/* 学习指南沿用官网的暖白与棕色；正文不依赖 JavaScript。 */
:root {
  color-scheme: light;
  --paper: #fffaf0;
  --surface: #fffdf8;
  --ink: #382b24;
  --muted: #716258;
  --accent: #8b4513;
  --line: #e5dacb;
  --soft: #f3ecdf;
  --green: #385846;
  --green-soft: #eaf0e8;
  --header-height: 80px;
}
* { box-sizing: border-box; }
html { scroll-padding-top: calc(var(--header-height) + 28px); }
body { margin: 0; background: var(--paper); color: var(--ink); font: 16px/1.8 -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif; -webkit-font-smoothing: antialiased; }
a { color: var(--accent); text-underline-offset: 5px; text-decoration-thickness: 1px; }
a:hover { text-decoration-thickness: 2px; }
a, summary { -webkit-tap-highlight-color: transparent; }
:focus-visible { outline: 3px solid var(--accent); outline-offset: 5px; border-radius: 2px; }
img, video { display: block; max-width: 100%; }
button, input { font: inherit; }
h1, h2, h3, p, ul, ol, dl, figure { margin: 0; }
h1, h2, h3 { text-wrap: balance; }
svg { flex: 0 0 auto; }
.shell { width: min(1120px, calc(100% - 80px)); margin-inline: auto; }
.skip-link { position: fixed; z-index: 30; top: 12px; left: 20px; padding: 10px 18px; background: var(--ink); color: white; transform: translateY(-160%); }
.skip-link:focus { transform: translateY(0); }
.site-header { position: sticky; z-index: 10; top: 0; background: var(--paper); border-bottom: 1px solid var(--line); }
.header-inner { min-height: var(--header-height); display: flex; justify-content: space-between; align-items: center; gap: 24px; }
.home-link { min-height: 44px; display: inline-flex; align-items: center; gap: 10px; font-size: 14px; font-weight: 650; text-decoration: none; }
.home-link svg { width: 18px; height: 18px; transition: transform .18s ease; }
.home-link:hover svg { transform: translateX(-3px); }
.brand { display: inline-flex; align-items: center; gap: 10px; color: var(--ink); text-decoration: none; font-size: 14px; font-weight: 650; min-height: 44px; }
.brand img { width: 30px; height: 30px; border-radius: 7px; }
.brand span { color: var(--muted); font-size: 12px; font-weight: 400; border-left: 1px solid var(--line); padding-left: 10px; }
.eyebrow { color: var(--accent); font-size: 12px; font-weight: 700; letter-spacing: .13em; }
.index-hero { display: grid; grid-template-columns: 1.5fr 1fr; gap: 72px; align-items: center; padding: 76px 0 68px; }
.index-hero h1 { margin: 19px 0 24px; font-size: clamp(36px, 4.2vw, 54px); line-height: 1.25; letter-spacing: -.045em; font-weight: 650; }
.index-hero .intro { max-width: 530px; color: var(--muted); font-size: 17px; line-height: 1.9; }
.hero-note { background: var(--soft); padding: 30px 32px; border-top: 3px solid var(--accent); }
.hero-note h2 { font-size: 21px; line-height: 1.55; font-weight: 600; margin: 14px 0; }
.hero-note p { font-size: 14px; color: var(--muted); }
.text-link { display: inline-flex; align-items: center; gap: 12px; min-height: 44px; font-size: 14px; font-weight: 600; }
.hero-note .text-link { margin-top: 16px; }
.section-label { display: flex; align-items: baseline; justify-content: space-between; gap: 16px; padding-bottom: 16px; border-bottom: 1px solid var(--ink); }
.section-label h2 { font-size: 20px; font-weight: 600; }
.section-label p { font-size: 13px; color: var(--muted); }
.guide-list { list-style: none; padding: 0; }
.guide-list li { border-bottom: 1px solid var(--line); }
.guide-row { display: grid; grid-template-columns: 64px 1fr 80px; align-items: center; gap: 24px; color: var(--ink); text-decoration: none; padding: 30px 16px 30px 0; transition: background-color .18s ease; }
.guide-row:hover { background: var(--soft); }
.guide-number { align-self: start; font-size: 13px; letter-spacing: .06em; color: var(--accent); padding-top: 5px; }
.guide-category { color: var(--muted); font-size: 12px; }
.guide-row h3 { margin: 3px 0 8px; font-size: 23px; font-weight: 600; line-height: 1.45; }
.guide-row p { color: var(--muted); font-size: 14px; max-width: 700px; }
.guide-arrow { justify-self: end; font-size: 24px; color: var(--accent); }
.index-bottom { display: grid; grid-template-columns: 1fr 1fr; gap: 48px; margin: 52px 0 72px; }
.index-bottom h2 { font-size: 17px; margin-bottom: 8px; }
.index-bottom p { color: var(--muted); font-size: 14px; }
.breadcrumb { display: flex; gap: 10px; align-items: center; padding-top: 28px; font-size: 13px; color: var(--muted); }
.breadcrumb a { display: inline-flex; align-items: center; min-height: 44px; }
.article-hero { max-width: 850px; padding: 28px 0 40px; }
.article-hero h1 { font-size: clamp(30px, 3.6vw, 44px); line-height: 1.35; margin: 13px 0 20px; letter-spacing: -.035em; font-weight: 650; }
.article-deck { max-width: 760px; color: var(--muted); font-size: 18px; line-height: 1.9; }
.article-meta { display: flex; flex-wrap: wrap; gap: 6px 20px; margin-top: 22px; color: var(--muted); font-size: 12px; }
.article-grid { display: grid; grid-template-columns: minmax(0, 760px) 228px; gap: 80px; align-items: start; padding-bottom: 76px; border-top: 1px solid var(--line); }
.article-body { min-width: 0; padding-top: 34px; }
.article-body > section + section { margin-top: 42px; }
.article-body h2 { font-size: 24px; line-height: 1.5; margin-bottom: 18px; font-weight: 650; }
.article-body h3 { font-size: 18px; line-height: 1.6; margin: 24px 0 8px; font-weight: 650; }
.article-body p + p { margin-top: 15px; }
.article-body ul, .article-body ol { padding-left: 24px; margin: 15px 0; }
.article-body li + li { margin-top: 8px; }
.article-body li::marker { color: var(--accent); }
.article-body strong { font-weight: 650; }
.article-body .lead-answer { font-size: 18px; line-height: 1.85; border-left: 3px solid var(--accent); padding: 4px 0 4px 22px; margin-bottom: 38px; }
.article-aside { position: sticky; top: calc(var(--header-height) + 32px); padding-top: 35px; }
.toc-title { font-size: 12px; color: var(--muted); margin-bottom: 12px; letter-spacing: .1em; }
.toc { list-style: none; padding: 0; border-left: 1px solid var(--line); }
.toc a { display: block; padding: 10px 0 10px 18px; font-size: 13px; line-height: 1.6; color: var(--muted); text-decoration: none; }
.toc a:hover { color: var(--accent); background: var(--soft); }
.aside-note { font-size: 13px; color: var(--muted); margin-top: 28px; padding-top: 20px; border-top: 1px solid var(--line); }
.aside-note a { display: inline-block; min-height: 44px; padding-top: 8px; }
.fact-list { border-top: 1px solid var(--line); }
.fact-list > div { display: grid; grid-template-columns: 116px minmax(0, 1fr); gap: 24px; padding: 16px 0; border-bottom: 1px solid var(--line); }
.fact-list dt { color: var(--muted); font-size: 14px; }
.fact-list dd { margin: 0; font-size: 15px; }
.step-list { list-style: none; padding: 0 !important; counter-reset: steps; }
.step-list > li { position: relative; padding: 1px 0 22px 50px; counter-increment: steps; }
.step-list > li::before { content: counter(steps, decimal-leading-zero); position: absolute; left: 0; top: 3px; color: var(--accent); font-size: 13px; }
.step-list h3 { margin: 0 0 7px; }
.step-list p { color: var(--muted); font-size: 15px; }
.note { background: var(--soft); padding: 22px 26px; margin-top: 22px; border-radius: 3px; }
.note h3 { margin: 0 0 8px; font-size: 16px; }
.note p, .note li { font-size: 14px; }
.note.green { background: var(--green-soft); color: var(--green); }
.note.green a { color: var(--green); }
.example { margin: 22px 0; padding: 26px 30px; background: var(--surface); border: 1px solid var(--line); border-radius: 3px; }
.example-label { color: var(--muted); font-size: 12px; letter-spacing: .07em; margin-bottom: 12px; }
.english { font-family: Georgia, "Times New Roman", serif; font-size: 24px; line-height: 1.6; color: var(--ink); }
.english + p { margin-top: 10px; }
.example .translation { font-size: 14px; color: var(--muted); }
.example .prompt { font-size: 16px; line-height: 1.8; }
.example .mistake { color: #925033; }
.example .correction { color: var(--green); }
.meaning-pair { display: grid; grid-template-columns: 1fr 1fr; gap: 24px; margin: 20px 0; }
.meaning-pair > div { border-top: 2px solid var(--line); padding-top: 16px; }
.meaning-pair h3 { margin: 0 0 5px; }
.meaning-pair p { font-size: 15px; }
.schedule { padding: 0 !important; list-style: none; border-top: 1px solid var(--line); }
.schedule > li { display: grid; grid-template-columns: 94px minmax(0, 1fr); gap: 24px; padding: 20px 0; border-bottom: 1px solid var(--line); margin: 0 !important; }
.schedule .minutes { color: var(--accent); font-size: 15px; font-weight: 600; }
.schedule h3 { margin: 0 0 6px; }
.schedule p { color: var(--muted); font-size: 15px; }
details { margin: 18px 0; border: 1px solid var(--line); border-radius: 3px; padding: 0 22px; background: var(--surface); }
summary { min-height: 52px; padding: 13px 0; cursor: pointer; color: var(--accent); font-size: 14px; font-weight: 600; }
details > div { padding: 3px 0 20px; }
details p { font-size: 15px; }
.source-list { list-style: none; padding: 0 !important; }
.source-list li { color: var(--muted); font-size: 13px; line-height: 1.8; }
.source-list a { overflow-wrap: anywhere; }
.small { color: var(--muted); font-size: 13px; }
.related { border-top: 1px solid var(--line); padding-top: 28px; }
.related ul { list-style: none; padding: 0; }
.related a { display: inline-block; padding: 8px 0; min-height: 44px; font-size: 15px; }
.site-footer { border-top: 1px solid var(--line); padding: 28px 0 32px; }
.footer-inner { display: flex; justify-content: space-between; gap: 24px; align-items: start; color: var(--muted); font-size: 12px; }
.footer-links { display: flex; flex-wrap: wrap; gap: 0 20px; }
.footer-links a { min-height: 44px; display: inline-flex; align-items: center; color: var(--muted); }
.footer-credit { padding-top: 10px; }
@media (max-width: 1000px) {
  .shell { width: min(900px, calc(100% - 48px)); }
  .index-hero { gap: 40px; }
  .article-grid { grid-template-columns: minmax(0, 1fr); gap: 0; }
  .article-aside { position: static; grid-row: 1; padding: 22px 0; border-bottom: 1px solid var(--line); }
  .toc { display: flex; flex-wrap: wrap; gap: 0 20px; border-left: 0; }
  .toc a { min-height: 44px; padding: 10px 0; }
  .toc-title { margin-bottom: 4px; }
  .aside-note { display: none; }
  .article-body { max-width: 760px; }
}
@media (max-width: 640px) {
  :root { --header-height: 68px; }
  .shell { width: calc(100% - 40px); }
  .header-inner { gap: 12px; }
  .brand { gap: 7px; font-size: 13px; }
  .brand img { width: 26px; height: 26px; }
  .brand span { display: none; }
  .index-hero { grid-template-columns: 1fr; gap: 30px; padding: 42px 0; }
  .index-hero h1 { margin: 15px 0 18px; }
  .index-hero .intro { font-size: 16px; }
  .hero-note { padding: 24px; }
  .section-label { align-items: center; }
  .section-label h2 { font-size: 18px; }
  .section-label p { font-size: 12px; }
  .guide-row { grid-template-columns: 26px minmax(0, 1fr) 20px; gap: 12px; padding: 25px 0; }
  .guide-row h3 { font-size: 20px; }
  .guide-number { font-size: 12px; }
  .guide-row p { font-size: 13px; }
  .index-bottom { grid-template-columns: 1fr; gap: 24px; margin: 36px 0 48px; }
  .breadcrumb { padding-top: 15px; }
  .article-hero { padding: 18px 0 28px; }
  .article-deck { font-size: 16px; }
  .article-meta { gap: 4px 12px; }
  .article-grid { padding-bottom: 45px; }
  .article-body { padding-top: 26px; }
  .article-body h2 { font-size: 22px; }
  .article-body .lead-answer { font-size: 17px; padding-left: 17px; }
  .fact-list > div { grid-template-columns: 78px minmax(0, 1fr); gap: 16px; }
  .fact-list dd { font-size: 14px; }
  .note { padding: 20px; }
  .example { padding: 22px 20px; }
  .english { font-size: 22px; }
  .meaning-pair { grid-template-columns: 1fr; gap: 18px; }
  .schedule > li { grid-template-columns: 66px minmax(0, 1fr); gap: 14px; }
  .schedule .minutes { font-size: 13px; }
  .step-list > li { padding-left: 36px; }
  .footer-inner { flex-direction: column; gap: 8px; }
  .footer-credit { padding-top: 0; }
}
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { transition: none !important; scroll-behavior: auto !important; }
}