/* Bauhaus shell shared by every section of the site: paper, ink, three primaries, hard edges, geometric type.
   Loaded first by index.html and math54/index.html; each app adds its own components on top. */
:root {
  --paper: #F4F1EA; --paper-2: #EDE8DD; --white: #FFFFFF;
  --ink: #141414; --ink-2: #5A5751; --rule: #D6D0C2;
  --red: #E63B2E; --yellow: #F2C230; --blue: #2757A8;
  --red-soft: #FBE3DF; --yellow-soft: #FCF1CB; --blue-soft: #DCE5F5;
  --good: #1F7A3F; --good-soft: #DCEFE2; --bad: var(--red); --bad-soft: var(--red-soft);
  --sans: "Jost", "Futura", "Century Gothic", system-ui, sans-serif;
  --mono: ui-monospace, "JetBrains Mono", Menlo, Consolas, monospace;
  --shadow: 5px 5px 0 var(--ink);
  --shadow-sm: 3px 3px 0 var(--ink);
  --side-w: 280px;
  --top-h: 64px;
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--paper); color: var(--ink); font: 400 17px/1.6 var(--sans); -webkit-font-smoothing: antialiased; }
a { color: var(--blue); text-decoration-thickness: 2px; text-underline-offset: 3px; }
a:hover { color: var(--red); }
h1, h2, h3, h4 { line-height: 1.1; margin: 0; font-weight: 700; letter-spacing: -0.01em; }
p { margin: 0 0 1em; }
code { font-family: var(--mono); font-size: 0.92em; background: var(--paper-2); padding: 0.05em 0.3em; }
button, input, select { font: inherit; color: inherit; }
button { cursor: pointer; }
[hidden] { display: none !important; }
:focus-visible { outline: 3px solid var(--blue); outline-offset: 2px; }
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 0.2em 0; margin: 0.6em 0; }
.katex { font-size: 1.06em; text-transform: none; letter-spacing: normal; }   /* math inside uppercase labels keeps its case */
svg { max-width: 100%; height: auto; }
.skip { position: absolute; left: -999px; top: 8px; z-index: 100; background: var(--ink); color: var(--white); padding: 8px 12px; }
.skip:focus { left: 8px; }

/* ---------- header: brand + the three sections ---------- */
.top { position: sticky; top: 0; z-index: 10; display: flex; align-items: center; gap: 28px; padding: 0 28px; height: var(--top-h); background: var(--paper); border-bottom: 4px solid var(--ink); }
.brand { display: flex; align-items: center; gap: 12px; text-decoration: none; color: var(--ink); }
.brand:hover { color: var(--ink); }
.brand .bars { display: flex; gap: 4px; height: 30px; }
.brand .bars i { display: block; width: 10px; }
.brand .bars .r { background: var(--red); } .brand .bars .y { background: var(--yellow); } .brand .bars .b { background: var(--blue); }
.brand .word { font-weight: 900; font-size: 1.5rem; letter-spacing: 0.12em; text-transform: uppercase; }
.topnav { display: flex; gap: 22px; margin-left: auto; }
.topnav a { color: var(--ink); text-decoration: none; text-transform: uppercase; letter-spacing: 0.1em; font-weight: 500; font-size: 0.86rem; padding: 6px 0; border-bottom: 4px solid transparent; }
.topnav a:hover { border-color: var(--rule); color: var(--ink); }
.topnav a[aria-current="page"] { border-color: var(--yellow); }
.menu { display: none; margin-left: auto; width: 44px; height: 44px; border: 2px solid var(--ink); background: var(--white); padding: 9px; flex-direction: column; justify-content: space-between; }
.menu span { display: block; height: 3px; background: var(--ink); }
.scrim { position: fixed; inset: 0; background: rgba(20,20,20,.35); z-index: 20; }

/* ---------- sub-bar: the current section's tabs ---------- */
.subnav { display: flex; align-items: stretch; background: var(--ink); overflow-x: auto; scrollbar-width: none; }
.subnav::-webkit-scrollbar { display: none; }
.subnav:empty { display: none; }
.subnav .inner { display: flex; width: 100%; max-width: 1180px; margin: 0 auto; padding: 0 28px; }
.subnav a { color: var(--white); text-decoration: none; text-transform: uppercase; letter-spacing: 0.1em; font-weight: 700; font-size: 0.74rem; padding: 9px 16px; white-space: nowrap; border-right: 2px solid rgba(255,255,255,.12); }
.subnav a:first-child { padding-left: 0; }
.subnav a:hover { color: var(--yellow); }
.subnav a[aria-current="page"] { background: var(--yellow); color: var(--ink); padding-left: 16px; }
.subnav.blue a[aria-current="page"] { background: var(--blue); color: var(--white); }
.subnav.red a[aria-current="page"] { background: var(--red); color: var(--white); }
.subnav.yellow a[aria-current="page"] { background: var(--yellow); color: var(--ink); }

/* ---------- layout: sticky sidebar + reading column ---------- */
.wrap { display: grid; grid-template-columns: var(--side-w) minmax(0, 1fr); gap: 40px; max-width: 1180px; margin: 0 auto; padding: 32px 28px 80px; }
#side { position: sticky; top: calc(var(--top-h) + 24px); align-self: start; max-height: calc(100vh - var(--top-h) - 46px); overflow: auto; font-size: 0.92rem; }
#main { min-width: 0; max-width: 760px; }
#main.wide { max-width: none; }
.foot { max-width: 1180px; margin: 0 auto; padding: 0 28px 40px; color: var(--ink-2); font-size: 0.82rem; border-top: 4px solid var(--ink); padding-top: 18px; }

/* sidebar primitives */
.side-head { border: 3px solid var(--ink); background: var(--white); padding: 12px 14px; margin-bottom: 18px; }
.side-head .pct { display: flex; justify-content: space-between; align-items: baseline; text-transform: uppercase; letter-spacing: 0.08em; font-size: 0.72rem; font-weight: 700; }
.side-head .pct b { font-size: 1.4rem; font-weight: 900; }
.bar { height: 10px; border: 2px solid var(--ink); margin-top: 8px; background: var(--white); }
.bar i { display: block; height: 100%; background: var(--blue); }
.unit-title { display: flex; justify-content: space-between; gap: 8px; text-transform: uppercase; letter-spacing: 0.1em; font-size: 0.72rem; font-weight: 700; padding: 8px 0 6px; border-bottom: 3px solid var(--ink); margin-bottom: 4px; }
.meter { display: inline-flex; gap: 3px; }
.meter i { width: 8px; height: 8px; border: 1.5px solid var(--ink); display: block; }
.meter i.on { background: var(--ink); }
.side-nav { display: none; }

/* ---------- shared atoms ---------- */
.eyebrow { text-transform: uppercase; letter-spacing: 0.14em; font-size: 0.74rem; font-weight: 700; color: var(--ink-2); }
.label { display: inline-block; text-transform: uppercase; letter-spacing: 0.12em; font-size: 0.7rem; font-weight: 700; }
.note, .muted { color: var(--ink-2); font-size: 0.92rem; }
.small { font-size: 0.85rem; }
.chips { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 10px; }
.chip { display: inline-block; border: 2px solid var(--ink); padding: 1px 9px; font-size: 0.74rem; text-transform: uppercase; letter-spacing: 0.08em; font-weight: 700; background: var(--white); color: var(--ink); text-decoration: none; white-space: nowrap; }
.chip.blue { background: var(--blue); color: var(--white); border-color: var(--blue); }
.chip.red, .chip.bad { background: var(--red); color: var(--white); border-color: var(--red); }
.chip.yellow, .chip.gold { background: var(--yellow); color: var(--ink); border-color: var(--ink); }
.chip.good { background: var(--good); color: var(--white); border-color: var(--good); }
.chip.plain { background: var(--paper-2); color: var(--ink-2); border-color: var(--rule); }
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; border: 2px solid var(--ink); background: var(--white); color: var(--ink); padding: 8px 16px; text-transform: uppercase; letter-spacing: 0.08em; font-weight: 700; font-size: 0.78rem; box-shadow: var(--shadow-sm); text-decoration: none; transition: transform 80ms, box-shadow 80ms; }
.btn:hover { background: var(--yellow); color: var(--ink); }
.btn:active { transform: translate(2px, 2px); box-shadow: 1px 1px 0 var(--ink); }
.btn.primary { background: var(--ink); color: var(--white); }
.btn.primary:hover { background: var(--blue); color: var(--white); }
.btn.ghost { box-shadow: none; }
.btn.ghost:hover { background: var(--paper-2); }
.btn.red, .btn.danger { background: var(--red); color: var(--white); }
.btn.blue { background: var(--blue); color: var(--white); }
.btn.big { font-size: 0.9rem; padding: 12px 22px; }
.btn.small { font-size: 0.7rem; padding: 5px 10px; box-shadow: 2px 2px 0 var(--ink); }
.btn:disabled { opacity: 0.45; cursor: default; transform: none; }
.actions { display: flex; flex-wrap: wrap; gap: 12px; margin: 12px 0; align-items: center; }
.tbl-wrap { overflow-x: auto; margin: 16px 0 22px; }
table.tbl { border-collapse: collapse; width: max-content; min-width: 60%; max-width: 100%; background: var(--white); font-size: 0.98rem; }
table.tbl th, table.tbl td { border: 2px solid var(--ink); padding: 8px 12px; text-align: left; vertical-align: top; }
table.tbl th { background: var(--ink); color: var(--white); text-transform: uppercase; font-size: 0.74rem; letter-spacing: 0.08em; }
table.tbl caption { caption-side: top; text-align: left; font-weight: 700; padding: 0 0 6px; }
.empty { border: 3px dashed var(--ink); padding: 24px; text-align: center; color: var(--ink-2); }
mark { background: var(--yellow); padding: 0 3px; }
kbd { font: 700 0.72rem var(--sans); border: 2px solid var(--ink); border-bottom-width: 3px; padding: 0 5px; background: var(--white); }
input[type="checkbox"] { appearance: none; -webkit-appearance: none; width: 20px; height: 20px; margin: 0; border: 2px solid var(--ink); background: var(--white); display: inline-grid; place-content: center; cursor: pointer; vertical-align: middle; flex: none; }
input[type="checkbox"]:checked { background: var(--ink); }
input[type="checkbox"]:checked::before { content: ""; width: 10px; height: 10px; background: var(--yellow); }
input[type="number"]::-webkit-inner-spin-button, input[type="number"]::-webkit-outer-spin-button { -webkit-appearance: none; margin: 0; }
input[type="number"] { -moz-appearance: textfield; appearance: textfield; }

/* ---------- responsive ---------- */
@media (max-width: 900px) {
  .wrap { grid-template-columns: 1fr; padding: 20px 16px 60px; gap: 0; }
  .topnav { display: none; }
  .menu { display: flex; }
  #side { position: fixed; top: 0; right: 0; bottom: 0; width: min(340px, 88vw); background: var(--paper); border-left: 4px solid var(--ink); padding: 20px 18px; z-index: 30; transform: translateX(100%); transition: transform 180ms; max-height: none; align-self: auto; height: 100%; overflow-y: auto; }
  body.nav-open #side { transform: none; }
  .side-nav { display: grid; grid-template-columns: 1fr 1fr; gap: 4px; margin-bottom: 18px; }
  .side-nav a { display: block; padding: 8px 10px; border: 2px solid var(--ink); color: var(--ink); text-decoration: none; text-transform: uppercase; letter-spacing: 0.08em; font-weight: 700; font-size: 0.78rem; background: var(--white); text-align: center; }
  .side-nav a[aria-current="page"] { background: var(--yellow); }
  .top { padding: 0 16px; gap: 16px; }
  .subnav .inner { padding: 0 16px; }
  .foot { padding: 18px 16px 40px; }
}
@media (prefers-reduced-motion: reduce) { *, *::before, *::after { transition: none !important; animation: none !important; } }