:root {
  color-scheme: light dark;
  --page: #f7f8fa;
  --paper: #ffffff;
  --ink: #17202b;
  --text: #344054;
  --muted: #667085;
  --line: #d8dee6;
  --line-strong: #aeb8c5;
  --accent: #8f1d35;
  --accent-dark: #6f1428;
  --accent-soft: #faedf0;
  --code-bg: #111827;
  --code-text: #edf2f7;
  --note-bg: #edf5fb;
  --note-line: #3977a8;
  --warning-bg: #fff7e8;
  --warning-line: #a66316;
  --check-bg: #eef8f1;
  --check-line: #3d7a50;
  --table-stripe: #f6f8fa;
  --plot-blue: #315e7d;
  --plot-orange: #a95316;
  --plot-green: #4f7f43;
  --plot-red: #8f1d35;
  --header-bg: rgba(255, 255, 255, 0.96);
  --max: 1180px;
}

:root[data-theme="dark"] {
  --page: #0f141b;
  --paper: #171e27;
  --ink: #eef2f6;
  --text: #cbd3dc;
  --muted: #9ca9b7;
  --line: #364250;
  --line-strong: #596878;
  --accent: #ff9aae;
  --accent-dark: #ffc1cd;
  --accent-soft: #3a2029;
  --code-bg: #090d12;
  --code-text: #eef2f7;
  --note-bg: #172b3a;
  --note-line: #77b8e4;
  --warning-bg: #33291b;
  --warning-line: #e6ad58;
  --check-bg: #183025;
  --check-line: #72bd89;
  --table-stripe: #1c2530;
  --plot-blue: #78c7ff;
  --plot-orange: #ffb36b;
  --plot-green: #9ed58b;
  --plot-red: #ff8da6;
  --header-bg: rgba(15, 20, 27, 0.96);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    --page: #0f141b;
    --paper: #171e27;
    --ink: #eef2f6;
    --text: #cbd3dc;
    --muted: #9ca9b7;
    --line: #364250;
    --line-strong: #596878;
    --accent: #ff9aae;
    --accent-dark: #ffc1cd;
    --accent-soft: #3a2029;
    --code-bg: #090d12;
    --code-text: #eef2f7;
    --note-bg: #172b3a;
    --note-line: #77b8e4;
    --warning-bg: #33291b;
    --warning-line: #e6ad58;
    --check-bg: #183025;
    --check-line: #72bd89;
    --table-stripe: #1c2530;
    --plot-blue: #78c7ff;
    --plot-orange: #ffb36b;
    --plot-green: #9ed58b;
    --plot-red: #ff8da6;
    --header-bg: rgba(15, 20, 27, 0.96);
  }
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: 132px;
}

body {
  margin: 0;
  background: var(--page);
  color: var(--text);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 1rem;
  line-height: 1.72;
}

a {
  color: var(--accent-dark);
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}

a:hover {
  color: var(--accent);
}

:where(a, summary, button, textarea):focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 3px;
  border-radius: 3px;
}

:where(pre, .table-wrap):focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 3px;
}

.visually-hidden {
  position: absolute !important;
  width: 1px !important;
  height: 1px !important;
  padding: 0 !important;
  margin: -1px !important;
  overflow: hidden !important;
  clip: rect(0, 0, 0, 0) !important;
  white-space: nowrap !important;
  border: 0 !important;
}

.skip-link {
  position: fixed;
  top: 8px;
  left: 8px;
  z-index: 100;
  padding: 8px 12px;
  background: var(--ink);
  color: var(--paper);
  transform: translateY(-160%);
}

.skip-link:focus {
  transform: translateY(0);
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  border-bottom: 1px solid var(--line);
  background: var(--header-bg);
  backdrop-filter: blur(12px);
}

.header-inner {
  width: min(var(--max), calc(100% - 32px));
  min-height: 60px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.home-link {
  color: var(--ink);
  font-weight: 750;
  text-decoration: none;
}

.course-label {
  color: var(--muted);
  font-size: 0.9rem;
  font-weight: 700;
  letter-spacing: 0.03em;
}

.page-intro {
  width: min(var(--max), calc(100% - 32px));
  margin: 0 auto;
  padding: 48px 0 28px;
  border-bottom: 1px solid var(--line);
}

h1,
h2,
h3 {
  color: var(--ink);
  font-family: Georgia, "Times New Roman", serif;
  line-height: 1.25;
}

h1 {
  max-width: 820px;
  margin: 0;
  font-size: clamp(2.1rem, 5vw, 3.7rem);
  letter-spacing: -0.035em;
}

h2 {
  margin: 0 0 18px;
  font-size: clamp(1.65rem, 3vw, 2.1rem);
  letter-spacing: -0.018em;
}

h3 {
  margin: 30px 0 10px;
  font-size: 1.25rem;
}

.lead {
  max-width: 72ch;
  margin: 18px 0 0;
  color: var(--text);
  font-size: 1.1rem;
}

.book-switcher-wrap {
  position: sticky;
  top: 60px;
  z-index: 15;
  border-bottom: 1px solid var(--line);
  background: var(--header-bg);
}

.book-switcher {
  width: min(var(--max), calc(100% - 32px));
  min-height: 58px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: 10px;
}

.book-switcher > span {
  margin-right: 2px;
  color: var(--muted);
  font-size: 0.8rem;
  font-weight: 750;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.book-switcher a {
  display: inline-flex;
  min-height: 40px;
  align-items: center;
  padding: 5px 13px;
  border: 1px solid var(--line);
  border-radius: 5px;
  color: var(--text);
  font-size: 0.91rem;
  font-weight: 720;
  text-decoration: none;
}

.book-switcher a:hover {
  border-color: var(--accent);
  color: var(--accent-dark);
}

.book-switcher a[aria-current="page"] {
  border-color: var(--accent);
  background: var(--accent-soft);
  color: var(--accent-dark);
}

.book-layout {
  width: min(var(--max), calc(100% - 32px));
  margin: 34px auto 72px;
  display: grid;
  grid-template-columns: minmax(210px, 250px) minmax(0, 790px);
  justify-content: space-between;
  gap: clamp(36px, 6vw, 76px);
}

.toc {
  position: sticky;
  top: 142px;
  align-self: start;
  max-height: calc(100vh - 166px);
  overflow-y: auto;
  padding: 18px 18px 20px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: var(--paper);
}

.toc-title {
  margin: 0 0 10px;
  color: var(--ink);
  font-size: 0.76rem;
  font-weight: 850;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.toc ol {
  margin: 0;
  padding: 0;
  list-style: none;
  counter-reset: toc;
}

.toc li {
  counter-increment: toc;
}

.toc a {
  display: grid;
  grid-template-columns: 24px minmax(0, 1fr);
  gap: 3px;
  padding: 6px 0;
  color: var(--text);
  font-size: 0.88rem;
  line-height: 1.38;
  text-decoration: none;
}

.toc nav a::before {
  content: counter(toc, decimal-leading-zero);
  color: var(--muted);
  font-size: 0.72rem;
  font-variant-numeric: tabular-nums;
}

.toc a:hover {
  color: var(--accent-dark);
}

.toc-downloads {
  margin-top: 15px;
  padding-top: 13px;
  border-top: 1px solid var(--line);
}

.toc-downloads a {
  display: block;
  padding: 4px 0;
  color: var(--accent-dark);
  font-size: 0.82rem;
}

.book {
  min-width: 0;
}

.r-runtime {
  margin: 0 0 38px;
  padding: 16px 18px;
  border: 1px solid var(--note-line);
  border-left-width: 4px;
  border-radius: 0 6px 6px 0;
  background: var(--note-bg);
}

.r-runtime-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px 24px;
}

.r-runtime-title {
  margin: 0 0 3px;
  color: var(--ink);
  font-weight: 820;
}

.r-runtime-message,
.r-runtime-detail,
.r-noscript {
  max-width: 74ch;
  margin: 0;
}

.r-runtime-message {
  color: var(--text);
}

.r-runtime-detail,
.r-noscript {
  margin-top: 7px;
  color: var(--muted);
  font-size: 0.86rem;
  line-height: 1.55;
}

.r-runtime-retry,
.r-actions button {
  min-height: 40px;
  border: 1px solid var(--line-strong);
  border-radius: 4px;
  background: var(--paper);
  color: var(--ink);
  font: inherit;
  font-size: 0.82rem;
  font-weight: 760;
  line-height: 1;
  cursor: pointer;
}

.r-runtime-retry {
  flex: 0 0 auto;
  padding: 8px 13px;
}

.r-runtime-retry:hover,
.r-actions button:hover:not(:disabled) {
  border-color: var(--accent);
  color: var(--accent-dark);
}

.r-runtime-retry:disabled,
.r-actions button:disabled {
  cursor: not-allowed;
  opacity: 0.55;
}

.chapter {
  padding: 0 0 48px;
  border-bottom: 1px solid var(--line);
}

.chapter + .chapter {
  padding-top: 48px;
}

.chapter:last-child {
  border-bottom: 0;
}

.chapter-number {
  display: block;
  margin-bottom: 7px;
  color: var(--accent-dark);
  font-size: 0.76rem;
  font-weight: 850;
  letter-spacing: 0.09em;
  text-transform: uppercase;
}

.chapter > p,
.chapter > ul,
.chapter > ol,
.chapter > .prose-limit,
.chapter details > *:not(summary) {
  max-width: 70ch;
}

p {
  margin: 0 0 16px;
}

ul,
ol {
  margin: 10px 0 20px;
  padding-left: 1.45rem;
}

li + li {
  margin-top: 6px;
}

strong {
  color: var(--ink);
}

code {
  padding: 0.08em 0.3em;
  border-radius: 3px;
  background: var(--accent-soft);
  color: var(--ink);
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 0.9em;
}

.code-block {
  margin: 18px 0 22px;
  border: 1px solid #2d3748;
  border-radius: 6px;
  overflow: hidden;
  background: var(--code-bg);
}

.code-label {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  padding: 7px 13px;
  border-bottom: 1px solid #334155;
  color: #b8c3d1;
  font-size: 0.76rem;
  font-weight: 750;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.code-label.r-code-header {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) auto;
  align-items: center;
}

.code-label.r-code-header > span:nth-child(2) {
  text-align: right;
}

.r-actions {
  display: flex;
  gap: 7px;
  margin-left: 6px;
}

.r-actions button {
  min-height: 34px;
  padding: 6px 11px;
  border-color: #526176;
  background: transparent;
  color: #edf2f7;
  font-size: 0.78rem;
  letter-spacing: 0;
  text-transform: none;
}

.r-actions .r-run {
  border-color: #cbd5e1;
  background: #edf2f7;
  color: #17202b;
}

.r-actions .r-run:hover:not(:disabled) {
  border-color: #ffffff;
  background: #ffffff;
  color: #17202b;
}

pre {
  margin: 0;
  padding: 16px;
  overflow-x: auto;
  color: var(--code-text);
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 0.9rem;
  line-height: 1.62;
  tab-size: 2;
  white-space: pre;
}

pre code {
  padding: 0;
  background: transparent;
  color: inherit;
  font-size: inherit;
}

.r-example.is-enhanced > .r-code-source {
  display: none;
}

.r-editor-shell {
  background: var(--code-bg);
}

.r-editor {
  display: block;
  width: 100%;
  min-height: 10rem;
  padding: 16px;
  resize: vertical;
  overflow: auto;
  border: 0;
  border-radius: 0;
  background: var(--code-bg);
  color: var(--code-text);
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 0.9rem;
  line-height: 1.62;
  tab-size: 2;
  white-space: pre;
}

.r-editor:focus-visible {
  position: relative;
  z-index: 1;
  outline-offset: -4px;
}

.r-editor[readonly] {
  opacity: 0.8;
}

.r-editor-help {
  margin: 0;
  padding: 0 13px 11px;
  color: #9aa8b8;
  font-size: 0.75rem;
  line-height: 1.45;
}

.r-example-status {
  margin: 0;
  padding: 8px 13px;
  border-top: 1px solid #334155;
  background: var(--code-bg);
  color: #cbd5e1;
  font-size: 0.8rem;
  line-height: 1.45;
}

.r-result {
  padding: 14px;
  border-top: 1px solid var(--line);
  background: var(--paper);
  color: var(--text);
}

.r-result-title {
  margin: 0 0 9px;
  color: var(--ink);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 0.82rem;
  font-weight: 820;
  letter-spacing: 0.035em;
  line-height: 1.3;
  text-transform: uppercase;
}

.r-result-text {
  padding: 12px 13px;
  border: 1px solid var(--line);
  border-left: 3px solid var(--line-strong);
  border-radius: 4px;
  background: var(--table-stripe);
  color: var(--text);
  font-size: 0.84rem;
  line-height: 1.55;
  white-space: pre-wrap;
  overflow-wrap: anywhere;
}

.r-example.has-r-error .r-result-text {
  border-left-color: var(--plot-red);
}

.r-result-plots:empty {
  display: none;
}

.r-result-plots {
  display: grid;
  gap: 12px;
  margin-top: 12px;
}

.r-plot-frame {
  margin: 0;
  padding: 10px;
  border: 1px solid var(--line);
  border-radius: 5px;
  background: #ffffff;
}

.r-plot-frame canvas {
  display: block;
  width: min(100%, 760px);
  height: auto;
  margin: 0 auto;
}

.r-plot-frame figcaption {
  margin-top: 8px;
  color: #4b5563;
  font-size: 0.76rem;
  line-height: 1.4;
  text-align: center;
}

.output {
  margin: -12px 0 22px;
  padding: 12px 15px;
  border-left: 3px solid var(--line-strong);
  background: var(--table-stripe);
  color: var(--text);
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 0.86rem;
  white-space: pre-wrap;
}

.output-label {
  display: block;
  margin-bottom: 5px;
  color: var(--ink);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 0.77rem;
  font-weight: 820;
  letter-spacing: 0.035em;
  text-transform: uppercase;
}

.folder-tree {
  margin: 18px 0 22px;
  padding: 12px 15px;
  border-left: 3px solid var(--line-strong);
  background: var(--table-stripe);
  color: var(--text);
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 0.86rem;
  white-space: pre-wrap;
}

.callout {
  max-width: 72ch;
  margin: 20px 0;
  padding: 15px 17px;
  border-left: 4px solid;
  border-radius: 0 5px 5px 0;
}

.callout p:last-child,
.callout ul:last-child {
  margin-bottom: 0;
}

.callout-title {
  margin: 0 0 5px;
  color: var(--ink);
  font-weight: 820;
}

.note {
  border-color: var(--note-line);
  background: var(--note-bg);
}

.warning {
  border-color: var(--warning-line);
  background: var(--warning-bg);
}

.check {
  border-color: var(--check-line);
  background: var(--check-bg);
}

.definition-list {
  display: grid;
  grid-template-columns: minmax(120px, 0.32fr) minmax(0, 1fr);
  gap: 0;
  margin: 20px 0;
  border: 1px solid var(--line);
  border-radius: 6px;
  overflow: hidden;
}

.definition-list dt,
.definition-list dd {
  margin: 0;
  padding: 10px 13px;
  border-bottom: 1px solid var(--line);
}

.definition-list dt {
  background: var(--table-stripe);
  color: var(--ink);
  font-weight: 780;
}

.definition-list dd {
  background: var(--paper);
}

.definition-list dt:last-of-type,
.definition-list dd:last-of-type {
  border-bottom: 0;
}

.table-wrap {
  width: 100%;
  margin: 20px 0 24px;
  overflow-x: auto;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: var(--paper);
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
  line-height: 1.48;
}

caption {
  padding: 11px 13px;
  border-bottom: 1px solid var(--line);
  color: var(--ink);
  font-weight: 760;
  text-align: left;
}

th,
td {
  padding: 9px 12px;
  border-bottom: 1px solid var(--line);
  text-align: left;
  vertical-align: top;
  white-space: nowrap;
}

th {
  background: var(--table-stripe);
  color: var(--ink);
  font-weight: 760;
}

tbody tr:last-child td,
tbody tr:last-child th {
  border-bottom: 0;
}

.diagram {
  width: 100%;
  margin: 24px 0;
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: var(--paper);
}

.diagram svg {
  display: block;
  width: 100%;
  height: auto;
}

.diagram figcaption {
  max-width: 74ch;
  margin-top: 12px;
  padding-top: 11px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 0.85rem;
}

.plain-diagram {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  align-items: stretch;
  gap: 12px;
  margin: 22px 0;
}

.diagram-step {
  position: relative;
  padding: 15px;
  border: 1px solid var(--line);
  border-top: 3px solid var(--accent);
  border-radius: 5px;
  background: var(--paper);
}

.diagram-step strong {
  display: block;
  margin-bottom: 5px;
}

.diagram-step p {
  margin: 0;
  color: var(--muted);
  font-size: 0.86rem;
}

.formula {
  max-width: 72ch;
  margin: 18px 0;
  padding: 14px 16px;
  border: 1px solid var(--line);
  border-radius: 5px;
  background: var(--paper);
  color: var(--ink);
  font-family: Georgia, "Times New Roman", serif;
  font-size: 1.05rem;
  overflow-x: auto;
}

details {
  max-width: 72ch;
  margin: 16px 0;
  border: 1px solid var(--line);
  border-radius: 5px;
  background: var(--paper);
}

summary {
  min-height: 44px;
  padding: 10px 14px;
  color: var(--ink);
  font-weight: 760;
  cursor: pointer;
}

details[open] summary {
  border-bottom: 1px solid var(--line);
}

details > :not(summary) {
  margin-left: 15px;
  margin-right: 15px;
}

details > :last-child {
  margin-bottom: 15px;
}

.chapter-nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 12px;
  margin-top: 34px;
  padding-top: 20px;
  border-top: 1px dashed var(--line-strong);
}

.chapter-nav a {
  font-weight: 720;
}

.source-list {
  font-size: 0.92rem;
}

.page-footer {
  border-top: 1px solid var(--line);
  background: var(--paper);
}

.footer-inner {
  width: min(var(--max), calc(100% - 32px));
  margin: 0 auto;
  padding: 26px 0 34px;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 12px 24px;
  color: var(--muted);
  font-size: 0.86rem;
}

.footer-inner p {
  margin: 0;
}

@media (max-width: 880px) {
  html {
    scroll-padding-top: 132px;
  }

  .book-layout {
    grid-template-columns: 1fr;
    gap: 28px;
  }

  .toc {
    position: static;
    max-height: none;
  }

  .toc ol {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    column-gap: 24px;
  }
}

@media (max-width: 620px) {
  .header-inner,
  .page-intro,
  .book-switcher,
  .book-layout,
  .footer-inner {
    width: min(100% - 24px, var(--max));
  }

  .header-inner {
    min-height: 54px;
  }

  .course-label {
    display: none;
  }

  .page-intro {
    padding-top: 34px;
  }

  .book-switcher-wrap {
    top: 54px;
  }

  .book-switcher {
    min-height: 68px;
    gap: 7px;
  }

  .book-switcher > span {
    display: none;
  }

  .book-switcher a {
    flex: 1 1 0;
    justify-content: center;
    padding-inline: 8px;
    font-size: 0.84rem;
    line-height: 1.25;
    text-align: center;
  }

  .book-layout {
    margin-top: 24px;
  }

  .toc ol,
  .plain-diagram {
    grid-template-columns: 1fr;
  }

  .definition-list {
    grid-template-columns: 1fr;
  }

  .definition-list dt,
  .definition-list dd {
    border-bottom: 1px solid var(--line);
  }

  .definition-list dd:last-of-type {
    border-bottom: 0;
  }

  h1 {
    font-size: 2.15rem;
  }

  pre {
    font-size: 0.82rem;
  }

  .r-runtime-row {
    align-items: stretch;
    flex-direction: column;
  }

  .r-runtime-retry {
    align-self: flex-start;
    min-height: 44px;
  }

  .code-label.r-code-header {
    grid-template-columns: auto minmax(0, 1fr);
  }

  .r-actions {
    grid-column: 1 / -1;
    margin: 3px 0 0;
  }

  .r-actions button {
    min-height: 44px;
    flex: 1 1 0;
  }

  .r-editor {
    font-size: 16px;
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
}

@media print {
  :root,
  :root[data-theme="dark"] {
    --page: #ffffff;
    --paper: #ffffff;
    --ink: #000000;
    --text: #1f2933;
    --muted: #4b5563;
    --line: #b9c0c7;
    --line-strong: #7a828a;
    --accent: #111111;
    --accent-dark: #111111;
    --accent-soft: #f2f3f5;
    --table-stripe: #f2f3f5;
    --code-bg: #ffffff;
    --code-text: #111111;
    --note-bg: #f7f7f7;
    --note-line: #555555;
    --warning-bg: #f7f7f7;
    --warning-line: #555555;
    --check-bg: #f7f7f7;
    --check-line: #555555;
  }

  body {
    background: #ffffff;
    color: #1f2933;
    font-size: 10.5pt;
  }

  .site-header,
  .book-switcher-wrap,
  .toc,
  .page-footer,
  .skip-link,
  .r-runtime,
  .r-actions,
  .r-editor-shell,
  .r-example-status {
    display: none !important;
  }

  .page-intro,
  .book-layout {
    width: 100%;
  }

  .page-intro {
    padding: 0 0 18pt;
  }

  .book-layout {
    display: block;
    margin: 22pt 0 0;
  }

  .chapter {
    break-before: page;
  }

  .chapter:first-child {
    break-before: auto;
  }

  .code-block,
  .callout,
  .table-wrap,
  .diagram,
  details {
    break-inside: avoid;
  }

  .code-block {
    border-color: #333333;
    background: #ffffff;
  }

  .code-label {
    border-color: #777777;
    color: #111111;
  }

  .r-example.is-enhanced > .r-code-source {
    display: block !important;
  }

  .r-result,
  .r-plot-frame {
    break-inside: avoid;
  }

  pre {
    color: #111111;
    white-space: pre-wrap;
  }

  .table-wrap {
    overflow: visible;
  }

  th,
  td {
    white-space: normal;
  }

  a {
    color: #000000;
  }

  details:not([open]) > :not(summary) {
    display: block;
  }
}