:root {
  --ink: #17243a; --muted: #66758b; --line: #dce3ec; --canvas: #f3f6f9;
  --panel: #fff; --nav: #10243c; --nav-2: #193753; --blue: #1676d2;
  --green: #18885c; --shadow: 0 9px 30px rgba(25,48,76,.09);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
html:not(.help-language-ready) .help-shell { visibility: hidden; }
body { margin: 0; color: var(--ink); background: var(--canvas); font-family: "Microsoft YaHei","PingFang SC",system-ui,sans-serif; line-height: 1.65; }
a { color: var(--blue); }
button { font: inherit; cursor: pointer; }
.help-shell { min-height: 100vh; display: grid; grid-template-columns: 260px minmax(0,1fr); grid-template-rows: 72px minmax(0,1fr); }
.help-topbar { grid-column: 1 / 3; display: flex; align-items: center; justify-content: space-between; padding: 0 28px; color: #fff; background: linear-gradient(100deg,#0e2036,#173b5c); border-bottom: 1px solid rgba(255,255,255,.12); }
.help-brand { display: flex; align-items: center; gap: 13px; color: #fff; text-decoration: none; }
.help-brand-mark { width: 42px; height: 42px; display: grid; place-items: center; border: 1px solid rgba(255,255,255,.55); border-radius: 10px; font-size: 13px; font-weight: 800; letter-spacing: .06em; }
.help-brand strong { display: block; font-size: 18px; }
.help-brand small { display: block; color: #b8c9da; font-size: 12px; letter-spacing: .08em; text-transform: uppercase; }
.help-actions { display: flex; align-items: center; gap: 10px; }
.help-language { min-height: 36px; padding: 7px 13px; color: #fff; background: rgba(255,255,255,.09); border: 1px solid rgba(255,255,255,.3); border-radius: 999px; font-size: 13px; font-weight: 700; }
.help-language:hover { background: rgba(255,255,255,.18); }
.help-language { min-width: 72px; }
.help-sidebar { grid-row: 2; padding: 24px 14px; background: var(--nav); border-right: 1px solid #203c56; }
.help-nav-title { margin: 0 10px 12px; color: #6f8ba5; font-size: 11px; font-weight: 800; letter-spacing: .14em; text-transform: uppercase; }
.help-nav { display: grid; gap: 6px; }
.help-nav a { padding: 11px 13px; color: #b8c9d7; text-decoration: none; border: 1px solid transparent; border-radius: 8px; font-size: 14px; font-weight: 700; }
.help-nav a:hover,.help-nav a.active { color: #fff; background: var(--nav-2); border-color: #315574; box-shadow: inset 3px 0 0 #4da1ed; }
.help-nav small { display: block; margin-top: 2px; color: #829bb0; font-size: 11px; font-weight: 500; }
.help-sidebar-note { margin: 28px 10px 0; padding-top: 18px; color: #87a0b4; border-top: 1px solid rgba(184,205,224,.16); font-size: 12px; }
.help-main { grid-row: 2; min-width: 0; padding: 34px 38px 70px; }
.help-content { max-width: 1180px; margin: 0 auto; }
.help-hero { padding: 34px; color: #fff; background: linear-gradient(120deg,#16436a,#1877bc); border-radius: 14px; box-shadow: 0 14px 36px rgba(19,80,127,.2); }
.eyebrow { margin: 0 0 6px; color: #267ebc; font-size: 12px; font-weight: 900; letter-spacing: .15em; text-transform: uppercase; }
.help-hero .eyebrow { color: #9bd4ff; }
.help-hero h1 { max-width: 820px; margin: 0; font-size: clamp(28px,4vw,42px); line-height: 1.2; }
.help-hero p { max-width: 780px; margin: 14px 0 0; color: #dcefff; font-size: 16px; }
.hero-meta { display: flex; flex-wrap: wrap; gap: 9px; margin-top: 22px; }
.hero-meta span { padding: 5px 10px; background: rgba(255,255,255,.11); border: 1px solid rgba(255,255,255,.2); border-radius: 999px; font-size: 12px; }
.section-heading { margin: 34px 0 15px; }
.section-heading h2 { margin: 0; font-size: 23px; }
.section-heading p { margin: 5px 0 0; color: var(--muted); }
.help-grid { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); gap: 16px; }
.help-card { display: block; min-height: 185px; padding: 22px; color: var(--ink); text-decoration: none; background: var(--panel); border: 1px solid var(--line); border-radius: 11px; box-shadow: var(--shadow); transition: .18s ease; }
.help-card:hover { transform: translateY(-2px); border-color: #9bc5e8; box-shadow: 0 14px 34px rgba(25,70,108,.13); }
.help-card .card-index { color: var(--blue); font-size: 12px; font-weight: 900; letter-spacing: .12em; }
.help-card h2 { margin: 16px 0 7px; font-size: 18px; }
.help-card p { margin: 0; color: var(--muted); font-size: 13px; }
.help-card .card-link { display: block; margin-top: 16px; color: var(--blue); font-size: 13px; font-weight: 800; }
.notice { margin: 22px 0; padding: 16px 18px; background: #fff8e8; border: 1px solid #e8bd66; border-left: 4px solid #d38a1d; border-radius: 8px; }
.notice strong { color: #885000; }
.notice p { margin: 5px 0 0; color: #67502d; font-size: 13px; }
.article-heading { margin-bottom: 22px; }
.article-heading h1 { margin: 3px 0 8px; font-size: clamp(28px,4vw,38px); line-height: 1.25; }
.article-heading > p { margin: 0; color: var(--muted); }
.article-meta { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 15px; }
.tag { display: inline-block; padding: 4px 9px; color: #36536d; background: #edf3f8; border-radius: 999px; font-size: 11px; font-weight: 800; }
.tag.available { color: #116943; background: #e6f6ef; }
.tag.reference { color: #8a5600; background: #fff2d9; }
.article-card { margin: 18px 0; padding: 23px; background: var(--panel); border: 1px solid var(--line); border-radius: 11px; box-shadow: var(--shadow); }
.article-card h2 { margin: 0 0 14px; font-size: 20px; }
.article-card h3 { margin: 22px 0 8px; font-size: 16px; }
.article-card p,.article-card ul,.article-card ol { color: #465a70; }
.definition-grid { display: grid; grid-template-columns: repeat(2,minmax(0,1fr)); gap: 12px; }
.definition { padding: 16px; background: #f8fafc; border: 1px solid #dce5ed; border-radius: 8px; }
.definition strong { display: block; margin: 0 0 6px; color: #294a67; }
.definition p { margin: 4px 0; font-size: 13px; }
.formula { display: block; margin: 10px 0; padding: 11px 13px; color: #153b59; background: #eef5fa; border: 1px solid #d2e2ed; border-radius: 6px; font-family: Cambria Math,"Times New Roman",serif; font-size: 14px; overflow-wrap: anywhere; }
.range-table-wrap { overflow-x: auto; border: 1px solid var(--line); border-radius: 9px; }
.range-table { width: 100%; min-width: 970px; border-collapse: collapse; background: #fff; font-size: 12px; }
.range-table th,.range-table td { padding: 11px 12px; text-align: left; vertical-align: top; border-bottom: 1px solid #e4eaf0; }
.range-table th { color: #294a67; background: #edf3f7; font-size: 11px; letter-spacing: .03em; }
.range-table tr:last-child td { border-bottom: 0; }
.range-table code { color: #284d6a; white-space: normal; }
.solver-options { min-width: 520px; }
.solver-options th:first-child { width: 55%; }
.solver-options code { font-size: 13px; }
.correlation-comparison { min-width: 760px; }
.correlation-comparison th:nth-child(1) { width: 7%; }
.correlation-comparison th:nth-child(2) { width: 20%; }
.correlation-comparison th:nth-child(3) { width: 50%; }
.correlation-comparison th:nth-child(4) { width: 23%; }
.equation-stack { display: grid; gap: 7px; min-width: 0; overflow-x: auto; color: #173b58; }
.equation-line { display: block; width: max-content; min-width: 100%; padding: 2px 0; }
.equation-line .katex { font-size: 1.08em; }
.moody-figure { margin: 18px 0 0; }
.moody-figure img { width: 100%; display: block; background: #fff; border: 1px solid var(--line); border-radius: 8px; }
.moody-figure figcaption { margin-top: 8px; color: var(--muted); font-size: 12px; }
.release-list { display: grid; gap: 17px; }
.release { position: relative; padding: 22px 22px 22px 29px; background: #fff; border: 1px solid var(--line); border-radius: 10px; box-shadow: var(--shadow); }
.release::before { content: ""; position: absolute; left: 0; top: 18px; bottom: 18px; width: 4px; background: var(--blue); border-radius: 0 4px 4px 0; }
.release header { display: flex; justify-content: space-between; gap: 15px; }
.release h2 { margin: 0; font-size: 19px; }
.release time { color: var(--muted); font-size: 13px; }
.release ul { margin-bottom: 0; color: #465a70; }
.help-footer { margin-top: 40px; padding-top: 20px; color: var(--muted); border-top: 1px solid var(--line); font-size: 12px; }
@media (max-width: 920px) {
  .help-shell { grid-template-columns: 190px minmax(0,1fr); }
  .help-main { padding: 28px 22px 60px; }
  .help-grid { grid-template-columns: 1fr 1fr; }
  .definition-grid { grid-template-columns: 1fr; }
}
@media (max-width: 680px) {
  .help-shell { display: block; }
  .help-topbar { min-height: 72px; padding: 10px 14px; }
  .help-brand small { display: none; }
  .help-sidebar { position: sticky; top: 0; z-index: 5; overflow-x: auto; padding: 7px; }
  .help-nav-title,.help-sidebar-note { display: none; }
  .help-nav { display: flex; width: max-content; }
  .help-nav a { min-width: 112px; padding: 9px 11px; text-align: center; }
  .help-nav small { display: none; }
  .help-main { padding: 22px 14px 48px; }
  .help-hero { padding: 25px 21px; }
  .help-grid { grid-template-columns: 1fr; }
  .article-card { padding: 18px; }
  .release header { display: block; }
}