/* Layout: one reading column (~68ch) with full-width figure plates and tables that scroll in place. */
:root {
  --bg: #fbf9f8;
  --surface: #ffffff;
  --subtle: #f4f3f2;
  --ink: #1a1a1a;
  --muted: #5f6166;
  --rule: #eaeaea;
  --accent: #005bb0;
  --accent-soft: #d5e3ff;
  --on-accent: #ffffff;
  --warn: #b4531a;
  --on-warn: #ffffff;
  --good: #1b7f5a;
  --plate: #ffffff;
  --digit-bg: #f4f3f2;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.04), 0 2px 10px rgba(0, 0, 0, 0.04);
  --font-display: "JetBrains Mono", ui-monospace, "SFMono-Regular", Menlo, monospace;
  --font-body: "IBM Plex Sans", system-ui, -apple-system, "Segoe UI", sans-serif;
  --font-data: "JetBrains Mono", ui-monospace, "SFMono-Regular", Menlo, monospace;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #121315; --surface: #1b1d20; --subtle: #23262a; --ink: #e9eaec; --muted: #a3a8b0; --rule: #2d3035;
    --accent: #8ab8ff; --accent-soft: #1f3552; --on-accent: #0b1a2e; --warn: #f0935a; --on-warn: #2a1204;
    --good: #4cc596; --plate: #f6f7f8; --digit-bg: #23262a; --shadow: 0 1px 2px rgba(0, 0, 0, 0.3);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #121315; --surface: #1b1d20; --subtle: #23262a; --ink: #e9eaec; --muted: #a3a8b0; --rule: #2d3035;
  --accent: #8ab8ff; --accent-soft: #1f3552; --on-accent: #0b1a2e; --warn: #f0935a; --on-warn: #2a1204;
  --good: #4cc596; --plate: #f6f7f8; --digit-bg: #23262a; --shadow: 0 1px 2px rgba(0, 0, 0, 0.3);
  color-scheme: dark;
}
*, *::before, *::after { box-sizing: border-box; }
html { scroll-padding-top: 76px; }
body {
  margin: 0;
  background: var(--bg); color: var(--ink); font-family: var(--font-body); font-size: 16px; line-height: 1.6;
  padding-left: env(safe-area-inset-left, 0px); padding-right: env(safe-area-inset-right, 0px);
}
main { width: min(760px, 100% - 32px); margin: 40px auto 72px; display: grid; gap: 56px; }
section { display: grid; gap: 16px; min-width: 0; }
.prose { max-width: none; }
/* summary blocks may run wider than the reading column on large screens */
.breakout { width: max(100%, min(1100px, 100vw - 64px)); justify-self: center; }
.takeaways.breakout { grid-template-columns: repeat(auto-fit, minmax(190px, 1fr)); }
h1, h2, h3 { font-family: var(--font-display); text-wrap: balance; line-height: 1.15; margin: 0; }
h1 { font-size: clamp(1.9rem, 4.6vw, 2.5rem); font-weight: 700; letter-spacing: -0.025em; }
h2 { font-size: 1.45rem; font-weight: 600; letter-spacing: -0.015em; }
h3 { font-size: 1.08rem; font-weight: 600; letter-spacing: -0.01em; }
p, ul { margin: 0; }
ul { padding-left: 1.2em; display: grid; gap: 6px; }
.eyebrow { font-family: var(--font-data); font-size: 0.74rem; font-weight: 600; letter-spacing: 0.06em; text-transform: uppercase; color: var(--accent); }
main > header:first-of-type .eyebrow { justify-self: start; background: var(--accent-soft); color: var(--accent); padding: 3px 8px; border-radius: 4px; }
main > header:first-of-type .meta { display: flex; flex-wrap: wrap; gap: 4px 14px; }
.lede { font-size: 1.15rem; color: var(--muted); }
.meta { font-family: var(--font-data); font-size: 0.82rem; color: var(--muted); }
code, .num { font-family: var(--font-data); font-size: 0.9em; }
.num { font-variant-numeric: tabular-nums; }
a { color: var(--accent); }

.table-wrap { overflow-x: auto; border: 1px solid var(--rule); border-radius: 10px; background: var(--surface); box-shadow: var(--shadow); }
table { border-collapse: collapse; width: 100%; font-size: 0.92rem; }
th, td { text-align: left; padding: 9px 12px; border-bottom: 1px solid var(--rule); vertical-align: top; }
th { font-family: var(--font-data); font-size: 0.7rem; letter-spacing: 0.05em; text-transform: uppercase; color: var(--muted); font-weight: 600; white-space: nowrap; }
thead th { background: var(--subtle); }
tbody tr:hover td { background-color: color-mix(in srgb, var(--subtle) 60%, transparent); }
tr:last-child td { border-bottom: 0; }
td.r, th.r { text-align: right; font-family: var(--font-data); font-variant-numeric: tabular-nums; white-space: nowrap; }
tr.ref td { font-weight: 600; }
.verdict { display: inline-block; font-family: var(--font-data); font-size: 0.7rem; font-weight: 600; letter-spacing: 0.03em; text-transform: uppercase; padding: 3px 8px; border-radius: 4px; white-space: nowrap; }
.v-yes { background: var(--accent); color: var(--on-accent); }
.v-no { background: var(--warn); color: var(--on-warn); }
.v-part { background: var(--accent-soft); color: var(--accent); }
.v-open { background: var(--subtle); color: var(--muted); box-shadow: inset 0 0 0 1px var(--rule); }

figure { margin: 0; display: grid; gap: 8px; }
figure .plate { background: var(--plate); border: 1px solid var(--rule); border-radius: 10px; padding: 10px; box-shadow: var(--shadow); }
figure img { display: block; width: 100%; height: auto; }
figcaption { font-size: 0.88rem; color: var(--muted); }

.takeaways { display: grid; gap: 12px; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); counter-reset: takeaway; }
.takeaway { counter-increment: takeaway; background: var(--surface); border: 1px solid var(--rule); border-radius: 10px; box-shadow: var(--shadow); padding: 14px 16px 16px; display: grid; gap: 6px; align-content: start; }
.takeaway::before { content: counter(takeaway); font: 600 0.82rem/1 var(--font-data); width: 1.75rem; height: 1.75rem; display: grid; place-items: center; border-radius: 4px; background: var(--subtle); color: var(--ink); }
.takeaway:first-child::before { background: var(--accent-soft); color: var(--accent); }
.takeaway b { font-family: var(--font-display); font-size: 0.98rem; letter-spacing: -0.01em; }
.takeaway span { color: var(--muted); font-size: 0.92rem; }

/* the two knife-edge digits of pi */
.ruler { display: grid; gap: 14px; }
.ruler-row { display: grid; gap: 6px; min-width: 0; }
.ruler-label { font-family: var(--font-data); font-size: 0.8rem; color: var(--muted); }
.digits { display: flex; gap: 4px; overflow-x: auto; padding-bottom: 4px; }
.digits { padding: 4px 2px 8px; }
.d { flex: 0 0 auto; width: 50px; display: grid; justify-items: center; gap: 2px; padding: 7px 0 6px; border-radius: 6px; background: var(--digit-bg); }
.d .g { font-family: var(--font-data); font-size: 1.35rem; font-weight: 600; line-height: 1.1; }
.d .m { font-family: var(--font-data); font-size: 0.7rem; color: var(--muted); font-variant-numeric: tabular-nums; }
.d .m { color: var(--accent); }
.d.edge { background: var(--accent); box-shadow: 0 2px 8px color-mix(in srgb, var(--accent) 35%, transparent); transform: scale(1.06); }
.d.edge .g, .d.edge .m { color: var(--on-accent); font-weight: 700; }
.d .p { font-family: var(--font-data); font-size: 0.62rem; color: var(--muted); }
.d.edge .p { color: var(--on-accent); }

footer { display: grid; gap: 6px; font-size: 0.88rem; color: var(--muted); border-top: 1px solid var(--rule); padding-top: 20px; }
footer::before { content: "π Bits of Pi"; font: 600 1rem var(--font-display); color: var(--ink); margin-bottom: 4px; }
hr { border: 0; border-top: 1px solid var(--rule); margin: 0; }
@media (max-width: 520px) { body { font-size: 15px; } main { gap: 44px; margin-block: 24px 48px; } }
/* reading guide: term / explanation pairs */
.guide { display: grid; grid-template-columns: minmax(150px, 13rem) 1fr; gap: 10px 20px; margin: 0; }
.guide dt { font-weight: 600; }
.guide dd { margin: 0; color: var(--ink); }
@media (max-width: 560px) { .guide { grid-template-columns: 1fr; gap: 2px; } .guide dd { margin-bottom: 10px; } }

/* top bar, shared by every page */
.topbar { position: sticky; top: 0; z-index: 20; background: color-mix(in srgb, var(--bg) 88%, transparent); backdrop-filter: blur(14px); -webkit-backdrop-filter: blur(14px); box-shadow: 0 1px 0 var(--rule), 0 1px 8px rgba(0, 0, 0, 0.03); }
.topbar-in { width: min(1240px, 100% - 32px); margin: 0 auto; min-height: 56px; display: flex; align-items: center; gap: 8px 20px; flex-wrap: wrap; }
.brand { display: inline-flex; align-items: baseline; gap: 6px; font: 600 1.02rem var(--font-display); letter-spacing: -0.02em; color: var(--ink); text-decoration: none; white-space: nowrap; }
.brand .pi { color: var(--accent); font-weight: 700; font-size: 1.15rem; }
.brand .sep { color: var(--rule); font-weight: 400; }
.brand .sub { font: 500 0.8rem var(--font-data); color: var(--muted); letter-spacing: 0.01em; }
.brand:hover .sub { color: var(--ink); }
.site-nav { display: flex; gap: 2px; margin-left: auto; font: 500 0.8rem var(--font-data); letter-spacing: 0.01em; overflow-x: auto; scrollbar-width: none; }
.site-nav a { color: var(--muted); text-decoration: none; padding: 5px 10px; border-radius: 4px; white-space: nowrap; }
.site-nav a:hover { color: var(--ink); background: var(--subtle); }
.site-nav a[aria-current="page"] { color: var(--accent); background: var(--accent-soft); font-weight: 600; }
.site-nav a.ext::after { content: " ↗"; }
@media (max-width: 760px) {
  .topbar-in { padding-block: 8px 6px; gap: 4px; }
  .brand .sep, .brand .sub { display: none; }
  .site-nav { margin-left: -10px; width: calc(100% + 10px); }
}
.next-pages { display: grid; gap: 12px; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); }
.next-pages a { display: grid; gap: 4px; background: var(--surface); border: 1px solid var(--rule); border-radius: 10px; box-shadow: var(--shadow); padding: 14px 16px; text-decoration: none; color: var(--ink); transition: border-color 0.15s; }
.next-pages a:hover { border-color: var(--accent); }
.next-pages a b { font-family: var(--font-display); font-size: 1.05rem; color: var(--accent); }
.next-pages a span { color: var(--muted); font-size: 0.92rem; }

/* prompts and model answers */
pre.prompt { font-family: var(--font-data); font-size: 0.84rem; line-height: 1.5; background: var(--surface); border: 1px solid var(--rule); border-left: 3px solid var(--accent); border-radius: 4px; padding: 10px 12px; margin: 0; white-space: pre-wrap; overflow-wrap: anywhere; }
pre.prompt.answer { border-left-color: var(--good); }
.label { font-family: var(--font-data); font-size: 0.72rem; letter-spacing: 0.06em; text-transform: uppercase; color: var(--muted); }
.mark-bad { background: var(--warn); color: var(--on-warn); padding: 0 2px; border-radius: 2px; }
.mark-off { color: var(--muted); text-decoration: line-through; }
.test { display: grid; gap: 8px; background: var(--surface); border: 1px solid var(--rule); border-radius: 10px; box-shadow: var(--shadow); padding: 14px 16px; }
.test h3 { display: flex; gap: 10px; align-items: baseline; flex-wrap: wrap; }
.test h3 .tag { font-family: var(--font-data); font-size: 0.8rem; color: var(--accent); }
.test pre.prompt { background: var(--bg); }

/* token strips: one box per token */
.tokstrip { display: flex; gap: 3px; overflow-x: auto; padding-bottom: 4px; align-items: stretch; }
.tk { flex: 0 0 auto; min-width: 26px; display: grid; place-items: center; font-family: var(--font-data); font-size: 0.95rem; padding: 4px 5px; border-radius: 3px; background: var(--digit-bg); }
.tk.pr { background: transparent; border: 1px dashed var(--rule); color: var(--muted); font-size: 0.78rem; }
.tk.bad { background: var(--warn); color: var(--on-warn); font-weight: 600; }
.tk.off { opacity: 0.45; }
.tk.gap { background: transparent; color: var(--muted); min-width: 16px; }

/* teacher-forcing table: one column per digit position */
table.tf { width: auto; font-family: var(--font-data); font-size: 0.85rem; }
table.tf th { text-transform: none; letter-spacing: 0; font-size: 0.78rem; white-space: nowrap; }
table.tf td { text-align: center; padding: 6px 6px; font-variant-numeric: tabular-nums; }
table.tf td.flip { background: var(--warn); color: var(--on-warn); font-weight: 600; }
table.tf td.thin { color: var(--warn); font-weight: 600; }

/* probability bars for one digit position */
.cards { display: grid; gap: 12px; grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); }
.card { background: var(--surface); border: 1px solid var(--rule); border-radius: 10px; box-shadow: var(--shadow); padding: 12px 14px; display: grid; gap: 10px; align-content: start; }
.card h4 { margin: 0; font-family: var(--font-display); font-size: 1.02rem; }
.card .ctx { font-family: var(--font-data); font-size: 0.8rem; color: var(--muted); }
.bars { display: grid; gap: 4px; }
.bars .who { font-family: var(--font-data); font-size: 0.75rem; color: var(--muted); margin-top: 4px; }
.bar-row { display: grid; grid-template-columns: 1.6rem 1fr 3.4rem; align-items: center; gap: 8px; font-size: 0.85rem; }
.bar-row .lab { font-family: var(--font-data); font-weight: 600; text-align: center; }
.bar-track { background: var(--digit-bg); border-radius: 3px; height: 14px; overflow: hidden; }
.bar-fill { height: 100%; background: var(--accent); border-radius: 3px; }
.bar-fill.wrong { background: var(--warn); }
.bar-row .v { font-family: var(--font-data); text-align: right; font-variant-numeric: tabular-nums; }
.card .verdict-line { font-size: 0.85rem; color: var(--muted); }
.legend-inline { display: flex; flex-wrap: wrap; gap: 6px 18px; font-size: 0.85rem; color: var(--muted); }
.legend-inline i { display: inline-block; width: 12px; height: 12px; border-radius: 2px; vertical-align: -1px; margin-right: 6px; }

/* formula / worked example */
.calc { font-family: var(--font-data); font-size: 0.88rem; background: var(--surface); border: 1px solid var(--rule); border-radius: 4px; padding: 10px 12px; overflow-x: auto; white-space: nowrap; }
.steps { counter-reset: step; display: grid; gap: 12px; padding: 0; list-style: none; }
.steps > li { counter-increment: step; display: grid; grid-template-columns: 2rem 1fr; gap: 10px; align-items: start; }
.steps > li::before { content: counter(step); font-family: var(--font-data); font-weight: 600; color: var(--on-accent); background: var(--accent); border-radius: 50%; width: 1.7rem; height: 1.7rem; display: grid; place-items: center; font-size: 0.85rem; }
table.tf tbody th, table.tf thead th:first-child { position: sticky; left: 0; background: var(--surface); text-align: left; }

/* pipeline diagram: files and programs joined by arrows */
.flow { display: flex; flex-wrap: wrap; align-items: stretch; gap: 8px; }
.flow .node { background: var(--surface); border: 1px solid var(--rule); border-left-width: 4px; border-radius: 8px; padding: 10px 12px; display: grid; gap: 4px; align-content: start; flex: 1 1 140px; min-width: 130px; }
.flow .node.file { border-left-color: var(--accent); }
.flow .node.prog { border-left-color: var(--good); }
.flow .node b { font-family: var(--font-data); font-size: 0.84rem; overflow-wrap: anywhere; }
.flow .node span { font-size: 0.8rem; color: var(--muted); }
.flow .arrow { align-self: center; color: var(--muted); font-family: var(--font-data); font-size: 1.1rem; }
@media (max-width: 640px) { .flow { flex-direction: column; } .flow .arrow { transform: rotate(90deg); align-self: center; } }
.tk.want { box-shadow: inset 0 -3px 0 var(--accent); }
table.matrix td.hit { background: var(--accent); color: var(--on-accent); font-weight: 600; }
table.matrix td .p { display: block; font-size: 0.72rem; opacity: 0.8; }
table.matrix td.dots, table.matrix th.dots { color: var(--muted); }

/* data.html: a wider page for the spreadsheet and the per-digit map */
main.wide { width: min(1240px, 100% - 32px); }
.tabs { display: flex; flex-wrap: wrap; gap: 4px; padding: 4px; background: var(--subtle); border-radius: 8px; justify-self: start; }
.tabs button { font: 600 0.8rem var(--font-data); letter-spacing: 0.01em; color: var(--muted); background: none; border: 0; border-radius: 6px; padding: 7px 14px; cursor: pointer; }
.tabs button:hover { color: var(--ink); }
.tabs button[aria-selected="true"] { color: var(--ink); background: var(--surface); box-shadow: var(--shadow); }
.controls { display: flex; flex-wrap: wrap; gap: 10px 18px; align-items: center; font-size: 0.88rem; }
.controls label { display: inline-flex; gap: 6px; align-items: center; color: var(--muted); }
.controls select, .controls input[type="search"], .controls input[type="number"], .controls button.btn {
  font: 0.88rem var(--font-body); color: var(--ink); background: var(--surface); border: 1px solid var(--rule); border-radius: 4px; padding: 5px 8px; }
.controls input[type="number"] { width: 5.5em; font-family: var(--font-data); }
.controls input[type="search"] { width: 14em; }
.controls button.btn { cursor: pointer; }
.controls button.btn:hover { border-color: var(--accent); }
.chips { display: flex; flex-wrap: wrap; gap: 6px; }
.chip { font: 0.8rem var(--font-data); color: var(--muted); background: var(--surface); border: 1px solid var(--rule); border-radius: 999px; padding: 3px 10px; cursor: pointer; user-select: none; }
.chip[aria-pressed="true"] { color: var(--ink); border-color: var(--accent); background: color-mix(in srgb, var(--accent) 12%, var(--surface)); }
.count { font-family: var(--font-data); font-size: 0.8rem; color: var(--muted); }
.sheet { max-height: 72vh; overflow: auto; }
.sheet table { width: max-content; min-width: 100%; font-size: 0.84rem; }
.sheet th, .sheet td { padding: 5px 10px; border-right: 1px solid var(--rule); }
.sheet thead th { position: sticky; top: 0; z-index: 2; background: var(--surface); cursor: pointer; text-transform: none; letter-spacing: 0; font-size: 0.76rem; vertical-align: bottom; }
.sheet thead tr.grp th { top: 0; cursor: default; text-align: left; color: var(--ink); border-bottom: 0; text-transform: uppercase; letter-spacing: 0.06em; font-size: 0.7rem; }
.sheet thead tr.col th { top: 26px; }
.sheet th[aria-sort="ascending"]::after { content: " ▲"; color: var(--accent); }
.sheet th[aria-sort="descending"]::after { content: " ▼"; color: var(--accent); }
.sheet td:first-child, .sheet th:first-child { position: sticky; left: 0; z-index: 1; background: var(--surface); }
.sheet thead th:first-child { z-index: 3; }
.sheet tbody tr:hover td { background-image: linear-gradient(color-mix(in srgb, var(--ink) 6%, transparent), color-mix(in srgb, var(--ink) 6%, transparent)); }
.sheet td.r { font-size: 0.82rem; }
.sheet td.txt { font-family: var(--font-data); font-size: 0.78rem; white-space: nowrap; }
.sheet td.wrap { white-space: normal; min-width: 18em; max-width: 34em; }
.tag { font: 600 0.68rem var(--font-data); color: var(--muted); border: 1px solid var(--rule); border-radius: 3px; padding: 0 4px; margin-left: 6px; vertical-align: 1px; }
.pager { display: flex; gap: 8px; align-items: center; }
dl.cols { display: grid; grid-template-columns: max-content 1fr; gap: 6px 16px; margin: 0; font-size: 0.88rem; }
dl.cols dt { font-family: var(--font-data); font-size: 0.8rem; }
dl.cols dd { margin: 0; color: var(--muted); }
details > summary { cursor: pointer; font-weight: 600; }
.heat { display: grid; grid-template-columns: max-content 1fr; gap: 0 10px; align-items: start; background: var(--surface); border: 1px solid var(--rule); border-radius: 10px; box-shadow: var(--shadow); padding: 12px; }
.heat-labels { display: grid; font: 0.74rem var(--font-data); }
.heat-labels div { white-space: nowrap; display: flex; align-items: center; }
.heat canvas { display: block; width: 100%; cursor: crosshair; }
.axis { font: 0.72rem var(--font-data); color: var(--muted); position: relative; height: 16px; }
.axis span { position: absolute; transform: translateX(-50%); }
.legend { display: flex; flex-wrap: wrap; gap: 6px 16px; align-items: center; font-size: 0.82rem; color: var(--muted); }
.legend .ramp { width: 180px; height: 12px; border-radius: 2px; border: 1px solid var(--rule); }
.legend .sw { display: inline-block; width: 12px; height: 12px; border-radius: 2px; vertical-align: -2px; margin-right: 5px; }
.tip { position: fixed; z-index: 10; pointer-events: none; background: var(--surface); color: var(--ink); border: 1px solid var(--rule); border-radius: 6px; padding: 8px 10px; font: 0.8rem/1.45 var(--font-data); box-shadow: 0 4px 14px rgba(0,0,0,0.15); display: none; max-width: 300px; }
.tip b { font-weight: 600; }
table.tf td.cur { outline: 2px solid var(--accent); outline-offset: -2px; }
[hidden] { display: none !important; }
.sheet td.clip { max-width: 30em; overflow: hidden; text-overflow: ellipsis; }
.heat-labels .tag { padding: 0 3px; font-size: 0.64rem; line-height: 1.2; }