:root {
  color-scheme: light dark;
  --paper: #f6f1e7;
  --paper-deep: #eee6d7;
  --ink: #231f20;
  --muted: #6d655f;
  --rule: #cfc3b0;
  --accent: #8f2d24;
  --accent-soft: #ead7d0;
  --focus: #126b83;
  --serif: "TeX Gyre Pagella", Palatino, "Book Antiqua", Georgia, serif;
  --sans: "TeX Gyre Heros", "Helvetica Neue", Arial, sans-serif;
  --mono: "JuliaMono", ui-monospace, SFMono-Regular, Consolas, monospace;
  --body-size: 18px;
  --topbar: 64px;
  --measure: 72ch;
}

@font-face { font-family: "TeX Gyre Pagella"; src: url("fonts/texgyrepagella-regular.woff2") format("woff2"); font-style: normal; font-weight: 400; font-display: swap; }
@font-face { font-family: "TeX Gyre Pagella"; src: url("fonts/texgyrepagella-italic.woff2") format("woff2"); font-style: italic; font-weight: 400; font-display: swap; }
@font-face { font-family: "TeX Gyre Pagella"; src: url("fonts/texgyrepagella-bold.woff2") format("woff2"); font-style: normal; font-weight: 700; font-display: swap; }
@font-face { font-family: "TeX Gyre Heros"; src: url("fonts/texgyreheros-regular.woff2") format("woff2"); font-style: normal; font-weight: 400; font-display: swap; }
@font-face { font-family: "TeX Gyre Heros"; src: url("fonts/texgyreheros-bold.woff2") format("woff2"); font-style: normal; font-weight: 700; font-display: swap; }

:root[data-theme="dark"] {
  --paper: #171614;
  --paper-deep: #211f1b;
  --ink: #eee9df;
  --muted: #b8afa4;
  --rule: #4a443d;
  --accent: #e4927f;
  --accent-soft: #422a25;
  --focus: #73cce3;
}

@media (prefers-color-scheme: dark) {
  :root[data-theme="system"] {
    --paper: #171614;
    --paper-deep: #211f1b;
    --ink: #eee9df;
    --muted: #b8afa4;
    --rule: #4a443d;
    --accent: #e4927f;
    --accent-soft: #422a25;
    --focus: #73cce3;
  }
}

:root[data-text="large"] { --body-size: 20px; }
:root[data-text="xlarge"] { --body-size: 23px; }

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: calc(var(--topbar) + 1rem); }
body { margin: 0; background: var(--paper); color: var(--ink); font-family: var(--serif); font-size: var(--body-size); line-height: 1.56; text-rendering: optimizeLegibility; }
a { color: var(--accent); text-decoration-thickness: .075em; text-underline-offset: .14em; }
a:hover { text-decoration-thickness: .12em; }
button, input { font: inherit; }
button { color: inherit; }
:focus-visible { outline: 3px solid var(--focus); outline-offset: 3px; }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }
.skip-link { position: fixed; z-index: 100; left: 1rem; top: .5rem; transform: translateY(-160%); background: var(--ink); color: var(--paper); padding: .6rem 1rem; }
.skip-link:focus { transform: none; }

.topbar { position: sticky; top: 0; z-index: 40; height: var(--topbar); display: grid; grid-template-columns: 260px 1fr auto; align-items: center; gap: 1rem; padding: 0 1.25rem; background: color-mix(in srgb, var(--paper) 92%, transparent); border-bottom: 1px solid var(--rule); backdrop-filter: blur(14px); font-family: var(--sans); }
.wordmark { display: flex; flex-direction: column; color: var(--ink); text-decoration: none; font-weight: 700; line-height: 1.05; letter-spacing: -.02em; }
.wordmark-kicker { color: var(--muted); font-size: .62rem; text-transform: uppercase; letter-spacing: .12em; }
.topbar-chapter { min-width: 0; overflow: hidden; white-space: nowrap; text-overflow: ellipsis; color: var(--muted); font-size: .82rem; text-align: center; }
.topbar-actions { display: flex; align-items: center; gap: .5rem; }
.icon-button, .text-button, .chapter-tools button, .settings-actions button, .segmented button { min-width: 2.75rem; min-height: 2.75rem; border: 1px solid var(--rule); background: transparent; border-radius: 999px; cursor: pointer; font-family: var(--sans); font-size: .78rem; }
.text-button { padding: 0 .9rem; }
kbd { font-family: var(--mono); font-size: .7rem; border: 1px solid var(--rule); padding: .05rem .3rem; border-radius: .2rem; }

.reading-layout { display: grid; grid-template-columns: minmax(220px, 280px) minmax(0, 1fr) minmax(190px, 250px); align-items: start; gap: clamp(1rem, 3vw, 3rem); max-width: 1680px; margin: 0 auto; padding: 0 1.25rem; }
.rail { position: sticky; top: calc(var(--topbar) + 1rem); max-height: calc(100vh - var(--topbar) - 2rem); overflow: auto; padding: 1rem 0 2rem; font-family: var(--sans); font-size: .76rem; color: var(--muted); }
.rail-heading { display: flex; align-items: center; justify-content: space-between; color: var(--ink); font-weight: 700; text-transform: uppercase; letter-spacing: .1em; margin-bottom: .75rem; }
.rail-heading h2 { margin: 0; font: inherit; }
.contents-link { display: block; margin-bottom: .8rem; }
.book-nav, .book-nav ol, .page-toc { list-style: none; margin: 0; padding: 0; }
.book-nav > li { margin: .65rem 0 1rem; }
.book-nav details > summary { color: var(--ink); font-weight: 700; font-size: .7rem; text-transform: uppercase; letter-spacing: .06em; margin-bottom: .35rem; cursor: pointer; }
.book-nav ol a, .page-toc a { display: block; color: var(--muted); text-decoration: none; padding: .25rem .5rem; border-left: 2px solid transparent; }
.book-nav a[aria-current="page"], .page-toc a[aria-current="location"] { color: var(--accent); border-left-color: var(--accent); background: var(--accent-soft); }
.reading-main { min-width: 0; width: 100%; max-width: var(--measure); margin: 0 auto; padding: clamp(2rem, 5vw, 5rem) 0 6rem; }

.chapter-header { padding-bottom: 2rem; border-bottom: 1px solid var(--rule); margin-bottom: 2rem; }
.breadcrumbs { display: flex; gap: .55rem; font: .72rem var(--sans); color: var(--muted); margin-bottom: 2.25rem; }
.chapter-kicker, .eyebrow { display: flex; align-items: center; gap: .65rem; color: var(--accent); font: 700 .7rem/1.3 var(--sans); letter-spacing: .12em; text-transform: uppercase; }
.chapter-header h1, .home-header h1 { font-family: var(--sans); font-size: clamp(2.35rem, 4.6vw, 4.25rem); line-height: 1; letter-spacing: -.05em; margin: .75rem 0 0; text-wrap: balance; }
.route-badge, .status-badge { display: inline-flex; align-items: center; border: 1px solid currentColor; border-radius: 999px; padding: .18rem .45rem; font-size: .58rem; letter-spacing: .08em; }
.route-star::before { content: "★"; margin-right: .25rem; }
.chapter-tools { display: flex; flex-wrap: wrap; gap: .5rem; margin: 0 0 2rem; font-family: var(--sans); }
.chapter-tools button, .settings-actions button { border-radius: .35rem; padding: .25rem .7rem; }
.chapter-content > :first-child { margin-top: 0; }
.chapter-content h2 { font-family: var(--sans); font-size: clamp(1.45rem, 3vw, 2rem); line-height: 1.14; letter-spacing: -.025em; margin: 3.5rem 0 1.25rem; scroll-margin-top: calc(var(--topbar) + 1.5rem); }
.chapter-content h3 { font-family: var(--sans); font-size: 1.1rem; margin: 2.25rem 0 .8rem; }
.chapter-content p { margin: 0 0 1rem; }
.chapter-content img { display: block; max-width: 100%; height: auto; margin-inline: auto; }
.chapter-content pre { overflow: auto; padding: 1rem; background: var(--paper-deep); border: 1px solid var(--rule); font: .76em/1.45 var(--mono); tab-size: 2; }
.chapter-content code { font-family: var(--mono); font-size: .82em; overflow-wrap: anywhere; }
.chapter-content table { width: 100%; border-collapse: collapse; margin: 1.5rem 0; font-size: .86em; }
.chapter-content th, .chapter-content td { padding: .45rem .6rem; border-bottom: 1px solid var(--rule); text-align: left; vertical-align: top; }
.chapter-content blockquote { margin: 1.4rem 0; padding: .2rem 0 .2rem 1rem; border-left: 2px solid var(--accent); color: var(--muted); }
.chapter-content em.term { color: color-mix(in srgb, var(--accent) 76%, var(--ink)); text-decoration: underline dotted; text-underline-offset: .15em; }
.math, .math-static { font-size: 1.02em; }
.math.display, .math-static.display { display: block; overflow-x: auto; overflow-y: hidden; padding: .75rem .2rem; margin: 1rem 0; text-align: center; }
.mathml-a11y { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }
.math-error { color: #a00; outline: 1px dashed currentColor; }
.statement { position: relative; margin: 2rem 0; padding: 1rem 0 1rem 1.15rem; border-left: 2px solid var(--rule); scroll-margin-top: calc(var(--topbar) + 1.5rem); }
.statement.definition { border-left-color: var(--accent); }
.statement-heading { margin: 0 0 .65rem !important; font: 700 .78rem/1.35 var(--sans) !important; letter-spacing: .04em; color: var(--accent); }
.statement-heading a { color: inherit; text-decoration: none; }
.proof { margin: 1.25rem 0 1.8rem; padding-left: 1.1rem; border-left: 1px solid var(--rule); }
.proof summary { cursor: pointer; font: 700 .78rem/1.5 var(--sans); color: var(--muted); padding: .25rem 0 .6rem; }
.proof[open] summary { color: var(--ink); }
.proof summary::marker { color: var(--accent); }
.proof-body > :last-child { margin-bottom: 0; }
.solution, .tutorial { margin: 1.25rem 0 2rem; border: 1px solid var(--rule); border-radius: .25rem; }
.solution > summary, .tutorial > summary { cursor: pointer; padding: .7rem 1rem; background: var(--paper-deep); font: 700 .78rem var(--sans); }
.solution-body, .tutorial-body { padding: 1rem; }
.backlinks { margin-top: .8rem; color: var(--muted); font: .72rem var(--sans); }
.backlinks summary { cursor: pointer; }
.permalink { margin-left: .45rem; opacity: 0; }
.statement:hover .permalink, .permalink:focus { opacity: 1; }
.exercise-rating { margin-right: .5rem; color: var(--accent); font: .78rem var(--sans); letter-spacing: .08em; }
.inference-rules { overflow-x: auto; margin: 1.8rem 0; padding: 1.4rem 1rem; color: var(--ink); border: 1px solid var(--rule); border-radius: .35rem; background: color-mix(in srgb, var(--paper-deep) 55%, var(--paper)); }
.rule-row { display: flex; width: max-content; min-width: 100%; justify-content: center; align-items: end; gap: clamp(2.5rem, 7vw, 5rem); }
.inference-rule { display: inline-grid; grid-template-columns: auto auto; grid-template-areas: "prem name" "bar name" "conc name"; align-items: center; text-align: center; font-size: 1.16em; }
.rule-premises { grid-area: prem; display: flex; justify-content: center; gap: .75rem; padding: 0 .45rem .2rem; }
.rule-bar { grid-area: bar; border-top: 1.6px solid var(--ink); min-width: 5rem; }
.rule-conclusion { grid-area: conc; padding: .2rem .45rem 0; }
.rule-name { grid-area: name; align-self: center; margin-left: .6rem; color: var(--muted); font: 700 .72rem/1 var(--sans); font-variant-caps: all-small-caps; letter-spacing: .04em; white-space: nowrap; }

.chapter-pagination { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; border-top: 1px solid var(--rule); margin-top: 4rem; padding-top: 1.5rem; font-family: var(--sans); }
.chapter-pagination a { display: flex; flex-direction: column; text-decoration: none; padding: .7rem; border: 1px solid var(--rule); border-radius: .35rem; }
.chapter-pagination a.next { text-align: right; grid-column: 2; }
.chapter-pagination span { color: var(--muted); font-size: .68rem; text-transform: uppercase; letter-spacing: .08em; }
.chapter-pagination strong { font-size: .78rem; color: var(--ink); }

.home-page { max-width: 1040px; margin-left: auto; margin-right: auto; }
.home-header { min-height: min(650px, 78vh); display: flex; flex-direction: column; justify-content: center; border-bottom: 1px solid var(--rule); }
.home-header h1 { font-size: clamp(4rem, 10vw, 8.8rem); }
.home-deck { max-width: 58ch; color: var(--muted); font-size: 1.14em; }
.home-actions { display: flex; align-items: center; gap: 1.25rem; font-family: var(--sans); font-size: .82rem; }
.primary-action { background: var(--ink); color: var(--paper); text-decoration: none; padding: .75rem 1rem; border-radius: .25rem; }
.section-heading { margin: 4rem 0 1.5rem; }
.section-heading h2 { font-family: var(--sans); font-size: 2rem; margin: .25rem 0; }
.part-grid { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(2, 1fr); gap: 1px; background: var(--rule); border: 1px solid var(--rule); }
.part-grid li { background: var(--paper); }
.part-grid a { min-height: 11rem; display: flex; flex-direction: column; justify-content: space-between; color: var(--ink); text-decoration: none; padding: 1.25rem; }
.part-grid strong { font-family: var(--sans); font-size: 1.25rem; line-height: 1.12; max-width: 24ch; }
.part-grid span { color: var(--muted); font: .68rem var(--sans); text-transform: uppercase; letter-spacing: .08em; }
.part-grid .part-number { color: var(--accent); }
.index-entry-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 1px; background: var(--rule); border: 1px solid var(--rule); }
.index-entry-grid a { display: flex; flex-direction: column; min-height: 6rem; padding: 1rem; background: var(--paper); color: var(--ink); text-decoration: none; }
.index-entry-grid strong { font-family: var(--sans); }
.index-entry-grid span { color: var(--muted); font-size: .82rem; }
.appendix-sections { margin-top: 3rem; }
.appendix-sections h2 { font-family: var(--sans); }
.appendix-sections ol { columns: 2; padding-left: 1.4rem; }

.search-dialog { width: min(760px, calc(100vw - 2rem)); max-height: min(760px, calc(100vh - 2rem)); padding: 0; border: 1px solid var(--rule); border-radius: .6rem; background: var(--paper); color: var(--ink); box-shadow: 0 25px 70px #0005; }
.search-dialog::backdrop { background: #1118; backdrop-filter: blur(4px); }
.search-shell { display: flex; flex-direction: column; max-height: inherit; }
.search-header { display: flex; align-items: center; justify-content: space-between; padding: 1rem 1.25rem; border-bottom: 1px solid var(--rule); font-family: var(--sans); }
.search-header h2 { margin: 0; font-size: 1rem; }
.search-field { padding: 1rem 1.25rem .5rem; }
.search-field input { width: 100%; border: 1px solid var(--rule); border-radius: .35rem; background: var(--paper-deep); color: var(--ink); font-family: var(--sans); padding: .8rem 1rem; }
.search-status { color: var(--muted); font: .72rem var(--sans); padding: 0 1.25rem; }
.search-results { overflow: auto; padding: 0 1.25rem 1.25rem; }
.search-result { display: block; color: var(--ink); text-decoration: none; padding: .9rem 0; border-top: 1px solid var(--rule); }
.search-result strong { display: block; font-family: var(--sans); }
.search-result p { color: var(--muted); font-size: .85rem; margin: .25rem 0; }
.settings-panel { position: fixed; z-index: 60; right: 1rem; top: calc(var(--topbar) + .75rem); width: min(360px, calc(100vw - 2rem)); padding: 1.1rem; border: 1px solid var(--rule); background: var(--paper); box-shadow: 0 18px 50px #0004; font-family: var(--sans); }
.settings-panel fieldset { border: 0; padding: 0; margin: 1rem 0; }
.settings-panel legend { font-size: .72rem; font-weight: 700; margin-bottom: .4rem; }
.segmented { display: grid; grid-template-columns: repeat(3, 1fr); }
.segmented button { border-radius: 0; }
.segmented button[aria-pressed="true"] { background: var(--ink); color: var(--paper); }
.settings-actions { display: grid; gap: .5rem; }
.segmented.two { grid-template-columns: repeat(2, 1fr); }
.drawer-scrim { position: fixed; inset: var(--topbar) 0 0; z-index: 44; background: #1118; }
.mobile-only { display: none; }

.search-filters { display: grid; grid-template-columns: 1fr 1fr; gap: .75rem; padding: 0 1.25rem; font: .72rem var(--sans); }
.search-filters label { display: grid; gap: .2rem; }
.search-filters select { min-height: 2.4rem; border: 1px solid var(--rule); background: var(--paper); color: var(--ink); }
.contents-part { display: grid; grid-template-columns: minmax(12rem, 1fr) 2fr; gap: 2rem; padding: 2rem 0; border-bottom: 1px solid var(--rule); }
.contents-part h2 { margin: .25rem 0; font-family: var(--sans); }
.contents-part ol, .part-chapters, .scholarly-index { list-style: none; margin: 0; padding: 0; }
.contents-part li a { display: grid; grid-template-columns: 2.5rem 1fr auto; gap: .6rem; padding: .35rem 0; text-decoration: none; color: var(--ink); font: .82rem var(--sans); }
.contents-part small { color: var(--muted); }
.part-chapters, .scholarly-index { display: grid; gap: 1px; background: var(--rule); border: 1px solid var(--rule); }
.part-chapters li, .scholarly-index li { background: var(--paper); }
.part-chapters a { min-height: 5rem; display: grid; grid-template-columns: 3rem 1fr auto; align-items: center; gap: 1rem; padding: 1rem; color: var(--ink); text-decoration: none; }
.part-chapters small { color: var(--muted); font: .7rem var(--sans); }
.scholarly-index a { display: flex; justify-content: space-between; gap: 1rem; padding: .7rem 1rem; color: var(--ink); text-decoration: none; }
.scholarly-index strong { font: 700 .8rem var(--sans); }
.scholarly-index span { color: var(--muted); font: .7rem var(--sans); }
.diagram { overflow: auto; margin: 2.5rem 0; text-align: center; }
.diagram, .diagram-group { display: block; }
.diagram img { min-width: min(14rem, 100%); }
.diagram-caption { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }
.anchor-alias { position: relative; scroll-margin-top: 5rem; }

:root[data-theme="dark"] .diagram img { filter: invert(.88); }
@media (prefers-color-scheme: dark) {
  :root[data-theme="system"] .diagram img { filter: invert(.88); }
}

:root[data-route-mode="core"] .route-star, :root[data-route-mode="core"] .route-terminal { opacity: .42; }
:root[data-rails="hide"] .reading-layout { grid-template-columns: minmax(0, 1fr); }
:root[data-rails="hide"] .rail { display: none; }
:root[data-rails="hide"] .reading-main { max-width: var(--measure); }

@media (max-width: 1120px) {
  .reading-layout { grid-template-columns: minmax(210px, 260px) minmax(0, 1fr); }
  .rail-right { position: fixed; z-index: 50; right: 0; top: var(--topbar); bottom: 0; width: min(340px, 88vw); max-height: none; padding: 1rem; background: var(--paper); transform: translateX(105%); transition: transform .2s ease; }
  .rail-right[data-open="true"] { transform: none; }
  .mobile-only { display: inline-flex; align-items: center; justify-content: center; }
}

@media (max-width: 760px) {
  :root { --topbar: 58px; --body-size: 17px; }
  .topbar { grid-template-columns: auto 1fr auto; padding: 0 .65rem; }
  .wordmark-kicker, .topbar-chapter, .text-button { display: none; }
  .wordmark { align-items: center; font-size: .88rem; }
  .reading-layout { display: block; padding: 0 1rem; }
  .reading-main { padding-top: 2.5rem; }
  .rail-left { position: fixed; z-index: 50; left: 0; top: var(--topbar); bottom: 0; width: min(360px, 90vw); max-height: none; padding: 1rem; background: var(--paper); transform: translateX(-105%); transition: transform .2s ease; }
  .rail-left[data-open="true"] { transform: none; }
  .chapter-header h1 { font-size: clamp(2.4rem, 12vw, 4rem); }
  .part-grid { grid-template-columns: 1fr; }
  .home-header { min-height: 70vh; }
  .home-actions { align-items: flex-start; flex-direction: column; }
  .index-entry-grid { grid-template-columns: 1fr; }
  .appendix-sections ol { columns: 1; }
  .chapter-pagination { grid-template-columns: 1fr; }
  .chapter-pagination a.next { grid-column: 1; }
  .contents-part { grid-template-columns: 1fr; gap: .5rem; }
  .contents-part li a { grid-template-columns: 2.5rem 1fr; }
  .contents-part small { grid-column: 2; }
  .part-chapters a { grid-template-columns: 2.5rem 1fr; }
  .part-chapters small { grid-column: 2; }
  .scholarly-index a { flex-direction: column; gap: .2rem; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; transition: none !important; }
}

@media print {
  .topbar, .rail, .chapter-tools, .settings-panel, .drawer-scrim, .chapter-pagination { display: none !important; }
  body { background: white; color: black; font-size: 11pt; }
  .reading-layout { display: block; padding: 0; }
  .reading-main { max-width: none; padding: 0; }
  details.proof:not([open]) > :not(summary) { display: block; }
  details.proof summary { list-style: none; }
  a { color: inherit; text-decoration: none; }
  .statement, h2, h3 { break-after: avoid; }
  .inference-rules, .math.display, table, figure { break-inside: avoid; }
}