:root{
  --bg:#ffffff;
  --bg-subtle:#fafafa;
  --border:#e7e8ea;
  --border-strong:#d9dadd;
  --text:#111214;
  --text-secondary:#55565b;
  --text-tertiary:#8b8d94;
  --accent:#2563eb;
  --accent-subtle:#eff4ff;
  --green:#16a34a;
  --green-subtle:#f0faf3;
  --red:#dc2626;
  --red-subtle:#fdf1f1;
  --shadow-sm:0 1px 2px rgba(0,0,0,.04);
  --shadow-md:0 1px 3px rgba(0,0,0,.05), 0 8px 24px rgba(0,0,0,.06);
}
*{margin:0;padding:0;box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  font-family:'Inter',-apple-system,BlinkMacSystemFont,sans-serif;
  background:var(--bg);color:var(--text);
  font-size:15px;line-height:1.6;
  -webkit-font-smoothing:antialiased;text-rendering:optimizeLegibility;
}
a{color:inherit;text-decoration:none}
.container{max-width:1120px;margin:0 auto;padding:0 24px}
h1,h2,h3{letter-spacing:-.02em;line-height:1.15;font-weight:600}

.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:6px;
  font-size:14px;font-weight:500;line-height:1;
  padding:0 16px;height:38px;border-radius:8px;border:1px solid transparent;
  cursor:pointer;transition:background .12s ease,border-color .12s ease;
  white-space:nowrap;
}
.btn-primary{background:var(--text);color:#fff}
.btn-primary:hover{background:#2b2c30}
.btn-secondary{background:var(--bg);color:var(--text);border-color:var(--border-strong)}
.btn-secondary:hover{border-color:#b9bbc0;background:var(--bg-subtle)}
.btn-lg{height:44px;padding:0 20px;font-size:15px}
.btn:focus-visible{outline:2px solid var(--accent);outline-offset:2px}

/* nav */
.nav-wrap{position:sticky;top:0;z-index:100;background:rgba(255,255,255,.82);backdrop-filter:blur(10px);border-bottom:1px solid var(--border)}
.nav{height:60px;display:flex;align-items:center;gap:32px}
.logo{display:flex;align-items:center;gap:8px;font-weight:600;font-size:16px;letter-spacing:-.01em}
.logo svg{display:block}
.nav-links{display:flex;gap:4px;flex:1}
.nav-links a{font-size:14px;color:var(--text-secondary);padding:6px 12px;border-radius:6px;transition:color .12s ease,background .12s ease}
.nav-links a:hover{color:var(--text);background:var(--bg-subtle)}
.nav-actions{display:flex;gap:10px;align-items:center}
.nav-actions .signin{font-size:14px;color:var(--text-secondary);padding:6px 10px}
.nav-actions .signin:hover{color:var(--text)}

/* page scaffold */
.page-head{padding:72px 0 20px;max-width:720px}
.kicker{font-size:13px;font-weight:600;color:var(--accent);margin-bottom:12px;display:block}
.page-head h1{font-size:clamp(30px,4.4vw,42px);letter-spacing:-.03em;margin-bottom:14px}
.page-head .lede{font-size:17px;color:var(--text-secondary)}
.page-body{padding:28px 0 88px}

/* prose */
.prose{max-width:720px}
.prose h2{font-size:23px;letter-spacing:-.025em;margin:44px 0 12px}
.prose h3{font-size:17px;margin:28px 0 8px}
.prose p{color:var(--text-secondary);margin-bottom:16px}
.prose ul,.prose ol{margin:0 0 16px 20px;color:var(--text-secondary)}
.prose li{margin-bottom:8px}
.prose b,.prose strong{color:var(--text);font-weight:600}
.prose a{color:var(--accent)}
.prose a:hover{text-decoration:underline}
.prose .callout{
  border:1px solid var(--border);border-left:3px solid var(--accent);
  border-radius:0 10px 10px 0;background:var(--bg-subtle);
  padding:16px 18px;margin:24px 0;font-size:14px;color:var(--text-secondary);
}
.prose .formula{
  font-family:ui-monospace,SFMono-Regular,Menlo,monospace;font-size:13.5px;
  border:1px solid var(--border);border-radius:10px;background:var(--bg-subtle);
  padding:16px 18px;margin:20px 0;color:var(--text);overflow-x:auto;
}

/* CTA band on subpages */
.page-cta{
  margin-top:56px;border:1px solid var(--border);border-radius:14px;
  background:var(--bg-subtle);padding:32px;max-width:720px;
  display:flex;align-items:center;justify-content:space-between;gap:20px;flex-wrap:wrap;
}
.page-cta h3{font-size:18px;margin-bottom:4px}
.page-cta p{font-size:14px;color:var(--text-secondary)}

/* blog cards */
.post-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:20px;padding-top:16px}
.post-card{
  border:1px solid var(--border);border-radius:12px;padding:24px;background:var(--bg);
  box-shadow:var(--shadow-sm);display:flex;flex-direction:column;gap:10px;
  transition:transform .15s ease,box-shadow .15s ease;
}
.post-card:hover{transform:translateY(-2px);box-shadow:var(--shadow-md)}
.post-meta{font-size:12px;color:var(--text-tertiary);display:flex;gap:8px;align-items:center}
.post-tag{
  font-size:11px;font-weight:600;color:var(--accent);background:var(--accent-subtle);
  border-radius:100px;padding:2px 9px;
}
.post-card h3{font-size:17px;letter-spacing:-.015em}
.post-card p{font-size:13.5px;color:var(--text-secondary);flex:1}
.post-card .read{font-size:13px;font-weight:500;color:var(--text-tertiary)}

/* contact */
.contact-grid{display:grid;grid-template-columns:1fr 1fr;gap:48px;align-items:start;padding-top:8px}
.contact-card{
  border:1px solid var(--border);border-radius:12px;padding:28px;background:var(--bg);box-shadow:var(--shadow-sm);
}
.field{margin-bottom:16px}
.field label{display:block;font-size:13px;font-weight:500;margin-bottom:6px}
.field input,.field textarea{
  width:100%;font-family:inherit;font-size:14px;color:var(--text);
  border:1px solid var(--border-strong);border-radius:8px;background:var(--bg);
  padding:10px 13px;transition:border-color .12s ease,box-shadow .12s ease;
}
.field textarea{min-height:120px;resize:vertical}
.field input:focus,.field textarea:focus{outline:none;border-color:var(--accent);box-shadow:0 0 0 3px rgba(37,99,235,.12)}
.contact-line{display:flex;gap:12px;align-items:flex-start;margin-bottom:18px;font-size:14.5px;color:var(--text-secondary)}
.contact-line b{color:var(--text);font-weight:600;display:block;font-size:14px}
.contact-line .ico{
  width:34px;height:34px;flex-shrink:0;border-radius:8px;background:var(--accent-subtle);
  color:var(--accent);display:flex;align-items:center;justify-content:center;
}

/* footer */
footer{border-top:1px solid var(--border);padding:56px 0 40px;background:var(--bg-subtle);margin-top:40px}
.foot-grid{display:grid;grid-template-columns:2fr 1fr 1fr 1fr;gap:40px;margin-bottom:48px}
.foot-brand p{font-size:13px;color:var(--text-tertiary);margin-top:12px;max-width:260px}
.foot-col h5{font-size:13px;font-weight:600;margin-bottom:14px}
.foot-col a{display:block;font-size:13.5px;color:var(--text-secondary);padding:4px 0}
.foot-col a:hover{color:var(--text)}
.foot-bottom{border-top:1px solid var(--border);padding-top:24px;display:flex;justify-content:space-between;align-items:center;font-size:13px;color:var(--text-tertiary);flex-wrap:wrap;gap:12px}

@media (max-width:960px){
  .nav-links{display:none}
  .post-grid{grid-template-columns:1fr}
  .contact-grid{grid-template-columns:1fr}
  .foot-grid{grid-template-columns:1fr 1fr}
  .page-head{padding-top:48px}
}