/* The Excel Lab page (excel.html): header, page layout, unit colours and shared bits.
   The lessons have their own look in css/ailp.css; the calculator is in css/calc.css. */
:root {
  color-scheme: light;
  --bg: #f6f4ee;
  --text: #1c1b19;
  --muted: #5f5c55;
  --mono: ui-monospace, "SF Mono", "JetBrains Mono", Menlo, Consolas, monospace;

  /* Each unit has an accent (tab, ink) and a tint (divider paper) */
  --fa: #2f7a63;  --fa-tint: #e2ede7;   /* Financial Accounting */
  --ma: #34609f;  --ma-tint: #e1e8f3;   /* Management Accounting */
  --pc: #6c49a0;  --pc-tint: #ebe4f3;   /* Professional Considerations */
  --tax: #a9562a; --tax-tint: #f4e5da;  /* Personal Taxation */
  --law: #8f3450; --law-tint: #f2e0e5;  /* Law for Business */
}
/* Dark mode: chosen with the toggle in the top bar (js/theme.js); light is the default. */
:root[data-theme="dark"] {
    --bg: #151514;
    --text: #efede8;
    --muted: #a9a59c;

    --fa: #5cc3a3;  --fa-tint: #1c2a25;
    --ma: #79a3e8;  --ma-tint: #1c2432;
    --pc: #b595e3;  --pc-tint: #261f33;
    --tax: #e5935f; --tax-tint: #2f231b;
    --law: #e5809e; --law-tint: #2e1e24;
  }
* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: "Inter", system-ui, -apple-system, "Segoe UI", sans-serif;
  line-height: 1.55;
}
a { color: inherit; }
.wrap {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 16px;
}
/* Header: one slim bar. The brand on the left, Lessons and Excel Lab on the right. */
.site-header {
  position: sticky;
  top: 0;
  z-index: 30;
  background: color-mix(in srgb, var(--bg) 92%, transparent);
  backdrop-filter: saturate(1.4) blur(10px);
  -webkit-backdrop-filter: saturate(1.4) blur(10px);
  border-bottom: 1px solid color-mix(in srgb, var(--text) 12%, transparent);
}
.site-header .bar { display: grid; grid-template-columns: 1fr auto; align-items: center; gap: 8px 18px; min-height: 60px; }
.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  font-weight: 700;
  letter-spacing: -0.01em;
  white-space: nowrap;
}
/* The double rule under a final total, as a little mark */
.brand-mark {
  display: grid;
  place-items: center;
  width: 30px;
  height: 30px;
  border-radius: 4px;
  background: var(--text);
  color: var(--bg);
  font-family: var(--mono);
  font-size: 0.72rem;
  font-weight: 800;
  letter-spacing: 0.02em;
  box-shadow: inset 0 -5px 0 -3px var(--bg), inset 0 -8px 0 -6px var(--bg);
}
.brand-name { font-size: 1.02rem; }
.mainnav { display: flex; align-items: center; gap: 2px; }
.nav-top {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 7px 11px;
  border-radius: 4px;
  color: var(--muted);
  font-size: 0.92rem;
  font-weight: 600;
  text-decoration: none;
  white-space: nowrap;
}
.nav-top:hover { color: var(--text); background: color-mix(in srgb, var(--text) 7%, transparent); }
.nav-top[aria-current="page"] { color: var(--text); box-shadow: inset 0 -2px 0 var(--text); border-radius: 4px 4px 0 0; }
@media (max-width: 1100px) { .brand-name { font-size: 0.95rem; } }
@media (max-width: 860px) {
  .site-header { position: static; backdrop-filter: none; -webkit-backdrop-filter: none; background: var(--bg); }
  .site-header .bar { gap: 8px 10px; padding-top: 8px; padding-bottom: 8px; min-height: 0; }
  .nav-top { padding: 7px 9px; font-size: 0.9rem; }
}
@media (max-width: 380px) {
  .site-header .bar { gap: 8px 6px; }
  .brand { gap: 7px; min-width: 0; }
  .brand-name { font-size: 0.88rem; overflow: hidden; text-overflow: ellipsis; }
  .brand-mark { width: 26px; height: 26px; }
}
/* Breadcrumbs: Lessons / Excel Lab / task */
.crumbs { display: flex; flex-wrap: wrap; align-items: center; gap: 4px; margin: 22px 0 38px; font-size: 0.9rem; color: var(--muted); }
.crumbs a { color: var(--muted); text-decoration: none; }
.crumbs a:hover { color: var(--text); text-decoration: underline; }
.crumbs > * + *::before { content: "/"; margin-right: 6px; opacity: 0.5; }
.crumbs span { color: var(--text); font-weight: 600; }
.tab {
  position: absolute;
  top: -26px;
  left: var(--tab-x, 0);
  height: 26px;
  padding: 0 12px;
  background: var(--accent);
  color: var(--bg);
  border-radius: 6px 6px 0 0;
  font-family: var(--mono);
  font-size: 0.8rem;
  font-weight: 700;
  line-height: 26px;
}
/* The page title card: a tinted panel with a tab sticking up, like a binder divider */
.ref {
  margin-top: auto;
  align-self: flex-end;
  font-family: var(--mono);
  font-size: 0.75rem;
  letter-spacing: 0.04em;
  color: var(--accent);
}
.fa { --accent: var(--fa);  --tint: var(--fa-tint); }
.ma { --accent: var(--ma);  --tint: var(--ma-tint); }
.pc { --accent: var(--pc);  --tint: var(--pc-tint); }
.tax { --accent: var(--tax); --tint: var(--tax-tint); }
.law { --accent: var(--law); --tint: var(--law-tint); }
.back {
  display: inline-block;
  margin: 0 0 40px;
  color: var(--muted);
  text-decoration: none;
  font-size: 0.95rem;
}
.back:hover { color: var(--text); }
.unit-hero {
  position: relative;
  padding: 28px;
  background: var(--tint);
  border-radius: 4px;
}
.unit-hero h2 {
  margin: 0 0 10px;
  font-size: 1.8rem;
  color: var(--accent);
}
.unit-hero p { margin: 0 0 12px; }
.unit-hero .ref { display: block; text-align: right; }
/* Footer */
.site-footer {
  padding: 56px 0 32px;
  text-align: center;
  color: var(--muted);
  font-size: 0.85rem;
}
/* Buttons, section titles and the unit chips */
.btn {
  display: inline-block;
  padding: 9px 16px;
  border: 1.5px solid var(--accent);
  border-radius: 4px;
  background: transparent;
  color: var(--accent);
  font: inherit;
  font-size: 0.92rem;
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
}
.btn:hover { background: var(--tint); }
.btn.solid { background: var(--accent); color: var(--bg); }
.btn.solid:hover { filter: brightness(1.08); background: var(--accent); }
.section-title {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  margin: 48px 0 16px;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--accent);
}
.section-title h2 { margin: 0; font-size: 1.4rem; }
.section-title .hint {
  font-family: var(--mono);
  font-size: 0.75rem;
  color: var(--muted);
}
/* Phone */
@media (max-width: 600px) {
  .back { margin-bottom: 34px; }
  .unit-hero { padding: 20px 18px; }
  .unit-hero h2 { font-size: 1.45rem; }
  .section-title { margin-top: 36px; }
  .section-title h2 { font-size: 1.2rem; }
}
/* No unit picked: neutral ink */
.all { --accent: var(--text); --tint: color-mix(in srgb, var(--text) 6%, var(--bg)); }
.unit-hero a { color: var(--accent); }
.chips { display: flex; flex-wrap: wrap; gap: 8px; }
.chip {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 14px;
  border: 1.5px solid color-mix(in srgb, var(--accent, var(--text)) 40%, transparent);
  border-radius: 999px;
  background: transparent;
  color: var(--text);
  font: inherit;
  font-size: 0.9rem;
  cursor: pointer;
}
.chip.active { background: var(--tint, color-mix(in srgb, var(--text) 8%, transparent)); border-color: var(--accent, var(--text)); font-weight: 600; }
/* Excel Lab: unit chips and back to the lesson path */
.lab-units { margin: 22px 0 6px; }
.lab-units a.chip { text-decoration: none; }
.course-back { display: inline-block; margin: -22px 0 18px; }
/* Light / dark toggle (js/theme.js) */
.theme-btn { width: 36px; height: 36px; margin-left: 4px; border: 0; border-radius: 4px; background: none; color: var(--muted); cursor: pointer; display: inline-grid; place-items: center; }
.theme-btn:hover { color: var(--text); background: color-mix(in srgb, var(--text) 7%, transparent); }
.theme-btn .sun, :root[data-theme="dark"] .theme-btn .moon { display: none; }
:root[data-theme="dark"] .theme-btn .sun { display: block; }
:root[data-theme="dark"] { color-scheme: dark; }
/* Search box: sends you to the lessons' search (index.html?q=…) */
.lab-search { position: relative; margin-right: 8px; }
.lab-search svg { position: absolute; left: 10px; top: 50%; transform: translateY(-50%); color: var(--muted); pointer-events: none; }
.lab-search input { width: 200px; padding: 7px 10px 7px 30px; border: 1.5px solid color-mix(in srgb, var(--text) 22%, transparent); border-radius: 4px; background: var(--bg); color: var(--text); font: inherit; font-size: 0.88rem; }
.lab-search input:focus { outline: none; border-color: var(--text); }
@media (max-width: 600px) { .lab-search input { width: 130px; } }
@media (max-width: 380px) { .lab-search { display: none; } }

/* Phones: the header stacks (brand, then the links wrapping under it) so the page never scrolls sideways. */
@media (max-width: 600px) {
  .site-header .bar { grid-template-columns: minmax(0, 1fr); }
  .site-header .mainnav { display: flex; flex-wrap: wrap; align-items: center; gap: 4px 6px; min-width: 0; }
  .site-header .lab-search { flex: 1 1 100%; min-width: 0; }
  .site-header .lab-search input { width: 100%; min-width: 0; }
}

/* Long formulas wrap on narrow screens instead of widening the page. */
.learn-sec { min-width: 0; } .learn-sec code { overflow-wrap: anywhere; word-break: break-word; } .learn-sec dl, .learn-sec dd, .learn-sec dt { min-width: 0; }