/* ============ Design tokens: paper / ink / signal orange (shared with homepage) ============ */
    :root {
      --paper: #f7f3ea;
      --paper-2: #efe9db;
      --ink: #171512;
      --ink-soft: #5c574d;
      --line: #171512;
      --line-soft: rgba(23, 21, 18, 0.16);
      --orange: #ff4d00;
      --orange-dark: #d63f00;
      --green: #1c7c4d;
      --font-sans: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
      --font-display: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
      --font-mono: "IBM Plex Mono", ui-monospace, monospace;
    }

    * { margin: 0; padding: 0; box-sizing: border-box; }
    html { scroll-behavior: smooth; }

    body {
      background: var(--paper);
      color: var(--ink);
      font-family: var(--font-sans);
      line-height: 1.75;
      overflow-x: hidden;
    }

    ::selection { background: var(--orange); color: var(--paper); }
    a { color: inherit; text-decoration: none; }
    ul, ol { list-style: none; }
    button { font-family: inherit; }

    .container { width: min(1200px, calc(100% - 40px)); margin: 0 auto; }
    .mono { font-family: var(--font-mono); }

    body::before {
      content: "";
      position: fixed; inset: 0; pointer-events: none; z-index: 0;
      background-image: radial-gradient(rgba(23, 21, 18, 0.045) 1px, transparent 1px);
      background-size: 22px 22px;
    }
    main, header, footer, .ticker { position: relative; z-index: 1; }

    .reveal { opacity: 0; transform: translateY(22px); transition: opacity .6s ease, transform .6s cubic-bezier(.22,1,.36,1); }
    .reveal.on { opacity: 1; transform: none; }

    /* ============ Top ticker ============ */
    .ticker {
      background: var(--orange); color: var(--paper);
      font-family: var(--font-mono); font-size: 12.5px; font-weight: 700; letter-spacing: 1px;
      overflow: hidden; white-space: nowrap; padding: 7px 0;
      border-bottom: 2px solid var(--ink);
    }
    .ticker-track { display: inline-block; animation: ticker-scroll 32s linear infinite; }
    .ticker-track span { margin: 0 26px; }
    @keyframes ticker-scroll { from { transform: translateX(0); } to { transform: translateX(-50%); } }

    /* ============ Nav ============ */
    .nav { position: sticky; top: 0; z-index: 100; background: var(--paper); border-bottom: 2px solid var(--ink); }
    .nav-inner { display: flex; align-items: stretch; height: 62px; }
    .logo {
      display: flex; align-items: center; gap: 10px;
      font-family: var(--font-display); font-weight: 900; font-size: 21px; letter-spacing: 1px;
      padding-right: 28px; border-right: 2px solid var(--ink);
    }
    .logo img { display: block; width: 32px; height: 32px; object-fit: contain; }
    .nav-links { display: flex; align-items: stretch; }
    .nav-links a {
      display: flex; align-items: center; padding: 0 22px;
      font-size: 14.5px; font-weight: 500;
      border-right: 1px solid var(--line-soft);
      transition: background .15s, color .15s;
    }
    .nav-links a:hover { background: var(--ink); color: var(--paper); }
    .nav-links a.active { background: var(--orange); color: var(--paper); border-right-color: var(--ink); }
    .nav-drop { position: relative; display: flex; align-items: stretch; border-right: 1px solid var(--line-soft); }
    .nav-drop-trigger { display: flex; align-items: center; gap: 6px; height: 100%; padding: 0 22px; font-size: 14.5px; font-weight: 500; transition: background .15s, color .15s; }
    .nav-drop-trigger.active { background: var(--orange); color: var(--paper); }
    .nav-drop:hover .nav-drop-trigger { background: var(--ink); color: var(--paper); }
    .nav-drop-caret { flex-shrink: 0; transition: transform .15s; }
    .nav-drop:hover .nav-drop-caret { transform: rotate(180deg); }
    .nav-drop-menu {
      position: absolute; left: 0; top: 100%;
      background: var(--paper); border: 2px solid var(--ink);
      box-shadow: 5px 5px 0 var(--ink); min-width: 190px; display: none; z-index: 110;
    }
    .nav-drop:hover .nav-drop-menu { display: block; }
    .nav-drop-menu a {
      display: block; padding: 11px 16px; font-size: 13.5px; font-weight: 500;
      border-bottom: 1px solid var(--line-soft); color: var(--ink);
    }
    .nav-drop-menu a:last-child { border-bottom: none; }
    .nav-drop-menu a:hover { background: var(--paper-2); color: var(--orange); }
    .nav-right { margin-left: auto; display: flex; align-items: center; gap: 10px; }
    .lang-switch { position: relative; }
    .lang-btn {
      display: flex; align-items: center; gap: 7px;
      background: transparent; border: 1.5px solid var(--ink); color: var(--ink);
      padding: 7px 13px; font-size: 13px; font-family: var(--font-mono);
      cursor: pointer; transition: background .15s, color .15s;
    }
    .lang-btn:hover { background: var(--ink); color: var(--paper); }
    .lang-menu {
      position: absolute; right: 0; top: calc(100% + 10px);
      background: var(--paper); border: 2px solid var(--ink);
      box-shadow: 5px 5px 0 var(--ink); min-width: 150px; display: none;
    }
    .lang-menu.open { display: block; }
    .lang-menu a { display: block; padding: 9px 14px; font-size: 13.5px; cursor: pointer; border-bottom: 1px solid var(--line-soft); text-decoration: none; color: inherit; }
    .lang-menu a:last-child { border-bottom: none; }
    .lang-menu a:hover { background: var(--paper-2); }
    .lang-menu a.current { background: var(--orange); color: var(--paper); }
    .nav-toggle {
      display: none; background: none; border: 1.5px solid var(--ink);
      width: 40px; height: 40px; font-size: 17px; cursor: pointer; color: var(--ink);
    }
    .nav-mobile { display: none; }
    @media (max-width: 720px) {
      .nav-links { display: none; }
      .nav-toggle { display: block; }
      .nav-mobile { display: none; flex-direction: column; border-top: 2px solid var(--ink); }
      .nav-mobile.open { display: flex; }
      .nav-mobile a { padding: 14px 0; font-size: 16px; border-bottom: 1px solid var(--line-soft); }
      .nav-mobile a.nav-mobile-sub { padding: 11px 0 11px 18px; font-size: 14px; color: var(--ink-soft); }
    }

    /* ============ Page header ============ */
    .page-head { border-bottom: 2px solid var(--ink); padding: 60px 0 40px; }
    .page-kicker {
      display: flex; align-items: center; gap: 14px;
      font-family: var(--font-mono); font-size: 13px; color: var(--ink-soft);
      margin-bottom: 20px;
    }
    .page-kicker::before { content: ""; width: 44px; height: 2px; background: var(--orange); }
    .page-head h1 {
      font-family: var(--font-display); font-weight: 900;
      font-size: clamp(32px, 5vw, 54px); line-height: 1.25; letter-spacing: 1px;
    }
    .page-head h1 .accent { color: var(--orange); }
    .page-head p { margin-top: 18px; color: var(--ink-soft); font-size: 16px; max-width: 720px; }
    .read-meta {
      display: flex; gap: 20px; flex-wrap: wrap;
      margin-top: 24px; font-family: var(--font-mono); font-size: 12.5px; color: var(--ink-soft);
    }
    .read-meta b { color: var(--ink); }

    /* ============ Doc layout: sticky TOC + content ============ */
    .doc-wrap { border-bottom: 2px solid var(--ink); }
    .doc-layout { display: grid; grid-template-columns: 230px 1fr; gap: 56px; padding: 48px 0 72px; align-items: start; }
    .doc-layout > * { min-width: 0; }
    .toc { position: sticky; top: 82px; }
    .toc .toc-label { font-family: var(--font-mono); font-size: 11.5px; letter-spacing: 2px; color: var(--ink-soft); text-transform: uppercase; margin-bottom: 14px; display: block; }
    .toc a {
      display: block; padding: 8px 0 8px 14px; font-size: 13.5px; color: var(--ink-soft);
      border-left: 2px solid var(--line-soft);
      transition: border-color .15s, color .15s;
    }
    .toc a:hover, .toc a.active { color: var(--ink); border-left-color: var(--orange); }
    .toc-mobile { display: none; }

    @media (max-width: 980px) {
      .doc-layout { grid-template-columns: 1fr; gap: 0; }
      .toc { display: none; }
      .toc-mobile {
        display: flex; flex-wrap: wrap; gap: 8px;
        padding: 24px 0 8px;
      }
      .toc-mobile a {
        font-family: var(--font-mono); font-size: 12px; font-weight: 700;
        border: 1.5px solid var(--ink); padding: 6px 12px;
      }
    }

    /* ============ Content sections ============ */
    .doc-section { padding: 44px 0; border-top: 1px solid var(--line-soft); scroll-margin-top: 80px; }
    .doc-section:first-child { border-top: none; padding-top: 0; }
    .doc-section h2 {
      font-family: var(--font-display); font-weight: 900;
      font-size: clamp(22px, 2.6vw, 30px); margin-bottom: 14px;
      display: flex; align-items: baseline; gap: 10px;
    }
    .doc-section h2 .idx { font-family: var(--font-mono); font-size: 15px; color: var(--orange); font-weight: 700; }
    .doc-section > p { color: var(--ink-soft); max-width: 760px; margin-bottom: 20px; }
    .doc-section h3 {
      font-family: var(--font-display); font-weight: 900; font-size: 18px;
      margin: 28px 0 12px;
    }
    .doc-section h3:first-of-type { margin-top: 8px; }

    /* Numbered step list */
    .steps { border: 2px solid var(--ink); margin-bottom: 4px; }
    .step-row {
      display: grid; grid-template-columns: 56px 1fr; gap: 18px;
      padding: 18px 22px; border-bottom: 1px solid var(--line-soft);
    }
    .step-row:last-child { border-bottom: none; }
    .step-row .num {
      font-family: var(--font-mono); font-size: 22px; font-weight: 700; color: var(--orange);
    }
    .step-row .body b { display: block; font-size: 15px; margin-bottom: 4px; }
    .step-row .body span { font-size: 13.5px; color: var(--ink-soft); }
    .step-row .body code {
      font-family: var(--font-mono); font-size: 12.5px;
      background: var(--paper-2); border: 1px solid var(--line-soft);
      padding: 1px 6px;
    }

    .tip-line {
      font-size: 13.5px; color: var(--ink-soft);
      border-left: 3px solid var(--orange);
      padding: 4px 0 4px 16px; margin-top: 18px; max-width: 760px;
    }
    .tip-line b { color: var(--ink); }

    /* Dark code / terminal block, echoes hero board on homepage */
    .code-box {
      background: var(--ink); color: #e8e2d4;
      border: 2px solid var(--ink);
      font-family: var(--font-mono); font-size: 13px; line-height: 1.85;
      padding: 20px 24px; margin: 18px 0 22px;
      overflow-x: auto;
    }
    .code-box .k { color: #7fd8ff; }
    .code-box .s { color: #ffb38a; }
    .code-box .c { color: #6f6a5e; }

    /* Rule / reference tables */
    .doc-table-wrap { border: 2px solid var(--ink); overflow-x: auto; margin: 6px 0 22px; }
    table.doc-table { width: 100%; border-collapse: collapse; font-size: 13.5px; min-width: 620px; }
    table.doc-table th {
      font-family: var(--font-mono); font-size: 11.5px; letter-spacing: 1px; text-transform: uppercase;
      text-align: left; color: var(--ink-soft);
      padding: 12px 16px; border-bottom: 2px solid var(--ink); background: var(--paper-2);
    }
    table.doc-table td { padding: 12px 16px; border-bottom: 1px solid var(--line-soft); vertical-align: top; }
    table.doc-table tr:last-child td { border-bottom: none; }
    table.doc-table td.code { font-family: var(--font-mono); font-size: 12.5px; color: var(--orange-dark); white-space: nowrap; }

    /* FAQ accordion via native <details> */
    .faq-list { border: 2px solid var(--ink); }
    .faq-item { border-bottom: 1px solid var(--line-soft); }
    .faq-item:last-child { border-bottom: none; }
    .faq-item summary {
      list-style: none; cursor: pointer;
      display: flex; align-items: center; justify-content: space-between; gap: 16px;
      padding: 18px 22px; font-weight: 700; font-size: 15px;
    }
    .faq-item summary::-webkit-details-marker { display: none; }
    .faq-item summary .plus {
      font-family: var(--font-mono); font-size: 18px; color: var(--orange);
      transition: transform .2s ease; flex-shrink: 0;
    }
    .faq-item[open] summary .plus { transform: rotate(45deg); }
    .faq-item[open] summary { background: var(--paper-2); }
    .faq-a { padding: 0 22px 20px; font-size: 14px; color: var(--ink-soft); max-width: 760px; }

    /* Glossary grid */
    .glossary-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 14px; }
    .gloss-item { border: 1.5px solid var(--ink); padding: 16px 18px; }
    .gloss-item b { display: block; font-family: var(--font-mono); font-size: 13px; color: var(--orange); margin-bottom: 6px; }
    .gloss-item span { font-size: 13.5px; color: var(--ink-soft); }

    /* CTA inline card at bottom of doc */
    .doc-cta {
      display: flex; align-items: center; justify-content: space-between; gap: 24px; flex-wrap: wrap;
      border: 2px solid var(--ink); background: var(--paper-2);
      padding: 26px 30px; margin-top: 8px;
    }
    .doc-cta b { font-family: var(--font-display); font-size: 17px; font-weight: 900; display: block; margin-bottom: 4px; }
    .doc-cta span { font-size: 13.5px; color: var(--ink-soft); }
    .btn {
      display: inline-flex; align-items: center; gap: 10px; font-size: 14.5px; font-weight: 700;
      padding: 12px 24px; border: 2px solid var(--ink); cursor: pointer;
      transition: transform .15s, box-shadow .15s, background .15s, color .15s;
    }
    .btn:hover { transform: translate(-3px, -3px); box-shadow: 5px 5px 0 var(--ink); }
    .btn:active { transform: translate(0, 0); box-shadow: 0 0 0 var(--ink); }
    .btn-primary { background: var(--orange); color: var(--paper); }

    /* ============ Footer (shared) ============ */
    footer { background: var(--paper-2); }
    .foot-grid {
      display: grid; grid-template-columns: 2fr 1fr 1fr 1.3fr; gap: 44px;
      padding: 56px 0 44px; border-bottom: 1px solid var(--line-soft);
    }
    .foot-grid h4 { font-family: var(--font-mono); font-size: 12px; letter-spacing: 2px; color: var(--ink-soft); margin-bottom: 18px; text-transform: uppercase; }
    .foot-grid ul li { margin-bottom: 10px; }
    .foot-grid a { font-size: 14.5px; border-bottom: 1px solid transparent; transition: border-color .15s, color .15s; }
    .foot-grid a:hover { color: var(--orange); border-bottom-color: var(--orange); }
    .foot-brand .logo { border-right: none; padding-right: 0; }
    .foot-brand p { color: var(--ink-soft); font-size: 14px; margin-top: 16px; max-width: 300px; }
    .foot-lang { display: flex; flex-wrap: wrap; gap: 8px; }
    .foot-lang a { font-size: 12.5px; font-family: var(--font-mono); border: 1.5px solid var(--line-soft); padding: 5px 12px; cursor: pointer; transition: all .15s; display: inline-block; text-decoration: none; color: inherit; }
    .foot-lang a:hover { border-color: var(--ink); }
    .foot-lang a.current { background: var(--ink); color: var(--paper); border-color: var(--ink); }
    .foot-bottom { padding: 24px 0 30px; display: flex; justify-content: space-between; flex-wrap: wrap; gap: 10px; font-size: 13px; color: var(--ink-soft); }

    @media (max-width: 720px) {
      .glossary-grid { grid-template-columns: 1fr; }
      .step-row { grid-template-columns: 40px 1fr; }
      .foot-grid { grid-template-columns: 1fr 1fr; }
      .doc-cta { flex-direction: column; align-items: flex-start; }
      .doc-table-wrap::before,
      .code-box::before {
        content: "← 可左右滑动 →";
        display: inline-block;
        position: sticky;
        left: 0;
        font-family: var(--font-mono);
        font-size: 10px;
        letter-spacing: .3px;
        color: var(--ink-soft);
        background: var(--paper-2);
        border: 1px solid var(--line-soft);
        padding: 3px 9px;
        margin: 8px 0 8px 8px;
      }
      .code-box::before { background: rgba(232, 226, 212, 0.12); color: rgba(232, 226, 212, 0.6); border-color: rgba(232, 226, 212, 0.2); margin: 0 0 10px; }
      html[lang="en"] .doc-table-wrap::before, html[lang="en"] .code-box::before { content: "← Scroll →"; }
      html[lang="ja"] .doc-table-wrap::before, html[lang="ja"] .code-box::before { content: "← 左右にスクロール →"; }
      html[lang="ko"] .doc-table-wrap::before, html[lang="ko"] .code-box::before { content: "← 좌우로 스크롤 →"; }
      html[lang="zh-TW"] .doc-table-wrap::before, html[lang="zh-TW"] .code-box::before { content: "← 可左右滑動 →"; }
    }

    @media (prefers-reduced-motion: reduce) {
      .ticker-track { animation: none; }
      .reveal { opacity: 1; transform: none; transition: none; }
      html { scroll-behavior: auto; }
    }