/* ============================================================
   BRAINZIE BOOKS: the reader.
   Shared by every book under site/books/ (the pages are generated by Build-BrainzieBook). A reading page, not a
   marketing page: a warm paper colour, a serif made for long reading, a comfortable measure, and three themes the
   reader picks (light, sepia, dark; the OS preference decides until they do). The Brainzie magenta is the accent.
   The shelf page (site/books/index.html) uses the site's own stylesheet plus the .shelf rules at the bottom.
   ============================================================ */

:root {
  --bg: #fbf8f2;
  --ink: #221c2e;
  --ink-soft: #4d4560;
  --muted: #857c95;
  --line: #e7ded0;
  --panel: #f5efe4;
  --accent: #b0155e;
  --accent-soft: rgba(216, 27, 114, .14);
  --nb-paper: #fffdf7;
  --nb-rule: rgba(80, 120, 190, .16);
  --nb-margin: rgba(214, 72, 72, .45);
  --nb-ink: #1f2744;
  --diary-ink: #1d47a1;
  --note-paper: #fff6cf;
  --note-ink: #2a2230;
  --phone: #f1ecf6;
  --chat-in: #ffffff;
  --chat-out: #b0155e;
  --stamp-seen: #17784c;
  --stamp-worked: #2556a6;
  --stamp-guess: #9a5700;
  --f-ink: #2a2336;
  --f-soft: #6d6380;
  --f-fill-1: #efe7f6;
  --f-fill-2: #e2d4f0;
  --f-fill-3: #fbdcea;
  --f-water: #d9edf7;
  --f-o: #d9483b;
  --f-c: #3a3446;
  --f-si: #8a7f99;
  --tray: #d9c7a6;
  --w-canvas-fade: rgba(251, 248, 242, .22);
  --w-food: rgba(24, 160, 107, .55);
  --w-cell: #221c2e;
  --w-ink: #4d4560;
  --shadow: 0 18px 44px -24px rgba(40, 20, 70, .45);
  --font-read: "Literata", Georgia, "Times New Roman", serif;
  --font-hand: "Caveat", "Segoe Print", cursive;
  --font-ui: "Inter", "Segoe UI", system-ui, sans-serif;
  --size: 1.18rem;
  --measure: 36rem;
  color-scheme: light;
}

:root[data-theme="sepia"] {
  --bg: #f3e9d4; --ink: #33281c; --ink-soft: #5a4a37; --muted: #8a7760; --line: #e0d1b3; --panel: #eadcc0;
  --nb-paper: #fbf3e2; --note-paper: #f8e9b8; --phone: #eadfc9; --chat-in: #fbf6ea;
  --f-ink: #33281c; --f-soft: #6d5d48; --f-fill-1: #eadcc0; --f-fill-2: #e0cca8; --f-fill-3: #f1d3c4; --f-water: #d8e3e0;
  --w-canvas-fade: rgba(243, 233, 212, .22); --w-cell: #33281c; --w-ink: #5a4a37;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    --bg: #15121d; --ink: #ece7f3; --ink-soft: #c5bdd6; --muted: #948ba8; --line: #2d2740; --panel: #1f1a2b;
    --accent: #f06aa6; --accent-soft: rgba(240, 106, 166, .16);
    --nb-paper: #1c1827; --nb-rule: rgba(140, 170, 230, .10); --nb-margin: rgba(230, 110, 110, .35); --nb-ink: #dfe5f7; --diary-ink: #9fbaf5;
    --note-paper: #2c2717; --note-ink: #f3ecd2; --phone: #221d30; --chat-in: #2e2840; --chat-out: #c02b73;
    --stamp-seen: #53c992; --stamp-worked: #7fa9f0; --stamp-guess: #e3a857;
    --f-ink: #e6e0ef; --f-soft: #a79fba; --f-fill-1: #231e31; --f-fill-2: #2d2542; --f-fill-3: #402136; --f-water: #1b2c3a;
    --f-o: #ef7467; --f-c: #d8d2e4; --f-si: #9d93ad; --tray: #5a4a36;
    --w-canvas-fade: rgba(21, 18, 29, .25); --w-food: rgba(47, 201, 140, .5); --w-cell: #ece7f3; --w-ink: #c5bdd6;
    --shadow: 0 18px 44px -24px rgba(0, 0, 0, .8);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #15121d; --ink: #ece7f3; --ink-soft: #c5bdd6; --muted: #948ba8; --line: #2d2740; --panel: #1f1a2b;
  --accent: #f06aa6; --accent-soft: rgba(240, 106, 166, .16);
  --nb-paper: #1c1827; --nb-rule: rgba(140, 170, 230, .10); --nb-margin: rgba(230, 110, 110, .35); --nb-ink: #dfe5f7; --diary-ink: #9fbaf5;
  --note-paper: #2c2717; --note-ink: #f3ecd2; --phone: #221d30; --chat-in: #2e2840; --chat-out: #c02b73;
  --stamp-seen: #53c992; --stamp-worked: #7fa9f0; --stamp-guess: #e3a857;
  --f-ink: #e6e0ef; --f-soft: #a79fba; --f-fill-1: #231e31; --f-fill-2: #2d2542; --f-fill-3: #402136; --f-water: #1b2c3a;
  --f-o: #ef7467; --f-c: #d8d2e4; --f-si: #9d93ad; --tray: #5a4a36;
  --w-canvas-fade: rgba(21, 18, 29, .25); --w-food: rgba(47, 201, 140, .5); --w-cell: #ece7f3; --w-ink: #c5bdd6;
  --shadow: 0 18px 44px -24px rgba(0, 0, 0, .8);
  color-scheme: dark;
}

:root[data-size="s"] { --size: 1.05rem; }
:root[data-size="l"] { --size: 1.32rem; }
:root[data-size="xl"] { --size: 1.48rem; --measure: 38rem; }

*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body.book-page, body.book-home {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font-read);
  font-size: var(--size);
  line-height: 1.72;
  font-optical-sizing: auto;
  text-rendering: optimizeLegibility;
  transition: background-color .3s, color .3s;
}
a { color: var(--accent); text-decoration-thickness: 1px; text-underline-offset: .18em; }
::selection { background: var(--accent-soft); }

/* ---- Top bar, progress, drawer ---- */
.readbar { position: fixed; inset: 0 0 auto 0; height: 3px; z-index: 30; }
.readbar span { display: block; height: 100%; width: 0; background: var(--accent); transition: width .15s linear; }
.bar {
  position: fixed; inset: 0 0 auto 0; z-index: 20; height: 52px;
  display: flex; align-items: center; gap: .9rem; padding: 0 1rem;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(8px); -webkit-backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line);
  font-family: var(--font-ui); font-size: .9rem;
}
.bar-brand img { display: block; }
.bar-title { color: var(--ink); font-weight: 600; text-decoration: none; white-space: nowrap; }
.bar-where { color: var(--muted); flex: 1; min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.bar-tools { display: flex; gap: .35rem; margin-left: auto; }
.bar-btn {
  font: 600 .82rem var(--font-ui); color: var(--ink-soft); background: transparent;
  border: 1px solid var(--line); border-radius: 999px; padding: .38rem .75rem; cursor: pointer;
}
.bar-btn:hover, .bar-btn:focus-visible { color: var(--accent); border-color: var(--accent); outline: none; }
.drawer { position: fixed; inset: 0; z-index: 40; background: rgba(10, 6, 20, .35); }
.drawer[hidden] { display: none; }
.drawer-inner {
  position: absolute; top: 0; right: 0; bottom: 0; width: min(24rem, 92vw); overflow-y: auto;
  background: var(--bg); border-left: 1px solid var(--line); padding: 1.2rem 1.2rem 2rem; box-shadow: var(--shadow);
  font-family: var(--font-ui); font-size: .92rem;
}
.drawer-title { font: 600 1.25rem var(--font-read); margin: .2rem 0 1rem; }
.drawer-title a { color: var(--ink); text-decoration: none; }

/* ---- Contents list (drawer and cover page) ---- */
.toc { list-style: none; margin: 0; padding: 0; }
.toc-part { margin: 1.1rem 0 .35rem; color: var(--muted); font: 500 .78rem var(--font-ui); letter-spacing: .08em; text-transform: uppercase; }
.toc-part span { color: var(--accent); font-weight: 700; margin-right: .3rem; }
.toc a { display: grid; grid-template-columns: 1.8rem 1fr auto; gap: .5rem; align-items: baseline; padding: .42rem .5rem; border-radius: 8px; color: var(--ink); text-decoration: none; }
.toc-extra a { grid-template-columns: 1fr; }
.toc a:hover, .toc a:focus-visible { background: var(--accent-soft); outline: none; }
.toc a[aria-current="page"] { background: var(--accent-soft); font-weight: 600; }
.toc-n { color: var(--muted); font-variant-numeric: tabular-nums; text-align: right; }
.toc-k { color: var(--muted); font-size: .8em; white-space: nowrap; }

/* ---- The page ---- */
.page { padding: 96px 1.25rem 3rem; }
.chapter { max-width: var(--measure); margin: 0 auto; }
.chapter-head { text-align: center; margin: 1.5rem 0 3rem; }
.chapter-part { font: 700 .75rem var(--font-ui); letter-spacing: .18em; text-transform: uppercase; color: var(--accent); margin: 0 0 1.4rem; }
.chapter-num { font: 500 .8rem var(--font-ui); letter-spacing: .22em; text-transform: uppercase; color: var(--muted); margin: 0; }
.chapter-head h1 { font-weight: 600; font-size: clamp(2rem, 5vw, 2.8rem); line-height: 1.15; margin: .5rem 0 .6rem; letter-spacing: -.01em; }
.kicker { font-style: italic; color: var(--ink-soft); margin: 0; }
.chapter-head::after { content: ""; display: block; width: 3rem; height: 2px; margin: 1.8rem auto 0; background: var(--accent); opacity: .6; }
.prose p { margin: 0 0 1.05em; hyphens: auto; }
.kind-chapter .prose > p:first-of-type::first-letter {
  float: left; font-size: 3.5em; line-height: .86; font-weight: 600; color: var(--accent); padding: .06em .08em 0 0;
}
.prose hr { border: 0; margin: 2.4em 0; text-align: center; }
.prose hr::after { content: "⁂"; color: var(--muted); font-size: 1.25em; letter-spacing: .3em; }
.prose blockquote { margin: 1.4em 0; padding: .6em 1.1em; border-left: 3px solid var(--accent); background: var(--panel); border-radius: 0 10px 10px 0; }
.prose blockquote p:last-child { margin-bottom: 0; }
.prose table { width: 100%; border-collapse: collapse; margin: 1.4em 0; font-family: var(--font-ui); font-size: .82em; }
.prose th, .prose td { padding: .5em .6em; border-bottom: 1px solid var(--line); text-align: left; }
.prose th { color: var(--ink-soft); font-weight: 600; }
.prose td:not(:first-child), .prose th:not(:first-child) { text-align: right; font-variant-numeric: tabular-nums; }
/* The back matter's tables hold sentences, not numbers: read them left to right, top first. */
.kind-back .prose td, .kind-back .prose th { text-align: left; vertical-align: top; font-variant-numeric: normal; }
.prose ul { padding-left: 1.2em; }
/* Help notes: a small ? that opens the step the running text skips. */
.help-btn {
  display: inline-flex; align-items: center; justify-content: center; width: 1.25em; height: 1.25em; margin: 0 .15em; padding: 0;
  vertical-align: .12em; border-radius: 50%; border: 1.5px solid var(--accent); background: transparent; color: var(--accent);
  font: 700 .66em/1 var(--font-ui); cursor: pointer;
}
.help-btn:hover, .help-btn[aria-expanded="true"] { background: var(--accent); color: #fff; }
.help-body { font: .82em/1.55 var(--font-ui); color: var(--ink-soft); }
.js .help-body { display: none; }
.js .help.open .help-body { display: block; margin: .5em 0 .8em; padding: .7em .9em; background: var(--panel); border: 1px solid var(--line); border-left: 3px solid var(--accent); border-radius: 0 10px 10px 0; }
html:not(.js) .help-btn { display: none; }
html:not(.js) .help-body::before { content: "("; }
html:not(.js) .help-body::after { content: ")"; }
.wl { color: inherit; text-decoration: underline dotted var(--accent); text-underline-offset: .22em; }
.nbref { text-decoration-style: dotted; }

/* ---- Ada's notebook ---- */
.notebook {
  position: relative; margin: 2.4em -2rem; padding: 1.7rem 1.9rem 1.5rem 3.4rem;
  color: var(--nb-ink); border-radius: 4px 12px 12px 4px; box-shadow: var(--shadow);
  background: var(--nb-paper) repeating-linear-gradient(to bottom, transparent 0, transparent calc(1.72em - 1px), var(--nb-rule) calc(1.72em - 1px), var(--nb-rule) 1.72em);
  background-position: 0 1.55rem;
}
.notebook::before { content: ""; position: absolute; top: 0; bottom: 0; left: 2.35rem; width: 2px; background: var(--nb-margin); }
.notebook + .notebook, .nb-cont { margin-top: -1.2em; }
.nb-head { margin-bottom: .6rem; }
.nb-num { font: 700 1.25rem var(--font-hand); color: var(--accent); }
.nb-title { font: 700 2.05rem/1.1 var(--font-hand); margin: 0 0 .4rem; color: var(--nb-ink); }
.nb-resume { font: 700 1.4rem/1 var(--font-hand); color: var(--muted); margin: 0 0 .2rem !important; }
.notebook strong { color: var(--nb-ink); }

/* Evidence marks and margin notes */
.stamp {
  display: inline-block; font: 700 .58em/1 var(--font-ui); letter-spacing: .07em; text-transform: uppercase;
  padding: .32em .55em .28em; margin: 0 .15em 0 .3em; border: 1.5px solid currentColor; border-radius: 999px;
  vertical-align: .2em; text-decoration: none; white-space: nowrap; transform: rotate(-2deg);
}
.stamp-seen { color: var(--stamp-seen); }
.stamp-worked-out { color: var(--stamp-worked); }
.stamp-best-guess { color: var(--stamp-guess); border-style: dashed; }
.stamp:hover { background: var(--accent-soft); }
/* A mark with its evidence is a button: press it for how we know. + closed, minus open. */
button.stamp { background: transparent; cursor: pointer; }
button.stamp::after { content: "+"; margin-left: .35em; font-weight: 700; }
button.stamp[aria-expanded="true"]::after { content: "\2212"; }
button.stamp[aria-expanded="true"] { background: var(--accent-soft); }
.evidence-body { display: block; margin: .5em 0 .9em; padding: .75em .95em; font: .82em/1.55 var(--font-ui); color: var(--ink-soft); background: var(--panel); border: 1px solid var(--line); border-left: 3px solid var(--stamp-seen); border-radius: 0 10px 10px 0; }
.evidence-worked-out .evidence-body { border-left-color: var(--stamp-worked); }
.evidence-best-guess .evidence-body { border-left-color: var(--stamp-guess); border-left-style: dashed; }
.js .evidence-body { display: none; }
.js .evidence.open .evidence-body { display: block; }
html:not(.js) button.stamp::after { content: none; }
.evidence-head { display: block; margin-bottom: .25em; font-weight: 700; letter-spacing: .06em; text-transform: uppercase; font-size: .78em; color: var(--ink); }
.evidence-mark { display: block; margin-top: .45em; font-size: .92em; }
.mnote-body {
  display: block; margin: .5em 0 .8em; padding: .5em .8em; border-left: 2px solid var(--nb-margin);
  font: 500 1.18em/1.25 var(--font-hand); color: var(--diary-ink); background: color-mix(in srgb, var(--nb-paper) 70%, var(--note-paper));
}
@media (min-width: 1240px) {
  .mnote-body {
    float: right; clear: right; width: 15rem; margin: -.4em -19rem .6em 0; padding: 0 0 0 .7rem;
    background: none; border-left: 2px solid var(--nb-margin); transform: rotate(-.6deg);
  }
}

/* Handwritten note, diary page, phone */
.handnote {
  max-width: 31rem; margin: 2em auto; padding: 1.3rem 1.6rem; transform: rotate(-.7deg);
  background: var(--note-paper); color: var(--note-ink); box-shadow: var(--shadow);
  font: 500 1.42em/1.3 var(--font-hand);
}
.handnote p { margin: 0 0 .55em; }
.diary {
  max-width: 32rem; margin: 2.2em auto; padding: 1.2rem 1.5rem 1rem 3rem; position: relative; color: var(--diary-ink);
  background: var(--nb-paper) repeating-linear-gradient(to bottom, transparent 0, transparent calc(1.5em - 1px), var(--nb-rule) calc(1.5em - 1px), var(--nb-rule) 1.5em);
  box-shadow: var(--shadow); transform: rotate(.5deg); font: 500 1.3em/1.5 var(--font-hand);
}
.diary::before { content: ""; position: absolute; top: 0; bottom: 0; left: 1.9rem; width: 2px; background: var(--nb-margin); }
.diary-date { font-weight: 700; color: var(--accent); margin: 0 0 .2em !important; }
.diary p { margin: 0 0 .5em; }
.texts {
  max-width: 23rem; margin: 1.8em auto; padding: 1rem .9rem; background: var(--phone); border: 1px solid var(--line);
  border-radius: 26px; font: .9rem/1.35 var(--font-ui); box-shadow: var(--shadow);
}
.msg { display: flex; flex-direction: column; margin: .15rem 0; }
.msg p { margin: 0; padding: .45rem .8rem; border-radius: 18px; max-width: 82%; }
.msg-in { align-items: flex-start; }
.msg-out { align-items: flex-end; }
.msg-in p { background: var(--chat-in); color: var(--ink); border-bottom-left-radius: 6px; }
.msg-out p { background: var(--chat-out); color: #fff; border-bottom-right-radius: 6px; }
.who { font-size: .72rem; color: var(--muted); margin: .55rem .7rem .15rem; }

/* ---- Figures ---- */
.fig, .widget { margin: 2.6em -3rem; }
.fig-art svg, .w-chart { display: block; width: 100%; height: auto; }
figcaption { max-width: var(--measure); margin: .9em auto 0; font: .84rem/1.5 var(--font-ui); color: var(--ink-soft); }
.fig-n { font-weight: 700; color: var(--ink); }
.fig-svg .f-label { font: 700 13px var(--font-ui); letter-spacing: .12em; fill: var(--f-ink); }
.fig-svg .f-note { font: 12.5px var(--font-ui); fill: var(--f-soft); }
.fig-svg .f-hand { font: 700 21px var(--font-hand); fill: var(--f-ink); }
.fig-svg .f-accent { fill: var(--accent); }
.fig-svg .f-fill-1 { fill: var(--f-fill-1); }
.fig-svg .f-fill-2 { fill: var(--f-fill-2); }
.fig-svg .f-fill-3 { fill: var(--f-fill-3); }
.fig-svg .f-stroke { stroke: var(--f-soft); stroke-width: 1.5; }
.fig-svg .f-stroke-accent { stroke: var(--accent); stroke-width: 2; }
.fig-svg .f-mol line, .fig-svg .f-bonds line { stroke: var(--f-ink); stroke-width: 2.2; }
.fig-svg .f-o { fill: var(--f-o); }
.fig-svg .f-c { fill: var(--f-c); }
.fig-svg .f-si { fill: var(--f-si); }
.fig-svg .f-motion path { stroke: var(--f-soft); stroke-width: 1.6; fill: none; stroke-dasharray: 3 4; }
.fig-svg .f-divider { stroke: var(--line); stroke-width: 1.5; }
.fig-svg .f-water { fill: var(--f-water); }
.fig-svg .f-surface { fill: none; stroke: #3b8fc4; stroke-width: 2.5; }
.fig-svg .f-swimmer { fill: var(--f-ink); }
.fig-svg .f-arm { stroke: var(--f-ink); stroke-width: 9; stroke-linecap: round; fill: none; }
.fig-svg .f-arrow { stroke: var(--f-soft); stroke-width: 1.6; fill: none; }
.cover-art { display: block; width: 100%; height: auto; }
.fig-pair .fig-art { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; align-items: center; }
.fig-svg .f3-bond { stroke: var(--f-soft); stroke-width: 2.4; stroke-linecap: round; }
.fig-svg .f3-o circle { fill: var(--f-o); }
.fig-svg .f3-c circle { fill: var(--f-c); }
.fig-svg .f3-si circle { fill: var(--f-si); }
.fig-svg .f3-o circle, .fig-svg .f3-c circle, .fig-svg .f3-si circle { stroke: rgba(0, 0, 0, .35); stroke-width: .8; }
.fig-svg circle.f3-shine { fill: #fff; opacity: .45; stroke: none; }
.fig-svg .fp-capsid { fill: var(--f-fill-3); stroke: var(--accent); stroke-width: 2; }
.fig-svg .fp-facets { fill: none; stroke: var(--accent); stroke-width: 1; opacity: .55; }
.fig-svg .fp-spikes line { stroke: var(--f-soft); stroke-width: 2.4; }
.fig-svg .fp-knobs circle { fill: var(--accent); }
.fig-svg .fp-cell { fill: var(--f-fill-1); stroke: var(--f-soft); stroke-width: 2.5; }
.fig-svg .fp-er { fill: none; stroke: var(--f-soft); stroke-width: 1.4; opacity: .7; }
.fig-svg .fp-nucleus { fill: var(--f-fill-2); stroke: var(--f-soft); stroke-width: 2; }
.fig-svg .fp-nucleolus { fill: var(--f-soft); }
.fig-svg .fp-mito ellipse { fill: var(--f-fill-3); stroke: var(--accent); stroke-width: 1.6; }
.fig-svg .fp-cristae { fill: none; stroke: var(--accent); stroke-width: 1.2; }
.fig-svg .fp-dino path, .fig-svg .fp-dino rect { fill: var(--f-ink); }
.fig-svg .fp-ground { stroke: var(--line); stroke-width: 2; }
.fig-svg .fp-scale { stroke: var(--f-ink); stroke-width: 3; stroke-linecap: butt; }
.frontispiece { max-width: 64rem; margin: 3.5rem auto 0; }
.fig-svg .fp-glow { fill: var(--accent); opacity: .18; }
.fig-svg .fp-dot { fill: var(--accent); }
.fig-svg .fp-cloud-0 { stop-color: var(--f-soft); stop-opacity: .55; }
.fig-svg .fp-cloud-1 { stop-color: var(--f-soft); stop-opacity: .2; }
.fig-svg .fp-cloud-2 { stop-color: var(--f-soft); stop-opacity: 0; }
.fig-svg .fp-bond { stroke: var(--f-soft); stroke-width: 5; }
.fig-svg .fp-oxygen { fill: var(--f-o); }
.fig-svg .fp-hydrogen { fill: var(--f-fill-2); stroke: var(--f-soft); stroke-width: 1.5; }
.fig-svg .fp-atom-label { font: 700 15px var(--font-ui); fill: var(--f-ink); }
svg.defs { position: absolute; width: 0; height: 0; overflow: hidden; }

/* Drawings from Ada's notebook: pencil, red pen and blue pencil on ruled paper, every line slightly wobbly and grainy
   (the #pencil filter each page carries). */
:root { --pencil: #3d3b47; --pencil-soft: rgba(61, 59, 71, .14); --red-pen: #c0392b; --red-pen-soft: rgba(192, 57, 43, .16); --blue-pencil: #2f6db3; --blue-pencil-soft: rgba(47, 109, 179, .12); }
:root[data-theme="dark"] { --pencil: #d9d5e3; --pencil-soft: rgba(217, 213, 227, .12); --red-pen: #ef7467; --red-pen-soft: rgba(239, 116, 103, .16); --blue-pencil: #7fa9f0; --blue-pencil-soft: rgba(127, 169, 240, .12); }
@media (prefers-color-scheme: dark) { :root:not([data-theme]) { --pencil: #d9d5e3; --pencil-soft: rgba(217, 213, 227, .12); --red-pen: #ef7467; --red-pen-soft: rgba(239, 116, 103, .16); --blue-pencil: #7fa9f0; --blue-pencil-soft: rgba(127, 169, 240, .12); } }
/* A canary's second wording: chosen per reader by the protected-area gate, hidden wherever the gate has not been. */
[data-tc-b] { display: none; }
.fig-later { display: inline-block; margin: 0 .35em 0 .1em; padding: .1em .5em; border: 1px solid var(--line); border-radius: 999px; font: 600 .78em var(--font-ui); letter-spacing: .04em; color: var(--muted); vertical-align: .05em; }
.fig-sketch .fig-art {
  padding: 1.2rem 1rem; border-radius: 3px; box-shadow: var(--shadow); transform: rotate(-.35deg);
  background: var(--nb-paper) repeating-linear-gradient(to bottom, transparent 0, transparent 27px, var(--nb-rule) 27px, var(--nb-rule) 28px);
}
.fig-sketch .fig-svg { filter: url(#pencil); }
.fig-sketch .fig-svg text { font-family: var(--font-hand) !important; fill: var(--pencil); letter-spacing: 0 !important; }
.fig-sketch .fig-svg .f-label { font-size: 23px; font-weight: 700; }
.fig-sketch .fig-svg .f-note { font-size: 18px; font-weight: 500; }
.fig-sketch .fig-svg .f-hand { font-size: 22px; }
.fig-sketch .fig-svg .f-accent { fill: var(--red-pen); }
.fig-sketch .fig-svg .f-fill-1, .fig-sketch .fig-svg .f-fill-2 { fill: none; stroke: var(--pencil); stroke-width: 2.2; }
.fig-sketch .fig-svg .f-fill-3 { fill: var(--red-pen-soft); stroke: var(--red-pen); stroke-width: 2.2; }
.fig-sketch .fig-svg .f-stroke-accent { stroke: var(--red-pen); }
.fig-sketch .fig-svg .f-mol line, .fig-sketch .fig-svg .f-bonds line, .fig-sketch .fig-svg .f-arrow, .fig-sketch .fig-svg .f-motion path { stroke: var(--pencil); stroke-width: 2; }
.fig-sketch .fig-svg .f-o { fill: var(--red-pen-soft); stroke: var(--red-pen); stroke-width: 2; }
.fig-sketch .fig-svg .f-c { fill: var(--pencil-soft); stroke: var(--pencil); stroke-width: 2.2; }
.fig-sketch .fig-svg .f-si { fill: var(--blue-pencil-soft); stroke: var(--blue-pencil); stroke-width: 2.2; }
.fig-sketch .fig-svg .f-divider { stroke: var(--pencil-soft); stroke-dasharray: 6 5; }
.fig-sketch .fig-svg .f-water { fill: var(--blue-pencil-soft); }
.fig-sketch .fig-svg .f-surface { stroke: var(--blue-pencil); stroke-width: 2.4; }
.fig-sketch .fig-svg .f-swimmer ellipse, .fig-sketch .fig-svg .f-swimmer circle { fill: var(--pencil-soft); stroke: var(--pencil); stroke-width: 2; }
.fig-sketch .fig-svg .f-arm { stroke: var(--pencil); stroke-width: 7; }
.maths {
  margin: 2em 0; padding: 1rem 1.3rem 1rem 1.2rem; border: 1px solid var(--line); border-left: 4px solid var(--accent);
  border-radius: 0 12px 12px 0; background: var(--panel); font: .88rem/1.6 var(--font-ui); color: var(--ink);
}
.maths-title { font: 700 .72rem var(--font-ui) !important; letter-spacing: .14em; text-transform: uppercase; color: var(--accent); margin: 0 0 .5rem !important; }
.maths p { margin: 0 0 .6em; }
.maths h4 { font: 700 .8rem var(--font-ui); letter-spacing: .06em; text-transform: uppercase; color: var(--ink); margin: 1.1rem 0 .5rem; }
.maths h4:first-of-type { margin-top: .4rem; }
.maths blockquote { margin: .4rem 0 .7rem; padding: .7rem 1rem; background: var(--bg); border: 1px solid var(--line); border-left: 0; border-radius: 10px; text-align: center; font: 500 1.15rem/1.4 var(--font-read); }
.maths blockquote p { margin: 0; }
.maths hr { border: 0; border-top: 1px dashed var(--line); margin: 1.1rem 0 .2rem; }
.maths hr::after { content: none; }
.maths li { margin: .25em 0; }
.maths ul { margin: 0 0 .6em; padding-left: 1.1em; }
.maths strong { font-weight: 700; }
.maths sub { font-size: .72em; }

/* ---- Widgets ---- */
.widget { background: var(--panel); border: 1px solid var(--line); border-radius: 16px; padding: 1.3rem 1.5rem 1.1rem; font-family: var(--font-ui); }
.widget figcaption { margin-top: 1rem; }
.w-controls { display: grid; gap: .8rem 1.4rem; grid-template-columns: repeat(auto-fit, minmax(15rem, 1fr)); margin-bottom: 1rem; }
.w-controls-row { display: flex; flex-wrap: wrap; align-items: center; gap: .6rem 1rem; }
.w-slider { display: grid; grid-template-columns: 1fr auto; gap: .2rem .6rem; font-size: .85rem; color: var(--ink-soft); }
.w-slider input { grid-column: 1 / -1; width: 100%; accent-color: var(--accent); }
.w-slider output { font-weight: 700; color: var(--ink); font-variant-numeric: tabular-nums; }
.w-check { font-size: .88rem; color: var(--ink); display: flex; gap: .45rem; align-items: center; }
.w-check small { color: var(--muted); }
.w-check input { accent-color: var(--accent); width: 1.05rem; height: 1.05rem; }
.w-btn, .w-presets button, .w-toggle label {
  font: 600 .8rem var(--font-ui); color: var(--ink); background: var(--bg); border: 1px solid var(--line);
  border-radius: 999px; padding: .4rem .85rem; cursor: pointer;
}
.w-btn:hover, .w-presets button:hover, .w-toggle label:hover { border-color: var(--accent); color: var(--accent); }
.w-presets { display: flex; flex-wrap: wrap; gap: .45rem; margin: 0 0 1rem; }
.w-readout { margin-top: .9rem; font-size: .93rem; line-height: 1.5; color: var(--ink); min-height: 2.8em; }
.w-hint { font-size: .8rem; color: var(--muted); }
.w-grab { cursor: grab; touch-action: none; }
.w-grab:active { cursor: grabbing; }
.w-small { font-size: .76rem; color: var(--muted); margin: .7rem 0 0; }
.w-noscript { font-size: .8rem; color: var(--muted); }
.w-meter { height: .7rem; border-radius: 999px; background: var(--bg); border: 1px solid var(--line); overflow: hidden; }
.w-meter span { display: block; height: 100%; width: 0; background: var(--accent); transition: width .25s; }
.w-numbers { display: grid; grid-template-columns: repeat(auto-fit, minmax(11rem, 1fr)); gap: .6rem; margin: 0; }
.w-numbers div { background: var(--bg); border: 1px solid var(--line); border-radius: 12px; padding: .6rem .8rem; }
.w-numbers dt { font-size: .74rem; color: var(--muted); }
.w-numbers dd { margin: .15rem 0 0; font-weight: 700; font-size: 1rem; color: var(--ink); font-variant-numeric: tabular-nums; }
.w-chart .w-grid { stroke: var(--line); stroke-width: 1; }
.w-chart .w-tick { font: 11px var(--font-ui); fill: var(--muted); }
.w-chart .w-axis-label { font: 12px var(--font-ui); fill: var(--ink-soft); }
.w-chart .w-zone { fill: var(--accent); opacity: .13; }
.w-chart .w-curve-hot { fill: none; stroke: var(--accent); stroke-width: 5; stroke-linecap: round; }
.w-chart .w-note-soft { fill: var(--muted); }
.w-chart .w-dot-alt { fill: var(--muted); }
.w-chart .w-curve { fill: none; stroke: var(--accent); stroke-width: 2.6; stroke-linejoin: round; }
.w-chart .w-curve-ref { fill: none; stroke: var(--muted); stroke-width: 1.6; stroke-dasharray: 5 5; }
.w-chart .w-threshold { stroke: var(--ink); stroke-width: 1.4; stroke-dasharray: 4 4; }
.w-chart .w-note { font: 700 17px var(--font-hand); fill: var(--ink); }
.w-chart .w-water { fill: var(--f-water); }
.w-chart .w-surface { stroke: #3b8fc4; stroke-width: 2.5; }
.w-chart .w-body { fill: var(--f-fill-2); stroke: var(--f-ink); stroke-width: 2; }
.w-chart .w-limb { stroke: var(--f-ink); stroke-width: 9; stroke-linecap: round; }
.w-chart .w-force-up { stroke: #2f6db3; stroke-width: 4; }
.w-chart .w-force-up-head { fill: #2f6db3; }
.w-chart .w-force-down { stroke: var(--accent); stroke-width: 4; }
.w-chart .w-force-down-head { fill: var(--accent); }
.w-chart .w-dot { fill: var(--accent); stroke: var(--bg); stroke-width: 2; }
.w-canvas { display: block; width: 100%; height: auto; border-radius: 12px; background: var(--bg); border: 1px solid var(--line); }

/* The tray (CSS only): gentle = settle into dents, one rare hop; hard = marbles thrown everywhere. */
.tray-demo { position: relative; }
.tray-input { position: absolute; opacity: 0; pointer-events: none; }
.w-toggle { display: flex; gap: .5rem; margin-bottom: .9rem; }
.w-toggle small { font-weight: 500; color: var(--muted); }
.tray-input-gentle:checked ~ .w-toggle label[for="tray-gentle"],
.tray-input-hard:checked ~ .w-toggle label[for="tray-hard"] { background: var(--accent); border-color: var(--accent); color: #fff; }
.tray-input-gentle:checked ~ .w-toggle label[for="tray-gentle"] small,
.tray-input-hard:checked ~ .w-toggle label[for="tray-hard"] small { color: rgba(255, 255, 255, .8); }
.tray-input:focus-visible ~ .w-toggle label { outline: 2px solid var(--accent); outline-offset: 2px; }
.tray {
  position: relative; aspect-ratio: 5 / 2; border-radius: 14px; overflow: hidden;
  background: var(--tray); box-shadow: inset 0 2px 10px rgba(0, 0, 0, .25);
}
.dent {
  position: absolute; left: var(--x); top: var(--y); width: 10%; aspect-ratio: 1; transform: translate(-50%, -50%); border-radius: 50%;
  background: radial-gradient(circle at 50% 38%, rgba(0, 0, 0, .34), rgba(0, 0, 0, .12) 55%, rgba(0, 0, 0, 0) 72%);
}
.marble {
  position: absolute; left: var(--x); top: var(--y); width: 6%; aspect-ratio: 1; border-radius: 50%;
  transform: translate(-50%, -50%);
  background: radial-gradient(circle at 35% 30%, #fff 0, #ffb3d4 18%, #d81b72 55%, #7a0c3e 100%);
  box-shadow: 0 3px 6px rgba(0, 0, 0, .35);
}
.tray-input-gentle:checked ~ .tray .marble { animation: tray-settle 2.8s cubic-bezier(.25, .7, .35, 1) both, tray-jiggle .16s ease-in-out 2.8s infinite alternate; }
.tray-input-gentle:checked ~ .tray .marble-rare { animation: tray-settle 2.8s cubic-bezier(.25, .7, .35, 1) both, tray-hop 7s ease-in-out 3.4s infinite; }
.tray-input-hard:checked ~ .tray .marble { animation: tray-wander 1.5s linear var(--d) infinite; }
@keyframes tray-settle {
  0% { transform: translate(calc(-50% + var(--sx)), calc(-50% + var(--sy))); }
  45% { transform: translate(calc(-50% + var(--sx) * -.35), calc(-50% + var(--sy) * .3)); }
  75% { transform: translate(calc(-50% + var(--sx) * .1), calc(-50% + var(--sy) * -.08)); }
  100% { transform: translate(-50%, -50%); }
}
@keyframes tray-jiggle { from { transform: translate(-54%, -48%); } to { transform: translate(-46%, -52%); } }
@keyframes tray-hop {
  0%, 78% { transform: translate(-50%, -50%); }
  81% { transform: translate(-10%, -170%); }
  85% { transform: translate(250%, -120%); }
  88%, 97% { transform: translate(350%, -50%); }
  100% { transform: translate(-50%, -50%); }
}
@keyframes tray-wander {
  0%, 100% { transform: translate(-50%, -50%); }
  25% { transform: translate(calc(-50% + var(--a1)), calc(-50% + var(--b1))); }
  50% { transform: translate(calc(-50% + var(--a2)), calc(-50% + var(--b2))); }
  75% { transform: translate(calc(-50% + var(--a3)), calc(-50% + var(--b3))); }
}
.tray-legend { font-size: .82rem; color: var(--ink-soft); margin: .7rem 0 0; }
.tray-legend-hard { display: none; }
.tray-input-hard:checked ~ .tray-legend .tray-legend-hard { display: inline; }
.tray-input-hard:checked ~ .tray-legend .tray-legend-gentle { display: none; }

/* Base pairing (CSS only): mismatches bounce off at once; matches linger, then a backbone joins them. */
.pair-demo { max-width: 30rem; margin: 0 auto; }
.pair-row { display: grid; grid-template-columns: repeat(6, 1fr); gap: .55rem; position: relative; }
.pair-loose { height: 7.2rem; }
.pair-slot { position: relative; }
.pair-slot .base { position: absolute; left: 0; right: 0; bottom: .25rem; }
.base { display: flex; align-items: center; justify-content: center; height: 2.4rem; border-radius: 8px; font: 700 1rem var(--font-ui); color: #fff; }
.base-A { background: #c2410c; }
.base-U { background: #0f766e; }
.base-G { background: #6d28d9; }
.base-C { background: #b0155e; }
.pair-template .base { border-radius: 8px 8px 3px 3px; box-shadow: inset 0 -5px 0 rgba(0, 0, 0, .18); }
.pair-miss { opacity: 0; animation: pair-miss 9s ease-in-out infinite; animation-delay: calc(var(--i) * .33s); }
.pair-hit { animation: pair-hit 9s ease-in-out infinite; animation-delay: calc(var(--i) * .33s); }
.pair-backbone { position: absolute; left: 4%; right: 4%; bottom: 2.62rem; height: 4px; border-radius: 2px; background: var(--ink); transform-origin: left; animation: pair-backbone 9s ease-in-out infinite; opacity: 0; }
@keyframes pair-miss {
  0% { transform: translateY(-5rem); opacity: 0; }
  6% { opacity: 1; }
  13% { transform: translateY(0); opacity: 1; }
  16% { transform: translateY(-.5rem) rotate(10deg); opacity: 1; }
  27% { transform: translate(var(--drift), -6rem) rotate(40deg); opacity: 0; }
  100% { transform: translateY(-5rem); opacity: 0; }
}
@keyframes pair-hit {
  0%, 30% { transform: translateY(-5rem); opacity: 0; }
  36% { opacity: 1; }
  46% { transform: translateY(0); }
  48% { transform: translateY(-.18rem); }
  51%, 90% { transform: translateY(0); opacity: 1; }
  97%, 100% { transform: translateY(-5rem); opacity: 0; }
}
@keyframes pair-backbone { 0%, 60% { opacity: 0; transform: scaleX(0); } 72%, 90% { opacity: 1; transform: scaleX(1); } 97%, 100% { opacity: 0; transform: scaleX(1); } }
.pair-legend { display: flex; justify-content: space-between; font-size: .78rem; color: var(--muted); margin: .5rem 0 0; }

@media (prefers-reduced-motion: reduce) {
  .tray .marble, .tray .marble-rare { animation: none !important; transform: translate(-50%, -50%); }
  .tray-input-hard:checked ~ .tray .marble { transform: translate(calc(-50% + var(--a2)), calc(-50% + var(--b2))); }
  .pair-miss { display: none; }
  .pair-hit { animation: none; opacity: 1; transform: none; }
  .pair-backbone { animation: none; opacity: 1; transform: none; }
  .readbar span, body.book-page { transition: none; }
}

/* ---- Turning the page, the foot ---- */
.turn { max-width: calc(var(--measure) + 6rem); margin: 4rem auto 0; display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; font-family: var(--font-ui); }
.turn a { display: block; padding: 1rem 1.2rem; border: 1px solid var(--line); border-radius: 14px; color: var(--ink); text-decoration: none; font-size: .95rem; font-weight: 600; background: var(--panel); }
.turn a span { display: block; font-size: .75rem; font-weight: 500; color: var(--muted); margin-bottom: .2rem; }
.turn a:hover { border-color: var(--accent); color: var(--accent); }
.turn-next { text-align: right; }

/* Invited readers: the lock on a locked chapter, the note where the free part ends, and the request-access page. */
.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.toc-lock { display: inline-block; width: .62em; height: .78em; margin-left: .45em; vertical-align: -.02em; background: var(--muted); -webkit-mask: var(--lock) center / contain no-repeat; mask: var(--lock) center / contain no-repeat;
  --lock: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 10 12'%3E%3Cpath d='M2 5V3.5a3 3 0 0 1 6 0V5h.5A1.5 1.5 0 0 1 10 6.5v4A1.5 1.5 0 0 1 8.5 12h-7A1.5 1.5 0 0 1 0 10.5v-4A1.5 1.5 0 0 1 1.5 5zm1.5 0h3V3.5a1.5 1.5 0 0 0-3 0z'/%3E%3C/svg%3E"); }
.free-ends { max-width: var(--measure); margin: 3.5rem auto 0; padding: 1.2rem 1.4rem; border: 1px solid var(--line); border-left: 3px solid var(--accent); border-radius: 0 14px 14px 0; background: var(--panel); font: .95rem/1.55 var(--font-ui); }
.free-ends-title { margin: 0 0 .4rem; font-weight: 700; color: var(--ink); }
.free-ends p:last-child { margin-bottom: 0; color: var(--ink-soft); }
.access-note { margin: 0 0 1.5rem; padding: 1rem 1.2rem; border: 1px solid var(--line); border-left: 3px solid var(--accent); border-radius: 0 14px 14px 0; background: var(--panel); font: .95rem/1.55 var(--font-ui); }
.home-free { font: .85rem var(--font-ui); color: var(--ink-soft); margin: .2rem 0 0; }
.access-go { margin: 1.2rem 0 2rem; }
.access-go .btn-read { display: inline-block; }
.access-offer { margin: 0 0 1.5rem; padding: .9rem 1.2rem; border-radius: 14px; background: color-mix(in srgb, var(--accent) 12%, var(--panel)); font: .95rem/1.55 var(--font-ui); }
.access-buy { margin: 1.2rem 0 2rem; }
.access-waive { display: flex; gap: .7rem; align-items: flex-start; font: .95rem/1.55 var(--font-ui); cursor: pointer; }
.access-waive input { margin-top: .3rem; width: 1.1rem; height: 1.1rem; flex: none; accent-color: var(--accent); }
.access-buy .access-go { margin: 1rem 0 0; }
button.btn-read { border: 0; cursor: pointer; }
.book-foot { text-align: center; font: .8rem var(--font-ui); color: var(--muted); padding: 2.5rem 1rem 3rem; }
.book-foot p { margin: .3rem 0; }
.book-foot a { color: var(--muted); }

/* ---- The word list ---- */
.words-intro { font-style: italic; color: var(--ink-soft); }
.words { margin: 2rem 0 0; }
.word { padding: 1rem 0; border-bottom: 1px solid var(--line); scroll-margin-top: 80px; }
.word:target { background: var(--accent-soft); border-radius: 10px; padding-left: .8rem; padding-right: .8rem; }
.word dt { font: 700 1.5rem var(--font-hand); color: var(--accent); }
.word dd { margin: .2rem 0 0; }
.word-first { display: block; font: .78rem var(--font-ui); color: var(--muted); margin-top: .4rem; }
.notebook, .fig, .widget { scroll-margin-top: 80px; }

/* ---- The cover page ---- */
.home { max-width: 70rem; margin: 0 auto; padding: 100px 1.25rem 2rem; }
.home-hero { display: grid; grid-template-columns: minmax(15rem, 22rem) 1fr; gap: 3rem; align-items: center; }
.home-cover { border-radius: 6px 14px 14px 6px; overflow: hidden; box-shadow: 0 30px 60px -28px rgba(20, 10, 50, .7), inset 4px 0 0 rgba(255, 255, 255, .06); transform: perspective(1200px) rotateY(-5deg); }
.home-byline { font: 700 .78rem var(--font-ui); letter-spacing: .2em; text-transform: uppercase; color: var(--accent); margin: 0; }
.home-text h1 { font-size: clamp(2.4rem, 6vw, 3.6rem); line-height: 1.05; margin: .4rem 0 .6rem; font-weight: 600; }
.home-sub { font-style: italic; color: var(--ink-soft); font-size: 1.1em; margin: 0 0 1.4rem; }
.home-blurb p { margin: 0 0 .9em; }
.home-actions { display: flex; flex-wrap: wrap; gap: .7rem; margin: 1.6rem 0 1rem; }
.btn-read, .btn-continue { font: 600 .95rem var(--font-ui); padding: .8rem 1.4rem; border-radius: 999px; text-decoration: none; }
.btn-read { background: var(--accent); color: #fff; }
.btn-continue { border: 1px solid var(--accent); color: var(--accent); }
.btn-read:hover { filter: brightness(1.08); }
.home-meta, .home-note { font: .85rem var(--font-ui); color: var(--muted); }
.home-section { max-width: 44rem; margin: 4rem auto 0; }
.home-section h2 { font-weight: 600; font-size: 1.7rem; border-bottom: 1px solid var(--line); padding-bottom: .5rem; }
.home-section .toc { font-family: var(--font-ui); font-size: .95rem; }
.nblist { list-style: none; padding: 0; margin: 0; font-family: var(--font-ui); font-size: .95rem; }
.nblist a { display: grid; grid-template-columns: 2rem 1fr auto; gap: .6rem; padding: .45rem .5rem; border-radius: 8px; color: var(--ink); text-decoration: none; }
.nblist a:hover { background: var(--accent-soft); }
.nbl-n { font: 700 1.2rem/1 var(--font-hand); color: var(--accent); text-align: right; }
.nbl-t { font-family: var(--font-hand); font-size: 1.3rem; line-height: 1.1; }
.nbl-w { color: var(--muted); font-size: .8em; }

/* ---- Small screens ---- */
@media (max-width: 760px) {
  .bar-where { display: none; }
  .bar-title { flex: 1; overflow: hidden; text-overflow: ellipsis; }
  .notebook { margin: 2em -.6rem; padding: 1.3rem 1rem 1.1rem 2.2rem; }
  .notebook::before { left: 1.35rem; }
  .fig, .widget { margin: 2em -.6rem; }
  .fig-pair .fig-art { grid-template-columns: 1fr; }
  .widget { padding: 1rem; }
  .home-hero { grid-template-columns: 1fr; gap: 2rem; }
  .home-cover { max-width: 17rem; margin: 0 auto; transform: none; }
  .turn { grid-template-columns: 1fr; }
  .turn-next { text-align: left; }
  .toc-k { display: none; }
}

@media print {
  .bar, .readbar, .drawer, .turn, .book-foot, .widget .w-controls, .w-presets { display: none !important; }
  .page { padding-top: 0; }
  body.book-page { background: #fff; color: #000; }
}

/* ============================================================
   The shelf (site/books/index.html), inside the site's own layout.
   ============================================================ */
.shelf { display: grid; gap: 2rem; }
.shelf-book {
  display: grid; grid-template-columns: 13rem 1fr; gap: 2rem; align-items: center; padding: 1.6rem;
  border: 1px solid var(--line, #ECE7F2); border-radius: 18px; background: #fff; color: inherit; text-decoration: none;
  box-shadow: 0 20px 54px -34px rgba(46, 16, 101, .5); transition: transform .2s, box-shadow .2s;
}
.shelf-book:hover { transform: translateY(-2px); box-shadow: 0 26px 60px -30px rgba(46, 16, 101, .6); }
.shelf-cover { border-radius: 4px 10px 10px 4px; overflow: hidden; box-shadow: 0 16px 30px -18px rgba(20, 10, 50, .7); }
.shelf-cover svg { display: block; width: 100%; height: auto; }
.shelf-by { font-weight: 700; font-size: .75rem; letter-spacing: .18em; text-transform: uppercase; color: #D81B72; margin: 0; }
.shelf-body h2 { font-family: "Literata", Georgia, serif; font-size: 2.2rem; margin: .3rem 0 .4rem; }
.shelf-sub { font-family: "Literata", Georgia, serif; font-style: italic; color: #4A4361; }
.shelf-meta { font-size: .85rem; color: #847B9C; }
.shelf-body .go { font-weight: 600; color: #D81B72; }
@media (max-width: 700px) { .shelf-book { grid-template-columns: 1fr; } .shelf-cover { max-width: 12rem; } }