .chapter-foot button:last-child { font-size: 10px; }
}

/* prefers-reduced-motion */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    transition-duration: 0.001ms !important;
  }
}

/* PRINT */
@media print {
  body::before { display: none; }
  .topbar, .progress, .index-overlay, .index-scrim, .continue-toast { display: none !important; }
  body { background: white; color: black; font-size: 11pt; }
  .panel { padding: 0; min-height: auto; }
  .panel-code { background: white; color: black; }
  .code-block { color: black; }
  .chapter { page-break-before: always; border: none; }
  .cover { min-height: auto; }
  a { color: black; border-bottom: none; }
}