:root {
  --red: #d91e3c;
  --red-deep: #8a0a26;
  --red-soft: #fde8ec;
  --red-line: #f6c3cd;
  --ink: #1b1416;
  --ink-2: #5b5052;
  --ink-3: #8f8487;
  --surface: #ffffff;
  --surface-2: #fdf7f8;
  --grid: #efe6e8;
  /* chart series */
  --s-base: #8f8d88;
  --s-redknot: #d6243f;
  --s-cacheblend: #2a78d6;
  --s-prophet: #eda100;
  --s-local: #f3b8c3;
  --radius: 14px;
  --max: 1080px;
  --prose: 720px;
  color-scheme: light;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font: 17px/1.65 "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color: var(--ink);
  background: var(--surface);
  -webkit-font-smoothing: antialiased;
}
a { color: var(--red); text-decoration: none; }
a:hover { text-decoration: underline; }
img { max-width: 100%; display: block; }

/* nav */
.nav {
  position: sticky; top: 0; z-index: 10;
  background: rgba(255,255,255,.92);
  backdrop-filter: saturate(1.4) blur(8px);
  border-bottom: 1px solid var(--grid);
}
.nav-inner {
  max-width: var(--max); margin: 0 auto; padding: 10px 24px;
  display: flex; align-items: center; gap: 28px;
}
.nav-logo img { height: 34px; width: auto; }
.nav-links { display: flex; gap: 22px; margin-left: auto; font-size: 15px; font-weight: 500; }
.nav-links a { color: var(--ink-2); }
.nav-links a:hover, .nav-links a.active { color: var(--red); text-decoration: none; }

/* layout helpers */
.wrap { max-width: var(--max); margin: 0 auto; padding: 0 24px; }
.prose { max-width: var(--prose); margin: 0 auto; padding: 0 24px; }
.section { padding: 72px 0; }
.section.tint { background: var(--surface-2); border-top: 1px solid var(--grid); border-bottom: 1px solid var(--grid); }
.eyebrow { font-size: 13px; font-weight: 600; letter-spacing: .12em; text-transform: uppercase; color: var(--red); margin: 0 0 8px; }
.muted { color: var(--ink-2); }
.small { font-size: 14px; }
.center { text-align: center; }

/* buttons */
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 11px 22px; border-radius: 999px; font-weight: 600; font-size: 15px;
  border: 1.5px solid var(--red); color: var(--red); background: var(--surface);
  transition: background .15s, color .15s;
}
.btn:hover { background: var(--red-soft); text-decoration: none; }
.btn.primary { background: var(--red); color: #fff; }
.btn.primary:hover { background: var(--red-deep); border-color: var(--red-deep); }
.btn-row { display: flex; gap: 12px; flex-wrap: wrap; justify-content: center; }

/* home hero */
.hero { padding: 64px 0 40px; text-align: center; }
.hero-logo { width: min(560px, 86vw); margin: 0 auto; }
.hero-tag { font-size: clamp(22px, 3.2vw, 30px); font-weight: 600; letter-spacing: -.01em; margin: 18px 0 6px; }
.hero-sub { color: var(--ink-2); margin: 0 0 28px; }

/* head grid visual */
.headviz { max-width: 860px; margin: 0 auto; }
.headviz svg { width: 100%; height: auto; display: block; }
.legend { display: flex; flex-wrap: wrap; gap: 18px; justify-content: center; font-size: 14px; color: var(--ink-2); margin-top: 12px; }
.legend i { display: inline-block; width: 12px; height: 12px; border-radius: 3px; margin-right: 6px; vertical-align: -1px; }

/* formula strip */
.formulas { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.formula {
  background: var(--surface); border: 1px solid var(--grid); border-radius: var(--radius);
  padding: 22px 18px 16px; text-align: center;
}
.formula .k { font-size: 19px; min-height: 52px; display: flex; align-items: center; justify-content: center; overflow-x: auto; }
.formula .cap { font-size: 14px; color: var(--ink-2); margin-top: 8px; }
.formula .num { font-size: 12px; font-weight: 700; color: var(--red); letter-spacing: .1em; }

/* stat tiles */
.stats { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.stat { border-top: 3px solid var(--red); padding: 18px 4px 0; }
.stat .v { font-size: 44px; font-weight: 700; letter-spacing: -.02em; line-height: 1.1; color: var(--ink); }
.stat .l { font-size: 15px; color: var(--ink-2); margin-top: 6px; }
.stat .src { font-size: 12px; color: var(--ink-3); margin-top: 4px; }

/* blog list */
.post-card {
  display: grid; grid-template-columns: 240px 1fr; gap: 28px; align-items: center;
  border: 1px solid var(--grid); border-radius: var(--radius); padding: 24px; background: var(--surface);
  transition: border-color .15s, box-shadow .15s;
}
.post-card:hover { border-color: var(--red-line); box-shadow: 0 6px 24px rgba(217,30,60,.08); text-decoration: none; }
.post-card h2 { margin: 4px 0 8px; font-size: 24px; color: var(--ink); line-height: 1.3; }
.post-card p { margin: 0; color: var(--ink-2); }
.post-card .thumb { background: var(--surface-2); border-radius: 10px; padding: 12px; }
.meta { font-size: 14px; color: var(--ink-3); }

/* article */
.article-head { padding-top: 56px; padding-bottom: 24px; }
.article-head h1 { font-size: clamp(30px, 4.6vw, 44px); line-height: 1.15; letter-spacing: -.02em; margin: 6px 0 14px; }
.article-head .dek { font-size: 20px; color: var(--ink-2); margin: 0 0 14px; }
.article h2 { font-size: 28px; letter-spacing: -.01em; margin: 64px 0 12px; line-height: 1.25; }
.article h3 { font-size: 20px; margin: 36px 0 8px; }
.article p, .article li { color: #2c2326; }
.article ul, .article ol { padding-left: 22px; }
.article strong { color: var(--ink); }
.tldr {
  background: var(--red-soft); border-left: 4px solid var(--red); border-radius: 0 var(--radius) var(--radius) 0;
  padding: 18px 22px; margin: 24px 0;
}
.tldr p { margin: 6px 0; }
.note {
  background: var(--surface-2); border: 1px solid var(--grid); border-radius: var(--radius);
  padding: 14px 18px; font-size: 15px; color: var(--ink-2); margin: 20px 0;
}
.insight {
  border: 1.5px solid var(--red-line); border-radius: var(--radius); padding: 16px 20px; margin: 24px 0;
  background: #fff;
}
.insight b.tag { color: var(--red); font-size: 13px; letter-spacing: .1em; text-transform: uppercase; display: block; margin-bottom: 2px; }
.math-block { overflow-x: auto; padding: 6px 0; text-align: center; font-size: 18px; }
.toc { font-size: 15px; border: 1px solid var(--grid); border-radius: var(--radius); padding: 14px 20px; margin: 28px 0; }
.toc ol { margin: 6px 0 0; }

/* figures */
figure.chart { margin: 32px -24px; padding: 22px 24px 16px; border: 1px solid var(--grid); border-radius: var(--radius); background: var(--surface); }
figure.chart .title { font-weight: 650; font-size: 17px; margin: 0 0 2px; }
figure.chart .subtitle { font-size: 14px; color: var(--ink-2); margin: 0 0 12px; }
figure.chart svg { width: 100%; height: auto; display: block; overflow: visible; }
figure.chart figcaption { font-size: 14px; color: var(--ink-2); margin-top: 12px; border-top: 1px solid var(--grid); padding-top: 10px; }
figure.chart figcaption b { color: var(--ink); }
figure.chart details { font-size: 13px; color: var(--ink-2); margin-top: 8px; }
figure.chart details table { border-collapse: collapse; margin-top: 6px; }
figure.chart details td, figure.chart details th { border-bottom: 1px solid var(--grid); padding: 3px 10px 3px 0; text-align: left; font-variant-numeric: tabular-nums; }
.chart-legend { display: flex; flex-wrap: wrap; gap: 16px; font-size: 13.5px; color: var(--ink-2); margin: 0 0 6px; }
.chart-legend span::before { content: ""; display: inline-block; width: 11px; height: 11px; border-radius: 3px; margin-right: 6px; vertical-align: -1px; background: var(--c); }
.ax text, .tick { font-size: 12px; fill: var(--ink-3); }
.axis-title { font-size: 12.5px; fill: var(--ink-2); font-weight: 500; }
.val { font-size: 12px; fill: var(--ink-2); font-weight: 600; }
.cat { font-size: 13px; fill: var(--ink-2); }
.toggle { display: inline-flex; border: 1px solid var(--red-line); border-radius: 999px; overflow: hidden; margin: 4px 0 10px; }
.toggle button { border: 0; background: #fff; color: var(--ink-2); font: inherit; font-size: 14px; padding: 6px 16px; cursor: pointer; }
.toggle button.on { background: var(--red); color: #fff; }

.tooltip {
  position: fixed; pointer-events: none; z-index: 50; opacity: 0;
  background: var(--ink); color: #fff; font-size: 13px; line-height: 1.4;
  padding: 7px 10px; border-radius: 8px; transition: opacity .1s; max-width: 260px;
}

/* cite */
pre.bib {
  background: #2a1d20; color: #fbe9ec; border-radius: var(--radius); padding: 18px 20px; overflow-x: auto;
  font: 13px/1.55 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; position: relative;
  white-space: pre-wrap; word-break: break-word;
}
.copy { position: absolute; top: 10px; right: 10px; font-size: 12px; background: var(--red); color: #fff; border: 0; border-radius: 6px; padding: 4px 10px; cursor: pointer; }
.cta-box { background: var(--red); color: #fff; border-radius: 20px; padding: 32px 28px; margin: 48px 0 24px; }
.cta-box h2 { color: #fff; margin-top: 0; }
.cta-box p, .cta-box li { color: #ffe9ed; }
.cta-box a { color: #fff; text-decoration: underline; }
.cta-box .btn { border-color: #fff; color: var(--red); background: #fff; text-decoration: none; }
.cta-box .btn.ghost { background: transparent; color: #fff; }

/* partners */
.partners { padding: 56px 0 24px; }
.partner-row { display: flex; flex-wrap: wrap; justify-content: center; align-items: center; gap: 24px 36px; margin-top: 18px; }
.partner-row a { display: block; opacity: .85; transition: opacity .15s, transform .15s; }
.partner-row a:hover { opacity: 1; transform: translateY(-2px); }
.partner-row img { width: auto; max-width: 220px; }

footer { border-top: 1px solid var(--grid); padding: 28px 0 40px; margin-top: 40px; font-size: 14px; color: var(--ink-3); }
footer .wrap { display: flex; gap: 18px; flex-wrap: wrap; justify-content: space-between; }

@media (max-width: 760px) {
  .formulas, .stats { grid-template-columns: 1fr; }
  .post-card { grid-template-columns: 1fr; }
  figure.chart { margin: 28px 0; padding: 16px 12px; }
  .nav-links { gap: 14px; }
}