@font-face { font-family: "Space Mono"; src: url("fonts/space-mono-700.woff2") format("woff2"); font-weight: 700; font-style: normal; font-display: swap; }

:root {
  --bg: #eef2e7;            /* engineering computation pad */
  --grid: rgba(31, 107, 69, 0.09);
  --paper: #fbfcf8;
  --ink: #17201a;
  --muted: #4a584e;
  --line: #bfcbbd;
  --rule: #dde5d8;
  --accent: #1f6b45;
  --accent-ink: #ffffff;
  --accent-soft: #dcebdf;
  --pen: #b3261e;
  --pen-soft: #f7e4e1;
  --ok: #1b6b38;
  --ok-soft: #e0efe3;
  --amber: #7d5200;
  --amber-soft: #f5ead2;
  --lcd: #c7d3b2;
  --lcd-ink: #1b2a1a;
  --head: "Space Mono", ui-monospace, "SF Mono", Menlo, Consolas, monospace;
  --sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --test: Verdana, "DejaVu Sans", Geneva, "Segoe UI", sans-serif;
  --r: 5px;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #121813; --grid: rgba(127, 208, 160, 0.06); --paper: #1a221c; --ink: #e4ebe2; --muted: #a8b6aa; --line: #36443b; --rule: #27312a;
    --accent: #80cfa0; --accent-ink: #0c1a11; --accent-soft: #1f3328; --pen: #ff8d7d; --pen-soft: #3a201c; --ok: #88d69f; --ok-soft: #1b3324;
    --amber: #f0c56e; --amber-soft: #3a301a; --lcd: #263020; --lcd-ink: #d8e9c2;
  }
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--bg); color: var(--ink); font: 17px/1.55 var(--sans); }
.wrap { max-width: 860px; margin: 0 auto; padding: 0 16px; }
a { color: var(--accent); }
.skip { position: absolute; left: -999px; top: 8px; background: var(--paper); padding: 8px 12px; z-index: 10; }
.skip:focus { left: 8px; }
:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
h1, h2 { font-family: var(--head); font-weight: 700; line-height: 1.15; letter-spacing: -0.01em; }
h1 { font-size: clamp(1.45rem, 4.6vw, 2.15rem); margin: 0 0 8px; }
h2 { font-size: 1.25rem; margin: 30px 0 10px; }
.hero { padding: 22px 0 12px; background-image: linear-gradient(var(--grid) 1px, transparent 1px), linear-gradient(90deg, var(--grid) 1px, transparent 1px); background-size: 18px 18px; background-position: -1px -1px; }
.lede { margin: 0 0 4px; color: var(--muted); max-width: 64ch; }

/* level switch: two calculator keys */
.levels { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; max-width: 520px; margin-top: 6px; }
.lvl { min-height: 54px; border: 1px solid var(--line); border-bottom-width: 3px; border-radius: var(--r); background: var(--paper); color: var(--ink); font: 700 1.02rem/1.15 var(--sans); cursor: pointer; padding: 6px 8px; }
.lvl small { display: block; font: 400 0.84rem var(--sans); color: var(--muted); }
.lvl[aria-checked="true"] { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.lvl[aria-checked="true"] small { color: var(--accent-ink); opacity: 0.9; }

/* the test card */
.card { background: var(--paper); border: 1px solid var(--line); border-left: 4px solid var(--accent); border-radius: var(--r); padding: 14px 16px; margin-top: 14px; }
.test-head { display: flex; align-items: center; justify-content: space-between; gap: 10px; flex-wrap: wrap; }
.test-id { margin: 0; font: 700 1.2rem var(--head); }
.code { letter-spacing: 0.06em; }
.peek { border-top: 1px solid var(--rule); margin-top: 10px; padding-top: 8px; display: grid; grid-template-columns: 1fr; gap: 6px 22px; font-family: var(--test); font-size: 0.98rem; }
.peek-list { list-style: none; margin: 0; padding: 0; }
.peek-list li { padding: 5px 0; display: flex; gap: 6px; align-items: baseline; }
.peek-geo { display: flex; gap: 6px; }
.peek-geo .gq { max-width: 280px; }
@media (min-width: 700px) { .peek { grid-template-columns: 1fr 280px; } }
.n { flex: 0 0 auto; min-width: 2.2em; color: var(--muted); font-variant-numeric: tabular-nums; font-family: var(--sans); }
.actions { display: flex; flex-wrap: wrap; gap: 10px; margin: 14px 0 6px; align-items: center; }
.btn { min-height: 46px; padding: 10px 18px; border-radius: var(--r); border: 1px solid var(--ink); border-bottom-width: 3px; background: var(--paper); color: var(--ink); font: 700 1rem var(--sans); cursor: pointer; }
.btn:hover { background: var(--accent-soft); }
.btn:active { border-bottom-width: 1px; transform: translateY(2px); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.btn.primary:hover { filter: brightness(1.08); }
.btn.ghost { border-color: var(--line); }
.btn.small { min-height: 44px; padding: 6px 12px; font-size: 0.95rem; }
.link { background: none; border: 0; padding: 10px 2px; min-height: 44px; color: var(--accent); text-decoration: underline; font: inherit; cursor: pointer; }
details.more { border-top: 1px solid var(--rule); margin-top: 10px; }
details.more > summary { cursor: pointer; padding: 11px 0; min-height: 44px; font-weight: 600; }
.opt-grid { display: flex; flex-wrap: wrap; gap: 12px 20px; align-items: center; }
label { font-weight: 600; }
select, input[type="text"], input:not([type]) { font: 16px var(--sans); color: var(--ink); background: var(--paper); border: 1px solid var(--muted); border-radius: var(--r); min-height: 44px; padding: 6px 8px; }
.opt-grid label, .drill-setup label, .myv { display: flex; align-items: center; gap: 8px; }
.check input { width: 22px; height: 22px; accent-color: var(--accent); }
.hint { margin: 6px 0; color: var(--muted); font-size: 0.95rem; }
.share-row { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; margin: 10px 0 12px; }
.open-code { display: flex; align-items: center; gap: 8px; }
.open-code input { width: 6.5em; text-transform: uppercase; font-family: var(--head); }
.note { padding: 10px 12px; border-left: 4px solid var(--accent); background: var(--accent-soft); border-radius: 0 var(--r) var(--r) 0; margin: 10px 0; overflow-wrap: anywhere; }
.note.warn { border-left-color: var(--pen); background: var(--pen-soft); }
.preview-list { list-style: none; padding: 0; margin: 0 0 12px; font-family: var(--test); font-size: 0.95rem; }
.preview-list li { padding: 8px 0; border-bottom: 1px solid var(--rule); }
.pv-q { display: flex; flex-wrap: wrap; gap: 4px 8px; align-items: baseline; }
.preview-list .k { margin: 4px 0 0 2.6em; font: 0.9rem var(--sans); color: var(--muted); }
.preview-list .gq { max-width: 260px; }

/* math bits */
.fr { display: inline-flex; flex-direction: column; vertical-align: middle; text-align: center; line-height: 1.15; margin: 1px 0.12em; }
.fr > span:first-child { border-bottom: 1px solid currentColor; padding: 0 0.2em 1px; }
.fr > span:last-child { padding: 1px 0.2em 0; }
.nw { white-space: nowrap; }
.rad { border-top: 1px solid currentColor; padding: 0.12em 0.1em 0; margin-left: 0.02em; display: inline-block; line-height: 1.2; }
.rad sup { line-height: 1; }
.ridx { font-size: 0.62em; vertical-align: 0.9em; margin-right: -0.25em; }
sup { font-size: 0.72em; line-height: 0; }
.bk { display: inline-flex; align-items: center; }
.bko { font-size: 1.7em; font-weight: 300; line-height: 1; }
.mode { color: var(--muted); }
.mx { display: inline-grid; vertical-align: middle; gap: 0 0.8em; padding: 1px 0.45em; margin: 0 0.15em; border-left: 1.5px solid currentColor; border-right: 1.5px solid currentColor; border-radius: 4px; text-align: right; line-height: 1.3; }
.mx2 { grid-template-columns: repeat(2, auto); }
.mx3 { grid-template-columns: repeat(3, auto); }
.fig { display: block; width: 100%; height: auto; color: var(--ink); }
.fig text { font: 13px var(--sans); fill: currentColor; stroke: none; }
.fig .sm { font-size: 11px; }
.fig .lb { paint-order: stroke; stroke: var(--paper); stroke-width: 4px; stroke-linejoin: round; }
.fig .fl { fill: currentColor; }
.gq { width: 100%; max-width: 340px; text-align: center; font-family: var(--test); }
.gq .gt { margin: 0 0 2px; font-size: 0.85rem; letter-spacing: 0.02em; }
.gq .gn { margin: 0; font-size: 0.95rem; }

/* the on-screen test */
.sheet { background: var(--paper); border: 1px solid var(--line); border-radius: var(--r); margin-top: 14px; padding: 0 16px 16px; }
.timer-bar { position: sticky; top: 0; z-index: 5; display: flex; align-items: center; gap: 10px; flex-wrap: wrap; background: var(--paper); border-bottom: 2px solid var(--ink); padding: 8px 0; margin: 0 0 4px; }
.clock { font: 700 1.8rem/1 var(--head); font-variant-numeric: tabular-nums; background: var(--lcd); color: var(--lcd-ink); padding: 6px 10px; border-radius: 4px; min-width: 4.4em; text-align: center; }
.clock.low { color: var(--pen); }
.answered { color: var(--muted); }
.bar-btns { margin-left: auto; display: flex; gap: 8px; }
.key-ins { font-family: var(--head); }
.sheet-title { font-size: 1.1rem; margin: 12px 0 2px; }
.sheet-hint { margin: 0 0 6px; }
.problems { list-style: none; margin: 0; padding: 0; font-family: var(--test); font-size: 1rem; }
.problems > li { display: flex; flex-wrap: wrap; align-items: center; gap: 6px 12px; padding: 10px 0; border-bottom: 1px solid var(--rule); scroll-margin-top: 96px; }
.problems > li.pg { display: block; padding: 14px 0 4px; border-bottom: 2px solid var(--line); font: 700 0.9rem var(--head); color: var(--muted); }
.pq-wrap { flex: 1 1 260px; min-width: 0; display: flex; gap: 6px; align-items: baseline; }
.pk-g .pq-wrap { align-items: flex-start; }
.qt { min-width: 0; overflow-wrap: break-word; }
.ans { display: flex; align-items: center; gap: 6px; font-family: var(--sans); font-size: 1rem; margin-left: auto; }
.problems input { width: 10em; font: 18px var(--sans); font-variant-numeric: tabular-nums; }
.unit { color: var(--muted); }
.mk { flex-basis: 100%; margin: 0; padding-left: 2.6em; font: 0.95rem/1.45 var(--sans); }
.mk.right { color: var(--ok); }
.mk.wrong { color: var(--pen); }
.mk.part { color: var(--amber); }
.mk .km { color: var(--muted); }
.tag { font-size: 0.85em; color: var(--muted); }
li.is-wrong > .pq-wrap .n, li.is-skip > .pq-wrap .n { color: var(--pen); text-decoration: line-through; }
li.is-right input { background: var(--ok-soft); }
li.is-wrong input, li.is-skip input { background: var(--pen-soft); }
li.is-part input { background: var(--amber-soft); }
.paused { padding: 30px 0; }
.paused p { font-size: 1.1rem; margin: 0 0 12px; }
.result { padding: 12px 0 6px; scroll-margin-top: 92px; }
.score-big { font: 700 2.6rem/1 var(--head); margin: 4px 0 8px; }
.score-line { margin: 0 0 6px; color: var(--muted); }
.sheet-foot { display: flex; flex-wrap: wrap; gap: 10px; padding-top: 14px; }

/* drill */
.drill { margin-top: 8px; }
.drill-setup { display: flex; flex-wrap: wrap; gap: 12px; align-items: center; }
.drill-setup .wide { flex: 1 1 100%; display: grid; grid-template-columns: 1fr; gap: 4px; }
.drill-setup .wide select { width: 100%; min-width: 0; }
.drill-run { background: var(--paper); border: 1px solid var(--line); border-radius: var(--r); padding: 4px 16px 16px; margin-top: 12px; }
.drill-bar { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 6px 12px; padding: 8px 0; border-bottom: 2px solid var(--ink); font-weight: 700; }
.drill-score { font-variant-numeric: tabular-nums; }
.chk { margin-left: 0; }

/* history */
.hist { list-style: none; padding: 0; margin: 0; }
.hist li { display: flex; flex-wrap: wrap; align-items: center; gap: 4px 12px; padding: 8px 0; border-bottom: 1px solid var(--rule); }
.hist .what { flex: 1 1 220px; }
.hist .when { color: var(--muted); font-size: 0.92rem; }
.hist .sc { font-weight: 700; font-variant-numeric: tabular-nums; }
.hist-tools { margin: 6px 0; }

/* content */
.content { margin-top: 26px; max-width: 70ch; }
.example { margin: 0; background: var(--paper); border: 1px solid var(--line); border-radius: var(--r); padding: 14px 16px; }
.ex-q { margin: 0 0 8px; font-family: var(--test); }
.ex-blank { white-space: nowrap; color: var(--muted); }
.ex-blank::before { content: "= ________ "; }
figcaption { color: var(--muted); font-size: 0.97rem; }
.faq details { border-bottom: 1px solid var(--rule); }
.faq summary { cursor: pointer; padding: 12px 0; min-height: 44px; font-weight: 600; }
.faq p { margin: 0 0 14px; }
.sources { font-size: 0.93rem; color: var(--muted); margin-top: 22px; }

footer { margin-top: 40px; border-top: 1px solid var(--line); padding: 18px 0 30px; color: var(--muted); font-size: 0.93rem; }
.indep { margin: 0 0 10px; }
.sb-more { line-height: 1.9; }
.sb-more a { color: var(--muted); }
.sb-privacy, .sb-credit { margin: 6px 0; }

[hidden] { display: none !important; }
.print-root { display: none; }
@media (prefers-reduced-motion: no-preference) { html { scroll-behavior: smooth; } }
@media (max-width: 560px) {
  .problems, .peek { font-size: 0.9rem; }
  .qt { max-width: 100%; overflow-x: auto; overflow-y: hidden; }
  .actions .btn { flex: 1 1 100%; }
  .problems input { width: 8.2em; }
  .timer-bar { gap: 6px 8px; }
  .answered { font-size: 0.88rem; }
  .bar-btns .btn.small { padding: 6px 9px; }
  .clock { font-size: 1.5rem; min-width: 4em; }
  .pq-wrap { flex-basis: 100%; }
  .ans { margin-left: 2.6em; flex-wrap: wrap; }
  .mk { padding-left: 0; }
}

/* ===================== print: the test, laid out like the contest pages, and the key ===================== */
@page { margin: 0.45in; }
@media print {
  body { background: #fff; color: #000; font: 10.5pt/1.3 var(--test); }
  main, footer, .skip { display: none !important; }
  .print-root { display: block; }
  .ps-page { height: 9.85in; display: flex; flex-direction: column; break-after: page; overflow: hidden; }
  .ps-page:last-child { break-after: auto; }
  .fig { color: #000; }
  .fig .lb { stroke: #fff; }
  .fig text { font-size: 12.5px; font-family: Arial, Helvetica, sans-serif; }
  /* cover */
  .ps-cover { font-family: var(--sans); }
  .cv-top { display: flex; justify-content: space-between; gap: 0.3in; align-items: flex-start; }
  .cv-tie { border: 1pt solid #000; padding: 6pt 8pt; width: 2.4in; font-size: 9.5pt; }
  .cv-tie p { margin: 0 0 14pt; }
  .cv-line { display: inline-block; width: 1.6in; border-bottom: 0.75pt solid #000; }
  .cv-score { border-collapse: collapse; font-size: 9.5pt; }
  .cv-score td { border: 1pt solid #000; padding: 4pt 8pt; }
  .cv-score td:last-child { width: 0.9in; text-align: right; vertical-align: top; }
  .cv-score .tot td { font-weight: 700; }
  .cv-num { margin: 12pt 0 0; text-align: right; font-size: 10pt; }
  .cv-title { text-align: center; margin: 0.35in 0 0.15in; border: 1.5pt solid #000; padding: 14pt 10pt; }
  .cv-h { font: 700 26pt/1.1 var(--head); margin: 0; }
  .cv-h2 { font: 700 18pt/1.2 var(--head); margin: 4pt 0 6pt; }
  .cv-sub { margin: 0; font-size: 10.5pt; }
  .cv-wait { text-align: center; font-weight: 700; margin: 6pt 0 10pt; }
  .cv-rules { margin: 0; padding-left: 1.2em; font-size: 10.5pt; line-height: 1.4; }
  .cv-rules li { margin: 0 0 7pt; }
  .cv-foot { margin-top: auto; font-size: 8.5pt; text-align: center; }
  /* test pages */
  .ps-run { font: 8.5pt var(--sans); display: flex; justify-content: space-between; border-bottom: 0.75pt solid #000; padding-bottom: 3pt; }
  .ps-body { flex: 1; display: flex; flex-direction: column; justify-content: space-around; min-height: 0; padding-top: 4pt; }
  .pr { display: flex; align-items: flex-end; gap: 4pt; break-inside: avoid; padding: 3pt 0; }
  .pn { flex: 0 0 0.42in; font-size: 10pt; align-self: center; }
  .pr-s .pn { align-self: flex-start; }
  .pq { flex: 0 1 auto; max-width: 4.9in; }
  .pr-c .pq { align-self: center; max-width: none; }
  .pr-s .pq { flex: 0 1 4.55in; }
  .lead { flex: 1 1 0.2in; border-bottom: 1pt dotted #000; margin: 0 2pt 4pt; min-width: 0.15in; }
  .pa { flex: 0 0 auto; white-space: nowrap; font-size: 10pt; }
  .bl { display: inline-block; width: 1.25in; border-bottom: 0.75pt solid #000; height: 1em; vertical-align: -1pt; margin: 0 2pt; }
  .pre { margin-left: 2pt; }
  .un { font-size: 9pt; }
  .gbox-row { display: grid; grid-template-columns: 1fr 1fr; border: 1pt solid #000; break-inside: avoid; margin: 4pt 0; }
  .gbox { padding: 4pt 8pt 6pt; display: flex; flex-direction: column; align-items: center; min-height: 0; }
  .gbox + .gbox { border-left: 1pt solid #000; }
  .gb-n { align-self: flex-start; margin: 0; font-size: 10pt; }
  .gb-t { margin: 0 0 2pt; font-size: 9pt; text-align: center; }
  .gb-f { width: 100%; max-width: 3.05in; }
  .gbox { min-width: 0; }
  .gb-note { margin: 1pt 0 0; font-size: 9.5pt; text-align: center; }
  .gb-a { align-self: flex-start; margin: 6pt 0 0; font-size: 10pt; }
  .gb-a .bl { width: 1.3in; }
  .mode { color: #000; }
  .fr > span:first-child { border-bottom: 0.75pt solid #000; }
  .rad { border-top-width: 0.75pt; }
  .mx { border-left-width: 1pt; border-right-width: 1pt; }
  /* key */
  .ps-keypage { font-family: var(--sans); }
  .ps-key-title { font: 700 11pt var(--head); margin: 0 0 4pt; }
  .ps-key { width: 100%; border-collapse: collapse; font-size: 8.6pt; table-layout: fixed; }
  .ps-key th { text-align: left; border-bottom: 1.2pt solid #000; padding: 2pt 4pt; font-size: 8.5pt; }
  .ps-key td { border-bottom: 0.5pt solid #888; padding: 1.7pt 4pt; vertical-align: top; white-space: nowrap; overflow: hidden; }
  .ps-key th:first-child { width: 0.4in; } .ps-key td:first-child { font-weight: 700; }
  .ps-key th:nth-child(2) { width: 2.45in; } .ps-key th:nth-child(3) { width: 2.4in; }
  .ps-key .tag { color: #000; font-size: 8pt; }
  .ps-key-note { font: 8pt/1.3 var(--sans); margin-top: 6pt; }
}