:root{
  --bg:#f7f8fa;--surface:#fff;--border:#dce3ea;--text:#172033;--muted:#596779;
  --accent:#b83232;--accent-soft:#fff3f1;--md-accent:#245bb5;--md-soft:#eff5ff;
  --radius:16px;--shadow:0 8px 28px rgba(23,32,51,.055);
}
*{box-sizing:border-box;margin:0;padding:0}
body{
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,sans-serif;
  background:var(--bg);color:var(--text);line-height:1.6;min-height:100vh;
  display:flex;flex-direction:column;
}
a{color:var(--accent)}
a:focus-visible,button:focus-visible,input:focus-visible,textarea:focus-visible,select:focus-visible{outline:3px solid rgba(36,91,181,.45);outline-offset:3px}

/* ---------- top navigation ---------- */
.topbar{background:var(--surface);border-bottom:1px solid var(--border)}
.topbar .inner{max-width:1200px;margin:0 auto;padding:12px 24px;display:flex;align-items:center;justify-content:space-between;gap:12px;flex-wrap:wrap}
.brand{font-weight:700;font-size:1rem;color:var(--text);text-decoration:none;letter-spacing:-.01em;white-space:nowrap;display:inline-flex;align-items:center;gap:9px}
.brand-mark{width:210px;height:auto;max-height:58px;display:block}
.topbar nav{display:flex;align-items:center;gap:24px;flex-wrap:wrap}
.topbar nav a{color:var(--muted);text-decoration:none;font-size:.9rem;padding:8px 0;display:inline-block;white-space:nowrap}
.topbar nav a:hover{color:var(--accent)}
.topbar nav a[aria-current="page"]{color:var(--text);font-weight:700;box-shadow:inset 0 -2px var(--accent)}
.topbar nav a[href="/guides"]{margin-left:6px}

/* ---------- page shell ---------- */
main{flex:1;min-width:0}
.wrap{max-width:780px;width:100%;margin:0 auto;padding:40px 24px 56px}
.wrap h1{font-size:1.9rem;letter-spacing:-.02em;margin-bottom:10px}
.wrap h2{font-size:1.25rem;margin:34px 0 10px;letter-spacing:-.01em}
.wrap h3{font-size:1.05rem;margin:24px 0 8px}
.wrap h4{font-size:1rem;margin:22px 0 6px}
.wrap p{margin-bottom:14px}
.wrap ul,.wrap ol{margin:0 0 16px 22px}
.wrap li{margin-bottom:6px}
.wrap .lede{color:var(--muted);font-size:1.05rem}
.wrap .updated{color:var(--muted);font-size:.85rem;margin-bottom:26px}
.wrap code{background:#eef2f7;padding:1px 5px;border-radius:4px;font-size:.88em;font-family:"SF Mono",Monaco,Consolas,"Courier New",monospace;overflow-wrap:anywhere}
.wrap pre{background:#1e293b;color:#e2e8f0;padding:14px 16px;border-radius:10px;overflow-x:auto;margin-bottom:18px;font-size:.8rem;line-height:1.5}
.wrap pre code{background:none;color:inherit;padding:0;font-size:inherit}
.wrap blockquote{border-left:3px solid var(--border);padding-left:14px;color:var(--muted);margin-bottom:16px}
.wrap table{width:100%;border-collapse:collapse;margin-bottom:18px;font-size:.88rem}
.wrap th,.wrap td{border:1px solid var(--border);padding:8px 10px;text-align:left;vertical-align:top}
.wrap th{background:#f1f5f9;font-weight:600}
.wrap hr{border:none;border-top:1px solid var(--border);margin:28px 0}
.affiliate-note{background:var(--surface);border:1px solid var(--border);border-left:4px solid var(--accent);border-radius:8px;padding:16px 18px;margin:24px 0}
.affiliate-note p:last-child{margin-bottom:0}
.affiliate-note__label{color:var(--muted);font-size:.78rem;font-weight:700;letter-spacing:.04em;text-transform:uppercase;margin-bottom:6px}

.card{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);padding:24px;box-shadow:var(--shadow);margin-bottom:20px}
.btn{display:inline-flex;align-items:center;justify-content:center;min-height:44px;min-width:44px;padding:10px 20px;background:var(--accent);color:#fff;text-decoration:none;border-radius:8px;font-size:.92rem;font-weight:500}
.btn:hover{background:#922626}
.guides-wrap{max-width:1080px}
.guides-wrap>p,.guides-wrap>ul{max-width:780px}
.guide-index{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:14px;margin:18px 0 28px}
.guide-index__group{background:var(--surface);border:1px solid var(--border);border-top:4px solid #cbd5e1;border-radius:var(--radius);padding:20px;box-shadow:var(--shadow)}
.guide-index__group--pdf{border-top-color:var(--accent)}
.guide-index__group--markdown{border-top-color:var(--md-accent)}
.guide-index__group--academic{border-top-color:#7867ad}
.guide-index__group--reference{border-top-color:#64748b}
.guide-index__group h3{margin:0 0 7px;font-size:1rem}
.guide-index__group p{font-size:.88rem;color:var(--muted);margin-bottom:12px}
.guide-index__group ul{margin:0 0 0 18px}
.guide-index__group li{margin-bottom:5px}
.guide-index__group a{text-decoration-thickness:1px;text-underline-offset:3px}

/* ---------- footer ---------- */
footer{background:#f2f4f7;border-top:1px solid var(--border);margin-top:auto}
footer .inner{max-width:1200px;margin:0 auto;padding:26px 24px;display:flex;align-items:center;justify-content:space-between;gap:12px 28px;flex-wrap:wrap}
footer nav{display:flex;align-items:center;gap:20px;flex-wrap:wrap}
footer nav a{color:var(--text);text-decoration:none;font-size:.85rem;font-weight:600;white-space:nowrap}
footer nav a:hover,footer nav a[aria-current="page"]{color:var(--accent)}
footer p{color:var(--muted);font-size:.78rem}
footer a{color:inherit}

@media(max-width:640px){
  .topbar .inner{padding:4px 16px}
  .topbar nav{width:100%;gap:16px}
  .topbar nav a[href="/guides"]{margin-left:0}
  /* 导航与页脚链接在手机上撑到 44px 高，避免误触 */
  .brand{min-height:44px;display:inline-flex;align-items:center}
  .topbar nav a{font-size:.9rem;min-height:44px;display:inline-flex;align-items:center;padding:0 6px}
  footer nav a{min-height:44px;display:inline-flex;align-items:center;padding:0 6px}
  .wrap{padding:28px 16px 44px}
  .wrap h1{font-size:1.5rem}
  .guide-index{grid-template-columns:1fr;gap:10px}
  footer .inner{padding:20px 16px;align-items:flex-start;flex-direction:column;gap:8px}
}

/* Shared direct navigation, 2026-10-14. */
.topbar{position:relative;z-index:30}
.topbar .inner{flex-wrap:nowrap;gap:16px}
.brand-mark{width:180px;max-height:50px}
#site-nav{flex-wrap:nowrap;gap:16px}
#site-nav>a{font-size:.875rem;min-height:44px;display:flex;align-items:center}
#site-nav>a[href="/guides"]{margin-left:0}
.nav-toggle{display:none;min-height:44px;padding:8px 14px;border:1px solid var(--border);border-radius:8px;background:var(--surface);color:var(--text);font:inherit;cursor:pointer}
.nav-group{position:relative}
.nav-group>summary{list-style:none;display:flex;align-items:center;gap:8px;min-height:44px;color:var(--muted);font-size:.875rem;font-weight:500;white-space:nowrap;cursor:pointer}
.nav-group>summary::-webkit-details-marker{display:none}
.nav-group>summary::after{content:"";width:6px;height:6px;flex:0 0 6px;margin-bottom:3px;border-right:1.5px solid currentColor;border-bottom:1.5px solid currentColor;transform:rotate(45deg)}
.nav-group[open]>summary::after{transform:rotate(225deg);margin-top:5px}
.nav-group>summary:hover,.nav-group[open]>summary,.nav-group[data-current="true"]>summary{color:var(--text)}
.nav-group>summary:focus-visible{outline:3px solid rgba(36,91,181,.45);outline-offset:3px;border-radius:4px}
/* The wrapper starts at the trigger edge. Its padding bridges the visual gap. */
.nav-menu{position:absolute;z-index:40;top:100%;left:-12px;width:278px;max-width:calc(100vw - 32px);padding-top:8px}
.nav-group:not([open])>.nav-menu{display:none}
.nav-menu-list{display:grid;gap:2px;padding:8px;background:var(--surface);border:1px solid var(--border);border-radius:12px;box-shadow:0 12px 28px rgba(23,32,51,.14)}
#site-nav .nav-menu a{display:flex;align-items:center;min-height:44px;padding:10px 12px;margin:0;white-space:normal;color:var(--text);font-size:.875rem;line-height:1.4;text-decoration:none;border-radius:7px;box-shadow:none}
#site-nav .nav-menu a:hover,#site-nav .nav-menu a:focus-visible{background:#f0f3f7;color:var(--accent)}
#site-nav .nav-menu a[aria-current="page"]{background:var(--accent-soft);color:var(--accent);font-weight:600}
.tool-directory{margin:28px 0}.tool-family{scroll-margin-top:20px;margin:18px 0;padding:18px;border:1px solid var(--border);border-radius:12px;background:var(--surface)}.tool-family ul{margin-bottom:0}.tool-family a{display:inline-block;padding:5px 0}
@media(max-width:959px){
  .topbar .inner{flex-wrap:wrap;padding:8px 16px;gap:8px}
  .brand-mark{width:160px}
  .nav-js .nav-toggle{display:block}
  #site-nav{display:grid;width:100%;grid-template-columns:repeat(2,minmax(0,1fr));gap:8px;padding:4px 0 8px}
  .nav-js #site-nav:not([data-open="true"]){display:none}
  #site-nav>a{min-height:44px;padding:10px 12px;white-space:normal;border:1px solid var(--border);border-radius:9px;background:var(--surface)}
  #site-nav>a[aria-current="page"]{background:var(--accent-soft);box-shadow:none}
  #site-nav>a[href="/guides"]{grid-column:1/-1}
  .nav-group{grid-column:1/-1;min-width:0;border:1px solid var(--border);border-radius:9px;background:var(--surface)}
  .nav-group>summary{justify-content:space-between;padding:10px 14px;min-height:46px}
  .nav-menu{position:static;width:auto;max-width:none;padding:0 8px 8px}
  .nav-menu-list{width:auto;border:0;border-top:1px solid var(--border);border-radius:0;padding:8px 0 0;box-shadow:none}
  #site-nav .nav-menu a{padding:10px 12px}
}

/* Evidence visuals: text remains selectable and reflows on narrow screens. */
.evidence-visual{margin:28px 0;padding:24px;border:1px solid var(--border);border-radius:14px;background:var(--surface);max-width:100%;min-width:0}
.evidence-visual figcaption{display:grid;gap:7px;margin-bottom:22px}
.evidence-kicker{display:block;color:var(--md-accent);font-size:.7rem;font-weight:750;letter-spacing:.1em;line-height:1.5}
.evidence-visual figcaption strong{font-size:1.25rem;line-height:1.35;letter-spacing:-.02em}
.evidence-visual figcaption>span:last-child{font-size:.86rem;color:var(--muted)}
.output-pair{display:grid;gap:12px}.output-case{padding:16px;background:#f5f7fa;border:1px solid var(--border);border-radius:10px;min-width:0}
.case-label{display:block;font-size:.78rem;font-weight:700;color:var(--muted);margin-bottom:10px}
.output-case code{display:block;background:none;padding:0;font-size:.86rem;white-space:normal;overflow-wrap:anywhere;line-height:1.8}
.output-case p{font-size:.8rem;color:var(--muted);margin:10px 0 0}
.space-marker{background:#d9eee5;color:#165b43;padding:1px 3px;border-radius:3px}.join-marker{background:#ffe7dc;color:#8b381a;padding:1px 3px;border-radius:3px}
.evidence-visual .evidence-caption{font-size:.78rem;line-height:1.65;color:var(--muted);margin:18px 0 0;max-width:78ch}
.pagination-chart{display:grid;gap:20px}.pagination-row{display:grid;grid-template-columns:minmax(160px,1fr) minmax(100px,1.2fr) 64px;align-items:center;gap:18px}
.pagination-row a{font-size:.9rem;font-weight:650}.pagination-row span{display:block;font-size:.77rem;color:var(--muted);margin-top:4px}.pagination-row>strong{font-size:.84rem;white-space:nowrap;text-align:right}
.page-bar-track{background:#edf1f5;border-radius:4px;height:14px;overflow:hidden}.page-bar{background:var(--md-accent);height:100%;border-radius:4px}.page-bar--warning{background:#a65a31}
.dataset-access{display:grid;gap:9px;padding:20px 22px;margin:24px 0 30px;background:var(--surface);border:1px solid var(--border);border-left:3px solid var(--md-accent);border-radius:10px}
.dataset-primary{display:inline-flex;align-items:center;gap:12px;font-size:1rem;font-weight:700;min-height:44px;color:var(--md-accent);text-underline-offset:4px}.dataset-access p{font-size:.85rem;line-height:1.65;color:var(--muted);margin:0}
@media(max-width:600px){.evidence-visual{padding:18px 16px}.pagination-row{grid-template-columns:minmax(0,1fr) 64px;gap:8px 12px}.pagination-row>div:first-child{grid-column:1/-1}.page-bar-track{height:12px}.dataset-access{padding:18px 16px}.output-case{padding:12px}}