/* ============================================================
   BAIDLABS — shared design system (subpages)
   Light editorial: warm paper, serif display, mono labels.
   ============================================================ */
:root{
  --paper:#fbfaf7;
  --paper-2:#ffffff;
  --ink:#101014;
  --muted:#5c5e66;
  --faint:#6e6f78;
  --line:#e7e4dc;
  --line-2:#efede6;
  --blue:#2438ff;
  --blue-soft:#eceeff;
  --serif:"Instrument Serif",Georgia,"Times New Roman",serif;
  --sans:"Inter",ui-sans-serif,system-ui,sans-serif;
  --mono:"IBM Plex Mono",ui-monospace,"SF Mono",monospace;
  --container:1160px;
  --pad:24px;
}
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
html,body{overflow-x:hidden}
body{
  background:var(--paper);color:var(--ink);font-family:var(--sans);
  font-size:16.5px;line-height:1.65;-webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
}
::selection{background:var(--blue);color:#fff}
img,svg{display:block;max-width:100%}
a{color:inherit;text-decoration:none}
button{font:inherit;color:inherit;background:none;border:0;cursor:pointer}
h1,h2,h3,h4{font-weight:400;letter-spacing:-.01em}
h1,h2{font-family:var(--serif);line-height:1.06}
:focus-visible{outline:2px solid var(--blue);outline-offset:3px;border-radius:4px}
em{font-family:var(--serif);font-style:italic}
.wrap{max-width:var(--container);margin:0 auto;padding:0 var(--pad)}
.accent{color:var(--blue)}
.mono{font-family:var(--mono)}

/* ---------- nav ---------- */
.nav{position:fixed;top:0;left:0;right:0;z-index:50;transition:background .3s,border-color .3s;border-bottom:1px solid transparent}
.nav.scrolled{background:rgba(251,250,247,.88);backdrop-filter:blur(12px);-webkit-backdrop-filter:blur(12px);border-bottom-color:var(--line)}
.nav-in{max-width:var(--container);margin:0 auto;padding:0 var(--pad);height:76px;display:flex;align-items:center;justify-content:space-between;gap:24px}
.logo{display:flex;align-items:center;gap:11px;font-weight:600;font-size:1.06rem}
.logo-mark{width:30px;height:30px;border-radius:8px;background:var(--blue);display:grid;place-items:center;flex:0 0 30px}
.logo-mark svg{width:16px;height:16px}
.logo span span{color:var(--faint);font-weight:500}
.nav-links{display:flex;align-items:center;gap:30px;font-size:.92rem;color:var(--muted)}
.nav-links a{position:relative;transition:color .2s}
.nav-links a::after{content:"";position:absolute;left:0;bottom:-5px;width:0;height:1px;background:var(--ink);transition:width .25s}
.nav-links a:hover{color:var(--ink)}
.nav-links a:hover::after{width:100%}
.nav-links a.on{color:var(--ink)}
.nav-links a.on::after{width:100%;background:var(--blue)}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:10px;font-weight:500;font-size:.95rem;border-radius:999px;padding:13px 26px;transition:background .25s,color .25s,border-color .25s,transform .25s;white-space:nowrap}
.btn-ink{background:var(--ink);color:var(--paper)}
.btn-ink:hover{background:var(--blue);transform:translateY(-1px)}
.btn-line{border:1px solid var(--line);color:var(--ink)}
.btn-line:hover{border-color:var(--ink)}
.btn-sm{padding:10px 20px;font-size:.88rem}
.btn .arr{transition:transform .25s}
.btn:hover .arr{transform:translateX(3px)}
.tlink{display:inline-flex;align-items:center;gap:8px;font-weight:500;border-bottom:1px solid var(--ink);padding-bottom:2px;transition:color .2s,border-color .2s}
.tlink:hover{color:var(--blue);border-color:var(--blue)}
.burger{display:none;width:42px;height:42px;border:1px solid var(--line);border-radius:10px;place-items:center;background:var(--paper)}
.burger span{display:block;width:16px;height:1.5px;background:var(--ink);position:relative;transition:.3s}
.burger span::before,.burger span::after{content:"";position:absolute;left:0;width:16px;height:1.5px;background:var(--ink);transition:.3s}
.burger span::before{top:-5px}.burger span::after{top:5px}
.burger.open span{background:transparent}
.burger.open span::before{top:0;transform:rotate(45deg)}
.burger.open span::after{top:0;transform:rotate(-45deg)}
.mobile-menu{position:fixed;inset:0;z-index:49;background:var(--paper);display:flex;flex-direction:column;justify-content:center;padding:0 8vw;opacity:0;pointer-events:none;transition:opacity .3s}
.mobile-menu.open{opacity:1;pointer-events:auto}
.mobile-menu a{font-family:var(--serif);font-size:2.1rem;padding:13px 0;border-bottom:1px solid var(--line)}
.mobile-menu a.btn{font-family:var(--sans);font-size:1.05rem;font-weight:500;border-bottom:none;margin-top:28px;justify-content:center;padding:16px 26px;display:inline-flex}

/* ---------- article header ---------- */
.crumbs{display:flex;align-items:center;gap:9px;flex-wrap:wrap;font-family:var(--mono);font-size:.7rem;letter-spacing:.1em;text-transform:uppercase;color:var(--faint);margin-bottom:26px}
.crumbs a{transition:color .2s}
.crumbs a:hover{color:var(--blue)}
.crumbs i{font-style:normal;opacity:.45}
.art-head{padding:150px 0 0}
.art-head h1{font-size:clamp(2.3rem,4.8vw,3.7rem);max-width:900px;margin-bottom:22px}
.art-meta{display:flex;gap:10px;flex-wrap:wrap;align-items:center;font-family:var(--mono);font-size:.7rem;letter-spacing:.1em;text-transform:uppercase;color:var(--faint)}
.art-meta .tag{border:1px solid var(--line);border-radius:999px;padding:5px 12px}
.art-meta .dot{opacity:.4}

/* answer-first box */
.answer-box{
  border-left:3px solid var(--blue);background:var(--paper-2);border-radius:0 14px 14px 0;
  border-top:1px solid var(--line);border-right:1px solid var(--line);border-bottom:1px solid var(--line);
  padding:28px 30px;margin:44px 0 8px;max-width:820px;
}
.answer-box .lbl{display:block;font-family:var(--mono);font-size:.68rem;letter-spacing:.16em;text-transform:uppercase;color:var(--blue);margin-bottom:12px}
.answer-box p{font-size:1.09rem;color:var(--ink);line-height:1.6}

/* ---------- article body ---------- */
.art-body{padding:20px 0 40px}
.art-body > *{max-width:868px}
.art-body h2{font-size:clamp(1.6rem,3vw,2.15rem);margin:52px 0 16px;scroll-margin-top:100px}
.art-body h3{font-size:1.16rem;font-weight:600;margin:32px 0 10px}
.art-body p{color:var(--muted);margin-bottom:18px}
.art-body p strong,.art-body li strong{color:var(--ink);font-weight:600}
.art-body a:not(.btn):not(.tlink){color:var(--blue);text-decoration:underline;text-underline-offset:3px;text-decoration-color:rgba(36,56,255,.35);transition:text-decoration-color .2s}
.art-body a:not(.btn):not(.tlink):hover{text-decoration-color:var(--blue)}
.art-body ul,.art-body ol{margin:0 0 20px 0;padding-left:22px;color:var(--muted)}
.art-body li{margin-bottom:10px}
.art-body li::marker{color:var(--blue)}
.art-body blockquote{border-left:2px solid var(--line);padding-left:22px;margin:26px 0;color:var(--muted);font-family:var(--serif);font-size:1.25rem;line-height:1.45}

/* table */
.tbl-wrap{overflow-x:auto;margin:26px 0;border:1px solid var(--line);border-radius:14px;background:var(--paper-2)}
table{border-collapse:collapse;width:100%;min-width:520px;font-size:.93rem}
th,td{text-align:left;padding:14px 18px;border-bottom:1px solid var(--line-2);vertical-align:top}
th{font-family:var(--mono);font-size:.68rem;letter-spacing:.1em;text-transform:uppercase;color:var(--faint);font-weight:500;background:var(--paper)}
tr:last-child td{border-bottom:none}
td strong{color:var(--ink)}

/* callouts */
.note{border:1px solid var(--line);border-radius:14px;background:var(--paper-2);padding:22px 26px;margin:28px 0;font-size:.95rem;color:var(--muted)}
.note b{color:var(--ink)}
.stat-row{display:grid;grid-template-columns:repeat(auto-fit,minmax(190px,1fr));gap:22px;margin:32px 0;padding:26px 0;border-top:1px solid var(--line);border-bottom:1px solid var(--line)}
.stat-row .s-n{font-family:var(--serif);font-size:2.2rem;line-height:1;color:var(--blue);display:block}
.stat-row .s-l{font-size:.88rem;color:var(--muted);margin-top:8px;display:block}
.stat-row .s-src{font-family:var(--mono);font-size:.64rem;letter-spacing:.08em;text-transform:uppercase;color:var(--faint);margin-top:8px;display:block}
.stat-row .s-src a{color:inherit;text-decoration:underline;text-underline-offset:2px}

/* checklist */
.chk{list-style:none;padding:0;margin:22px 0}
.chk li{display:flex;gap:13px;align-items:flex-start;margin-bottom:13px;color:var(--muted)}
.chk .tick{flex:0 0 21px;width:21px;height:21px;border-radius:50%;background:var(--blue-soft);color:var(--blue);display:grid;place-items:center;font-size:.68rem;margin-top:2px}

/* FAQ */
.faq{border-bottom:1px solid var(--line)}
.faq:first-of-type{border-top:1px solid var(--ink)}
.faq summary{list-style:none;cursor:pointer;display:flex;justify-content:space-between;align-items:center;gap:20px;padding:22px 4px;font-weight:600;font-size:1.01rem;transition:color .2s}
.faq summary:hover{color:var(--blue)}
.faq summary::-webkit-details-marker{display:none}
.faq summary .plus{flex:0 0 26px;width:26px;height:26px;border-radius:50%;border:1px solid var(--line);display:grid;place-items:center;font-weight:400;color:var(--muted);transition:.3s}
.faq[open] summary .plus{transform:rotate(45deg);background:var(--ink);border-color:var(--ink);color:var(--paper)}
.faq-body{padding:0 4px 24px;color:var(--muted);font-size:.96rem;max-width:700px}

/* related + CTA */
.rel{display:grid;grid-template-columns:repeat(auto-fit,minmax(250px,1fr));gap:18px;margin:26px 0 0}
.rel a{border:1px solid var(--line);border-radius:14px;background:var(--paper-2);padding:22px 24px;transition:transform .3s,border-color .3s}
.rel a:hover{transform:translateY(-3px);border-color:var(--blue)}
.rel .k{font-family:var(--mono);font-size:.65rem;letter-spacing:.12em;text-transform:uppercase;color:var(--blue);display:block;margin-bottom:9px}
.rel .t{font-family:var(--serif);font-size:1.2rem;display:block;line-height:1.25}
.cta-band{border:1px solid var(--line);border-radius:20px;background:radial-gradient(700px 300px at 12% 0%,rgba(36,56,255,.07),transparent 60%),var(--paper-2);padding:44px 46px;margin:64px 0 0;display:flex;justify-content:space-between;gap:32px;align-items:center;flex-wrap:wrap}
.cta-band h3{font-family:var(--serif);font-size:1.8rem;font-weight:400;margin-bottom:8px}
.cta-band p{color:var(--muted);font-size:.95rem;max-width:460px}

/* section heads */
.eyebrow{display:flex;align-items:center;gap:14px;font-family:var(--mono);font-size:.72rem;letter-spacing:.14em;text-transform:uppercase;color:var(--faint);margin-bottom:24px}
.eyebrow b{color:var(--blue);font-weight:500}
.eyebrow::after{content:"";height:1px;flex:0 0 56px;background:var(--line)}
section{padding:96px 0}

/* ---------- footer ---------- */
footer{border-top:1px solid var(--line);padding-top:56px;margin-top:90px;overflow:hidden}
.foot-grid{display:flex;justify-content:space-between;gap:40px;flex-wrap:wrap;margin-bottom:50px}
.foot-brand{max-width:310px}
.foot-brand p{color:var(--faint);font-size:.9rem;margin-top:14px}
.foot-cols{display:flex;gap:64px;flex-wrap:wrap}
.foot-col h4{font-family:var(--mono);font-size:.68rem;letter-spacing:.16em;text-transform:uppercase;color:var(--faint);margin-bottom:16px;font-weight:500}
.foot-col a,.foot-col span{display:block;color:var(--muted);font-size:.92rem;padding:4px 0;transition:color .2s}
.foot-col a:hover{color:var(--blue)}
.foot-base{display:flex;justify-content:space-between;gap:20px;flex-wrap:wrap;border-top:1px solid var(--line);padding:22px 0;color:var(--faint);font-size:.8rem}

/* reveal */
.reveal{opacity:0;transform:translateY(16px);transition:opacity .6s cubic-bezier(.2,.6,.2,1),transform .6s cubic-bezier(.2,.6,.2,1)}
.reveal.in{opacity:1;transform:none}

@media (max-width:860px){
  .nav-links,.nav-in > .btn{display:none}
  .burger{display:grid}
  .art-head{padding-top:120px}
  section{padding:70px 0}
  .cta-band{padding:32px 26px}
}
@media (max-width:620px){
  body{font-size:15.5px}
  .answer-box{padding:22px 20px}
  .cta-band .btn{width:100%}
}
@media (prefers-reduced-motion:reduce){
  *,*::before,*::after{animation:none!important;transition:none!important;scroll-behavior:auto!important}
  .reveal{opacity:1;transform:none}
}