/* Find the Breaks. Warm neutral base, one ochre accent, borders over shadows. */

:root {
  --bg: #f5f2ec;
  --surface: #fffdf8;
  --surface-2: #efebe3;
  --ink: #221f1a;
  --ink-2: #4a453d;
  --muted: #6d665b;
  --rule: #d8d1c4;
  --rule-strong: #b9b0a0;
  --accent: #9c5f12;
  --accent-ink: #ffffff;
  --accent-soft: #f3e6cf;
  --ok: #2c6a3a;
  --ok-soft: #e3efe2;
  --bad: #a3322a;
  --bad-soft: #f6e3df;
  --err: #4b4f63;
  --err-soft: #e7e7ec;
  --code-bg: #f0ece4;
  --focus: #1f5fbf;

  --sans: 'IBM Plex Sans', system-ui, -apple-system, 'Segoe UI', sans-serif;
  --mono: 'IBM Plex Mono', ui-monospace, 'SFMono-Regular', Menlo, monospace;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #171512;
    --surface: #1f1c18;
    --surface-2: #29251f;
    --ink: #ece6da;
    --ink-2: #cfc7b9;
    --muted: #a0978a;
    --rule: #3a352d;
    --rule-strong: #575046;
    --accent: #e0a64a;
    --accent-ink: #1a1408;
    --accent-soft: #3a2c15;
    --ok: #86c995;
    --ok-soft: #1c2c1f;
    --bad: #ec8b80;
    --bad-soft: #351d1a;
    --err: #b9bdd3;
    --err-soft: #25262e;
    --code-bg: #24211c;
    --focus: #7fb0ff;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #171512;
  --surface: #1f1c18;
  --surface-2: #29251f;
  --ink: #ece6da;
  --ink-2: #cfc7b9;
  --muted: #a0978a;
  --rule: #3a352d;
  --rule-strong: #575046;
  --accent: #e0a64a;
  --accent-ink: #1a1408;
  --accent-soft: #3a2c15;
  --ok: #86c995;
  --ok-soft: #1c2c1f;
  --bad: #ec8b80;
  --bad-soft: #351d1a;
  --err: #b9bdd3;
  --err-soft: #25262e;
  --code-bg: #24211c;
  --focus: #7fb0ff;
  color-scheme: dark;
}

*, *::before, *::after { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 16px/1.55 var(--sans);
  font-variant-numeric: tabular-nums;
}

a { color: inherit; text-underline-offset: 3px; }
a:hover { color: var(--accent); }
:focus-visible { outline: 2px solid var(--focus); outline-offset: 2px; }

h1, h2, h3 { line-height: 1.2; margin: 0 0 0.5rem; font-weight: 600; }
h1 { font-size: 1.9rem; letter-spacing: -0.01em; }
h2 { font-size: 1.3rem; }
h3 { font-size: 1rem; }
p { margin: 0 0 0.75rem; }

.muted { color: var(--muted); }
.small { font-size: 0.85rem; }
.eyebrow {
  font: 500 0.75rem/1.2 var(--mono);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
  margin-bottom: 0.4rem;
  display: flex;
  gap: 0.6rem;
  align-items: center;
}

/* ---------- site chrome ---------- */

header.site, footer.site, main.task, main.page {
  max-width: 1280px;
  margin: 0 auto;
  padding-left: 24px;
  padding-right: 24px;
}
header.site {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 1rem;
  padding-top: 14px;
  padding-bottom: 14px;
  border-bottom: 1px solid var(--rule);
  flex-wrap: wrap;
  row-gap: 0.5rem;
}
.brand {
  font: 600 1rem/1 var(--mono);
  text-decoration: none;
  letter-spacing: -0.01em;
}
.brand::before { content: '\25A0'; color: var(--accent); margin-right: 0.45em; font-size: 0.8em; }
header.site nav { display: flex; gap: 1.25rem; font-size: 0.95rem; }
header.site nav a { text-decoration: none; color: var(--ink-2); }
header.site nav a[aria-current="page"] { color: var(--ink); border-bottom: 2px solid var(--accent); padding-bottom: 2px; }

/* ---------- landing and about: left aligned, prose width ---------- */

main.page { padding-top: 32px; }
main.page > * { max-width: 68ch; }
main.page h1 { font-size: 1.35rem; font-weight: 500; line-height: 1.4; margin-bottom: 1rem; }
main.page p { color: var(--ink-2); }
.tasks { list-style: none; padding: 0; margin: 1.5rem 0 0; border-top: 1px solid var(--rule); }
.tasks li { border-bottom: 1px solid var(--rule); }
.tasks a { display: block; padding: 0.7rem 0; font: 500 1rem var(--mono); text-decoration: none; }
.tasks a::after { content: ' \2192'; color: var(--accent); }
.tasks a:hover { background: var(--surface-2); }
footer.site {
  border-top: 1px solid var(--rule);
  padding-top: 18px;
  padding-bottom: 32px;
  margin-top: 48px;
  color: var(--muted);
  font-size: 0.85rem;
}
.noscript { padding: 16px 24px; }

/* ---------- intro ---------- */

.intro { padding: 28px 0 20px; }
.intro > p { max-width: 76ch; }
.lede { font-size: 1.1rem; color: var(--ink-2); }

.chips {
  list-style: none;
  padding: 0;
  margin: 1rem 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0;
  border: 1px solid var(--rule);
  background: var(--surface);
  width: fit-content;
  max-width: 100%;
}
.chip {
  display: grid;
  grid-template-columns: auto 1fr;
  column-gap: 0.55rem;
  padding: 0.5rem 0.85rem;
  border-right: 1px solid var(--rule);
  font-size: 0.9rem;
  min-width: 10.5rem;
}
.chip:last-child { border-right: 0; }
.chip-count { font: 600 1.15rem/1.2 var(--mono); grid-row: span 2; color: var(--accent); }
.chip-state { font: 0.75rem/1.3 var(--mono); color: var(--muted); }
.chip.found { background: var(--ok-soft); }
.chip.found .chip-count, .chip.found .chip-state { color: var(--ok); }

/* ---------- layout ---------- */

.layout {
  display: grid;
  grid-template-columns: minmax(260px, 340px) minmax(0, 1fr);
  gap: 28px;
  align-items: start;
  border-top: 1px solid var(--rule);
  padding-top: 20px;
}
.side { min-width: 0; display: grid; grid-template-columns: minmax(0, 1fr); gap: 36px; }

/* ---------- drill list ---------- */

.drill-list { list-style: none; margin: 0; padding: 0; border-top: 1px solid var(--rule); }
.drill { border-bottom: 1px solid var(--rule); }
.drill-head {
  all: unset;
  box-sizing: border-box;
  cursor: pointer;
  width: 100%;
  display: grid;
  grid-template-columns: 2.1rem 1fr auto 1.1rem;
  gap: 0.5rem;
  align-items: baseline;
  padding: 0.6rem 0.4rem;
}
.drill-head:hover .title { color: var(--accent); }
.drill-head:focus-visible { outline: 2px solid var(--focus); outline-offset: -2px; }
.drill .num { font: 500 0.85rem var(--mono); color: var(--muted); }
.drill .title { font-weight: 500; }
.drill.open { background: var(--surface); }
.drill.open .num { color: var(--accent); }
.drill.open .title { font-weight: 600; }
.drill .status { font: 600 0.9rem var(--mono); color: var(--ok); text-align: right; }
.tag {
  font: 0.7rem/1.4 var(--mono);
  color: var(--muted);
  border: 1px solid var(--rule);
  padding: 0 0.35rem;
  white-space: nowrap;
  text-transform: none;
  letter-spacing: 0;
}
.drill-body { padding: 0 0.6rem 0.7rem 2.9rem; font-size: 0.9rem; color: var(--ink-2); }
.drill-body p { margin: 0; }
.key-flag {
  margin: -0.3rem 0 0.55rem 2.9rem;
  font: 600 0.72rem/1.3 var(--mono);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--accent);
}

.panel-item { border-bottom: 1px solid var(--rule); padding: 0.9rem 0; }
.panel {
  border: 1px solid var(--rule-strong);
  border-top: 3px solid var(--ink);
  background: var(--surface);
  padding: 0.85rem 0.9rem 0.6rem;
}
.panel h3 { font-size: 0.95rem; }
.panel p { font-size: 0.88rem; }
.compare { margin: 0 0 0.7rem; border: 1px solid var(--rule); background: var(--code-bg); }
.compare dt {
  font: 600 0.7rem/1 var(--mono);
  text-transform: uppercase;
  letter-spacing: 0.07em;
  color: var(--accent);
  padding: 0.55rem 0.7rem 0.2rem;
}
.compare dd { margin: 0; padding: 0 0.7rem 0.55rem; border-bottom: 1px solid var(--rule); }
.compare dd:last-child { border-bottom: 0; }
.compare code { font: 0.8rem/1.45 var(--mono); white-space: pre-wrap; overflow-wrap: anywhere; }
.verdict .panel { margin-top: 0; }
.v .note { border-top: 1px solid var(--rule); padding-top: 0.5rem; font-size: 0.9rem; }
.notice { border: 1px solid var(--rule-strong); background: var(--surface-2); padding: 0.5rem 0.75rem; font-size: 0.9rem; }

/* ---------- working area ---------- */

.work {
  border: 1px solid var(--rule);
  background: var(--surface);
  padding: 0 18px 18px;
  min-width: 0;
}
.tabs {
  display: flex;
  gap: 0;
  border-bottom: 1px solid var(--rule);
  margin: 0 -18px 16px;
  padding: 0 10px;
  overflow-x: auto;
}
.tab {
  all: unset;
  cursor: pointer;
  font: 500 0.9rem var(--mono);
  padding: 0.65rem 0.9rem;
  color: var(--muted);
  border-bottom: 2px solid transparent;
  margin-bottom: -1px;
  display: inline-flex;
  gap: 0.45rem;
  align-items: baseline;
}
.tab[aria-selected="true"] { color: var(--ink); border-bottom-color: var(--accent); }
.tab:focus-visible { outline: 2px solid var(--focus); outline-offset: -2px; }
.tab .count { font-size: 0.75rem; color: var(--muted); }
.tabs.small { margin: 0 0 0; padding: 0; }
.reference .tabs.small .tab { padding: 0.5rem 0.8rem; }

.work-head h2 { margin-bottom: 0.4rem; }
.question { font-size: 1.02rem; }
.hint {
  border: 1px solid var(--accent);
  background: var(--accent-soft);
  padding: 0.55rem 0.8rem;
  font-size: 0.93rem;
}
.engine-note { font: 0.78rem/1.45 var(--mono); color: var(--muted); margin: 0.25rem 0 0.4rem; }

.editor {
  display: block;
  width: 100%;
  min-height: 9.5rem;
  resize: vertical;
  font: 0.92rem/1.5 var(--mono);
  color: var(--ink);
  background: var(--code-bg);
  border: 1px solid var(--rule-strong);
  border-radius: 0;
  padding: 0.7rem 0.8rem;
  tab-size: 2;
}
.editor:focus { outline: 2px solid var(--focus); outline-offset: -1px; }
.editor::placeholder { color: var(--muted); }

.actions { display: flex; flex-wrap: wrap; gap: 0.5rem; margin: 0.75rem 0; }
.btn {
  font: 500 0.9rem/1 var(--sans);
  padding: 0.6rem 0.95rem;
  border: 1px solid var(--rule-strong);
  background: var(--surface);
  color: var(--ink);
  cursor: pointer;
  border-radius: 0;
}
.btn:hover { border-color: var(--ink); }
.btn.primary { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); font-weight: 600; }
.btn.primary:hover { filter: brightness(1.08); }
.btn.quiet { border-color: transparent; color: var(--muted); text-decoration: underline; text-underline-offset: 3px; padding-left: 0.4rem; padding-right: 0.4rem; }
.btn.quiet:hover { color: var(--ink); }
.btn.small { font-size: 0.8rem; padding: 0.35rem 0.5rem; }
.btn:disabled { opacity: 0.6; cursor: progress; }

.answer:empty { display: none; }
.answer { margin-bottom: 0.75rem; }
.answer-label { font: 600 0.75rem var(--mono); text-transform: uppercase; letter-spacing: 0.06em; color: var(--muted); margin-bottom: 0.3rem; }
.why { font-size: 0.92rem; color: var(--ink-2); }

.code {
  font: 0.85rem/1.55 var(--mono);
  background: var(--code-bg);
  border: 1px solid var(--rule);
  padding: 0.7rem 0.8rem;
  margin: 0 0 0.6rem;
  overflow-x: auto;
  white-space: pre;
}

/* Verdicts: label text and a mark carry the meaning, colour backs it up */
.verdict:empty { display: none; }
.v { border: 1px solid; padding: 0.7rem 0.9rem; margin-bottom: 0.9rem; }
.v p:last-child { margin-bottom: 0; }
.v .btn { margin-top: 0.2rem; }
.v-label { font: 600 0.95rem var(--mono); display: flex; gap: 0.55rem; align-items: baseline; margin-bottom: 0.35rem; }
.v-mark { display: inline-block; width: 1.3rem; height: 1.3rem; line-height: 1.3rem; text-align: center; font-weight: 700; }
.v-correct { border-color: var(--ok); background: var(--ok-soft); }
.v-correct .v-label { color: var(--ok); }
.v-correct .v-mark { background: var(--ok); color: var(--surface); }
.v-wrong { border-color: var(--bad); border-style: dashed; background: var(--bad-soft); }
.v-wrong .v-label { color: var(--bad); }
.v-wrong .v-mark { border: 2px solid var(--bad); line-height: 1rem; }
.v-error { border-color: var(--err); border-width: 1px 1px 1px 4px; background: var(--err-soft); }
.v-error .v-label { color: var(--err); }
.v-error .v-mark { border: 2px solid var(--err); border-radius: 50%; line-height: 1rem; }

/* Timed run */
.timed-bar {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  gap: 0.5rem 1rem;
  font: 0.85rem var(--mono);
  border: 1px solid var(--rule-strong);
  padding: 0.45rem 0.7rem;
  margin-bottom: 0.9rem;
  background: var(--surface-2);
}
.clock { font: 600 1.35rem/1 var(--mono); }
.clock.over { color: var(--bad); }
.clock.over::after { content: ' over'; font-size: 0.75rem; font-weight: 500; }

/* ---------- tables ---------- */

.table-wrap { overflow-x: auto; max-width: 100%; border: 1px solid var(--rule); background: var(--surface); }
.table-wrap:focus-visible { outline: 2px solid var(--focus); }
table.data { border-collapse: collapse; width: 100%; font: 0.8rem/1.35 var(--mono); }
table.data caption { text-align: left; font: 500 0.75rem var(--mono); color: var(--muted); padding: 0.4rem 0.6rem; border-bottom: 1px solid var(--rule); caption-side: top; }
table.data th {
  text-align: left;
  font-weight: 600;
  background: var(--surface-2);
  border-bottom: 1px solid var(--rule-strong);
  padding: 0.35rem 0.6rem;
  white-space: nowrap;
  position: sticky;
  top: 0;
}
table.data td { padding: 0.22rem 0.6rem; border-bottom: 1px solid var(--rule); white-space: nowrap; }
table.data tr:last-child td { border-bottom: 0; }
table.data tbody tr:hover td { background: var(--surface-2); }
table.data .num { text-align: right; }
table.data td.null { color: var(--muted); font-style: italic; }
.result .table-wrap { max-height: 24rem; overflow: auto; }

.reference .table-wrap { max-height: 30rem; overflow: auto; border-top: 0; }

/* ---------- small screens ---------- */

@media (max-width: 860px) {
  header.site, footer.site, main.task, main.page { padding-left: 16px; padding-right: 16px; }
  header.site nav { gap: 1rem; }
  main.page { padding-top: 24px; }
  main.page h1 { font-size: 1.2rem; }
  .layout { grid-template-columns: minmax(0, 1fr); gap: 20px; }
  .intro { padding-top: 20px; }
  h1 { font-size: 1.55rem; }
  .chips { width: 100%; }
  .chip { flex: 1 1 50%; border-bottom: 1px solid var(--rule); min-width: 0; }
  .chip:last-child:nth-child(odd) { flex-basis: 100%; border-bottom: 0; }
  .work { padding: 0 14px 14px; scroll-margin-top: 8px; }
  .tabs { margin: 0 -14px 14px; }
}

/* ---------- solved states ---------- */

.drill .status.hollow, .legend .status.hollow {
  color: transparent;
  -webkit-text-stroke: 1px var(--ok);
}
.legend {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
  font: 0.75rem var(--mono);
  color: var(--muted);
  margin: 0.6rem 0.4rem 0;
}
.legend .status { font: 600 0.9rem var(--mono); color: var(--ok); }
.chip.found-hollow { background: var(--surface); outline: 1px dashed var(--ok); outline-offset: -1px; }
.chip.found-hollow .chip-state { color: var(--ok); }

/* ---------- Excel tab ---------- */

.frame { font-size: 0.93rem; margin-bottom: 0.4rem; }
.frame p { margin-bottom: 0.3rem; }
.frame ul { margin: 0 0 0.4rem; padding-left: 1.1rem; }
.frame li { margin: 0.1rem 0; }
.frame code, .why code { font: 0.85em var(--mono); background: var(--code-bg); padding: 0 0.25em; }

.formulas { display: grid; gap: 0.4rem; }
.formula-row {
  display: grid;
  grid-template-columns: 3.2rem minmax(5rem, 11rem) minmax(0, 1fr);
  align-items: center;
  border: 1px solid var(--rule-strong);
  background: var(--code-bg);
}
.formula-row .cell-ref { font: 600 0.8rem var(--mono); padding: 0 0.5rem; color: var(--accent); border-right: 1px solid var(--rule); align-self: stretch; display: flex; align-items: center; }
.formula-row .col-name { font: 0.78rem var(--mono); color: var(--muted); padding: 0 0.5rem; border-right: 1px solid var(--rule); align-self: stretch; display: flex; align-items: center; overflow-wrap: anywhere; }
.formula {
  font: 0.9rem/1.4 var(--mono);
  color: var(--ink);
  background: transparent;
  border: 0;
  border-radius: 0;
  padding: 0.55rem 0.6rem;
  min-width: 0;
  width: 100%;
}
.formula:focus { outline: 2px solid var(--focus); outline-offset: -2px; }
.formula::placeholder { color: var(--muted); }

table.sheet th { text-align: center; }
table.sheet th.corner { width: 2.4rem; }
table.sheet th.user, table.sheet td.user { background: var(--accent-soft); }
table.sheet tr.names td { font-weight: 600; background: var(--surface-2); }
table.sheet tr.names td.user { background: var(--accent-soft); }
table.sheet th.rownum { color: var(--muted); font-weight: 500; text-align: right; background: var(--surface-2); position: static; border-right: 1px solid var(--rule); }
table.sheet tr.kept td { background: var(--ok-soft); }
table.sheet tr.kept td.user { background: var(--ok-soft); }
table.sheet tr.kept th.rownum { color: var(--ok); font-weight: 600; }
table.sheet td.err { color: var(--bad); font-weight: 600; }
table.sheet td.err-focus { outline: 2px solid var(--bad); outline-offset: -2px; }
table.sheet tr.total td { border-top: 1px solid var(--rule-strong); }
table.sheet tr.total td.label { text-align: right; color: var(--muted); }
.sheet-wrap { max-height: 26rem; }

@media (max-width: 860px) {
  .formula-row { grid-template-columns: 2.8rem minmax(0, 1fr); }
  .formula-row .col-name { border-right: 0; }
  .formula-row .formula { grid-column: 1 / -1; border-top: 1px solid var(--rule); }
}
.sheet-caption { font: 500 0.75rem var(--mono); color: var(--ink-2); margin: 0 0 0.3rem; }

/* ---------- laytime page ---------- */

.worked { margin-top: 1.4rem; max-width: 80ch; }
.terms { display: grid; grid-template-columns: max-content 1fr; gap: 0.15rem 1rem; margin: 0 0 0.8rem; font-size: 0.93rem; border: 1px solid var(--rule-strong); padding: 0.45rem 0.8rem; background: var(--surface); }
.terms dt { font: 600 0.78rem/1.6 var(--mono); color: var(--muted); text-transform: uppercase; letter-spacing: 0.05em; }
.terms dd { margin: 0; font-family: var(--mono); font-size: 0.88rem; }
.code.calc { font-size: 0.8rem; line-height: 1.55; }
.contrast { max-width: 80ch; margin: 1.2rem 0 1.6rem; }
.contrast-line { font: 600 0.95rem var(--mono); color: var(--ink); border-top: 1px solid var(--rule); padding-top: 0.6rem; }
.how { max-width: 80ch; }
.rules { margin: 0.4rem 0 0.8rem; font-size: 0.93rem; }
.rules summary { cursor: pointer; font-weight: 500; }
.rules ul { margin: 0.4rem 0 0; padding-left: 1.2rem; }
.text-drill .text-item { display: grid; gap: 0.3rem; margin-bottom: 0.8rem; }
.editor.short { min-height: 3.2rem; }
.model-note { font-size: 0.92rem; background: var(--ok-soft); border: 1px solid var(--ok); padding: 0.45rem 0.7rem; margin: 0; }
@media (max-width: 860px) {
  .terms { grid-template-columns: 1fr; }
  /* On a phone the worked example wraps rather than hiding its last figures off to the side */
  .code.calc { white-space: pre-wrap; overflow-wrap: anywhere; font-size: 0.72rem; }
}