/* Chat Picker (aiselect.chat) — token source of truth. Signal yellow + ink on a neutral white. */
:root {
  --bg: oklch(0.985 0 0);
  --surface: oklch(1 0 0);
  --band: oklch(0.955 0.004 100);
  --ink: oklch(0.19 0.01 100);
  --ink-2: oklch(0.36 0.01 100);
  --ink-3: oklch(0.47 0.01 100);
  --rule: oklch(0.86 0.005 100);
  --rule-strong: oklch(0.19 0.01 100);
  --signal: oklch(0.89 0.18 98);
  --signal-deep: oklch(0.82 0.17 92);
  --flag: oklch(0.52 0.19 28);
  --flag-bg: oklch(0.95 0.03 28);
  --link: oklch(0.36 0.14 265);
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  --wrap: 1120px;
  --read: 720px;
  --z-sticky: 20;
  --z-menu: 30;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
}
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body { margin: 0; background: var(--bg); color: var(--ink); font-family: var(--sans); font-size: 17px; line-height: 1.6; }
img { max-width: 100%; height: auto; }
a { color: var(--link); text-underline-offset: 0.18em; }
a:hover { color: var(--ink); }
:focus-visible { outline: 3px solid var(--ink); outline-offset: 2px; }
h1, h2, h3 { text-wrap: balance; line-height: 1.12; letter-spacing: -0.02em; margin: 0; }
p { margin: 0 0 1em; }
.wrap { max-width: var(--wrap); margin-inline: auto; padding-inline: 24px; }
.read { max-width: var(--read); }
.skip { position: absolute; left: -999px; }
.skip:focus { left: 12px; top: 12px; background: var(--ink); color: var(--bg); padding: 8px 12px; z-index: var(--z-menu); }

/* header */
.top { background: var(--surface); border-bottom: 2px solid var(--rule-strong); position: relative; z-index: var(--z-sticky); }
.top .wrap { display: flex; align-items: center; gap: 24px; min-height: 64px; }
.mark { display: inline-flex; align-items: center; gap: 10px; font-weight: 800; font-size: 19px; color: var(--ink); text-decoration: none; letter-spacing: -0.02em; }
.mark i { display: grid; place-items: center; width: 30px; height: 30px; background: var(--signal); border: 2px solid var(--ink); font: 800 12px/1 var(--mono); font-style: normal; }
.nav { margin-left: auto; display: flex; gap: 4px; align-items: center; }
.nav a { color: var(--ink); text-decoration: none; font-weight: 600; font-size: 15px; padding: 10px 12px; }
.nav a:hover, .nav a[aria-current="page"] { background: var(--signal); }
.menu-btn { display: none; margin-left: auto; background: var(--surface); border: 2px solid var(--ink); font: 700 14px var(--sans); padding: 9px 14px; min-height: 44px; color: var(--ink); cursor: pointer; }
@media (max-width: 760px) {
  .menu-btn { display: block; }
  .nav { display: none; position: absolute; left: 0; right: 0; top: 100%; background: var(--surface); border-bottom: 2px solid var(--ink); flex-direction: column; align-items: stretch; padding: 8px 16px 16px; gap: 0; z-index: var(--z-menu); }
  .nav.open { display: flex; }
  .nav a { padding: 14px 8px; border-bottom: 1px solid var(--rule); font-size: 17px; }
}

/* hero */
.hero { background: var(--signal); border-bottom: 2px solid var(--ink); }
.hero .wrap { padding-block: 56px 48px; display: grid; gap: 40px; grid-template-columns: minmax(0, 1.05fr) minmax(0, 1fr); align-items: start; }
.hero h1 { font-size: clamp(2.3rem, 5.2vw, 4.1rem); font-weight: 850; letter-spacing: -0.035em; }
.hero h1 em { font-style: normal; background: var(--ink); color: var(--signal); padding: 0 0.14em; }
.hero .lede { font-size: 1.14rem; max-width: 34em; margin: 20px 0 28px; color: var(--ink); }
.pick { display: grid; grid-template-columns: 1fr auto 1fr; gap: 10px; align-items: end; max-width: 520px; }
.pick label { display: grid; gap: 6px; font-size: 13px; font-weight: 700; }
.pick select { width: 100%; font: 600 17px var(--sans); padding: 12px 12px; min-height: 48px; background: var(--surface); color: var(--ink); border: 2px solid var(--ink); border-radius: 0; }
.pick .v { font: 800 15px var(--mono); padding-bottom: 14px; }
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; background: var(--ink); color: var(--bg); border: 2px solid var(--ink); font: 700 16px var(--sans); padding: 12px 20px; min-height: 48px; text-decoration: none; cursor: pointer; transition: transform 180ms var(--ease), box-shadow 180ms var(--ease); }
.btn:hover { color: var(--bg); transform: translate(-2px, -2px); box-shadow: 4px 4px 0 var(--ink-3); }
.btn.alt { background: var(--surface); color: var(--ink); }
.btn.alt:hover { color: var(--ink); }
.pick .btn { grid-column: 1 / -1; }
.hero-links { margin-top: 18px; font-size: 15px; display: flex; flex-wrap: wrap; gap: 6px 18px; }
.hero-links a { color: var(--ink); font-weight: 600; }

/* price ladder (hero data visual) */
.ladder { background: var(--surface); border: 2px solid var(--ink); box-shadow: 8px 8px 0 var(--ink); }
.ladder caption { caption-side: top; text-align: left; padding: 14px 16px 10px; font-weight: 800; font-size: 15px; border-bottom: 2px solid var(--ink); }
.ladder table, table.ladder { width: 100%; border-collapse: collapse; font-size: 14.5px; }
.ladder th, .ladder td { padding: 11px 12px; text-align: left; vertical-align: top; border-bottom: 1px solid var(--rule); }
.ladder thead th { font-size: 13px; background: var(--band); }
.ladder tbody th { font-weight: 600; color: var(--ink-2); width: 24%; }
.ladder td b { font: 700 16px var(--mono); display: block; letter-spacing: -0.02em; }
.ladder td span { color: var(--ink-3); font-size: 12.5px; }
.ladder tfoot td { font-size: 12.5px; color: var(--ink-2); border-bottom: 0; }
@media (max-width: 900px) { .hero .wrap { grid-template-columns: 1fr; padding-block: 40px 44px; } .ladder { box-shadow: 5px 5px 0 var(--ink); } }
@media (max-width: 480px) {
  .pick { grid-template-columns: 1fr; } .pick .v { padding: 0; }
  .ladder th, .ladder td { padding: 9px 8px; } .ladder td b { font-size: 14px; } .ladder { font-size: 13px; }
}

/* sections */
.sec { padding-block: 64px; }
.sec + .sec { border-top: 1px solid var(--rule); }
.sec.band { background: var(--band); }
.sec h2 { font-size: clamp(1.6rem, 3vw, 2.2rem); font-weight: 800; margin-bottom: 10px; }
.sec .sub { color: var(--ink-2); max-width: 44em; margin-bottom: 30px; }

/* fixture rows */
.fixtures { list-style: none; margin: 0; padding: 0; border-top: 2px solid var(--ink); }
.fixtures li { border-bottom: 1px solid var(--rule); }
.fixtures a { display: grid; grid-template-columns: minmax(0, 1.1fr) minmax(0, 1.4fr) auto; gap: 24px; align-items: center; padding: 22px 8px; color: var(--ink); text-decoration: none; transition: background 160ms var(--ease); }
.fixtures a:hover { background: var(--signal); }
.fixtures .t { font-size: clamp(1.25rem, 2.4vw, 1.7rem); font-weight: 800; letter-spacing: -0.025em; }
.fixtures .t small { font: 700 0.6em var(--mono); color: var(--ink-3); padding: 0 0.3em; }
.fixtures .d { color: var(--ink-2); font-size: 15.5px; }
.fixtures .go { font: 700 14px var(--mono); white-space: nowrap; }
@media (max-width: 760px) { .fixtures a { grid-template-columns: 1fr; gap: 6px; padding: 18px 4px; } }

.method { display: grid; gap: 28px 48px; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); counter-reset: m; }
.method div { counter-increment: m; }
.method h3 { font-size: 1.12rem; margin-bottom: 8px; }
.method h3::before { content: counter(m); font: 800 14px var(--mono); background: var(--ink); color: var(--signal); padding: 3px 8px; margin-right: 10px; }
.method p { color: var(--ink-2); font-size: 15.5px; margin: 0; }

.list { list-style: none; margin: 0; padding: 0; columns: 2; column-gap: 48px; }
.list li { break-inside: avoid; padding: 12px 0; border-bottom: 1px solid var(--rule); }
.list a { color: var(--ink); font-weight: 600; text-decoration: none; }
.list a:hover { text-decoration: underline; }
.list p { margin: 4px 0 0; font-size: 14px; color: var(--ink-3); }
@media (max-width: 760px) { .list { columns: 1; } }
.more { margin-top: 24px; }

/* ask box */
.ask { border: 2px solid var(--ink); background: var(--surface); padding: 24px; max-width: 760px; }
.ask h2, .ask h3 { font-size: 1.3rem; margin-bottom: 6px; }
.ask p { color: var(--ink-2); font-size: 15px; }
.ask form { display: flex; gap: 10px; flex-wrap: wrap; }
.ask input { flex: 1 1 260px; font: 16px var(--sans); padding: 12px; min-height: 48px; border: 2px solid var(--ink); border-radius: 0; background: var(--bg); color: var(--ink); }
.ask input::placeholder { color: var(--ink-3); }
.ask [data-ask-note] { margin: 10px 0 0; font-size: 14px; min-height: 1.3em; }

/* page heads */
.phead { background: var(--surface); border-bottom: 2px solid var(--ink); padding-block: 40px 36px; }
.crumbs { list-style: none; display: flex; flex-wrap: wrap; gap: 6px; padding: 0; margin: 0 0 18px; font-size: 14px; color: var(--ink-3); }
.crumbs li + li::before { content: "/"; margin-right: 6px; }
.crumbs a { color: var(--ink-2); }
.phead h1 { font-size: clamp(2rem, 4.4vw, 3.2rem); font-weight: 850; letter-spacing: -0.03em; max-width: 20em; }
.phead .lede { font-size: 1.1rem; color: var(--ink-2); max-width: 46em; margin: 16px 0 0; }
.stamp { display: inline-flex; flex-wrap: wrap; gap: 6px 14px; margin-top: 20px; font: 600 13px var(--mono); }
.stamp span { background: var(--signal); border: 1.5px solid var(--ink); padding: 4px 9px; }
.stamp span.plain { background: transparent; }

/* comparison page */
.answer { border: 2px solid var(--ink); background: var(--surface); padding: 24px 26px; margin-bottom: 44px; box-shadow: 6px 6px 0 var(--signal-deep); }
.answer h2 { font-size: 1.3rem; margin-bottom: 12px; }
.answer ul { margin: 0; padding-left: 1.15em; }
.answer li { margin-bottom: 8px; }
.cmp h2 { font-size: clamp(1.45rem, 2.6vw, 1.9rem); font-weight: 800; margin: 52px 0 6px; }
.cmp h2:first-child { margin-top: 0; }
.cmp .note { color: var(--ink-2); font-size: 15px; max-width: 46em; }
.matrix { width: 100%; border-collapse: collapse; margin-top: 18px; background: var(--surface); border: 2px solid var(--ink); font-size: 15px; }
.matrix th, .matrix td { text-align: left; vertical-align: top; padding: 14px 16px; border-bottom: 1px solid var(--rule); }
.matrix thead th { background: var(--ink); color: var(--bg); font-size: 15px; position: sticky; top: 0; z-index: 1; }
.matrix thead th small { display: block; font-weight: 500; opacity: 0.8; font-size: 12px; }
.matrix tbody th { width: 19%; font-weight: 700; background: var(--band); }
.matrix td + td { border-left: 1px solid var(--rule); }
.matrix .src { display: block; margin-top: 8px; font: 500 12px var(--mono); color: var(--ink-3); }
.matrix .src a { color: var(--ink-2); }
.matrix .cav { display: block; margin-top: 6px; font-size: 13px; color: var(--ink-2); }
.nv { display: inline-block; font: 700 11.5px var(--mono); color: var(--flag); background: var(--flag-bg); border: 1.5px solid var(--flag); padding: 2px 7px; margin-bottom: 6px; }
@media (max-width: 760px) {
  .matrix, .matrix tbody, .matrix tr, .matrix th, .matrix td { display: block; width: 100%; }
  .matrix thead { display: none; }
  .matrix tbody th { width: 100%; border-bottom: 0; padding: 12px 14px 8px; font-size: 15.5px; }
  .matrix td { padding: 10px 14px 14px; }
  .matrix td + td { border-left: 0; }
  .matrix td::before { content: attr(data-p); display: block; font: 800 12.5px var(--mono); margin-bottom: 4px; }
  .matrix tr { border-bottom: 2px solid var(--ink); }
  .matrix tr:last-child { border-bottom: 0; }
}
.fits { display: grid; gap: 0; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); border: 2px solid var(--ink); background: var(--surface); margin-top: 18px; }
.fits > div { padding: 22px 24px; border-right: 1px solid var(--rule); border-bottom: 1px solid var(--rule); }
.fits h3 { font-size: 1.25rem; margin-bottom: 14px; }
.fits h4 { margin: 14px 0 6px; font: 800 12.5px var(--mono); }
.fits h4.y::before { content: "+ "; } .fits h4.n::before { content: "\2212  "; }
.fits ul { margin: 0; padding-left: 1.1em; font-size: 15px; }
.fits li { margin-bottom: 8px; }
.srcs { padding-left: 1.2em; font-size: 15px; }
.srcs li { margin-bottom: 8px; overflow-wrap: anywhere; }
.faq dt { font-weight: 800; margin-top: 20px; font-size: 1.05rem; }
.faq dd { margin: 6px 0 0; color: var(--ink-2); max-width: 46em; }
.related { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 16px; }

/* legacy article + generic docs */
main > article, .doc { max-width: calc(var(--read) + 48px); margin-inline: auto; padding: 44px 24px 24px; }
main > article > p:first-child { font: 700 12.5px var(--mono); color: var(--ink-2); margin: 0 0 14px; }
main > article > p:first-child::before { content: "Guide / "; }
main > article > h1 { font-size: clamp(1.9rem, 4vw, 2.7rem); font-weight: 850; letter-spacing: -0.03em; margin-bottom: 16px; }
main > article > h1 + p { font-size: 1.1rem; color: var(--ink-2); padding-bottom: 24px; border-bottom: 2px solid var(--ink); margin-bottom: 28px; }
.article-prose, .doc { line-height: 1.75; text-wrap: pretty; }
.article-prose h2, .doc h2 { font-size: 1.5rem; margin: 2em 0 0.6em; }
.article-prose h3, .doc h3 { font-size: 1.18rem; margin: 1.6em 0 0.5em; }
.article-prose ul, .article-prose ol, .doc ul { padding-left: 1.2em; margin: 0 0 1em; }
.article-prose li { margin-bottom: 0.4em; }
.article-prose blockquote { margin: 1.4em 0; padding: 14px 18px; background: var(--band); border: 1px solid var(--rule); }
.article-prose table { display: block; overflow-x: auto; border-collapse: collapse; width: 100%; font-size: 15px; margin: 1.2em 0; }
.article-prose th, .article-prose td { border: 1px solid var(--rule); padding: 8px 10px; text-align: left; }
.article-prose th { background: var(--band); }
.article-prose pre { overflow-x: auto; background: var(--ink); color: var(--bg); padding: 16px; font: 14px/1.5 var(--mono); }
.article-prose code { font: 0.92em var(--mono); }
.article-prose img { display: block; margin: 1.2em 0; }
.after { max-width: calc(var(--read) + 48px); margin: 12px auto 0; padding: 0 24px 24px; }
.after .to-vs { display: flex; flex-wrap: wrap; gap: 12px 20px; align-items: center; justify-content: space-between; background: var(--signal); border: 2px solid var(--ink); padding: 18px 20px; }
.after .to-vs p { margin: 0; font-weight: 700; }
.zh-contact[hidden] { display: none; }

/* topics */
.topic h2 { font-size: 1.35rem; margin: 40px 0 4px; padding-top: 18px; border-top: 2px solid var(--ink); }
.topic h2 span { font: 600 13px var(--mono); color: var(--ink-3); margin-left: 8px; }
.jump { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 8px; }
.jump a { border: 1.5px solid var(--ink); padding: 8px 12px; color: var(--ink); text-decoration: none; font-weight: 600; font-size: 14px; background: var(--surface); }
.jump a:hover { background: var(--signal); }

/* footer */
.foot { margin-top: 72px; background: var(--ink); color: oklch(0.86 0.005 100); }
.foot .wrap { padding-block: 40px; display: grid; gap: 24px 48px; grid-template-columns: 1.4fr 1fr 1fr; font-size: 14.5px; }
.foot a { color: oklch(0.97 0 0); }
.foot h2 { font-size: 13px; font-family: var(--mono); letter-spacing: 0; color: var(--signal); margin-bottom: 10px; }
.foot ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 8px; }
.foot .fine { grid-column: 1 / -1; border-top: 1px solid oklch(0.4 0.01 100); padding-top: 18px; font-size: 13px; }
@media (max-width: 760px) { .foot .wrap { grid-template-columns: 1fr; } }

.nf { padding: 96px 24px; text-align: center; }
.nf h1 { font-size: clamp(2.2rem, 6vw, 3.6rem); font-weight: 850; margin-bottom: 14px; }
@media (prefers-reduced-motion: reduce) { * { transition: none !important; scroll-behavior: auto !important; } }