/* Shared design system for the Learn concept-guide family.
   Matches index.html / guides.html tokens (cream paper, ink, spot-blue,
   Archivo Black display, boxy 2px borders). Light theme only, as the rest
   of the site. One stylesheet for all learn/ articles + learn.html. */

:root {
  --paper: #f6f1e5; --surface: #ece7db; --ink: #14120e; --muted: #4a463f;
  --spot: #0f62e8; --spot-dark: #0c4fb4; --warn: #8b3b14; --warn-bg: #f6e7dc;
  --good: #1f7a4d; --good-bg: #e3f0e7;
  --line: #c7c0b2;
  --display: "Archivo Black", "Arial Black", Impact, sans-serif;
  --body: Inter, Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: "American Typewriter", "Courier New", Courier, monospace;
  /* series colors for multi-line charts */
  --s1: #0f62e8; --s2: #8b3b14; --s3: #1f7a4d; --s4: #7a1f6b; --s5: #b58900;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; background: var(--paper); color: var(--ink); font: 15px/1.62 var(--body); }
a { color: inherit; text-decoration: none; border-bottom: 2px solid transparent; }
.prose a, a.inline { border-bottom: 1px solid var(--spot); color: var(--spot-dark); }
a:hover { border-bottom-color: currentColor; }
a:focus-visible, button:focus-visible { outline: 2px solid var(--spot); outline-offset: 2px; }
.wrap { max-width: 1120px; margin: 0 auto; padding: 0 18px; }
.col { max-width: 760px; }
.skip { position: absolute; left: 9px; top: -60px; z-index: 100; padding: 9px 14px; background: var(--ink); color: var(--paper); font: 12px var(--mono); }
.skip:focus { top: 9px; }

/* ---- shared nav (copied structure from guides.html) ---- */
.site-nav { position: sticky; top: 0; z-index: 20; background: rgba(246,241,229,.97); border-bottom: 2px solid var(--ink); }
.site-nav .wrap { min-height: 56px; display: flex; align-items: stretch; }
.brand { display: flex; align-items: center; flex: 0 0 auto; border: 0; font: 16px var(--display); text-transform: uppercase; letter-spacing: -.02em; }
.brand-mark { margin-right: 8px; color: var(--spot); letter-spacing: -3px; }
nav { display: flex; align-items: stretch; margin-left: auto; overflow-x: auto; scrollbar-width: none; font: 700 11.5px var(--mono); text-transform: uppercase; letter-spacing: .05em; }
nav::-webkit-scrollbar { display: none; }
nav a { display: flex; align-items: center; flex: 0 0 auto; padding: 0 13px; border-bottom: 4px solid transparent; }
nav a:hover, nav a[aria-current="page"] { color: var(--spot-dark); border-bottom-color: var(--spot); }
nav .github { align-self: center; min-height: 32px; margin-left: 8px; border: 2px solid var(--ink); }
nav .github:hover { background: var(--ink); color: var(--paper); border-color: var(--ink); }

/* ---- hero ---- */
header.hero { padding: 46px 0 34px; background: var(--spot); color: #fff; border-bottom: 2px solid var(--ink); }
header.hero.dark { background: var(--ink); }
.eyebrow { margin: 0 0 8px; font: 700 11px var(--mono); letter-spacing: .1em; text-transform: uppercase; opacity: .92; }
header.hero h1 { max-width: 20ch; margin: 0; font: 900 clamp(28px,4.6vw,50px)/1.05 var(--display); text-transform: uppercase; letter-spacing: -.01em; }
header.hero p { max-width: 68ch; margin: 15px 0 0; font-size: 16px; opacity: .96; }
.breadcrumb { margin: 0 0 14px; font: 700 10.5px var(--mono); text-transform: uppercase; letter-spacing: .06em; }
.breadcrumb a { border-bottom: 1px solid rgba(255,255,255,.5); }

/* ---- body / prose ---- */
main { padding: 34px 0 10px; }
.prose h2 { margin: 38px 0 10px; font: 900 25px/1.1 var(--display); text-transform: uppercase; letter-spacing: -.01em; }
.prose h3 { margin: 26px 0 8px; font: 800 17px var(--body); }
.prose p { margin: 0 0 14px; }
.prose ul, .prose ol { margin: 0 0 16px; padding-left: 22px; }
.prose li { margin: 5px 0; }
.prose strong { color: var(--ink); }
.prose code, code { font: 12.5px var(--mono); background: var(--surface); padding: 1px 5px; border: 1px solid var(--line); }
.command { overflow-x: auto; margin: 16px 0 20px; padding: 14px 16px; border: 2px solid var(--ink); background: var(--surface); color: var(--ink); font: 12.5px/1.6 var(--mono); }
.command code { padding: 0; border: 0; background: transparent; font: inherit; white-space: pre; }
.lede { font-size: 17px; color: var(--muted); }

/* TL;DR / at-a-glance */
.tldr { margin: 6px 0 26px; padding: 16px 18px; border: 2px solid var(--ink); background: var(--surface); }
.tldr h2 { margin: 0 0 8px; font: 900 13px var(--mono); text-transform: uppercase; letter-spacing: .06em; }
.tldr p, .tldr ul { margin: 0; }
.tldr ul { padding-left: 20px; }

/* callouts */
.callout { margin: 20px 0; padding: 14px 16px 14px 18px; border: 2px solid var(--ink); border-left-width: 7px; background: var(--surface); }
.callout .tag { display: block; margin-bottom: 5px; font: 700 10.5px var(--mono); text-transform: uppercase; letter-spacing: .06em; }
.callout p:last-child { margin-bottom: 0; }
.callout.key { border-left-color: var(--spot); }
.callout.key .tag { color: var(--spot-dark); }
.callout.warn { border-left-color: var(--warn); background: var(--warn-bg); }
.callout.warn .tag { color: var(--warn); }
.callout.good { border-left-color: var(--good); background: var(--good-bg); }
.callout.good .tag { color: var(--good); }

/* metric strip */
.metrics { display: grid; grid-template-columns: repeat(auto-fit,minmax(150px,1fr)); gap: 12px; margin: 22px 0; }
.metric { padding: 13px 14px; border: 2px solid var(--ink); background: var(--paper); }
.metric b { display: block; font: 900 27px/1 var(--display); }
.metric span { display: block; margin-top: 5px; color: var(--muted); font-size: 12px; }

/* charts */
figure.chart { margin: 24px 0; padding: 14px 14px 10px; border: 2px solid var(--ink); background: var(--paper); }
figure.chart h4 { margin: 0 0 4px; font: 700 12px var(--mono); text-transform: uppercase; }
figure.chart svg { display: block; width: 100%; height: auto; overflow: visible; }
figure.chart figcaption { margin: 8px 0 0; color: var(--muted); font-size: 12.5px; }
figure.chart figcaption a { border-bottom: 1px solid currentColor; }
.chart .axis { stroke: var(--ink); stroke-width: 1.5; }
.chart .grid { stroke: var(--line); stroke-width: 1; stroke-dasharray: 3 4; }
.chart .lbl { fill: var(--muted); font: 10px var(--mono); }
.chart .s1 { stroke: var(--s1); } .chart .s2 { stroke: var(--s2); }
.chart .s3 { stroke: var(--s3); } .chart .s4 { stroke: var(--s4); } .chart .s5 { stroke: var(--s5); }
.chart .curve { fill: none; stroke-width: 3; stroke-linejoin: round; stroke-linecap: round; }
.chart .bar-s1 { fill: var(--s1); } .chart .bar-s2 { fill: var(--s2); }
.chart .dot { stroke-width: 2; fill: var(--paper); }
.legend { display: flex; flex-wrap: wrap; gap: 6px 16px; margin: 10px 0 2px; font: 11px var(--mono); }
.legend span { display: inline-flex; align-items: center; gap: 6px; color: var(--muted); }
.legend i { width: 16px; height: 3px; display: inline-block; }

/* data tables */
.scroller { overflow-x: auto; margin: 20px 0; border: 2px solid var(--ink); }
table.data { border-collapse: collapse; width: 100%; font-size: 13.5px; background: var(--paper); }
table.data th, table.data td { padding: 8px 11px; border-bottom: 1px solid var(--line); text-align: left; white-space: nowrap; }
table.data thead th { background: var(--surface); font: 700 11px var(--mono); text-transform: uppercase; letter-spacing: .04em; position: sticky; top: 0; }
table.data td.num, table.data th.num { text-align: right; font-variant-numeric: tabular-nums; }
table.data tbody tr:last-child td { border-bottom: 0; }
table.data .best { font-weight: 800; color: var(--spot-dark); }
table.data .muted { color: var(--muted); }
.badge { display: inline-block; padding: 1px 6px; border: 1px solid currentColor; font: 700 9.5px var(--mono); text-transform: uppercase; letter-spacing: .04em; }
.badge.lab { color: var(--good); }
.badge.comm { color: var(--spot-dark); }
.badge.spec { color: var(--warn); }

/* related guides + footer */
.related { margin: 40px 0 8px; padding-top: 22px; border-top: 2px solid var(--ink); }
.related h2 { margin: 0 0 12px; font: 900 15px var(--mono); text-transform: uppercase; letter-spacing: .05em; }
.related-grid { display: grid; grid-template-columns: repeat(auto-fill,minmax(220px,1fr)); gap: 12px; }
.related-grid a { display: block; padding: 12px 13px; border: 2px solid var(--ink); background: var(--paper); }
.related-grid a:hover { background: var(--spot); color: #fff; border-color: var(--spot); }
.related-grid b { display: block; font: 800 13px var(--body); }
.related-grid span { display: block; margin-top: 3px; color: var(--muted); font-size: 11.5px; }
.related-grid a:hover span { color: rgba(255,255,255,.85); }
footer { margin-top: 40px; border-top: 2px solid var(--ink); padding: 18px 0 44px; color: var(--muted); font: 11px var(--mono); }
footer .wrap { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 10px 18px; }
footer a { color: var(--ink); border-bottom: 1px solid currentColor; }

/* learn.html landing grid */
.guide-cards { display: grid; grid-template-columns: repeat(auto-fill,minmax(260px,1fr)); gap: 14px; margin: 8px 0 10px; }
.guide-card { display: flex; flex-direction: column; border: 2px solid var(--ink); background: var(--paper); }
.guide-card:hover { border-color: var(--spot); }
.guide-card .gc-top { padding: 15px 16px 12px; border-bottom: 1px solid var(--ink); }
.guide-card .gc-n { font: 700 10px var(--mono); color: var(--muted); text-transform: uppercase; letter-spacing: .06em; }
.guide-card h3 { margin: 6px 0 0; font: 900 18px/1.1 var(--display); text-transform: uppercase; }
.guide-card .gc-body { flex: 1; padding: 13px 16px 16px; color: var(--muted); font-size: 13px; }
.guide-card .gc-go { padding: 10px 16px; border-top: 1px solid var(--line); font: 700 10.5px var(--mono); text-transform: uppercase; color: var(--spot-dark); }
.guide-card:hover .gc-go { background: var(--spot); color: #fff; }

@media (max-width: 720px) {
  body { font-size: 14.5px; }
  .site-nav .wrap { padding-right: 0; }
  .brand { font: 700 11px var(--mono); }
  /* Wrap instead of scrolling: a hidden-scrollbar nav silently drops
     Contribute and GitHub off the right edge on a phone. */
  nav { font-size: 10px; flex-wrap: wrap; overflow-x: visible; justify-content: flex-end; }
  .site-nav .wrap { flex-wrap: wrap; padding-bottom: 4px; }
  nav a { padding: 0 9px; } nav .github { display: none; }
  header.hero { padding: 34px 0 28px; }
  .prose h2 { font-size: 21px; }
}

/* ML Bottleneck projections (learn/assets/mlbottleneck-bridge.js) */
.projection { margin: 14px 0 22px; padding: 14px 16px; border: 2px solid var(--ink); background: var(--paper); }
.projection-status { margin: 0 0 10px; color: var(--muted); font: 11px var(--mono); }
.projection h3 { margin: 14px 0 6px; font: 900 14px var(--mono); text-transform: uppercase; letter-spacing: .05em; }
.projection figure.chart { margin: 0 0 8px; }
.projection-table summary { cursor: pointer; font: 700 11px var(--mono); text-transform: uppercase; letter-spacing: .05em; color: var(--spot-dark); }
.projection-table table { margin-top: 8px; }
.projection-foot { margin: 10px 0 0; color: var(--muted); font-size: 13px; }