/* ============================================================
   5G NR PHY BOOK — KINDLE SKIN (paper / sepia / night)
   Scoped: body[data-kindle="on"] for global theme,
           .ch-kindle for upgraded chapter typography.
   Author: CafeTele · 2026-05-28
   ============================================================ */

/* --- KATEX (loaded via CDN) renders math; we don't ship the font here --- */

/* ------------ THEME TOKENS ------------
   DEFAULT "paper" = clean professional BLACK & WHITE book.
   Crisp white page, near-black ink, neutral-gray rules. The only
   colour in the reading surface comes from the figures themselves.
   ------------------------------------------------------------- */
body[data-kindle="on"] {
  --k-paper:        #ffffff;   /* pure white page */
  --k-paper-soft:   #f7f7f8;
  --k-paper-edge:   #ececef;
  --k-ink:          #18181b;   /* near-black ink */
  --k-ink-soft:     #3f3f46;
  --k-ink-mute:     #71717a;
  --k-accent:       #18181b;   /* monochrome — black emphasis */
  --k-accent-soft:  #52525b;
  --k-rule:         #d4d4d8;   /* light neutral hairline */
  --k-mark:         #eceef1;   /* subtle grey highlight (was yellow) */
  --k-margin:       #f4f4f5;
  --k-callout-bg:   #f4f4f5;
  --k-callout-ed:   #a1a1aa;
  --k-spec-bg:      #f5f5f6;
  --k-spec-ed:      #a1a1aa;
  --k-tip-bg:       #f7f7f8;
  --k-link:         #18181b;
  --k-link-hover:   #52525b;
  --k-shadow:       0 1px 2px rgba(24,24,27,0.05), 0 6px 18px rgba(24,24,27,0.06);
  --k-serif:        'Source Serif Pro','Lora','Cardo','Georgia','Times New Roman',serif;
  --k-sans:         'Source Sans Pro','Inter','Segoe UI',sans-serif;
  --k-mono:         'JetBrains Mono','Fira Code','SF Mono','Consolas',monospace;
}

body[data-kindle="on"][data-theme="sepia"] {
  --k-paper:        #f0e2c2;
  --k-paper-soft:   #e6d5ac;
  --k-paper-edge:   #d4bd84;
  --k-ink:          #3a2e14;
  --k-ink-soft:     #6b5524;
  --k-rule:         #c8b176;
  --k-mark:         #f0d77a;
  --k-margin:       #e5d3a1;
  --k-callout-bg:   #ead488;
  --k-spec-bg:      #e0cb7e;
  --k-tip-bg:       #d9c378;
}

body[data-kindle="on"][data-theme="night"] {
  --k-paper:        #1b1d1f;
  --k-paper-soft:   #25282b;
  --k-paper-edge:   #313538;
  --k-ink:          #d6cdb8;
  --k-ink-soft:     #aa9f86;
  --k-ink-mute:     #7d735d;
  --k-accent:       #f1b878;
  --k-accent-soft:  #d68f3e;
  --k-rule:         #3a3d40;
  --k-mark:         #4a3a18;
  --k-margin:       #2d2f32;
  --k-callout-bg:   #2a2620;
  --k-callout-ed:   #6a5a30;
  --k-spec-bg:      #28251f;
  --k-spec-ed:      #5e5028;
  --k-tip-bg:       #2c281f;
  --k-link:         #f1b878;
  --k-link-hover:   #ffd8a3;
  --k-shadow:       none;
}

/* ------------ GLOBAL CANVAS OVERRIDE (gentle takeover) ------------ */
body[data-kindle="on"] {
  background: var(--k-paper) !important;
  color: var(--k-ink) !important;
  transition: background-color 0.25s ease, color 0.25s ease;
  font-feature-settings: "kern", "liga", "onum", "pnum";
}

/* Soften the existing colorful chapter headers slightly so they blend on cream */
body[data-kindle="on"] .chapter-header { box-shadow: var(--k-shadow); }
body[data-kindle="on"][data-theme="night"] .chapter-header { filter: brightness(0.85) saturate(0.7); }

/* ------------ KINDLE READER CHROME (top bar) ------------ */
.k-chrome {
  position: fixed; top: 0; left: 0; right: 0; height: 48px;
  background: var(--k-paper-soft);
  border-bottom: 1px solid var(--k-rule);
  display: flex; align-items: center; gap: 8px;
  padding: 0 14px;
  z-index: 9000;
  font-family: var(--k-sans);
  font-size: 13px;
  color: var(--k-ink-soft);
  backdrop-filter: blur(8px);
}
.k-chrome button {
  background: transparent; border: 1px solid transparent;
  color: var(--k-ink-soft);
  padding: 6px 10px; border-radius: 6px; cursor: pointer;
  font-family: var(--k-sans); font-size: 13px; font-weight: 600;
  display: inline-flex; align-items: center; gap: 6px;
  transition: background 0.15s, border-color 0.15s, color 0.15s;
}
.k-chrome button:hover { background: var(--k-paper-edge); color: var(--k-ink); }
.k-chrome button.active { background: var(--k-paper-edge); color: var(--k-ink); border-color: var(--k-rule); }
.k-chrome .k-sep { width: 1px; height: 22px; background: var(--k-rule); margin: 0 4px; }
.k-chrome .k-progress {
  flex: 1; min-width: 80px; max-width: 260px; height: 4px;
  background: var(--k-paper-edge); border-radius: 2px; overflow: hidden; position: relative;
}
.k-chrome .k-progress > i {
  display: block; height: 100%; width: 0%;
  background: linear-gradient(90deg, var(--k-accent), var(--k-accent-soft));
  transition: width 0.2s ease;
}
.k-chrome .k-pct { font-variant-numeric: tabular-nums; min-width: 38px; text-align: right; opacity: 0.8; }
.k-chrome .k-title {
  flex: 0 1 auto; min-width: 0;
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
  font-family: var(--k-serif); font-style: italic; opacity: 0.7;
  font-size: 13px;
}
.k-chrome .k-search {
  background: var(--k-paper); border: 1px solid var(--k-rule); border-radius: 6px;
  padding: 5px 10px; font-family: var(--k-sans); font-size: 13px; color: var(--k-ink);
  width: 0; opacity: 0; transition: width 0.2s, opacity 0.2s, padding 0.2s;
  pointer-events: none;
}
.k-chrome.search-on .k-search { width: 220px; opacity: 1; pointer-events: auto; padding: 5px 10px; }

/* Body gets top padding so content isn't hidden under chrome */
body[data-kindle="on"] { padding-top: 48px; }

/* ------------ TOC DRAWER ------------ */
.k-toc {
  position: fixed; top: 48px; left: 0; bottom: 0; width: 320px;
  background: var(--k-paper-soft);
  border-right: 1px solid var(--k-rule);
  transform: translateX(-100%); transition: transform 0.25s ease;
  overflow-y: auto;
  z-index: 8500;
  padding: 18px 18px 80px;
  font-family: var(--k-sans);
}
.k-toc.open { transform: translateX(0); }
.k-toc .k-toc-title {
  font-family: var(--k-serif); font-size: 14px; font-weight: 700;
  color: var(--k-ink-soft); letter-spacing: 2px; text-transform: uppercase;
  margin-bottom: 14px;
}
.k-toc ul { list-style: none; padding: 0; margin: 0; }
.k-toc li { margin: 0; }
.k-toc a {
  display: block; padding: 6px 10px; border-radius: 4px;
  color: var(--k-ink); text-decoration: none; font-size: 14px;
  border-left: 2px solid transparent;
}
.k-toc a:hover { background: var(--k-paper-edge); border-left-color: var(--k-accent); }
.k-toc a.k-current { background: var(--k-paper-edge); border-left-color: var(--k-accent); font-weight: 700; }
.k-toc li.k-l2 a { padding-left: 22px; font-size: 13px; color: var(--k-ink-soft); }
.k-toc li.k-l3 a { padding-left: 36px; font-size: 12.5px; color: var(--k-ink-mute); }
.k-toc-backdrop {
  position: fixed; inset: 48px 0 0 0; background: rgba(43,36,24,0.35);
  opacity: 0; pointer-events: none; transition: opacity 0.2s; z-index: 8400;
}
.k-toc-backdrop.show { opacity: 1; pointer-events: auto; }

/* ------------ KINDLE CHAPTER (deep typography, only chapters with .ch-kindle) ------------ */
.ch-kindle {
  font-family: var(--k-serif);
  font-size: var(--k-font-size, 20px);
  line-height: 1.75;
  color: var(--k-ink);
  max-width: 920px;
  margin: 0 auto;
  padding: 68px 56px 110px;
  letter-spacing: 0.005em;
}
@media (max-width: 960px) {
  .ch-kindle { padding: 44px 26px 90px; font-size: calc(var(--k-font-size, 20px) - 1px); }
}

.ch-kindle h1.kch-title {
  font-family: var(--k-serif); font-weight: 700;
  font-size: 2.8em; line-height: 1.12;
  margin: 0.2em 0 0.45em;
  color: var(--k-ink);
  letter-spacing: -0.01em;
}
.ch-kindle .kch-eyebrow {
  font-family: var(--k-sans); text-transform: uppercase;
  letter-spacing: 4px; font-size: 0.8em; font-weight: 700;
  color: var(--k-accent); margin-bottom: 10px;
}
.ch-kindle .kch-tagline {
  font-family: var(--k-serif); font-style: italic;
  font-size: 1.22em; line-height: 1.55;
  color: var(--k-ink-soft); margin: 0 0 28px;
  border-bottom: 1px solid var(--k-rule); padding-bottom: 22px;
}
.ch-kindle .kch-specchip {
  display: inline-block; font-family: var(--k-mono);
  font-size: 0.78em; padding: 4px 10px;
  background: var(--k-spec-bg); border: 1px solid var(--k-spec-ed);
  border-radius: 3px; color: var(--k-ink-soft);
  margin: 6px 8px 0 0;
}

.ch-kindle h2 {
  font-family: var(--k-serif); font-weight: 700;
  font-size: 1.75em; line-height: 1.22;
  margin: 2.1em 0 0.65em; color: var(--k-ink);
  border-bottom: 1px solid var(--k-rule); padding-bottom: 8px;
  letter-spacing: -0.005em;
}
.ch-kindle h3 {
  font-family: var(--k-serif); font-weight: 700;
  font-size: 1.32em; line-height: 1.3;
  margin: 1.7em 0 0.45em; color: var(--k-ink);
}
.ch-kindle h4 {
  font-family: var(--k-sans); font-weight: 700;
  font-size: 0.95em; text-transform: uppercase; letter-spacing: 2px;
  margin: 1.5em 0 0.55em; color: var(--k-ink-soft);
}

.ch-kindle p { margin: 0 0 1.05em; text-align: justify; hyphens: auto; }
.ch-kindle p + p { text-indent: 1.6em; }
.ch-kindle h2 + p, .ch-kindle h3 + p, .ch-kindle .kch-figure + p,
.ch-kindle .kch-callout + p, .ch-kindle .kch-widget + p,
.ch-kindle ul + p, .ch-kindle ol + p, .ch-kindle table + p { text-indent: 0; }

/* drop cap on first paragraph of each chapter */
.ch-kindle > p.kch-lead::first-letter,
.ch-kindle > h2 + p::first-letter {
  /* off by default; we use explicit .kch-drop instead */
}
.ch-kindle .kch-drop::first-letter {
  float: left; font-family: var(--k-serif); font-weight: 700;
  font-size: 4.6em; line-height: 0.86; padding: 4px 10px 0 0;
  color: var(--k-accent);
}

.ch-kindle em, .ch-kindle i { color: var(--k-ink); }
.ch-kindle strong, .ch-kindle b { color: var(--k-ink); font-weight: 700; }
.ch-kindle a { color: var(--k-link); text-decoration: underline; text-decoration-color: var(--k-rule); text-underline-offset: 3px; }
.ch-kindle a:hover { color: var(--k-link-hover); text-decoration-color: var(--k-link-hover); }

/* "Key term" — Kindle highlight style */
.ch-kindle .kt {
  background: var(--k-mark);
  border-bottom: 1px solid var(--k-callout-ed);
  padding: 0 2px;
  border-radius: 2px;
  font-weight: 600;
}

/* ------------ FOOTNOTE CITATIONS ------------ */
.ch-kindle .kfn {
  display: inline; vertical-align: super; font-size: 0.68em;
  font-family: var(--k-sans); font-weight: 700;
  color: var(--k-accent);
  cursor: pointer; padding: 0 2px;
  border-bottom: 1px dotted var(--k-accent-soft);
  user-select: none;
}
.ch-kindle .kfn:hover { color: var(--k-link-hover); }
.kfn-pop {
  position: absolute; max-width: 360px; background: var(--k-paper-soft);
  border: 1px solid var(--k-rule); border-radius: 6px;
  padding: 12px 14px; font-family: var(--k-sans); font-size: 13px;
  line-height: 1.5; color: var(--k-ink); box-shadow: var(--k-shadow);
  z-index: 9500; opacity: 0; transform: translateY(-4px);
  transition: opacity 0.15s, transform 0.15s; pointer-events: none;
}
.kfn-pop.show { opacity: 1; transform: translateY(0); pointer-events: auto; }
.kfn-pop .kfn-spec { font-family: var(--k-mono); font-size: 12px; color: var(--k-accent); font-weight: 700; }
.kfn-pop .kfn-quote { font-family: var(--k-serif); font-style: italic; margin-top: 6px; }

/* ------------ CALLOUT BLOCKS (specs / tips / definitions) ------------ */
.ch-kindle .kch-callout {
  background: var(--k-callout-bg);
  border-left: 3px solid var(--k-callout-ed);
  padding: 14px 18px;
  margin: 18px 0;
  border-radius: 0 4px 4px 0;
  font-size: 0.95em;
}
.ch-kindle .kch-callout .kch-callout-label {
  font-family: var(--k-sans); font-weight: 700;
  font-size: 0.72em; text-transform: uppercase; letter-spacing: 2.5px;
  color: var(--k-accent); margin-bottom: 4px;
}
.ch-kindle .kch-spec {
  background: var(--k-spec-bg);
  border-left: 3px solid var(--k-spec-ed);
  padding: 12px 16px;
  margin: 14px 0;
  font-family: var(--k-mono); font-size: 0.86em; line-height: 1.55;
  color: var(--k-ink-soft);
  border-radius: 0 4px 4px 0;
}
.ch-kindle .kch-spec b { color: var(--k-accent); font-weight: 700; font-family: var(--k-sans); }
.ch-kindle .kch-spec .kch-spec-cite {
  font-family: var(--k-sans); font-weight: 700; font-size: 0.85em;
  color: var(--k-accent); display: block; margin-bottom: 6px;
  letter-spacing: 0.5px;
}

.ch-kindle .kch-defn {
  background: var(--k-tip-bg);
  border: 1px solid var(--k-rule);
  padding: 14px 16px;
  margin: 16px 0;
  border-radius: 4px;
  font-size: 0.95em;
}
.ch-kindle .kch-defn b { color: var(--k-accent); }

/* ------------ MARGIN NOTE (the Kindle "Note" feel) ------------ */
.ch-kindle .kch-margin {
  background: var(--k-margin);
  border-left: 3px solid var(--k-accent-soft);
  padding: 10px 14px;
  margin: 14px 0;
  font-family: var(--k-sans); font-size: 0.88em;
  line-height: 1.5; color: var(--k-ink-soft);
  font-style: italic;
  border-radius: 0 4px 4px 0;
}
.ch-kindle .kch-margin b { font-style: normal; font-weight: 700; color: var(--k-ink); }

/* ------------ MATH (KaTeX) blocks ------------ */
.ch-kindle .kch-math {
  background: var(--k-paper-soft);
  border-top: 1px solid var(--k-rule);
  border-bottom: 1px solid var(--k-rule);
  padding: 16px 14px;
  margin: 18px 0;
  text-align: center;
  overflow-x: auto;
}
.ch-kindle .kch-math-label {
  font-family: var(--k-sans); font-size: 0.75em;
  text-transform: uppercase; letter-spacing: 2px;
  color: var(--k-ink-mute); margin-top: 8px;
}
.ch-kindle .katex { font-size: 1.05em; color: var(--k-ink); }
body[data-kindle="on"][data-theme="night"] .ch-kindle .katex { color: var(--k-ink); }

/* ------------ TABLES (book-style) ------------ */
.ch-kindle table.kch-table {
  width: 100%; border-collapse: collapse; margin: 22px 0;
  font-family: var(--k-sans); font-size: 1em;
  background: var(--k-paper-soft);
}
.ch-kindle table.kch-table th,
.ch-kindle table.kch-table td {
  text-align: left; padding: 11px 14px;
  border-bottom: 1px solid var(--k-rule);
  vertical-align: top;
}
.ch-kindle table.kch-table th {
  background: var(--k-paper-edge);
  color: var(--k-ink); font-weight: 700;
  border-bottom: 2px solid var(--k-accent-soft);
  text-transform: uppercase; letter-spacing: 1px;
  font-size: 0.9em;
}
.ch-kindle table.kch-table tbody tr:hover { background: var(--k-paper-edge); }
.ch-kindle table.kch-table .kch-highlight { background: var(--k-mark) !important; font-weight: 600; }
.ch-kindle table.kch-table caption {
  caption-side: bottom; text-align: left; padding-top: 8px;
  font-family: var(--k-serif); font-style: italic; font-size: 0.82em;
  color: var(--k-ink-mute);
}
.ch-kindle table.kch-table code {
  font-family: var(--k-mono); font-size: 0.92em;
  background: var(--k-paper); padding: 1px 5px; border-radius: 3px;
  border: 1px solid var(--k-rule); color: var(--k-accent);
}

/* Bit-field table (special, monospace) */
.ch-kindle .kch-bitfield {
  font-family: var(--k-mono); font-size: 0.78em;
  background: var(--k-paper); border: 1px solid var(--k-rule);
  border-radius: 4px; padding: 12px; margin: 14px 0;
  overflow-x: auto;
}
.ch-kindle .kch-bitfield table { border-collapse: collapse; width: 100%; }
.ch-kindle .kch-bitfield th { background: var(--k-paper-edge); padding: 4px 8px; font-weight: 700; color: var(--k-accent); text-align: left; }
.ch-kindle .kch-bitfield td { padding: 4px 8px; border-top: 1px solid var(--k-rule); }
.ch-kindle .kch-bitfield .kch-bits { color: var(--k-accent-soft); }

/* ------------ FIGURE / DIAGRAM ------------ */
.ch-kindle .kch-figure {
  width: min(960px, 96vw);             /* a touch wider than the prose column */
  position: relative; left: 50%; transform: translateX(-50%);
  margin: 42px 0 48px;
  background: #ffffff;                 /* figures always sit on clean white */
  border: 1px solid #e4e7ec;
  border-radius: 14px;
  padding: 30px 36px 24px;
  box-shadow: 0 10px 34px rgba(15,23,42,0.09), 0 2px 6px rgba(15,23,42,0.05);
  cursor: zoom-in;
}
.ch-kindle .kch-figure:hover { box-shadow: 0 16px 46px rgba(37,99,235,0.17), 0 3px 8px rgba(15,23,42,0.06); }
.ch-kindle .kch-figure::after {
  content: "\2922  click to enlarge";
  position: absolute; top: 12px; right: 16px;
  font-family: var(--k-sans); font-size: 11px; font-weight: 800;
  letter-spacing: .04em; color: #2563eb; background: #eef4ff;
  padding: 3px 10px; border-radius: 999px;
  opacity: 0; transition: opacity .15s; pointer-events: none;
}
.ch-kindle .kch-figure:hover::after { opacity: .92; }
.ch-kindle .kch-figure svg {
  display: block; width: 100%; max-width: 100%;
  height: auto; margin: 0 auto;
  shape-rendering: geometricPrecision;  /* crisp edges on laptop screens */
  text-rendering: optimizeLegibility;
}
.ch-kindle .kch-figure .kch-fig-title {
  font-family: var(--k-sans); font-weight: 800;
  font-size: 0.92em; text-transform: uppercase; letter-spacing: 1.5px;
  color: var(--k-ink); margin-bottom: 18px;
  padding: 2px 0 12px 14px; border-bottom: 2px solid #e6eaf0;
  border-left: 4px solid #2563eb;
}
.ch-kindle .kch-figure .kch-fig-caption {
  font-family: var(--k-serif); font-style: italic;
  font-size: 1.02em; line-height: 1.6;
  color: var(--k-ink-soft); margin-top: 12px;
  border-top: 1px solid var(--k-rule); padding-top: 10px;
}
.ch-kindle .kch-figure .kch-fig-caption b { font-style: normal; color: var(--k-ink); }

/* ------------ EXPERT READ box (sits under a figure) ------------ */
.ch-kindle .kch-expert {
  margin: -14px 0 30px; padding: 15px 22px 15px 22px;
  background: rgba(37,99,235,0.055);
  border-left: 4px solid #1d4ed8; border-radius: 0 10px 10px 0;
  font-family: var(--k-sans); font-size: 0.97em; line-height: 1.62; color: var(--k-ink);
}
.ch-kindle .kch-expert .kch-expert-label {
  display: block; font-weight: 800; text-transform: uppercase;
  letter-spacing: 1.6px; font-size: 0.72em; color: #1d4ed8; margin-bottom: 9px;
}
.ch-kindle .kch-expert ul { margin: 0 0 0 18px; padding: 0; }
.ch-kindle .kch-expert li { margin: 5px 0; }
.ch-kindle .kch-expert b { color: var(--k-ink); }
.ch-kindle .kch-expert code { font-family: var(--k-mono, monospace); font-size: 0.92em; background: rgba(37,99,235,0.10); padding: 1px 5px; border-radius: 4px; }

/* ------------ INTERACTIVE WIDGETS (paper-themed) ------------ */
.ch-kindle .kch-widget {
  background: var(--k-paper-soft);
  border: 1px solid var(--k-rule);
  border-radius: 6px;
  margin: 26px 0;
  font-family: var(--k-sans); font-size: 1.02em;
  color: var(--k-ink);
  box-shadow: var(--k-shadow);
  overflow: hidden;
}
.ch-kindle .kch-widget-head {
  background: var(--k-paper-edge);
  border-bottom: 1px solid var(--k-rule);
  padding: 10px 14px;
  display: flex; align-items: center; gap: 10px;
  font-weight: 700; color: var(--k-accent); font-size: 0.88em;
  text-transform: uppercase; letter-spacing: 1.5px;
}
.ch-kindle .kch-widget-head .kch-widget-tag {
  font-family: var(--k-mono); font-size: 0.85em;
  background: var(--k-paper); color: var(--k-ink-soft);
  padding: 1px 6px; border: 1px solid var(--k-rule);
  border-radius: 3px; margin-left: auto; text-transform: none; letter-spacing: 0;
  font-weight: 600;
}
.ch-kindle .kch-widget-body { padding: 14px 16px; }
.ch-kindle .kch-widget label {
  display: block; font-size: 0.78em; font-weight: 700; letter-spacing: 1px;
  text-transform: uppercase; color: var(--k-ink-soft); margin-bottom: 4px;
}
.ch-kindle .kch-widget input[type="number"],
.ch-kindle .kch-widget input[type="text"],
.ch-kindle .kch-widget select {
  background: var(--k-paper); border: 1px solid var(--k-rule);
  border-radius: 4px; padding: 7px 10px;
  font-family: var(--k-mono); font-size: 0.95em; color: var(--k-ink);
  width: 100%;
}
.ch-kindle .kch-widget input[type="range"] {
  width: 100%; accent-color: var(--k-accent);
}
.ch-kindle .kch-widget .kch-row { display: grid; gap: 10px 14px; grid-template-columns: repeat(auto-fit,minmax(140px,1fr)); }
.ch-kindle .kch-widget .kch-out {
  background: var(--k-paper);
  border: 1px solid var(--k-rule);
  border-radius: 4px;
  padding: 10px 12px;
  margin-top: 10px;
  font-family: var(--k-mono); font-size: 0.92em; color: var(--k-ink);
  line-height: 1.7;
}
.ch-kindle .kch-widget .kch-out .kch-out-key { color: var(--k-ink-mute); }
.ch-kindle .kch-widget .kch-out .kch-out-val { color: var(--k-accent); font-weight: 700; }
.ch-kindle .kch-widget .kch-out .kch-out-big {
  font-size: 1.4em; color: var(--k-accent); font-weight: 700;
  display: inline-block; margin: 4px 0;
}
.ch-kindle .kch-widget button.kch-btn {
  background: var(--k-paper-edge); border: 1px solid var(--k-rule);
  color: var(--k-ink); padding: 6px 14px; border-radius: 4px;
  font-family: var(--k-sans); font-size: 0.88em; font-weight: 700;
  cursor: pointer; transition: background 0.15s;
}
.ch-kindle .kch-widget button.kch-btn:hover { background: var(--k-mark); }
.ch-kindle .kch-widget button.kch-btn.kch-btn-primary { background: var(--k-accent); color: var(--k-paper); border-color: var(--k-accent); }
.ch-kindle .kch-widget button.kch-btn.kch-btn-primary:hover { background: var(--k-link-hover); }

/* ------------ CROSS-LINK CARD (to /labs/...) ------------ */
.ch-kindle .kch-labcard {
  display: flex; align-items: center; gap: 14px;
  background: var(--k-paper-soft);
  border: 1px solid var(--k-rule);
  border-left: 4px solid var(--k-accent);
  border-radius: 4px;
  padding: 12px 16px;
  margin: 18px 0;
  text-decoration: none; color: var(--k-ink);
  font-family: var(--k-sans); font-size: 0.92em;
  transition: background 0.15s, transform 0.15s;
}
.ch-kindle .kch-labcard:hover {
  background: var(--k-paper-edge); transform: translateX(2px);
  text-decoration: none;
}
.ch-kindle .kch-labcard .kch-labcard-icon { font-size: 1.4em; }
.ch-kindle .kch-labcard .kch-labcard-text { flex: 1; }
.ch-kindle .kch-labcard .kch-labcard-eyebrow {
  font-size: 0.72em; text-transform: uppercase; letter-spacing: 1.5px;
  color: var(--k-accent); font-weight: 700;
}
.ch-kindle .kch-labcard .kch-labcard-arrow { color: var(--k-accent); font-size: 1.2em; }

/* ------------ WORKED-EXAMPLE BLOCK ------------ */
.ch-kindle .kch-example {
  background: var(--k-paper-soft);
  border: 1px solid var(--k-rule);
  border-radius: 6px;
  padding: 16px 20px;
  margin: 22px 0;
  font-size: 0.94em; line-height: 1.65;
}
.ch-kindle .kch-example .kch-example-label {
  font-family: var(--k-sans); font-weight: 700;
  font-size: 0.74em; text-transform: uppercase; letter-spacing: 2.5px;
  color: var(--k-accent); margin-bottom: 8px;
}
.ch-kindle .kch-example ol { margin: 10px 0 0 0; padding-left: 22px; }
.ch-kindle .kch-example ol li { margin: 8px 0; }
.ch-kindle .kch-example code, .ch-kindle .kch-example .v {
  font-family: var(--k-mono); font-size: 0.92em;
  background: var(--k-paper); border: 1px solid var(--k-rule);
  padding: 1px 6px; border-radius: 3px; color: var(--k-accent);
}

/* ------------ END-OF-CHAPTER REFERENCES BLOCK ------------ */
.ch-kindle .kch-refs {
  margin: 36px 0 0;
  border-top: 1px solid var(--k-rule); padding-top: 20px;
  font-family: var(--k-sans); font-size: 0.86em; color: var(--k-ink-soft);
}
.ch-kindle .kch-refs h4 { color: var(--k-accent); margin-bottom: 8px; }
.ch-kindle .kch-refs ul { list-style: none; padding: 0; margin: 0; }
.ch-kindle .kch-refs li { padding: 4px 0; border-bottom: 1px dotted var(--k-rule); }
.ch-kindle .kch-refs li .kch-refs-tag {
  display: inline-block; font-family: var(--k-mono); font-size: 0.85em;
  color: var(--k-accent); font-weight: 700; min-width: 90px;
}

/* ------------ MARK / SEARCH HIGHLIGHT ------------ */
.kch-search-hit { background: var(--k-mark); border-radius: 2px; padding: 0 2px; }

/* ------------ KEYBOARD HELP OVERLAY ------------ */
.k-help {
  position: fixed; inset: 0; background: rgba(43,36,24,0.55);
  display: none; align-items: center; justify-content: center;
  z-index: 9800;
}
.k-help.open { display: flex; }
.k-help .k-help-card {
  background: var(--k-paper); color: var(--k-ink);
  border: 1px solid var(--k-rule);
  border-radius: 8px; padding: 24px 28px;
  max-width: 460px; box-shadow: 0 10px 40px rgba(0,0,0,0.3);
  font-family: var(--k-sans); font-size: 14px;
}
.k-help h3 { font-family: var(--k-serif); margin: 0 0 14px; color: var(--k-accent); }
.k-help table { width: 100%; border-collapse: collapse; }
.k-help td { padding: 5px 8px; border-bottom: 1px solid var(--k-rule); }
.k-help kbd {
  font-family: var(--k-mono); font-size: 12px;
  background: var(--k-paper-soft); border: 1px solid var(--k-rule);
  padding: 1px 6px; border-radius: 3px;
}

/* ============================================================
   FIGURE COLOUR REMAP  —  "black-&-white book, colourful images"
   ------------------------------------------------------------
   Every diagram was hand-drawn in a washed-out sepia/brown palette
   (low contrast, looks dull on a laptop). The SVGs carry their colours
   as inline presentation attributes (fill="#8a3b00" …). CSS rules win
   over presentation attributes, so we remap the ENTIRE sepia base to a
   crisp, modern blue/teal/slate technical palette in one place — every
   one of the 50+ figures across all chapters is recoloured at once.
   Already-vivid accents (purple / sky / amber / red / green) are kept.
   Applies in every theme so the figures stay colourful "plates".
   ============================================================ */

/* ---- FILLS (sepia base → BOLD vivid; saturated enough to read clearly) ---- */
.ch-kindle .kch-figure svg [fill="#8a3b00"]{fill:#1d4ed8}   /* primary: labels, DMRS, emphasis  → strong blue */
.ch-kindle .kch-figure svg [fill="#5b3a00"]{fill:#1e3a8a}   /* dark accent                      → navy   */
.ch-kindle .kch-figure svg [fill="#b66a2a"]{fill:#0d9488}   /* secondary blocks (white text)    → teal   */
.ch-kindle .kch-figure svg [fill="#5b4a32"]{fill:#334155}   /* caption / sub text               → dark slate */
.ch-kindle .kch-figure svg [fill="#8a7754"]{fill:#64748b}   /* muted italic notes               → slate  */
.ch-kindle .kch-figure svg [fill="#aa9f86"]{fill:#64748b}
.ch-kindle .kch-figure svg [fill="#2b2418"]{fill:#0f172a}   /* near-black                       → ink slate */
.ch-kindle .kch-figure svg [fill="#3a2e14"]{fill:#0f172a}
.ch-kindle .kch-figure svg [fill="#ebe2c5"]{fill:#bfdbfe}   /* light cell fill   → clearly-visible blue-200 */
.ch-kindle .kch-figure svg [fill="#ddd3b0"]{fill:#c7ddfb}   /* container fill                   → light blue */
.ch-kindle .kch-figure svg [fill="#fbe9bd"]{fill:#dbeafe}   /* group container                  → pale blue */
.ch-kindle .kch-figure svg [fill="#f5edd6"]{fill:#eef4fe}   /* panel                            → near white */
.ch-kindle .kch-figure svg [fill="#f2e7c6"]{fill:#eef4fe}   /* callout panel                    → near white */
.ch-kindle .kch-figure svg [fill="#e8d49a"]{fill:#bfdbfe}
.ch-kindle .kch-figure svg [fill="#e8c89b"]{fill:#bfdbfe}
.ch-kindle .kch-figure svg [fill="#c8a44a"]{fill:#2563eb}   /* gold accent                      → blue   */
.ch-kindle .kch-figure svg [fill="#b08d3a"]{fill:#3b82f6}

/* ---- STROKES (sepia base → BOLD; borders must be clearly visible) ---- */
.ch-kindle .kch-figure svg [stroke="#8a3b00"]{stroke:#1d4ed8}
.ch-kindle .kch-figure svg [stroke="#5b3a00"]{stroke:#1e3a8a}
.ch-kindle .kch-figure svg [stroke="#b66a2a"]{stroke:#0f766e}
.ch-kindle .kch-figure svg [stroke="#5b4a32"]{stroke:#475569}
.ch-kindle .kch-figure svg [stroke="#8a7754"]{stroke:#64748b}
.ch-kindle .kch-figure svg [stroke="#b08d3a"]{stroke:#2563eb}  /* gold cell border → strong blue */
.ch-kindle .kch-figure svg [stroke="#a48a4c"]{stroke:#2563eb}
.ch-kindle .kch-figure svg [stroke="#c8a44a"]{stroke:#2563eb}
.ch-kindle .kch-figure svg [stroke="#d8c89e"]{stroke:#94a3b8}  /* rule → slate hairline */
.ch-kindle .kch-figure svg [stroke="#fbe9bd"]{stroke:#93c5fd}

/* Bolder, more legible figure labels + crisper plate */
.ch-kindle .kch-figure svg text { font-weight: 600; }
.ch-kindle .kch-figure svg { filter: saturate(1.08) contrast(1.02); }

/* Keep the figure plate WHITE even in sepia / night so colours read true */
body[data-kindle="on"][data-theme="sepia"] .ch-kindle .kch-figure,
body[data-kindle="on"][data-theme="night"] .ch-kindle .kch-figure {
  background: #ffffff; border-color: #e4e4e7;
}
body[data-kindle="on"][data-theme="night"] .ch-kindle .kch-figure .kch-fig-title { color: #18181b; }

/* ------------ PRINT (clean B&W, colour figures preserved) ------------ */
@media print {
  .k-chrome, .k-toc, .k-toc-backdrop, .k-help { display: none !important; }
  body[data-kindle="on"] { padding-top: 0 !important; background: #fff !important; color:#000 !important; }
  .ch-kindle { max-width: 100%; padding: 0; font-size: 11pt; }
  .ch-kindle .kch-figure { break-inside: avoid; box-shadow: none; }
  .ch-kindle .kch-widget, .ch-kindle .kch-labcard { box-shadow: none; }
}

/* ============================================================
   BEAUTY PASS — refined book reading design · 2026-05-30
   Appended overrides (win by source order). Theme-aware via vars.
   ============================================================ */

/* — Chapter opener: pill eyebrow + larger title + accent rule — */
.ch-kindle .kch-eyebrow{
  display:inline-block; letter-spacing:4.5px; font-size:.72em;
  padding:5px 15px; border:1px solid var(--k-rule); border-radius:999px;
  color:var(--k-ink-soft); margin-bottom:16px;
}
.ch-kindle h1.kch-title{ font-size:3.0em; line-height:1.08; margin:.32em 0 .34em; letter-spacing:-.018em; }
.ch-kindle .kch-tagline{ border-bottom:none; padding-bottom:2px; font-size:1.26em; }
.ch-kindle .kch-tagline::after{
  content:""; display:block; width:78px; height:3px; border-radius:3px;
  background:var(--k-accent); margin:20px 0 2px;
}

/* — Section headings: leading accent bar + keep hairline — */
.ch-kindle h2{ position:relative; padding-left:18px; }
.ch-kindle h2::before{
  content:""; position:absolute; left:0; top:.16em; height:1.0em; width:5px;
  border-radius:3px; background:var(--k-accent);
}
.ch-kindle h3{ padding-left:13px; border-left:3px solid var(--k-rule); }

/* — Drop cap — */
.ch-kindle .kch-drop::first-letter{ font-size:5.0em; line-height:.78; padding:6px 12px 2px 0; }

/* — Boxes: soft elevation, rounding, even rhythm — */
.ch-kindle .kch-callout,.ch-kindle .kch-defn,.ch-kindle .kch-spec,.ch-kindle .kch-example{
  border-radius:10px; box-shadow:var(--k-shadow); margin:22px 0; padding:16px 20px;
}
.ch-kindle .kch-callout{ border-left-width:4px; }
.ch-kindle .kch-defn{ border-left:4px solid var(--k-accent-soft); }
.ch-kindle .kch-spec{ border-left-width:4px; }
.ch-kindle .kch-margin{ border-radius:0 10px 10px 0; box-shadow:var(--k-shadow); }
.ch-kindle .kch-example{ background:var(--k-paper-soft); border-left:4px solid var(--k-accent); }
.ch-kindle .kch-example .kch-example-label{
  font-family:var(--k-sans); font-weight:800; text-transform:uppercase;
  letter-spacing:1.5px; font-size:.74em; color:var(--k-accent);
  display:block; margin-bottom:8px;
}

/* — Lists: gentle spacing + accented markers — */
.ch-kindle li{ margin:.42em 0; }
.ch-kindle ol>li::marker{ color:var(--k-accent); font-weight:700; }
.ch-kindle ul>li::marker{ color:var(--k-accent-soft); }

/* — Tables: rounded, soft shadow, zebra — */
.ch-kindle table.kch-table{ border-radius:10px; overflow:hidden; box-shadow:var(--k-shadow); }
.ch-kindle table.kch-table tbody tr:nth-child(even){ background:var(--k-paper-soft); }
.ch-kindle table.kch-table tbody tr:last-child td{ border-bottom:none; }

/* — References block — */
.ch-kindle .kch-refs{
  background:var(--k-paper-soft); border:1px solid var(--k-rule);
  border-radius:12px; padding:18px 22px; margin:26px 0;
}

/* — Reading rhythm — */
.ch-kindle{ line-height:1.78; }

/* — Optional ornamental divider (use <hr class="kch-hr">) — */
.ch-kindle .kch-hr{ border:none; text-align:center; margin:32px 0; line-height:1; }
.ch-kindle .kch-hr::before{ content:"\2756"; color:var(--k-accent-soft); letter-spacing:10px; font-size:1.05em; }


/* ============================================================
   COVER → BOOK-COVER CARD · 2026-05-30
   Turns the full-bleed cover into a centered portrait book thumbnail.
   ============================================================ */
.cover-page{
  background:#070b1c !important;
  padding:48px 24px !important;
  min-height:100vh;
}
.cover-page::after{ display:none !important; }   /* drop full-viewport border */
.cover-page::before{ opacity:.45; }               /* keep ambient glow, dimmer */

.cover-card{
  position:relative; z-index:2;
  width:min(600px, 92vw);
  min-height:min(86vh, 858px);
  display:flex; flex-direction:column; justify-content:center; align-items:center;
  text-align:center;
  padding:52px 46px 58px;
  background:linear-gradient(170deg,#0d1b3e 0%,#1a237e 25%,#0d47a1 50%,#01579b 75%,#0d1b3e 100%);
  border-radius:16px;
  border:1px solid rgba(255,215,0,0.30);
  box-shadow:0 36px 90px rgba(0,0,0,.55), 0 0 0 1px rgba(255,215,0,.07);
  overflow:hidden;
}
.cover-card::before{               /* book spine */
  content:""; position:absolute; left:0; top:0; bottom:0; width:12px; z-index:5;
  background:linear-gradient(90deg, rgba(0,0,0,.55) 0%, rgba(255,215,0,.30) 55%, rgba(0,0,0,.10) 100%);
}
.cover-card::after{                /* inner gold frame */
  content:""; position:absolute; inset:18px; border:1px solid rgba(255,215,0,0.20);
  border-radius:9px; pointer-events:none; z-index:4;
}
.cover-card .cover-content{ position:relative; z-index:6; }

/* compact the content to a designed-cover rhythm */
.cover-card .cover-badge{ margin-bottom:26px !important; padding:8px 22px !important; font-size:.62rem !important; letter-spacing:4px !important; }
.cover-card .cover-title{ font-size:3.1rem !important; line-height:1.05 !important; margin-bottom:10px !important; }
.cover-card .cover-subtitle{ font-size:1.1rem !important; letter-spacing:2px !important; margin-bottom:16px !important; }
.cover-card .cover-spec-badge{ font-size:.64rem !important; padding:5px 11px !important; margin:3px !important; }
.cover-card .cover-author-section{ margin-top:30px !important; padding-top:18px !important; }
.cover-card .cover-author{ font-size:1.4rem !important; }
.cover-card .cover-brand{ font-size:.85rem !important; letter-spacing:8px !important; }
.cover-card .cover-grid{ opacity:.45; }
.cover-card .cover-logo-watermark{ position:absolute; bottom:13px; left:50%; transform:translateX(-50%); font-size:.5rem; }

@media (max-width:640px){
  .cover-card{ padding:38px 22px 46px; min-height:min(90vh,760px); }
  .cover-card .cover-title{ font-size:2.4rem !important; }
  .cover-card .cover-subtitle{ font-size:1rem !important; }
}