/* APES Math Practice: an answer booklet on unbleached paper. Deep lake-blue ink for actions and part letters, a sun
   yellow for the setup strip edge, and one signature: units that cancel are struck through in rust red, as students
   do by hand. Scenario text is set in a book serif like an exam stem; parts and keys in a humanist sans. Drawings stay
   white in both themes, as on paper. On paper everything is black on white with ruled work space. */
:root {
  --bg: #f4f3ee;
  --paper: #ffffff;
  --ink: #1b2328;
  --muted: #4b555c;
  --line: #d8d6cc;
  --edge: #747c80;
  --accent: #0b4f6c;
  --accent-ink: #ffffff;
  --accent-soft: #e1edf2;
  --sun: #e2a92b;
  --rust: #b8401a;
  --given: #f7f1df;
  --info: #0b5d80;
  --ok: #17663a;
  --ok-soft: #ddefe3;
  --close: #7a5300;
  --close-soft: #f6ecd2;
  --bad: #a3241d;
  --bad-soft: #f8e0dd;
  --focus: #c2185b;
  --head: "Avenir Next", Avenir, "Segoe UI Variable Display", "Segoe UI", "Gill Sans", "Trebuchet MS", system-ui, sans-serif;
  --sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --serif: Charter, "Bitstream Charter", "Iowan Old Style", "Sitka Text", Cambria, Georgia, serif;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, "DejaVu Sans Mono", monospace;
  --r: 4px;
  color-scheme: light dark;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #11191d;
    --paper: #182228;
    --ink: #e4e9eb;
    --muted: #a7b3b9;
    --line: #2d3a41;
    --edge: #66757d;
    --accent: #7cc3e6;
    --accent-ink: #082331;
    --accent-soft: #17303d;
    --sun: #e3b341;
    --rust: #ff9a73;
    --given: #232a22;
    --info: #8fd0f0;
    --ok: #8adca6;
    --ok-soft: #14301f;
    --close: #f0c56b;
    --close-soft: #352a12;
    --bad: #ff9c8f;
    --bad-soft: #3a1c18;
    --focus: #f48fb1;
  }
}
* { box-sizing: border-box; }
[hidden] { display: none !important; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--bg); color: var(--ink); font: 17px/1.55 var(--sans); }
.wrap { max-width: 1120px; margin: 0 auto; padding: 0 16px; }
a { color: var(--info); text-underline-offset: 2px; }
.skip { position: absolute; left: -999px; top: 8px; background: var(--paper); padding: 8px 12px; z-index: 10; }
.skip:focus { left: 8px; }
.sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
:focus-visible { outline: 3px solid var(--focus); outline-offset: 2px; }
h1, h2, h3 { font-family: var(--head); line-height: 1.15; font-weight: 700; }
.hero { padding: 20px 0 14px; }
.hero h1 { font: 700 clamp(28px, 4.8vw, 44px)/1.08 var(--head); margin: 0 0 6px; letter-spacing: -0.015em; }
.lede { margin: 0; max-width: 66ch; }

/* ---------- controls: a light strip with a sun-yellow top edge ---------- */
.tool { display: grid; gap: 14px; }
.setup { background: var(--paper); border: 1px solid var(--line); border-top: 4px solid var(--sun); padding: 10px 12px 2px; border-radius: var(--r); }
.ctl { display: grid; gap: 8px 10px; grid-template-columns: minmax(0, 3fr) minmax(0, 1fr) auto; align-items: end; }
.fld { display: grid; gap: 2px; min-width: 0; }
.fld span { font: 600 14px var(--sans); color: var(--muted); }
.fld select { width: 100%; }
.more { display: flex; flex-wrap: wrap; gap: 0 22px; }
.more details[open] { flex-basis: 100%; }
.more details > fieldset, .more details > div { padding: 2px 0 10px; }
fieldset { border: 0; margin: 0; padding: 0; min-width: 0; }
legend { padding: 0; }
.tdet summary, .rules summary { cursor: pointer; font-weight: 600; min-height: 44px; padding: 10px 0; display: list-item; color: var(--accent); }
.tsum { font-weight: 400; color: var(--muted); font-size: 15px; }
.toggles { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 6px; }
.tg { display: flex; gap: 8px; align-items: flex-start; padding: 8px; border: 1px solid var(--line); border-radius: var(--r); cursor: pointer; min-height: 44px; }
.tg input { width: 20px; height: 20px; margin: 2px 0 0; accent-color: var(--accent); flex: none; }
.tg b { display: block; font-weight: 600; font-size: 15.5px; }
.tg small { display: block; color: var(--muted); font-size: 14px; line-height: 1.3; }
select, input { font: inherit; font-size: 16px; color: var(--ink); background: var(--paper); border: 1px solid var(--edge); border-radius: var(--r); min-height: 44px; padding: 6px 10px; max-width: 100%; }
.btn { font: 600 16px var(--sans); min-height: 44px; padding: 8px 16px; border-radius: var(--r); border: 1px solid var(--edge); background: var(--paper); color: var(--ink); cursor: pointer; }
.btn:hover { border-color: var(--ink); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.btn.small { min-height: 42px; padding: 6px 14px; font-size: 15px; }
.link { font: inherit; background: none; border: 0; color: var(--info); text-decoration: underline; text-underline-offset: 2px; cursor: pointer; min-height: 44px; padding: 0 4px; }
.rl { margin: 0; padding-left: 20px; font-size: 15.5px; line-height: 1.45; max-width: 80ch; }
.rl li { margin: 0 0 4px; }

/* ---------- the sheet ---------- */
.note { margin: 0 0 10px; padding: 10px 12px; border: 1px solid var(--bad); background: var(--bad-soft); font-size: 16px; border-radius: var(--r); }
#store-note { overflow-wrap: anywhere; }
.note.info { border-color: var(--info); background: var(--paper); }
.sheet:focus { outline: none; }
.sheet-head { display: flex; flex-wrap: wrap; align-items: baseline; justify-content: space-between; gap: 4px 14px; }
.sheet-head h2 { font-size: 26px; margin: 4px 0 0; }
.code { font-family: var(--mono); letter-spacing: 0.06em; }
.score { margin: 0; color: var(--muted); font-size: 15px; }
.sline { margin: 2px 0 10px; color: var(--muted); font-size: 15px; }
.qs { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: minmax(0, 1fr); gap: 18px; }
.q { background: var(--paper); border: 1px solid var(--line); border-radius: var(--r); min-width: 0; }
.qhead { padding: 12px 16px 0; }
.q h3 { margin: 0; font-size: 22px; display: flex; align-items: baseline; gap: 10px; }
.qn { font: 700 16px var(--mono); color: var(--accent-ink); background: var(--accent); min-width: 1.9em; text-align: center; padding: 1px 6px; border-radius: 3px; }
.qbody { display: grid; grid-template-columns: minmax(0, 1fr); }
.setupq { padding: 6px 16px 4px; min-width: 0; }
.scen { margin: 0 0 10px; font: 18px/1.5 var(--serif); max-width: 70ch; }
.given { background: var(--given); border: 1px solid var(--sun); border-radius: var(--r); padding: 6px 12px 6px; margin: 0 0 12px; font-size: 16px; }
.given .gl { font-weight: 700; font-size: 16px; color: var(--muted); }
.given ul { margin: 2px 0 0; padding-left: 18px; }
.given li { margin: 0; }
.figview { min-width: 0; margin: 0 0 8px; }
.qparts { display: grid; grid-template-columns: minmax(0, 1fr); gap: 14px; padding: 8px 16px 14px; border-top: 1px dashed var(--line); min-width: 0; }

/* ---------- drawings and tables: white like paper in both themes ---------- */
.figbox { background: #fff; border: 1px solid #c9ccc4; max-width: 560px; }
.fb-pyramid { max-width: 440px; }
.fb-chain { max-width: 320px; }
svg.fig { display: block; width: 100%; height: auto; color: #1b2328; }
svg text { font-family: "Helvetica Neue", Arial, sans-serif; }
.pyb { stroke: #1b2328; stroke-width: 1.5; }
.pyb.b0 { fill: #dcebd2; } .pyb.b1 { fill: #e8efd9; } .pyb.b2 { fill: #f3efd9; } .pyb.b3 { fill: #f7e8d6; }
.pyn { font-size: 17px; font-weight: 700; text-anchor: middle; fill: #111; }
.pr { font-size: 13.5px; text-anchor: middle; fill: #333; }
.pv { font-size: 15px; font-weight: 700; text-anchor: middle; fill: #0b4f6c; }
.pv.kv { fill: #b8401a; }
.cb { fill: #f2f4ef; stroke: #1b2328; stroke-width: 1.5; }
.cn { font-size: 17px; font-weight: 700; text-anchor: middle; fill: #111; }
.cv { font-size: 15px; font-weight: 700; text-anchor: middle; fill: #0b4f6c; }
.ca { stroke: #1b2328; stroke-width: 2.2; }
.cah { fill: #1b2328; }
.gm { stroke: #d9dde0; stroke-width: 1; }
.gM { stroke: #a8b0b6; stroke-width: 1.2; }
.ax { stroke: #111; stroke-width: 1.8; }
.gx { font-size: 17px; text-anchor: middle; fill: #111; }
.gy { font-size: 17px; text-anchor: end; fill: #111; }
.gt { font-size: 17px; font-weight: 700; text-anchor: middle; fill: #111; }
.ln { fill: none; stroke: #0b4f6c; stroke-width: 2.4; stroke-linejoin: round; }
.ln.s1 { stroke: #8a3b12; }
.ln.dash { stroke-dasharray: 8 5; }
.pt.s0 { fill: #0b4f6c; }
.pt.s1 { fill: #8a3b12; }
.lgbox { fill: #fff; stroke: #a8b0b6; }
.lg { font-size: 16.5px; fill: #111; }
.km { stroke: #b8401a; stroke-width: 2; stroke-dasharray: 6 4; }
.kr { fill: none; stroke: #b8401a; stroke-width: 2; }
.tw { max-width: 100%; overflow-x: auto; }
table.dt { border-collapse: collapse; background: #fff; color: #1b2328; font-size: 15.5px; font-variant-numeric: tabular-nums; border: 1.5px solid #1b2328; }
table.dt th, table.dt td { border: 1px solid #b9bec2; padding: 6px 10px; text-align: left; }
table.dt thead th { background: #eef0ec; font-size: 14.5px; }
table.dt td { white-space: nowrap; }

/* answer boxes */
.part { border: 0; margin: 0; padding: 0; min-width: 0; }
.part .prompt, .part legend { display: block; font-weight: 500; font-size: 16.5px; line-height: 1.4; margin-bottom: 6px; color: var(--ink); }
.pl { font: 700 16px var(--mono); color: var(--accent); margin-right: 2px; }
.ain { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.ain input { width: 12em; max-width: 100%; font-variant-numeric: tabular-nums; }
.ain .unit { color: var(--muted); font-weight: 600; }
.ain .unit.pre { margin-right: -4px; }
.opts { display: grid; gap: 4px; }
.opt { display: flex; gap: 10px; align-items: flex-start; min-height: 44px; padding: 8px 10px; border: 1px solid var(--line); border-radius: var(--r); cursor: pointer; }
.opt input { width: 20px; height: 20px; margin: 2px 0 0; accent-color: var(--accent); flex: none; }
.part.is-right input:not([type]) { border-color: var(--ok); background: var(--ok-soft); }
.part.is-wrong input:not([type]) { border-color: var(--bad); background: var(--bad-soft); }
.part.is-close input:not([type]), .part.is-unread input:not([type]), .part.is-units input:not([type]) { border-color: var(--close); background: var(--close-soft); }
.part.is-right .opts { outline: 2px solid var(--ok); outline-offset: 2px; }
.part.is-wrong .opts { outline: 2px solid var(--bad); outline-offset: 2px; }
.fb { margin: 4px 0 0; font-size: 15px; line-height: 1.4; padding: 4px 8px; }
.fb.right { color: var(--ok); background: var(--ok-soft); }
.fb.wrong { color: var(--bad); background: var(--bad-soft); }
.fb.close, .fb.unread, .fb.units { color: var(--close); background: var(--close-soft); }
.qfoot { display: flex; gap: 10px; align-items: center; }
details.work { border-top: 1px dashed var(--line); padding-top: 4px; }
details.work summary { cursor: pointer; color: var(--info); min-height: 44px; display: flex; align-items: center; font-weight: 600; }
.keyfig { margin: 6px 0 10px; }
.kp { margin: 0 0 12px; }
.ans { margin: 6px 0 4px; }
.st { margin: 2px 0 4px; color: var(--muted); font-size: 15.5px; }

/* ---------- dimensional analysis: fractions, units that cancel struck through ---------- */
.da { display: flex; flex-wrap: wrap; align-items: center; gap: 4px 6px; margin: 4px 0 8px; font-size: 15.5px; font-variant-numeric: tabular-nums; }
.fr { display: inline-grid; text-align: center; vertical-align: middle; }
.fr .nu { border-bottom: 1.5px solid currentColor; padding: 0 4px 1px; }
.fr .de { padding: 1px 4px 0; }
.tm { padding: 0 2px; }
.op { color: var(--muted); }
.eq { font-weight: 700; padding-left: 4px; }
s.cx { text-decoration: line-through; text-decoration-color: var(--rust); text-decoration-thickness: 2px; color: var(--muted); }
.un { color: var(--ink); }

.sheet-foot { display: flex; flex-wrap: wrap; align-items: center; gap: 8px 14px; margin: 14px 0 6px; }
.ask { display: inline-flex; flex-wrap: wrap; align-items: center; gap: 6px 10px; background: var(--accent-soft); padding: 6px 10px; }
.share { margin: 16px 0 6px; }
.print-row { display: flex; flex-wrap: wrap; gap: 8px 12px; align-items: center; }
.print-row label { display: inline-flex; align-items: center; gap: 8px; font-weight: 600; max-width: 100%; }
.print-row select { max-width: 100%; min-width: 0; }
.share-out label { display: grid; gap: 4px; font-weight: 600; margin-top: 8px; }
.share-out input { width: 100%; }
.recent { margin-top: 12px; background: var(--paper); border: 1px solid var(--line); padding: 4px 12px; }
.recent summary { cursor: pointer; min-height: 44px; display: flex; align-items: center; font-weight: 600; }
.recent ul { list-style: none; margin: 0; padding: 0; }
.recent li { display: flex; justify-content: space-between; align-items: center; gap: 10px; padding: 6px 0; border-top: 1px solid var(--line); }
.recent small { display: block; color: var(--muted); font-size: 14px; }
.hint { color: var(--muted); font-size: 15px; margin: 0; }
.toast { position: fixed; left: 50%; bottom: 16px; transform: translateX(-50%) translateY(150%); background: var(--ink); color: var(--paper); padding: 10px 16px; max-width: min(92vw, 520px); font-size: 15.5px; transition: transform 0.2s; z-index: 20; }
.toast.on { transform: translateX(-50%) translateY(0); }
@media (prefers-reduced-motion: reduce) { .toast { transition: none; } }

/* ---------- content ---------- */
.content { max-width: 72ch; padding: 26px 0 20px; }
.content h2 { font-size: 26px; margin: 26px 0 6px; }
.faq details { border-top: 1px solid var(--line); }
.faq summary { cursor: pointer; font-weight: 600; padding: 10px 0; min-height: 44px; }
.faq p { margin: 0 0 12px; }
.sources { font-size: 15px; color: var(--muted); }
footer { border-top: 1px solid var(--line); padding: 16px 0 28px; font-size: 15px; color: var(--muted); }
.indep { margin: 0 0 10px; }
.sb-footer p { margin: 6px 0; }
.sb-more { line-height: 1.8; }
.print-root { display: none; }

@media (min-width: 1000px) {
  .qbody { grid-template-columns: minmax(0, 11fr) minmax(0, 9fr); }
  .qparts { border-top: 0; border-left: 1px dashed var(--line); padding-top: 6px; }
}
@media (max-width: 560px) {
  .ctl { grid-template-columns: minmax(0, 1fr) 6.5em; }
  .f-new { grid-column: 1 / -1; }
  .hero { padding: 10px 0 10px; }
  .hero h1 { font-size: 28px; }
  .lede { font-size: 15.5px; line-height: 1.45; }
  .q h3 { font-size: 20px; }
  .qhead { padding: 10px 10px 0; }
  .setupq { padding: 6px 10px 4px; }
  .qparts { padding: 8px 10px 12px; }
  .scen { font-size: 17px; }
  table.dt { font-size: 14px; }
  table.dt th, table.dt td { padding: 4px 6px; }
  .tdet summary, .rules summary { min-height: 42px; padding: 8px 0; }
}

/* ---------- print ---------- */
@media print {
  :root { --ink: #000; --muted: #333; --line: #999; --paper: #fff; --edge: #555; --rust: #000; --accent: #000; --given: #fff; }
  @page { margin: 12mm 12mm; }
  body { background: #fff; color: #000; font: 10.5pt/1.36 var(--sans); }
  main, footer, .toast, .skip { display: none !important; }
  .print-root { display: block; }
  svg, .figbox, table.dt, thead th, .pyb { print-color-adjust: exact; -webkit-print-color-adjust: exact; }
  table.pt { width: 100%; border-collapse: collapse; }
  table.pt > tbody > tr > td, table.pt > thead > tr > td { padding: 0; }
  .prun { font: 8.5pt var(--sans); color: #444; padding-bottom: 5pt !important; }
  .ph { display: flex; justify-content: space-between; align-items: baseline; gap: 10pt; border-bottom: 2pt solid #000; margin-bottom: 4pt; }
  .ph h2 { font: 700 17pt var(--head); margin: 0; white-space: nowrap; }
  .ph p { margin: 0; font-size: 9pt; text-align: right; }
  .pmeta { display: flex; justify-content: space-between; gap: 12pt; margin: 4pt 0 4pt; }
  .pround { margin: 0 0 6pt; font-size: 8.2pt; line-height: 1.28; border: 0.8pt solid #000; padding: 3pt 6pt; break-inside: avoid; }
  .prh { margin: 0 0 1pt; font-weight: 700; font-size: 8.6pt; }
  .pround ul { margin: 0; padding-left: 11pt; columns: 2; column-gap: 8mm; font-size: 8.2pt; line-height: 1.28; max-width: none; }
  .pround li { break-inside: avoid; margin: 0 0 1pt; }
  .pq, .pk { list-style: none; margin: 0; padding: 0; }
  .pq > li { padding: 6pt 0 4pt; border-top: 1.2pt solid #000; }
  .pq > li + li { break-before: page; page-break-before: always; }
  .phead { break-inside: avoid; break-after: avoid; }
  .pq h3, .pk h3 { font: 700 12.5pt var(--head); margin: 0 0 2pt; }
  .pscen { margin: 0 0 4pt; font: 10.5pt/1.38 var(--serif); }
  .given { margin: 0 0 5pt; padding: 2pt 6pt; border: 0.8pt solid #000; font-size: 9.2pt; }
  .given .gl { font-size: 8.6pt; color: #000; }
  .pfig { display: flex; flex-direction: column; gap: 3mm; align-items: flex-start; margin: 0 0 4pt; }
  .pstem.side { display: grid; grid-template-columns: minmax(0, 1fr) 84mm; column-gap: 6mm; align-items: start; }
  .pstem.side .pfig { align-items: flex-end; }
  .pfig .figbox { width: 84mm; max-width: 100%; border: 0.6pt solid #000; }
  .pfig .fb-pyramid { width: 80mm; }
  .pfig .fb-chain { width: 52mm; }
  .pkfig .figbox { width: 70mm; border: 0.6pt solid #000; }
  .pkfig .fb-pyramid { width: 62mm; }
  table.dt { font-size: 9.6pt; border-width: 1pt; }
  table.dt th, table.dt td { padding: 2pt 6pt; border-color: #777; }
  table.dt thead th { font-size: 9pt; background: #eee; }
  .tw { overflow: visible; }
  .pparts { display: grid; grid-template-columns: 1fr 1fr; gap: 5pt 6mm; font-size: 10pt; align-items: end; }
  .pp { display: grid; grid-template-rows: 1fr auto auto; }
  .pp { break-inside: avoid; page-break-inside: avoid; }
  .pp p { margin: 0; }
  .work-space { height: 34mm; border: 0.6pt solid #888; margin: 2pt 0 2pt; background: repeating-linear-gradient(to bottom, transparent 0 6.6mm, #ccc 6.6mm 6.8mm); print-color-adjust: exact; -webkit-print-color-adjust: exact; }
  .pline { margin: 1pt 0 4pt !important; text-align: right; }
  .uline { display: inline-block; width: 34mm; border-bottom: 0.8pt solid #000; }
  .popts { display: grid; gap: 1pt; margin: 2pt 0 4pt !important; }
  .pkey { break-before: page; page-break-before: always; }
  .psheet + .psheet { break-before: page; page-break-before: always; }
  .pkey + .pkey { break-before: page; page-break-before: always; }
  .pk > li { padding: 5pt 0 4pt; border-top: 1pt solid #000; break-inside: avoid; }
  .pkp { break-inside: avoid; margin: 0 0 3pt; }
  .pka { margin: 2pt 0 1pt; font-size: 10pt; }
  .pk .st { font-size: 9pt; color: #222; margin: 0 0 1pt; }
  .pk .da { font-size: 9.2pt; margin: 1pt 0 3pt; gap: 2pt 4pt; }
  s.cx { text-decoration-color: #000; color: #333; }
  .pk > li .pkfig { float: right; margin: 0 0 3pt 5mm; }
  .pk > li::after { content: ""; display: block; clear: both; }
}