/* Shared styles for the project hub and section pages.
   E-ink palette: warm paper, near-black ink, one teal accent (a nod to ITO's faint tint). */
:root {
  --paper: #f4f1ea;
  --paper-deep: #e9e4d8;
  --ink: #1b1b1a;
  --ink-soft: #55524c;
  --rule: #d3cdbf;
  --accent: #1f5f6b;
  --accent-soft: #dce8e8;
  --warn: #8a4b14;
  --warn-soft: #f3e6d4;
  --serif: "Literata", Georgia, serif;
  --sans: "Inter", system-ui, sans-serif;
  --nav-h: 56px;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: calc(var(--nav-h) + 16px); }
body { margin: 0; background: var(--paper); color: var(--ink); font-family: var(--serif); font-size: 18px; line-height: 1.65; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }

/* ---------- Section navigation (sticky, on every section page) ---------- */
.site-nav {
  position: sticky; top: 0; z-index: 10;
  display: flex; align-items: center; gap: 8px;
  height: var(--nav-h); padding: 0 16px;
  background: color-mix(in srgb, var(--paper) 92%, transparent);
  backdrop-filter: blur(6px);
  border-bottom: 1px solid var(--rule);
  font-family: var(--sans); font-size: 14px;
}
.site-nav a { color: var(--ink-soft); text-decoration: none; padding: 6px 10px; border-radius: 6px; white-space: nowrap; }
.site-nav a:hover, .site-nav a:focus-visible { color: var(--ink); background: var(--paper-deep); }
.site-nav .back { color: var(--ink); font-weight: 600; margin-right: auto; }
.site-nav a[aria-current="page"] { color: var(--accent); font-weight: 600; background: var(--accent-soft); }
/* On narrow screens the section tabs would crowd out the back link, so keep only the back link. */
@media (max-width: 720px) { .site-nav .tab { display: none; } }

/* ---------- Layout ---------- */
main { width: min(840px, calc(100% - 32px)); margin: 0 auto; padding: 0 0 96px; }
section { padding-top: 72px; }
main > section:first-child { padding-top: 48px; }

.kicker { font-family: var(--sans); font-size: 13px; font-weight: 600; letter-spacing: 0.16em; text-transform: uppercase; color: var(--accent); margin: 0 0 8px; }
h1, h2, h3 { line-height: 1.2; text-wrap: pretty; }
h1 { font-size: clamp(36px, 6vw, 56px); margin: 0 0 16px; }
h2 { font-size: clamp(28px, 4.5vw, 40px); margin: 0 0 20px; }
h3 { font-size: 22px; margin: 40px 0 8px; }
p { margin: 0 0 18px; }
.lede { font-size: 21px; color: var(--ink-soft); }
sub, sup { line-height: 0; }
a { color: var(--accent); }

hr.chapter { border: 0; text-align: center; margin: 72px 0 0; }
hr.chapter::before { content: "• • •"; letter-spacing: 1em; color: var(--rule); }

/* ---------- Hub: three section cards ---------- */
.hub { width: min(1100px, calc(100% - 32px)); margin: 0 auto; padding: 48px 0 96px; }
.hub .hub-intro { padding-top: 0; }
.hub-intro h1 { margin-bottom: 0; }
.hub-about { max-width: 840px; margin-top: 56px; }
.cards { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; margin: 32px 0 16px; }
@media (max-width: 760px) { .cards { grid-template-columns: 1fr; } }
.card { position: relative; display: block; aspect-ratio: 1; overflow: hidden; border-radius: 8px; background: var(--ink); outline: none; }
.card img { width: 100%; height: 100%; object-fit: cover; display: block; transition: transform 400ms ease, filter 400ms ease; }
.card .label {
  position: absolute; inset: 0; display: grid; place-items: center; padding: 16px;
  font-family: var(--serif); font-size: clamp(22px, 2.4vw, 30px); font-weight: 700; line-height: 1.2; text-align: center;
  color: #fff; background: rgba(20, 20, 18, 0.55);
  opacity: 0; transition: opacity 250ms ease;
}
.card:hover img, .card:focus-visible img { transform: scale(1.05); filter: grayscale(0.4); }
.card:hover .label, .card:focus-visible .label { opacity: 1; }
.card:focus-visible { box-shadow: 0 0 0 3px var(--paper), 0 0 0 5px var(--accent); }
/* Touch screens can't hover, so show the labels as a strip along the bottom instead. */
@media (hover: none) {
  .card .label { opacity: 1; inset: auto 0 0 0; background: rgba(20, 20, 18, 0.7); font-size: 20px; }
}
@media (prefers-reduced-motion: reduce) { .card img, .card .label { transition: none; } .card:hover img { transform: none; } }
.hub-hint { font-family: var(--sans); font-size: 14px; color: var(--ink-soft); text-align: center; }

/* ---------- Figures ---------- */
figure { margin: 32px 0; }
figure img, figure svg { display: block; width: 100%; height: auto; border-radius: 4px; }
figure.framed img { background: #fff; padding: 12px; border: 1px solid var(--rule); }
figcaption { font-family: var(--sans); font-size: 14px; line-height: 1.5; color: var(--ink-soft); margin-top: 10px; }
figcaption b { color: var(--ink); }
.pair { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; align-items: start; }
.pair figure { margin: 0; }
.pair-wrap { margin: 32px 0; }
.narrow { max-width: 560px; margin-left: auto; margin-right: auto; }
@media (max-width: 640px) { .pair { grid-template-columns: 1fr; } }

/* ---------- Tables ---------- */
.table-wrap { overflow-x: auto; margin: 28px 0; }
table { width: 100%; border-collapse: collapse; font-family: var(--sans); font-size: 15px; font-variant-numeric: tabular-nums; }
th, td { padding: 9px 12px; text-align: left; border-bottom: 1px solid var(--rule); }
th { font-weight: 600; font-size: 12px; letter-spacing: 0.08em; text-transform: uppercase; color: var(--ink-soft); border-bottom: 2px solid var(--ink); }
td.num, th.num { text-align: right; }
caption { caption-side: bottom; text-align: left; font-size: 14px; color: var(--ink-soft); padding-top: 10px; }
caption b { color: var(--ink); }

/* ---------- Callouts ---------- */
.stats { display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 12px; margin: 28px 0; }
.stats.four { grid-template-columns: repeat(4, 1fr); }
@media (max-width: 640px) { .stats.four { grid-template-columns: 1fr 1fr; } }
.stat { background: var(--paper-deep); border-radius: 6px; padding: 16px; }
.stat .v { font-size: 30px; font-weight: 700; line-height: 1.1; }
.stat .l { font-family: var(--sans); font-size: 13px; color: var(--ink-soft); margin-top: 6px; line-height: 1.4; }

.calc { background: #fff; border: 1px solid var(--rule); border-left: 4px solid var(--accent); border-radius: 4px; padding: 20px 22px; margin: 28px 0; font-family: var(--sans); font-size: 15px; }
.calc h4 { margin: 0 0 12px; font-size: 13px; letter-spacing: 0.1em; text-transform: uppercase; color: var(--accent); }
.calc .eq { font-family: var(--serif); font-size: 18px; margin: 6px 0; overflow-x: auto; overflow-y: hidden; padding: 2px 0; white-space: nowrap; }
.calc .result { font-weight: 600; margin-top: 12px; }
.calc var { font-style: italic; }

.note { background: var(--accent-soft); border-radius: 6px; padding: 16px 20px; margin: 28px 0; font-size: 16px; }
.note.warn { background: var(--warn-soft); }
.note strong { font-family: var(--sans); font-size: 13px; letter-spacing: 0.08em; text-transform: uppercase; display: block; margin-bottom: 4px; color: var(--accent); }
.note.warn strong { color: var(--warn); }
.note p:last-child { margin: 0; }

ol.steps { padding-left: 22px; }
ol.steps li { margin-bottom: 10px; }

.takeaway { font-size: 24px; line-height: 1.45; border-top: 2px solid var(--ink); border-bottom: 2px solid var(--ink); padding: 24px 0; margin: 40px 0; }

/* ---------- Page-end navigation ---------- */
.page-end { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 72px; font-family: var(--sans); }
.page-end a { display: block; padding: 18px 20px; border: 1px solid var(--rule); border-radius: 8px; text-decoration: none; color: var(--ink); background: #fff; }
.page-end a:hover, .page-end a:focus-visible { border-color: var(--accent); }
.page-end small { display: block; font-size: 12px; letter-spacing: 0.1em; text-transform: uppercase; color: var(--ink-soft); margin-bottom: 4px; }
.page-end .next { text-align: right; }
@media (max-width: 640px) { .page-end { grid-template-columns: 1fr; } .page-end .next { text-align: left; } }

/* ---------- Sources & footer ---------- */
.sources { font-family: var(--sans); font-size: 14px; color: var(--ink-soft); }
.sources li { margin-bottom: 8px; overflow-wrap: anywhere; }
footer { border-top: 1px solid var(--rule); padding: 32px 16px 48px; text-align: center; font-family: var(--sans); font-size: 14px; color: var(--ink-soft); }
footer a { color: var(--ink); }