:root {
  /* Layout: graph-paper study sheet; interactive graphs up top, reference and quiz below. Shared by every lab.
     Series colors: --accent (primary), --c1 orange, --c2 green, --c3 purple, --c4 magenta. */
  --paper: #f3f5f8;
  --surface: #ffffff;
  --ink: #18202c;
  --muted: #5a6577;
  --rule: #d7dde6;
  --grid: #e7ebf1;
  --accent: #002e5d;      /* PMS 648 C navy */
  --accent-soft: #e1e8f1;
  --c1: #c8641e;
  --c2: #17806a;
  --ghost: #a9b2c0;
  --good: #1d7a4a;
  --good-soft: #e1f3e8;
  --bad: #b3322f;
  --bad-soft: #f8e3e2;
  --c3: #7b4cc0;
  --c4: #a8326e;
  --display: "Source Serif 4", Georgia, "Times New Roman", serif;
  --body: "IBM Plex Sans", system-ui, -apple-system, "Segoe UI", sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, Menlo, monospace;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper: #12161d; --surface: #1a2029; --ink: #e6eaf0; --muted: #9aa5b6;
    --rule: #2c3442; --grid: #222a35; --accent: #8db4e2; --accent-soft: #13263d;
    --c1: #f0995a; --c2: #4cc7a6; --ghost: #566070;
    --good: #5ccb8d; --good-soft: #17301f; --bad: #ff8a85; --bad-soft: #3a1d1d; --c3: #b896f5; --c4: #f080b4;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --paper: #12161d; --surface: #1a2029; --ink: #e6eaf0; --muted: #9aa5b6;
  --rule: #2c3442; --grid: #222a35; --accent: #8db4e2; --accent-soft: #13263d;
  --c1: #f0995a; --c2: #4cc7a6; --ghost: #566070;
  --good: #5ccb8d; --good-soft: #17301f; --bad: #ff8a85; --bad-soft: #3a1d1d; --c3: #b896f5; --c4: #f080b4;
  color-scheme: dark;
}
* { box-sizing: border-box; }
html, body { margin: 0; }
body {
  background: var(--paper);
  color: var(--ink);
  font-family: var(--body);
  font-size: 16px;
  line-height: 1.55;
}
.wrap { max-width: 1120px; margin: 0 auto; padding: 28px 20px 64px; display: grid; gap: 36px; }
h1, h2, h3 { font-family: var(--display); text-wrap: balance; margin: 0; line-height: 1.2; }
h1 { font-size: clamp(1.9rem, 4vw, 2.6rem); }
h2 { font-size: 1.55rem; }
h3 { font-size: 1.12rem; }
p { margin: 0; }
.lede { max-width: 68ch; color: var(--muted); font-size: 1.06rem; margin-top: 10px; }
header { display: grid; gap: 4px; border-bottom: 2px solid var(--ink); padding-bottom: 18px; }
.kicker { font-family: var(--mono); font-size: .78rem; letter-spacing: .08em; text-transform: uppercase; color: var(--accent); }
section { display: grid; gap: 16px; }
.sec-head { display: grid; gap: 6px; }
.sec-head p { color: var(--muted); max-width: 70ch; }

.card { background: var(--surface); border: 1px solid var(--rule); border-radius: 10px; padding: 18px; }

/* Lab */
.lab { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
.graph-card { display: grid; gap: 8px; }
.graph-card h3 { display: flex; justify-content: space-between; align-items: baseline; gap: 8px; flex-wrap: wrap; }
.graph-card h3 small { font-family: var(--body); font-weight: 400; font-size: .82rem; color: var(--muted); }
svg.chart { width: 100%; height: auto; display: block; }
svg text { font-family: var(--body); fill: var(--muted); font-size: 11px; }
svg .lbl { font-weight: 600; font-size: 12px; }
.controls { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 14px 18px; }
.ctl { display: grid; gap: 4px; }
.ctl label { font-size: .86rem; font-weight: 500; display: flex; justify-content: space-between; gap: 6px; }
.ctl output { font-family: var(--mono); font-size: .82rem; color: var(--accent); white-space: nowrap; }
.ctl .hint { font-size: .76rem; color: var(--muted); }
input[type="range"] { width: 100%; accent-color: var(--accent); }
.scenarios { display: flex; flex-wrap: wrap; gap: 8px; }
button {
  font: inherit; font-size: .88rem; cursor: pointer;
  border: 1px solid var(--rule); background: var(--surface); color: var(--ink);
  border-radius: 999px; padding: 6px 14px;
}
button:hover { border-color: var(--accent); }
button:focus-visible, input:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
button.primary { background: var(--accent); border-color: var(--accent); color: var(--surface); font-weight: 600; }
button.primary:disabled { opacity: .45; cursor: not-allowed; }
.readout { display: grid; grid-template-columns: repeat(4, minmax(0,1fr)); gap: 10px; }
.stat { border: 1px solid var(--rule); border-radius: 8px; padding: 10px 12px; background: var(--surface); }
.stat .k { font-size: .76rem; color: var(--muted); }
.stat .v { font-family: var(--mono); font-size: 1.2rem; font-variant-numeric: tabular-nums; }
.pill { display: inline-block; font-size: .78rem; font-weight: 600; padding: 2px 10px; border-radius: 999px; }
.pill.bad { background: var(--bad-soft); color: var(--bad); }
.pill.acc { background: var(--accent-soft); color: var(--accent); }
.pill.good { background: var(--good-soft); color: var(--good); }
.story { border-left: 4px solid var(--accent); padding: 12px 16px; background: var(--surface); border-radius: 0 8px 8px 0; display: grid; gap: 8px; }
.story ul { margin: 0; padding-left: 20px; display: grid; gap: 4px; }
.lab-bar { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; justify-content: space-between; }
.legend { display: flex; gap: 14px; flex-wrap: wrap; font-size: .8rem; color: var(--muted); }
.legend span::before { content: ""; display: inline-block; width: 18px; height: 3px; margin-right: 6px; vertical-align: middle; background: currentColor; }
.legend .l-c1 { color: var(--c1); } .legend .l-c2 { color: var(--c2); }
.legend .l-ghost { color: var(--ghost); }
.legend .l-ghost::before { background: none; border-top: 2px dashed currentColor; height: 0; }

/* Concepts */
.concepts { display: grid; grid-template-columns: repeat(3, minmax(0,1fr)); gap: 14px; }
.concepts .card { display: grid; gap: 6px; align-content: start; }
.concepts .card p { font-size: .95rem; }
.tag { font-family: var(--mono); font-size: .72rem; color: var(--muted); letter-spacing: .05em; text-transform: uppercase; }

/* Table */
.tbl-wrap { overflow-x: auto; }
table { width: 100%; border-collapse: collapse; background: var(--surface); border: 1px solid var(--rule); border-radius: 10px; overflow: hidden; min-width: 560px; }
th, td { text-align: left; padding: 10px 14px; border-bottom: 1px solid var(--rule); font-size: .94rem; vertical-align: top; }
th { font-size: .8rem; letter-spacing: .02em; color: var(--muted); background: var(--paper); }
tr:last-child td { border-bottom: 0; }
td b { color: var(--accent); }
td .shift { color: var(--c1); font-weight: 600; }
td .lshift { color: var(--c2); font-weight: 600; }

.two { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; }
.two ul { margin: 8px 0 0; padding-left: 20px; display: grid; gap: 6px; font-size: .95rem; }

/* Quiz */
.quiz { display: grid; gap: 14px; }
.q { display: grid; gap: 10px; }
.q .qn { font-family: var(--mono); font-size: .76rem; color: var(--muted); }
.q .stem { font-weight: 500; }
.opts { display: grid; gap: 8px; }
.opt { text-align: left; border-radius: 8px; padding: 9px 14px; width: 100%; }
.opt.right { background: var(--good-soft); border-color: var(--good); color: var(--good); font-weight: 600; }
.opt.wrong { background: var(--bad-soft); border-color: var(--bad); color: var(--bad); }
.opt:disabled { cursor: default; }
.why { font-size: .92rem; color: var(--muted); border-top: 1px dashed var(--rule); padding-top: 8px; }
.score { font-family: var(--mono); font-size: .95rem; }

@media (max-width: 860px) {
  .lab, .two { grid-template-columns: 1fr; }
  .concepts { grid-template-columns: 1fr 1fr; }
  .controls, .readout { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 520px) {
  .concepts, .controls { grid-template-columns: 1fr; }
}

/* Shared navigation */
.topnav { display: flex; flex-wrap: wrap; gap: 8px 14px; align-items: center; justify-content: space-between; font-size: .86rem; }
.topnav a { color: var(--accent); text-decoration: none; font-weight: 500; }
.topnav a:hover { text-decoration: underline; }
.topics { display: flex; flex-wrap: wrap; gap: 6px; }
.topics a { font-family: var(--mono); font-size: .76rem; padding: 3px 9px; border-radius: 999px; border: 1px solid var(--rule); color: var(--muted); text-decoration: none; background: var(--surface); }
.topics a[aria-current="page"] { background: var(--accent); border-color: var(--accent); color: var(--surface); }
.topics a:hover { border-color: var(--accent); }
.pager { display: flex; justify-content: space-between; gap: 12px; flex-wrap: wrap; border-top: 1px solid var(--rule); padding-top: 18px; }
.pager a { color: var(--accent); text-decoration: none; font-weight: 500; }
.legend .l-ad { color: var(--accent); } .legend .l-c3 { color: var(--c3); } .legend .l-c4 { color: var(--c4); }
.formula { font-family: var(--mono); font-size: 1rem; background: var(--accent-soft); color: var(--ink); padding: 8px 12px; border-radius: 6px; display: inline-block; }
.calc { display: grid; gap: 8px; }
.calc .row { display: flex; justify-content: space-between; gap: 12px; font-variant-numeric: tabular-nums; border-bottom: 1px dashed var(--rule); padding: 4px 0; }
.calc .row:last-child { border-bottom: 0; font-weight: 600; }

/* Glossary viewer */
.gloss { display: grid; gap: 14px; }
.g-bar { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; justify-content: space-between; }
.g-tabs { display: inline-flex; border: 1px solid var(--rule); border-radius: 999px; padding: 3px; background: var(--surface); gap: 2px; }
.g-tabs button { border: 0; background: none; padding: 6px 14px; }
.g-tabs button[aria-selected="true"] { background: var(--accent); color: var(--surface); font-weight: 600; }
.g-search { flex: 1 1 260px; max-width: 420px; }
.g-search input, .g-topic select { font: inherit; font-size: .92rem; width: 100%; padding: 8px 12px; border: 1px solid var(--rule); border-radius: 8px; background: var(--surface); color: var(--ink); }
.g-search input:focus-visible, .g-topic select:focus-visible { outline: 3px solid var(--accent); outline-offset: 1px; }
.g-filters { display: flex; flex-wrap: wrap; gap: 10px 16px; align-items: center; }
.g-chips { display: flex; flex-wrap: wrap; gap: 6px; }
.g-chip { font-size: .82rem; padding: 4px 12px; }
.g-chip[aria-pressed="true"] { background: var(--accent-soft); border-color: var(--accent); color: var(--accent); font-weight: 600; }
.g-topic { display: flex; align-items: center; gap: 8px; font-size: .86rem; color: var(--muted); flex: 1 1 280px; max-width: 520px; }
.g-count { font-family: var(--mono); font-size: .8rem; color: var(--muted); margin-left: auto; }
.g-unit { font-size: 1.3rem; margin-top: 14px; padding-bottom: 6px; border-bottom: 2px solid var(--ink); }
.g-tp { font-family: var(--body); font-size: .98rem; font-weight: 600; margin: 8px 0 0; color: var(--ink); scroll-margin-top: 16px; }
.g-tpn { font-family: var(--mono); font-size: .8rem; color: var(--accent); }
.g-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 10px; }
.g-term { background: var(--surface); border: 1px solid var(--rule); border-radius: 8px; padding: 12px 14px; break-inside: avoid; }
.g-term dl, .g-term dd { margin: 0; }
.g-term dl { display: grid; gap: 6px; }
.g-term dt { font-weight: 600; color: var(--ink); }
.g-def { font-size: .94rem; }
.g-where { font-size: .78rem; color: var(--muted); font-style: italic; }
.g-x { font-size: .86rem; color: var(--muted); border-left: 3px solid var(--rule); padding-left: 8px; }
.g-f .formula { font-size: .84rem; padding: 3px 8px; }
.g-r { font-size: .8rem; color: var(--muted); display: flex; flex-wrap: wrap; gap: 4px; align-items: center; }
.g-rel { font-size: .78rem; padding: 1px 8px; border-radius: 999px; border: 1px solid var(--rule); background: var(--paper); color: var(--accent); }
span.g-rel { color: var(--muted); }
.g-empty { color: var(--muted); }
.g-cardwrap { display: grid; gap: 12px; justify-items: center; }
.g-prog, .g-cardstats, .g-hint { font-size: .82rem; color: var(--muted); margin: 0; }
.g-card { width: 100%; max-width: 640px; min-height: 240px; border-radius: 14px; border: 1px solid var(--rule); background: var(--surface); box-shadow: 0 6px 22px rgba(20,30,50,.08); padding: 28px; display: grid; place-items: center; text-align: center; cursor: pointer; }
.g-card.is-flipped { background: var(--accent-soft); border-color: var(--accent); }
.g-face { display: grid; gap: 12px; justify-items: center; }
.g-small { font-family: var(--mono); font-size: .74rem; text-transform: uppercase; letter-spacing: .06em; color: var(--muted); }
.g-big { font-family: var(--display); font-size: clamp(1.5rem, 4vw, 2.1rem); font-weight: 700; line-height: 1.2; text-wrap: balance; }
.g-mid { font-size: 1.08rem; line-height: 1.5; max-width: 52ch; }
.g-cardbtns { display: flex; flex-wrap: wrap; gap: 8px; justify-content: center; }
.g-know { background: var(--good); border-color: var(--good); color: var(--surface); }
.g-opts { display: flex; flex-wrap: wrap; gap: 8px 16px; align-items: center; justify-content: center; font-size: .86rem; color: var(--muted); }
.g-opts label { display: inline-flex; gap: 6px; align-items: center; }
.g-quote { margin: 0; padding: 12px 16px; background: var(--paper); border-left: 4px solid var(--accent); border-radius: 0 8px 8px 0; font-size: 1rem; }
.g-done { display: grid; gap: 10px; }
.g-missed { margin: 0; padding-left: 20px; display: grid; gap: 6px; font-size: .92rem; }
.unit-cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 12px; }
.unit-cards a { text-decoration: none; color: var(--ink); display: grid; gap: 4px; }
.unit-cards a:hover { border-color: var(--accent); }
.unit-cards .num { font-family: var(--mono); font-size: .78rem; color: var(--accent); }
.unit-cards .meta { font-size: .84rem; color: var(--muted); }
@media print {
  .g-bar, .g-filters, .topnav, .pager, .g-r { display: none !important; }
  .g-term { border-color: #bbb; }
  body { background: #fff; }
}
.sec-head a, .lede a { color: var(--accent); }
.g-lablink { font-family: var(--body); font-size: .8rem; font-weight: 500; color: var(--accent); margin-left: 10px; text-decoration: none; }
.g-lablink:hover { text-decoration: underline; }
.explainer { width: 100%; height: auto; display: block; border-radius: 12px; border: 1px solid var(--rule); background: var(--surface); box-shadow: 0 6px 22px rgba(20,30,50,.08); }

/* Statistics additions */
pre.stem { font-family: var(--mono); font-size: .95rem; line-height: 1.5; margin: 0; padding: 12px 16px; background: var(--surface); border: 1px solid var(--rule); border-radius: 8px; overflow-x: auto; color: var(--ink); }
.datatable { font-family: var(--mono); font-size: .86rem; display: flex; flex-wrap: wrap; gap: 4px; }
.datatable span { padding: 2px 7px; border: 1px solid var(--rule); border-radius: 6px; background: var(--surface); }
.datatable span.hi { background: var(--accent-soft); border-color: var(--accent); color: var(--accent); font-weight: 600; }
textarea.data { font: inherit; font-family: var(--mono); font-size: .9rem; width: 100%; min-height: 76px; padding: 8px 10px; border: 1px solid var(--rule); border-radius: 8px; background: var(--surface); color: var(--ink); resize: vertical; }
textarea.data:focus-visible, select:focus-visible { outline: 3px solid var(--accent); outline-offset: 1px; }
select { font: inherit; font-size: .9rem; padding: 6px 10px; border: 1px solid var(--rule); border-radius: 8px; background: var(--surface); color: var(--ink); }
.seg { display: inline-flex; flex-wrap: wrap; border: 1px solid var(--rule); border-radius: 18px; overflow: hidden; }
.seg button { border: 0; border-radius: 0; padding: 6px 12px; }
.seg button[aria-pressed="true"] { background: var(--accent); color: var(--surface); font-weight: 600; }
.note { font-size: .86rem; color: var(--muted); }
.sort-pool { display: flex; flex-wrap: wrap; gap: 8px; }
.sort-bins { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 12px; }
.sort-bin { border: 2px dashed var(--rule); border-radius: 10px; padding: 12px; min-height: 90px; display: grid; gap: 8px; align-content: start; }
.sort-bin h4 { margin: 0; font-size: .9rem; }
.chip { font-size: .86rem; padding: 6px 12px; border-radius: 999px; }
.chip.right { background: var(--good-soft); border-color: var(--good); color: var(--good); }
.chip.wrong { background: var(--bad-soft); border-color: var(--bad); color: var(--bad); }
.chip[aria-pressed="true"] { border-color: var(--accent); background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.sr { position: absolute; left: -9999px; }
.nc { text-transform: none; }