:root {
  --paper: #f7f5f0;
  --surface: #fffefb;
  --ink: #20231f;
  --muted: #686b64;
  --line: #d8d5cd;
  --accent: #b43a2f;
  --accent-strong: #8f2c24;
  --forest: #315d4b;
  --amber: #b7791f;
  --header-height: 68px;
  --sidebar-width: 286px;
  --content-width: 760px;
  --font-sans: Inter, ui-sans-serif, system-ui, -apple-system, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-serif: "Songti SC", SimSun, "Noto Serif CJK SC", Georgia, serif;
  color-scheme: light;
}

html.dark {
  --paper: #171816;
  --surface: #1e201d;
  --ink: #efeee8;
  --muted: #aaa9a2;
  --line: #373a35;
  --accent: #e16a5f;
  --accent-strong: #f08378;
  --forest: #7fb49d;
  --amber: #d4a14d;
  color-scheme: dark;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: calc(var(--header-height) + 24px); scrollbar-gutter: stable; }
body { margin: 0; background: var(--paper); color: var(--ink); font: 16px/1.75 var(--font-sans); -webkit-font-smoothing: antialiased; }
a { color: inherit; text-decoration: none; }
a:hover { color: var(--accent); }
button, input { font: inherit; }
button { color: inherit; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; }

.site-header { position: sticky; top: 0; z-index: 60; height: var(--header-height); border-bottom: 1px solid color-mix(in srgb, var(--line) 76%, transparent); background: color-mix(in srgb, var(--paper) 94%, transparent); backdrop-filter: blur(16px); }
.site-header-inner { display: flex; align-items: center; gap: 20px; width: min(1440px, 100%); height: 100%; margin: 0 auto; padding: 0 28px; }
.site-brand { display: inline-flex; align-items: center; gap: 10px; flex: none; color: var(--ink); font-size: 15px; font-weight: 700; }
.site-brand:hover { color: var(--ink); }
.brand-mark { display: grid; width: 31px; height: 31px; place-items: center; background: var(--accent); color: #fff; font: 700 16px/1 var(--font-serif); }
.site-search { position: relative; display: flex; align-items: center; width: min(500px, 42vw); margin-left: auto; }
.site-search > svg { position: absolute; left: 13px; width: 18px; height: 18px; fill: none; stroke: var(--muted); stroke-width: 1.8; }
.site-search input { width: 100%; height: 40px; padding: 0 66px 0 40px; border: 1px solid var(--line); border-radius: 4px; background: var(--surface); color: var(--ink); }
.site-search input::placeholder { color: var(--muted); }
.site-search button { position: absolute; right: 5px; height: 30px; padding: 0 10px; border: 0; background: transparent; color: var(--muted); cursor: pointer; font-size: 13px; }
.header-actions { display: flex; align-items: center; gap: 2px; }
.icon-action { display: grid; width: 40px; height: 40px; place-items: center; border: 0; border-radius: 4px; background: transparent; color: var(--muted); cursor: pointer; }
.icon-action:hover { background: var(--surface); color: var(--ink); }
.icon-action svg { width: 20px; height: 20px; fill: none; stroke: currentColor; stroke-linecap: round; stroke-linejoin: round; stroke-width: 1.8; }
.github-link svg { fill: currentColor; stroke: none; }
.language-switcher { position: relative; }
.language-menu { position: absolute; top: 46px; right: 0; width: 202px; padding: 6px; border: 1px solid var(--line); border-radius: 6px; background: var(--surface); box-shadow: 0 18px 45px rgba(20, 20, 18, .16); }
.language-menu a { display: flex; justify-content: space-between; padding: 8px 10px; border-radius: 3px; color: var(--muted); font-size: 14px; }
.language-menu a:hover, .language-menu a[aria-current="page"] { background: var(--paper); color: var(--ink); }
.language-menu small { color: var(--muted); }
.chapter-menu-button { display: none; }

.home-hero { min-height: min(620px, calc(100vh - var(--header-height))); width: min(1180px, calc(100% - 48px)); margin: 0 auto; padding: clamp(72px, 10vh, 122px) 0 72px; border-bottom: 1px solid var(--line); }
.home-hero-kicker, .section-label, .chapter-number { margin: 0 0 18px; color: var(--accent); font-size: 12px; font-weight: 800; letter-spacing: 0; text-transform: uppercase; }
.home-hero h1 { max-width: 780px; margin: 0; font: 800 clamp(48px, 7.2vw, 96px)/1.05 var(--font-serif); letter-spacing: 0; }
.home-lede { max-width: 760px; margin: 30px 0 0; color: var(--muted); font: 400 clamp(20px, 2.1vw, 28px)/1.65 var(--font-serif); }
.home-facts { display: flex; flex-wrap: wrap; gap: 12px 28px; margin-top: 34px; color: var(--muted); font-size: 14px; }
.home-facts span { position: relative; }
.home-facts span + span::before { position: absolute; left: -16px; color: var(--line); content: "/"; }
.home-facts strong { color: var(--ink); font-size: 18px; }
.home-actions { display: flex; align-items: center; gap: 28px; margin-top: 42px; }
.primary-link { display: inline-flex; align-items: center; justify-content: center; min-height: 44px; padding: 0 22px; border: 1px solid var(--accent); border-radius: 4px; background: var(--accent); color: #fff; font-weight: 700; }
.primary-link:hover { background: var(--accent-strong); color: #fff; }
.text-link { padding: 10px 0; border-bottom: 1px solid var(--line); font-weight: 700; }

.home-principle { display: grid; grid-template-columns: minmax(260px, .8fr) minmax(320px, 1.2fr); gap: 80px; width: min(1180px, calc(100% - 48px)); margin: 0 auto; padding: 84px 0; border-bottom: 1px solid var(--line); }
.home-principle h2, .home-reading-note h2 { margin: 0; font: 700 34px/1.3 var(--font-serif); letter-spacing: 0; }
.home-principle > p { max-width: 690px; margin: 33px 0 0; color: var(--muted); font-size: 18px; line-height: 1.9; }

.home-directory { width: min(1180px, calc(100% - 48px)); margin: 0 auto; padding: 88px 0 100px; }
.home-directory-head { display: flex; align-items: end; justify-content: space-between; gap: 30px; margin-bottom: 30px; }
.home-directory-head h2 { margin: 0; font: 750 clamp(30px, 4vw, 50px)/1.2 var(--font-serif); letter-spacing: 0; }
.directory-search { flex: none; padding: 9px 0; border-bottom: 1px solid var(--line); color: var(--muted); font-size: 14px; font-weight: 700; }
.chapter-directory { border-top: 2px solid var(--ink); }
.chapter-row { display: grid; grid-template-columns: 64px minmax(0, 1fr) 28px; align-items: center; gap: 18px; min-height: 76px; border-bottom: 1px solid var(--line); transition: background .16s ease, color .16s ease; }
.chapter-row:hover { padding-left: 8px; background: var(--surface); color: var(--accent); }
.chapter-row-number { color: var(--accent); font: 700 15px/1 var(--font-sans); font-variant-numeric: tabular-nums; }
.chapter-row-copy { display: grid; grid-template-columns: minmax(220px, .65fr) minmax(340px, 1.35fr); align-items: center; gap: 30px; min-width: 0; }
.chapter-row-copy strong { color: var(--ink); font: 700 20px/1.4 var(--font-serif); }
.chapter-row-copy small { overflow: hidden; color: var(--muted); font-size: 14px; text-overflow: ellipsis; white-space: nowrap; }
.chapter-row-arrow { color: var(--muted); font-size: 17px; }
.home-reading-note { display: grid; grid-template-columns: 190px 1fr 1fr; gap: 46px; width: min(1180px, calc(100% - 48px)); margin: 0 auto; padding: 72px 0 86px; border-top: 1px solid var(--line); }
.home-reading-note p:last-child { max-width: 520px; margin: 4px 0 0; color: var(--muted); }

.chapter-shell { display: grid; grid-template-columns: var(--sidebar-width) minmax(0, 1fr); min-height: calc(100vh - var(--header-height)); }
.chapter-sidebar { position: sticky; top: var(--header-height); align-self: start; height: calc(100vh - var(--header-height)); padding: 26px 20px 48px 28px; overflow-y: auto; border-right: 1px solid var(--line); background: color-mix(in srgb, var(--paper) 96%, var(--surface)); }
.chapter-sidebar-head { display: flex; align-items: center; justify-content: space-between; margin-bottom: 14px; color: var(--muted); font-size: 12px; text-transform: uppercase; }
.drawer-close { display: none; }
.chapter-sidebar nav { display: flex; flex-direction: column; }
.chapter-sidebar nav a { display: grid; grid-template-columns: 28px 1fr; gap: 9px; padding: 7px 8px; border-left: 2px solid transparent; color: var(--muted); font-size: 13px; line-height: 1.45; }
.chapter-sidebar nav a span { color: var(--muted); font-size: 11px; font-variant-numeric: tabular-nums; }
.chapter-sidebar nav a strong { font-weight: 600; }
.chapter-sidebar nav a:hover { color: var(--ink); }
.chapter-sidebar nav a[aria-current="page"] { border-left-color: var(--accent); background: var(--surface); color: var(--ink); }
.chapter-main { min-width: 0; padding: 0 clamp(28px, 6vw, 104px) 100px; }
.chapter-article { max-width: var(--content-width); margin: 0 auto; }
.breadcrumbs { display: flex; align-items: center; gap: 9px; padding: 28px 0 50px; color: var(--muted); font-size: 13px; }
.breadcrumbs a { border-bottom: 1px solid var(--line); }
.chapter-intro { padding-bottom: 46px; border-bottom: 1px solid var(--line); }
.chapter-intro h1 { margin: 0; font: 800 clamp(38px, 5vw, 64px)/1.18 var(--font-serif); letter-spacing: 0; overflow-wrap: anywhere; }
.chapter-summary { margin: 24px 0 0; color: var(--forest); font-size: 19px; font-weight: 650; line-height: 1.75; }
.chapter-intro-copy { margin-top: 28px; color: var(--muted); font-family: var(--font-serif); font-size: 17px; }
.chapter-intro-copy p { margin: 10px 0; }
.entry-toc { margin: 40px 0 54px; padding: 26px 30px 28px; border-left: 3px solid var(--accent); background: var(--surface); }
.entry-toc > p { margin: 0 0 12px; color: var(--muted); font-size: 12px; font-weight: 800; text-transform: uppercase; }
.entry-toc ol { columns: 2; column-gap: 38px; margin: 0; padding: 0; list-style: none; }
.entry-toc li { break-inside: avoid; }
.entry-toc a { display: grid; grid-template-columns: 28px 1fr; gap: 8px; padding: 5px 0; color: var(--muted); font-size: 14px; line-height: 1.5; }
.entry-toc a:hover { color: var(--accent); }
.entry-toc a span { color: var(--accent); font-size: 11px; font-variant-numeric: tabular-nums; }
.chapter-entry { padding: 42px 0 34px; border-top: 1px solid var(--line); }
.chapter-entry:first-child { border-top: 2px solid var(--ink); }
.chapter-entry h2 { margin: 0 0 22px; font: 750 27px/1.45 var(--font-serif); letter-spacing: 0; overflow-wrap: anywhere; }
.chapter-entry h2 a:hover { color: var(--accent); }
.entry-body { color: color-mix(in srgb, var(--ink) 89%, var(--muted)); font-family: var(--font-serif); font-size: 16px; }
.entry-body p, .entry-body ul, .entry-body ol, .entry-body blockquote { margin: 12px 0; }
.entry-body ul, .entry-body ol { padding-left: 24px; }
.entry-body li { margin: 8px 0; }
.entry-body strong { color: var(--ink); font-family: var(--font-sans); font-weight: 750; }
.entry-body a { color: var(--forest); text-decoration: underline; text-decoration-color: color-mix(in srgb, var(--forest) 40%, transparent); text-underline-offset: 3px; overflow-wrap: anywhere; }
.entry-body blockquote { padding: 2px 0 2px 18px; border-left: 2px solid var(--amber); color: var(--muted); }
.entry-body code { padding: 2px 5px; border-radius: 3px; background: var(--surface); font: 13px/1.5 ui-monospace, monospace; }
.chapter-prev-next { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; margin-top: 44px; padding-top: 34px; border-top: 2px solid var(--ink); }
.chapter-prev-next a { min-height: 98px; padding: 18px; border: 1px solid var(--line); background: var(--surface); }
.chapter-prev-next a:hover { border-color: var(--accent); }
.chapter-prev-next small { display: block; margin-bottom: 8px; color: var(--muted); font-size: 12px; }
.chapter-prev-next strong { font: 700 16px/1.5 var(--font-serif); }
.chapter-prev-next strong span { color: var(--accent); font: 700 12px/1 var(--font-sans); }
.chapter-next { text-align: right; }
.back-directory { display: block; margin-top: 24px; color: var(--muted); text-align: center; text-decoration: underline; text-underline-offset: 4px; }

.site-footer { display: grid; grid-template-columns: .7fr 1.3fr; gap: 70px; padding: 46px max(28px, calc((100vw - 1180px) / 2)); border-top: 1px solid var(--line); background: var(--surface); color: var(--muted); font-size: 13px; }
.site-footer strong { color: var(--ink); font-family: var(--font-serif); font-size: 18px; }
.site-footer p { margin: 6px 0 0; }
.site-footer a { color: var(--ink); text-decoration: underline; text-underline-offset: 3px; }
.chapter-drawer-backdrop { display: none; }
.chapter-drawer-backdrop[hidden] { display: none; }

@media (max-width: 1100px) {
  .site-brand span:last-child { display: none; }
  .chapter-row-copy { grid-template-columns: minmax(200px, .8fr) minmax(280px, 1.2fr); }
  .home-reading-note { grid-template-columns: 150px 1fr 1fr; }
}

@media (min-width: 1280px) {
  body[data-page-type="chapter"] .chapter-main { padding-right: 200px; }
}

@media (max-width: 900px) {
  :root { --header-height: 60px; }
  .site-header-inner { gap: 8px; padding: 0 14px; }
  .site-search { width: auto; flex: 1; }
  .site-search button { display: none; }
  .site-search input { padding-right: 12px; }
  .github-link { display: none; }
  .chapter-menu-button { display: grid; }
  body[data-page-type="home"] .chapter-menu-button { display: none; }
  .chapter-shell { display: block; }
  .chapter-sidebar { position: fixed; top: 0; bottom: 0; left: 0; z-index: 82; width: min(340px, calc(100vw - 48px)); height: 100vh; padding-top: 20px; transform: translateX(-105%); transition: transform .2s ease; }
  .chapter-sidebar.is-open { transform: translateX(0); }
  .drawer-close { display: grid; }
  .chapter-drawer-backdrop { position: fixed; inset: 0; z-index: 81; display: block; background: rgba(18, 18, 16, .55); }
  .chapter-main { padding: 0 28px 80px; }
  .home-principle { grid-template-columns: 1fr; gap: 22px; }
  .home-principle > p { margin-top: 0; }
  .chapter-row-copy { display: block; }
  .chapter-row-copy small { display: block; margin-top: 5px; white-space: normal; }
  .home-reading-note { grid-template-columns: 1fr; gap: 14px; }
}

@media (max-width: 640px) {
  .site-brand { gap: 0; }
  .brand-mark { width: 28px; height: 28px; }
  .site-search input { height: 38px; font-size: 14px; }
  .header-actions { gap: 0; }
  .icon-action { width: 36px; height: 36px; }
  .home-hero { min-height: auto; width: calc(100% - 36px); padding: 64px 0 58px; }
  .home-hero h1 { font-size: 48px; overflow-wrap: anywhere; }
  .home-lede { font-size: 20px; }
  .home-facts { display: grid; grid-template-columns: 1fr 1fr; gap: 8px 18px; }
  .home-facts span + span::before { display: none; }
  .home-actions { align-items: flex-start; flex-direction: column; gap: 12px; }
  .home-principle, .home-directory, .home-reading-note { width: calc(100% - 36px); padding-top: 58px; padding-bottom: 64px; }
  .home-principle h2, .home-reading-note h2 { font-size: 28px; }
  .home-directory-head { align-items: flex-start; flex-direction: column; }
  .home-directory-head h2 { font-size: 34px; }
  .chapter-row { grid-template-columns: 42px minmax(0, 1fr) 18px; gap: 10px; min-height: 90px; }
  .chapter-row:hover { padding-left: 0; }
  .chapter-row-copy strong { font-size: 18px; }
  .chapter-row-copy small { display: -webkit-box; overflow: hidden; -webkit-box-orient: vertical; -webkit-line-clamp: 2; }
  .site-footer { grid-template-columns: 1fr; gap: 24px; padding: 36px 18px 96px; }
  .chapter-main { padding: 0 18px 72px; }
  .breadcrumbs { padding: 22px 0 36px; }
  .chapter-intro h1 { font-size: 38px; }
  .chapter-summary { font-size: 17px; }
  .entry-toc { padding: 22px 20px; }
  .entry-toc ol { columns: 1; }
  .chapter-entry { padding: 34px 0 26px; }
  .chapter-entry h2 { font-size: 23px; }
  .chapter-prev-next { grid-template-columns: 1fr; }
  .chapter-next { text-align: left; }
  .chapter-prev-next .is-empty { display: none; }
}

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