:root {
  color-scheme: light;
  --page: #f9f9f7;
  --band: #f2f1ed;
  --surface: #fcfcfb;
  --ink: #0b0b0b;
  --ink-2: #52514e;
  --muted: #7a7873;
  --line: #e1e0d9;
  --ring: rgba(11, 11, 11, 0.1);
  --accent: #2a78d6;
  --accent-ink: #1c5cab;
  --slice: #eb6834;
  --code-bg: #f0efec;
  --err: #b42f2f;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.04), 0 8px 24px rgba(0, 0, 0, 0.04);
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    color-scheme: dark;
    --page: #0d0d0d; --band: #131312; --surface: #1a1a19; --ink: #ffffff; --ink-2: #c3c2b7; --muted: #99978f;
    --line: #2c2c2a; --ring: rgba(255, 255, 255, 0.1); --accent: #3987e5; --accent-ink: #86b6ef; --slice: #d95926; --code-bg: #232321; --err: #e66767;
    --shadow: none;
  }
}
:root[data-theme="dark"] {
  color-scheme: dark;
  --page: #0d0d0d; --band: #131312; --surface: #1a1a19; --ink: #ffffff; --ink-2: #c3c2b7; --muted: #99978f;
  --line: #2c2c2a; --ring: rgba(255, 255, 255, 0.1); --accent: #3987e5; --accent-ink: #86b6ef; --slice: #d95926; --code-bg: #232321; --err: #e66767;
  --shadow: none;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 72px; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }
body {
  margin: 0; background: var(--page); color: var(--ink);
  font: 16px/1.55 Inter, system-ui, -apple-system, "Segoe UI", sans-serif;
  -webkit-font-smoothing: antialiased; overflow-x: hidden;
}
a { color: var(--accent-ink); }
code { font-family: "JetBrains Mono", ui-monospace, monospace; font-size: 0.86em; background: var(--code-bg); padding: 0.1em 0.35em; border-radius: 5px; }
h1, h2, h3 { line-height: 1.15; margin: 0 0 0.5em; letter-spacing: -0.015em; }
h1 { font-size: clamp(2rem, 4.6vw, 3.2rem); font-weight: 700; }
h2 { font-size: clamp(1.5rem, 3vw, 2rem); font-weight: 650; }
h3 { font-size: 1.05rem; font-weight: 600; }
.wrap { max-width: 1160px; margin: 0 auto; padding: 0 16px; }
.narrow { max-width: 760px; }
section { padding: 64px 0; }
.band { background: var(--band); }
.skip { position: absolute; left: -999px; }
.skip:focus { left: 16px; top: 8px; z-index: 10; background: var(--surface); padding: 8px 12px; border-radius: 8px; }

/* header */
.top { position: sticky; top: 0; z-index: 5; background: var(--page); background: color-mix(in srgb, var(--page) 88%, transparent); backdrop-filter: saturate(1.4) blur(10px); border-bottom: 1px solid var(--line); }
.top-inner { display: flex; align-items: center; gap: 20px; height: 60px; }
.brand { display: flex; align-items: center; gap: 9px; color: var(--ink); text-decoration: none; }
.wordmark { font-size: 1.12rem; letter-spacing: -0.025em; line-height: 1; }
.wordmark b { font-weight: 700; }
.wordmark span { font-weight: 450; color: var(--ink-2); }
nav { display: flex; gap: 20px; margin-left: auto; }
nav a { color: var(--ink-2); text-decoration: none; font-size: 0.94rem; }
nav a:hover { color: var(--ink); }
.icon { background: none; border: 1px solid var(--line); color: var(--ink-2); border-radius: 8px; width: 36px; height: 36px; display: grid; place-items: center; cursor: pointer; }
.icon:hover { color: var(--ink); }
@media (max-width: 720px) { nav { display: none; } .icon { margin-left: auto; } }

/* hero */
.hero { display: grid; grid-template-columns: minmax(0, 0.9fr) minmax(0, 1.1fr); gap: 40px; align-items: center; padding-top: 56px; }
@media (max-width: 960px) { .hero { grid-template-columns: 1fr; } }
.eyebrow { color: var(--accent-ink); font-weight: 600; font-size: 0.85rem; letter-spacing: 0.04em; text-transform: uppercase; margin: 0 0 12px; }
.lede { color: var(--ink-2); font-size: 1.12rem; max-width: 36em; }
.cta { display: flex; gap: 12px; margin: 24px 0; flex-wrap: wrap; }
.btn { display: inline-block; background: var(--accent); color: #fff; text-decoration: none; padding: 10px 18px; border-radius: 10px; font-weight: 600; }
.btn:hover { filter: brightness(1.08); }
.btn.secondary { background: transparent; color: var(--ink); border: 1px solid var(--line); }
.hero-fig { margin: 0; }
figcaption { color: var(--muted); font-size: 0.82rem; padding: 8px 4px 2px; }

/* cards + charts */
.card { background: var(--surface); border: 1px solid var(--ring); border-radius: 14px; padding: 12px; box-shadow: var(--shadow); min-width: 0; }
.chart { width: 100%; }
.grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 20px; }
.grid.one { grid-template-columns: 1fr; }
@media (max-width: 860px) { .grid { grid-template-columns: 1fr; } }
.card-head { padding: 4px 6px 0; }
.card-head p { color: var(--ink-2); margin: 2px 0 0; font-size: 0.92rem; }
.fn { font-family: "JetBrains Mono", ui-monospace, monospace; font-size: 0.85rem; color: var(--accent-ink); font-weight: 500; }
.section-lede { color: var(--ink-2); max-width: 44em; margin: -4px 0 24px; }
.ghost { background: none; border: none; color: var(--accent-ink); font: inherit; font-weight: 600; font-size: 0.9rem; padding: 8px 6px 2px; cursor: pointer; }
.ghost:hover { text-decoration: underline; }

/* formula blocks */
.formula { display: flex; align-items: flex-start; gap: 8px; background: var(--code-bg); border-radius: 10px; padding: 10px 10px 10px 12px; margin-top: 10px; }
.formula code { background: none; padding: 0; flex: 1; min-width: 0; white-space: pre-wrap; word-break: break-word; font-size: 0.8rem; line-height: 1.5; color: var(--ink); }
.copy { flex: none; background: var(--surface); color: var(--ink-2); border: 1px solid var(--line); border-radius: 7px; font: 500 0.78rem Inter, system-ui, sans-serif; padding: 4px 10px; cursor: pointer; }
.copy:hover { color: var(--ink); }
#hero-formula .formula, .hero-copy .formula { margin-top: 8px; }

/* how it works */
.steps { list-style: none; padding: 0; margin: 24px 0; display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 20px; }
@media (max-width: 860px) { .steps { grid-template-columns: 1fr; } }
.steps li { background: var(--surface); border: 1px solid var(--ring); border-radius: 14px; padding: 18px; }
.steps p { color: var(--ink-2); margin: 0; font-size: 0.95rem; }
.n { display: inline-grid; place-items: center; width: 28px; height: 28px; border-radius: 50%; background: var(--accent); color: #fff; font-weight: 700; font-size: 0.85rem; margin-bottom: 10px; }
.diagram svg { width: 100%; height: auto; max-height: 150px; }
.d-box { fill: var(--surface); stroke: var(--line); }
.d-t { fill: var(--ink); font-weight: 600; }
.d-s { fill: var(--muted); font-size: 12px; font-family: "JetBrains Mono", ui-monospace, monospace; }
.d-arrow { stroke: var(--accent); stroke-width: 2; fill: none; marker-end: url(#ah); }
.d-arrow.back { stroke-dasharray: none; opacity: 0.6; }
.d-head { fill: var(--accent); }
.facts { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 10px 28px; padding: 0; list-style: none; margin: 24px 0 0; color: var(--ink-2); }
@media (max-width: 860px) { .facts { grid-template-columns: 1fr; } }
.facts strong { color: var(--ink); }

/* real data */
.card.wide .card-head h3 { margin: 0; font-size: 1.15rem; }
details { margin-top: 10px; }
summary { cursor: pointer; color: var(--ink-2); font-size: 0.9rem; }
.table-wrap { max-height: 300px; overflow: auto; margin-top: 8px; border: 1px solid var(--line); border-radius: 8px; }
table { border-collapse: collapse; width: 100%; font-size: 0.85rem; font-variant-numeric: tabular-nums; }
th, td { text-align: left; padding: 6px 10px; border-bottom: 1px solid var(--line); white-space: nowrap; }
th { position: sticky; top: 0; background: var(--surface); color: var(--ink-2); font-weight: 600; }
.source { color: var(--muted); font-size: 0.82rem; margin: 10px 4px 0; }

/* editor */
.editor { display: grid; grid-template-columns: minmax(0, 0.8fr) minmax(0, 1.2fr); gap: 20px; align-items: start; }
@media (max-width: 960px) { .editor { grid-template-columns: 1fr; } }
.ed-form { display: flex; flex-direction: column; gap: 12px; padding: 16px; }
.field { display: flex; flex-direction: column; gap: 4px; min-width: 0; flex: 1; }
.field > span { font-size: 0.8rem; font-weight: 600; color: var(--ink-2); }
.field small { color: var(--muted); font-size: 0.76rem; }
.row { display: flex; gap: 10px; flex-wrap: wrap; }
.row .field { min-width: 130px; }
input, select, textarea {
  font: inherit; font-size: 0.9rem; color: var(--ink); background: var(--page); border: 1px solid var(--line); border-radius: 8px; padding: 7px 9px; width: 100%;
}
textarea { font-family: "JetBrains Mono", ui-monospace, monospace; font-size: 0.8rem; resize: vertical; line-height: 1.45; }
input:focus, select:focus, textarea:focus, button:focus-visible, a:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }
.msg { color: var(--muted); font-size: 0.85rem; margin: 10px 4px 0; min-height: 1.3em; }
.msg.err { color: var(--err); }

.foot { color: var(--muted); font-size: 0.84rem; padding: 32px 16px 48px; border-top: 1px solid var(--line); }
.chart-missing { display: grid; place-items: center; text-align: center; color: var(--muted); font-size: 0.9rem; padding: 24px; border: 1px dashed var(--line); border-radius: 10px; }