:root {
  --paper: #fcfcfe;
  --surface: #f3f2fb;
  --raised: #ffffff;
  --ink: #1d1d22;
  --muted: #5b5f6e;
  --faint: #8b8fa0;
  --rule: #e3e2ee;
  --accent: #5148cf;
  --accent-soft: #eeedfc;
  --tip: #1f7a52;
  --tip-soft: #e6f4ec;
  --mark: #fff3c4;
  --code-bg: #f1f0f8;
  --shadow: 0 1px 2px rgba(29, 29, 34, 0.06), 0 6px 18px rgba(81, 72, 207, 0.07);
  --sans: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", sans-serif;
  --serif: "Charter", "Iowan Old Style", "Georgia", "Songti SC", serif;
  --mono: "SF Mono", Menlo, Consolas, monospace;
  color-scheme: light;
}

:root[data-theme="dark"] {
  --paper: #15151b;
  --surface: #1d1d26;
  --raised: #23232e;
  --ink: #e9e8f2;
  --muted: #a6a8b8;
  --faint: #7e8092;
  --rule: #33334a;
  --accent: #aaa4f7;
  --accent-soft: #2a2850;
  --tip: #6fd3a2;
  --tip-soft: #1b3328;
  --mark: #4a4120;
  --code-bg: #262533;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.3), 0 6px 18px rgba(0, 0, 0, 0.25);
  color-scheme: dark;
}

* {
  box-sizing: border-box;
}

html {
  scroll-padding-top: 4.5rem;
}

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--accent);
  text-decoration-thickness: 1px;
  text-underline-offset: 2px;
}

a:focus-visible,
button:focus-visible,
input:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 0.6rem 1.25rem;
  background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: saturate(1.4) blur(10px);
  border-bottom: 1px solid var(--rule);
}

@font-face {
  font-family: "LemmaLoom Brand";
  src: url("Ubuntu-B.ttf") format("truetype");
  font-weight: 700;
  font-display: swap;
}

.brand {
  display: inline-flex;
  align-items: baseline;
  gap: 0.5rem;
  color: var(--ink);
  text-decoration: none;
  white-space: nowrap;
}

.wordmark {
  font-family: "LemmaLoom Brand", var(--sans);
  font-weight: 700;
  letter-spacing: -0.01em;
  color: var(--ink);
}

.wordmark .lemma {
  color: var(--accent);
}

.brand .wordmark {
  font-size: 1.12rem;
}

.brand .guide-name {
  color: var(--muted);
  font-weight: 550;
}

.menu-toggle {
  display: none;
}

.search {
  position: relative;
  flex: 1 1 18rem;
  max-width: 26rem;
  margin-left: auto;
}

.search input {
  width: 100%;
  padding: 0.4rem 0.75rem;
  border: 1px solid var(--rule);
  border-radius: 7px;
  background: var(--raised);
  color: var(--ink);
  font: inherit;
  font-size: 0.92rem;
}

.results {
  position: absolute;
  top: calc(100% + 6px);
  left: 0;
  right: 0;
  max-height: 60vh;
  overflow-y: auto;
  background: var(--raised);
  border: 1px solid var(--rule);
  border-radius: 9px;
  box-shadow: var(--shadow);
}

.results a {
  display: block;
  padding: 0.55rem 0.8rem;
  color: var(--ink);
  text-decoration: none;
  border-bottom: 1px solid var(--rule);
}

.results a:last-child {
  border-bottom: 0;
}

.results a:hover,
.results a.active {
  background: var(--accent-soft);
}

.results .where {
  display: block;
  color: var(--muted);
  font-size: 0.8rem;
}

.results .empty {
  padding: 0.6rem 0.8rem;
  color: var(--muted);
  font-size: 0.9rem;
}

.languages {
  display: flex;
  gap: 0.15rem;
  font-size: 0.85rem;
}

.languages a {
  padding: 0.2rem 0.5rem;
  border-radius: 6px;
  color: var(--muted);
  text-decoration: none;
}

.languages a[aria-current] {
  background: var(--surface);
  color: var(--ink);
}

.theme-toggle,
.pdf-link,
.menu-toggle {
  padding: 0.25rem 0.6rem;
  border: 1px solid var(--rule);
  border-radius: 6px;
  background: transparent;
  color: var(--muted);
  font: inherit;
  font-size: 0.85rem;
  text-decoration: none;
  cursor: pointer;
  white-space: nowrap;
}

.layout {
  display: grid;
  grid-template-columns: 16.5rem minmax(0, 1fr) 14rem;
  gap: 2.5rem;
  max-width: 88rem;
  margin: 0 auto;
  padding: 0 1.25rem;
}

.sidebar {
  position: sticky;
  top: 3.6rem;
  align-self: start;
  max-height: calc(100vh - 3.6rem);
  overflow-y: auto;
  padding: 1.5rem 0.5rem 2rem 0;
  font-size: 0.9rem;
}

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

.sidebar li {
  counter-increment: chapter;
}

.sidebar li.unnumbered {
  counter-increment: none;
}

.sidebar li.unnumbered a::before {
  content: "";
  min-width: 0;
}

.sidebar a {
  display: flex;
  gap: 0.55rem;
  padding: 0.28rem 0.6rem;
  border-radius: 6px;
  color: var(--muted);
  text-decoration: none;
  line-height: 1.35;
}

.sidebar a::before {
  content: counter(chapter);
  min-width: 1.3rem;
  color: var(--faint);
  font-variant-numeric: tabular-nums;
}

.sidebar a:hover {
  color: var(--ink);
  background: var(--surface);
}

.sidebar li.current a {
  color: var(--ink);
  background: var(--accent-soft);
  font-weight: 600;
}

.content {
  min-width: 0;
  padding: 2.25rem 0 4rem;
}

article {
  max-width: 44rem;
}

article h1 {
  margin: 0 0 1.5rem;
  font-size: 2.25rem;
  line-height: 1.15;
  letter-spacing: -0.02em;
  text-wrap: balance;
}

article h2 {
  margin: 2.6rem 0 0.8rem;
  padding-top: 1.2rem;
  border-top: 1px solid var(--rule);
  font-size: 1.45rem;
  line-height: 1.25;
  letter-spacing: -0.01em;
  text-wrap: balance;
}

article h3 {
  margin: 2rem 0 0.6rem;
  font-size: 1.15rem;
  line-height: 1.3;
}

article h4 {
  margin: 1.6rem 0 0.4rem;
  font-size: 1rem;
}

article h2 .anchor,
article h3 .anchor,
article h4 .anchor {
  margin-left: 0.4rem;
  color: var(--faint);
  text-decoration: none;
  opacity: 0;
}

article h2:hover .anchor,
article h3:hover .anchor,
article h4:hover .anchor {
  opacity: 1;
}

article p,
article li {
  font-family: var(--serif);
  font-size: 1.06rem;
  line-height: 1.68;
}

article :lang(zh-Hans) p,
html[lang="zh-Hans"] article p,
html[lang="zh-Hans"] article li {
  font-family: var(--sans);
  font-size: 1.02rem;
  line-height: 1.85;
}

article ol,
article ul {
  padding-left: 1.5rem;
}

article li {
  margin: 0.3rem 0;
}

article li > p {
  margin: 0.3rem 0;
}

strong.ui {
  font-family: var(--sans);
  font-size: 0.94em;
  font-weight: 600;
  white-space: nowrap;
}

code {
  padding: 0.08rem 0.32rem;
  border-radius: 4px;
  background: var(--code-bg);
  font-family: var(--mono);
  font-size: 0.86em;
}

pre {
  overflow-x: auto;
  padding: 0.9rem 1rem;
  border-radius: 8px;
  background: var(--code-bg);
  font-size: 0.88rem;
  line-height: 1.5;
}

pre code {
  padding: 0;
  background: none;
  font-size: inherit;
}

.callout {
  margin: 1.5rem 0;
  padding: 0.75rem 1rem 0.85rem;
  border-left: 3px solid var(--accent);
  border-radius: 0 8px 8px 0;
  background: var(--accent-soft);
}

.callout.tip {
  border-left-color: var(--tip);
  background: var(--tip-soft);
}

.callout.tip .callout-title {
  color: var(--tip);
}

.callout-title {
  margin: 0 0 0.25rem;
  color: var(--accent);
  font-family: var(--sans) !important;
  font-size: 0.82rem !important;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

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

.math-display {
  overflow-x: auto;
  margin: 1.2rem 0;
  text-align: center;
}

.math svg {
  overflow: visible;
}

.math-display svg {
  max-width: 100%;
}

.math-inline svg {
  display: inline-block;
}

.math-failed {
  color: #b42318;
}

.table-wrap {
  overflow-x: auto;
  margin: 1.4rem 0;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95rem;
}

th,
td {
  padding: 0.5rem 0.7rem;
  border-bottom: 1px solid var(--rule);
  text-align: left;
  vertical-align: top;
}

th {
  color: var(--muted);
  font-size: 0.82rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  border-bottom-width: 2px;
}

td {
  font-variant-numeric: tabular-nums;
}

figure.shot {
  margin: 1.8rem 0;
}

figure.shot img {
  display: block;
  max-width: 100%;
  height: auto;
  margin: 0 auto;
  border-radius: 10px;
  box-shadow: var(--shadow);
}

.shot-dark {
  display: none !important;
}

:root[data-theme="dark"] .shot-light {
  display: none !important;
}

:root[data-theme="dark"] .shot-dark {
  display: block !important;
}

.shot-pending {
  display: grid;
  place-items: center;
  min-height: 12rem;
  border: 1px dashed var(--rule);
  border-radius: 10px;
  color: var(--faint);
  font-size: 0.9rem;
}

figcaption {
  margin-top: 0.7rem;
  color: var(--muted);
  font-size: 0.9rem;
  line-height: 1.5;
  text-align: center;
}

blockquote {
  margin: 1.2rem 0;
  padding-left: 1rem;
  border-left: 3px solid var(--rule);
  color: var(--muted);
}

.pager {
  display: flex;
  gap: 1rem;
  justify-content: space-between;
  max-width: 44rem;
  margin-top: 3.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--rule);
}

.pager a {
  display: flex;
  flex-direction: column;
  max-width: 48%;
  color: var(--ink);
  text-decoration: none;
  font-weight: 600;
}

.pager a span {
  color: var(--muted);
  font-size: 0.8rem;
  font-weight: 400;
}

.pager .next {
  margin-left: auto;
  text-align: right;
}

.page-toc {
  position: sticky;
  top: 3.6rem;
  align-self: start;
  max-height: calc(100vh - 3.6rem);
  overflow-y: auto;
  padding: 2.4rem 0 2rem;
  font-size: 0.84rem;
}

.page-toc p {
  margin: 0 0 0.5rem;
  color: var(--faint);
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.page-toc ul {
  list-style: none;
  margin: 0;
  padding: 0;
  border-left: 1px solid var(--rule);
}

.page-toc li a {
  display: block;
  padding: 0.2rem 0 0.2rem 0.75rem;
  color: var(--muted);
  text-decoration: none;
  line-height: 1.35;
}

.page-toc li.level-3 a {
  padding-left: 1.5rem;
  font-size: 0.8rem;
}

.page-toc li a.active {
  margin-left: -1px;
  border-left: 2px solid var(--accent);
  color: var(--ink);
}

.chapter-list {
  list-style: none;
  padding-left: 0;
  counter-reset: chapter;
}

.chapter-list li {
  position: relative;
  margin: 0.9rem 0;
  padding-left: 2.2rem;
  counter-increment: chapter;
}

.chapter-list li::before {
  content: counter(chapter);
  position: absolute;
  left: 0;
  top: 0.05rem;
  color: var(--accent);
  font-family: var(--sans);
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}

.chapter-list li.unnumbered {
  counter-increment: none;
}

.chapter-list li.unnumbered::before {
  content: "";
}

.chapter-list a {
  font-family: var(--sans);
  font-weight: 600;
}

.chapter-list p {
  margin: 0.15rem 0 0;
  color: var(--muted);
  font-size: 0.95rem;
}

@media (max-width: 1180px) {
  .layout {
    grid-template-columns: 15rem minmax(0, 1fr);
  }

  .page-toc {
    display: none;
  }
}

@media (max-width: 820px) {
  .layout {
    display: block;
    padding: 0 16px;
  }

  .menu-toggle {
    display: inline-block;
  }

  .sidebar {
    display: none;
    position: static;
    max-height: none;
    padding: 1rem 0;
    border-bottom: 1px solid var(--rule);
  }

  body.menu-open .sidebar {
    display: block;
  }

  .topbar {
    flex-wrap: wrap;
    gap: 0.5rem;
    padding: 0.5rem 16px;
  }

  .search {
    order: 5;
    flex-basis: 100%;
    max-width: none;
  }

  .pdf-link {
    display: none;
  }

  article h1 {
    font-size: 1.8rem;
  }
}

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

@media print {
  .topbar,
  .sidebar,
  .page-toc,
  .pager {
    display: none;
  }

  .layout {
    display: block;
  }
}

.hero {
  position: relative;
  margin: -0.5rem 0 2.5rem;
  padding-top: 0.5rem;
}

.hero .mosaic {
  margin: 0 0 1.6rem;
  border-radius: 14px;
  overflow: hidden;
  -webkit-mask-image: linear-gradient(to bottom, #000 55%, transparent);
  mask-image: linear-gradient(to bottom, #000 55%, transparent);
}

.hero .mosaic img {
  display: block;
  width: 100%;
  height: auto;
}

.hero-title {
  margin: 0;
  font-size: clamp(2.4rem, 6vw, 3.4rem);
  line-height: 1.05;
}

.hero-guide,
.hero-meta {
  font-family: var(--sans);
}

.hero-guide {
  margin: 0.35rem 0 0;
  font-size: 1.5rem;
  font-weight: 650;
}

.hero-meta {
  margin: 0.4rem 0 0;
  color: var(--muted);
}

.epigraph {
  margin: 2rem 0 0;
  padding: 0 0 0 1rem;
  border-left: 3px solid var(--accent);
}

.epigraph p {
  margin: 0;
  font-family: var(--serif);
  font-size: 1.15rem;
  font-style: italic;
}

.epigraph .translation {
  margin-top: 0.3rem;
  color: var(--muted);
  font-size: 1rem;
}

.epigraph cite {
  display: block;
  margin-top: 0.4rem;
  color: var(--muted);
  font-size: 0.85rem;
  font-style: normal;
}

.site-footer {
  margin: 3rem 0 1rem;
  padding-top: 1rem;
  border-top: 1px solid var(--rule);
  color: var(--faint);
  font-size: 0.82rem;
}

article h2::before {
  content: "";
  display: inline-block;
  width: 0.55rem;
  height: 0.55rem;
  margin-right: 0.55rem;
  border-radius: 2px;
  background: var(--accent);
  vertical-align: 0.15em;
}

.hero-downloads {
  margin: 0.9rem 0 0;
  font-family: var(--sans);
  font-size: 0.92rem;
  color: var(--muted);
}

.hero-downloads a {
  font-weight: 600;
}

.hero-downloads .sep {
  margin: 0 0.55rem;
  color: var(--faint);
}