/* Chess Puzzle Practice: grey test paper, a dark diagram frame like the printed contest, a red grading pen. */
:root {
  --bg: #f2f1ec;
  --paper: #fbfaf7;
  --ink: #1d2226;
  --muted: #545b61;
  --line: #cfccc2;
  --accent: #a3302b;
  --accent-ink: #ffffff;
  --right: #1f6b3a;
  --right-bg: #e3f0e6;
  --wrong: #a3302b;
  --wrong-bg: #f7e3e1;
  --sq-light: #ebe8df;
  --sq-dark: #a7afb6;
  --frame: #2b3034;
  --frame-ink: #f3f3f0;
  --focus: #1d5fbf;
  --radius: 6px;
  color-scheme: light dark;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #16191d;
    --paper: #1f2328;
    --ink: #e9e7e2;
    --muted: #a9b0b6;
    --line: #3a4047;
    --accent: #e0726b;
    --accent-ink: #16191d;
    --right: #7fcf98;
    --right-bg: #1d3226;
    --wrong: #f08c85;
    --wrong-bg: #3a2220;
    --sq-light: #d4d0c6;
    --sq-dark: #848e97;
    --frame: #0c0e10;
    --frame-ink: #e9e7e2;
    --focus: #8ab4ff;
  }
}

* { 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 system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}
.sprite { position: absolute; width: 0; height: 0; overflow: hidden; }
.wrap { max-width: 1120px; margin: 0 auto; padding: 0 16px; }
a { color: var(--accent); }
a:focus-visible, button:focus-visible, select:focus-visible, input:focus-visible, [tabindex]:focus-visible { outline: 3px solid var(--focus); outline-offset: 2px; }
.skip { position: absolute; left: -999px; top: 0; background: var(--paper); padding: 8px 12px; z-index: 10; }
.skip:focus { left: 8px; }

.hero { padding: 22px 0 6px; }
h1 { font-size: clamp(1.7rem, 4.2vw, 2.4rem); line-height: 1.15; margin: 0 0 6px; letter-spacing: -0.01em; }
.lede { margin: 0; max-width: 62ch; color: var(--muted); }

/* ---- controls ---- */
.setup { display: flex; flex-wrap: wrap; gap: 10px 18px; align-items: center; padding: 14px 0 10px; }
.seg, .mode { display: inline-flex; border: 1px solid var(--ink); border-radius: var(--radius); overflow: hidden; }
.seg button, .mode button {
  font: inherit; font-size: 0.95rem; min-height: 44px; padding: 0 14px; border: 0; background: transparent; color: var(--ink); cursor: pointer;
  border-left: 1px solid var(--ink); white-space: nowrap;
}
.seg button:first-child, .mode button:first-child { border-left: 0; }
.seg button[aria-checked="true"], .mode button[aria-checked="true"] { background: var(--ink); color: var(--bg); font-weight: 600; }
.testline { display: flex; flex-wrap: wrap; align-items: center; gap: 8px 12px; }
.testname { font-variant-numeric: tabular-nums; }
.testname b { letter-spacing: 0.06em; }
select, input { font: inherit; font-size: 16px; color: var(--ink); background: var(--paper); border: 1px solid var(--line); border-radius: var(--radius); min-height: 44px; padding: 0 8px; }
.btn {
  font: inherit; font-size: 0.95rem; min-height: 44px; padding: 0 16px; border-radius: var(--radius); cursor: pointer;
  border: 1px solid var(--ink); background: var(--paper); color: var(--ink);
}
a.btn { display: inline-flex; align-items: center; text-decoration: none; }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); font-weight: 600; }
.btn:disabled { opacity: 0.45; cursor: default; }
.link { font: inherit; background: none; border: 0; color: var(--accent); text-decoration: underline; cursor: pointer; padding: 10px 0; min-height: 44px; }
.note { margin: 0 0 10px; padding: 10px 12px; border-left: 4px solid var(--accent); background: var(--paper); }
.note.info { border-left-color: var(--muted); }

/* ---- question + sheet ---- */
.desk { display: grid; grid-template-columns: minmax(0, 1fr) 300px; gap: 24px; align-items: start; }
.q-area { background: var(--paper); border: 1px solid var(--line); border-radius: var(--radius); padding: 16px 18px 18px; }
.q-area:focus { outline: none; }
.q-head { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: baseline; gap: 0 12px; margin-bottom: 10px; }
.q-title { font-size: 1.15rem; margin: 0; }
.q-kind { color: var(--muted); font-size: 0.9rem; }
/* contest time beside the question on narrow screens, where the answer sheet (and its clock) sits below */
.q-clock { display: none; font-weight: 700; font-variant-numeric: tabular-nums; }
.q-clock.low { color: var(--wrong); }
.board-wrap { max-width: 440px; }
.board { display: block; width: 100%; height: auto; }
.board .l { fill: var(--sq-light); }
.board .d { fill: var(--sq-dark); }
.board .fr { fill: var(--frame); }
.board text { fill: var(--frame-ink); font: 600 7px system-ui, sans-serif; }
.q-ask { font-size: 1.08rem; font-weight: 600; margin: 14px 0 8px; max-width: 46ch; }
.opts { list-style: none; margin: 0; padding: 0; display: grid; gap: 8px; max-width: 520px; }
.opt {
  width: 100%; display: flex; align-items: center; gap: 12px; text-align: left; font: inherit; color: var(--ink);
  min-height: 48px; padding: 8px 12px; background: var(--bg); border: 1px solid var(--line); border-radius: var(--radius); cursor: pointer;
}
.opt:hover:not(:disabled) { border-color: var(--ink); }
.opt .ltr { flex: 0 0 auto; width: 28px; height: 28px; border-radius: 50%; border: 1.5px solid var(--ink); display: inline-grid; place-items: center; font-weight: 600; font-size: 0.9rem; }
.opt[aria-pressed="true"] { border-color: var(--ink); box-shadow: inset 0 0 0 1px var(--ink); }
.opt[aria-pressed="true"] .ltr { background: var(--ink); color: var(--bg); }
.opt.is-right { border-color: var(--right); background: var(--right-bg); }
.opt.is-right .ltr { background: var(--right); border-color: var(--right); color: var(--paper); }
.opt.is-wrong { border-color: var(--wrong); background: var(--wrong-bg); }
.opt.is-wrong .ltr { background: var(--wrong); border-color: var(--wrong); color: var(--paper); }
.opt:disabled { cursor: default; }
.fig { width: 1.25em; height: 1.25em; vertical-align: -0.28em; margin-right: 1px; }
.mv { white-space: nowrap; font-variant-numeric: tabular-nums; }
.feedback { min-height: 1.5em; margin-top: 12px; max-width: 60ch; }
.feedback p { margin: 0 0 6px; }
.feedback .verdict { font-weight: 700; }
.feedback .verdict.ok { color: var(--right); }
.feedback .verdict.no { color: var(--wrong); }
.feedback .src { color: var(--muted); font-size: 0.9rem; }
.q-nav { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 14px; }

.sheet { background: var(--paper); border: 1px solid var(--line); border-radius: var(--radius); padding: 14px; position: sticky; top: 12px; }
.sheet-head { display: grid; gap: 8px; }
.mode { width: 100%; }
.mode button { flex: 1 1 0; padding: 0 8px; }
.clock { margin: 0; font-size: 1.4rem; font-weight: 700; font-variant-numeric: tabular-nums; }
.clock.low { color: var(--wrong); }
.sheet-label { font-size: 0.95rem; margin: 12px 0 4px; }
.bubbles { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: 1fr 1fr; grid-template-rows: repeat(var(--rows, 10), auto); grid-auto-flow: column; column-gap: 10px; }
.bubbles li { display: flex; align-items: center; gap: 2px; }
.bubbles .qn {
  font: inherit; font-size: 0.85rem; font-weight: 600; width: 30px; min-height: 30px; text-align: right; padding: 0 4px 0 0;
  background: none; border: 0; color: var(--ink); cursor: pointer; font-variant-numeric: tabular-nums;
}
.bubbles .qn .chosen { display: none; }
.bubbles li.cur .qn { color: var(--accent); text-decoration: underline; text-underline-offset: 3px; }
.bub { font: inherit; font-size: 0.72rem; width: 24px; height: 24px; margin: 2px 0; border-radius: 50%; border: 1px solid var(--muted); background: transparent; color: var(--muted); padding: 0; cursor: pointer; line-height: 1; }
.bub.on { background: var(--ink); color: var(--paper); border-color: var(--ink); }
.bub.r { background: var(--right); border-color: var(--right); color: var(--paper); }
.bub.w { background: var(--wrong); border-color: var(--wrong); color: var(--paper); }
.bub.k { box-shadow: 0 0 0 2px var(--right); }
.bub:disabled { cursor: default; }
.score { font-weight: 700; margin: 12px 0 6px; min-height: 1.5em; }
.sheet-actions { display: flex; flex-wrap: wrap; gap: 8px; }
.sheet-actions .btn { flex: 1 1 auto; }
.share-out { margin: 10px 0 0; }
.share-out label { display: grid; gap: 4px; font-size: 0.9rem; }
.share-out input { width: 100%; }
.sheet-small { margin: 4px 0 0; }

.extras { display: flex; flex-wrap: wrap; gap: 12px 24px; align-items: flex-start; margin: 18px 0 8px; }
.drill { display: grid; gap: 4px; font-size: 0.95rem; }
.history { font-size: 0.95rem; }
.history h3 { font-size: 0.95rem; margin: 0 0 4px; }
.history ul { margin: 0; padding: 0; list-style: none; display: flex; flex-wrap: wrap; gap: 4px 14px; }
.history button { font: inherit; background: none; border: 0; color: var(--accent); text-decoration: underline; cursor: pointer; min-height: 44px; padding: 0; }

/* ---- content ---- */
.content { max-width: 72ch; padding: 20px 0 30px; }
.content h2 { font-size: 1.35rem; margin: 30px 0 8px; line-height: 1.25; }
.content h3 { font-size: 1.05rem; margin: 18px 0 4px; }
.content p { margin: 0 0 10px; }
.kinds { padding-left: 1.2em; margin: 0 0 10px; }
.kinds li { margin: 2px 0; }
.sources, .indep { font-size: 0.95rem; color: var(--muted); }
.sources { margin-top: 26px !important; }

footer { border-top: 1px solid var(--line); padding: 18px 0 30px; font-size: 0.95rem; color: var(--muted); }
.sb-footer p { margin: 0 0 8px; }
.sb-more { line-height: 1.9; }
.sb-more a, .sb-credit a { color: var(--ink); }

/* ---- phone ---- */
@media (max-width: 860px) {
  .desk { grid-template-columns: 1fr; }
  .sheet { position: static; }
  .q-clock { display: inline; }
}
@media (max-width: 560px) {
  body { font-size: 16px; }
  .hero { padding-top: 14px; }
  .q-area { padding: 12px 10px 14px; margin: 0 -6px; }
  .board-wrap { max-width: none; }
  .seg { width: 100%; }
  .seg button { flex: 1 1 0; padding: 0 6px; font-size: 0.92rem; }
  .bubbles { grid-template-columns: repeat(5, 1fr); grid-template-rows: none; grid-auto-flow: row; gap: 6px; }
  .bubbles li { display: block; }
  .bubbles .bub { display: none; }
  .bubbles .qn { width: 100%; min-height: 44px; text-align: center; padding: 0; border: 1px solid var(--line); border-radius: var(--radius); display: grid; place-items: center; line-height: 1.1; }
  .bubbles .qn .chosen { display: block; font-size: 0.75rem; font-weight: 400; color: var(--muted); }
  .bubbles li.r .qn { border-color: var(--right); background: var(--right-bg); }
  .bubbles li.w .qn { border-color: var(--wrong); background: var(--wrong-bg); }
  .bubbles li.a .qn { border-color: var(--ink); }
}
@media (prefers-reduced-motion: reduce) { * { scroll-behavior: auto !important; transition: none !important; } }

/* ---- print ---- */
.print-root { display: none; }
@page { margin: 0.45in 0.5in; }
@media print {
  body { background: #fff; color: #000; font-size: 11pt; }
  body > :not(.print-root) { display: none !important; }
  .print-root { display: block; }
  .pg { break-after: page; page-break-after: always; }
  .pg:last-child { break-after: auto; page-break-after: auto; }
  .run { display: flex; justify-content: space-between; font-size: 9pt; border-bottom: 1px solid #000; padding-bottom: 3pt; margin-bottom: 10pt; }
  .qgrid { display: grid; grid-template-columns: 1fr 1fr; column-gap: 0.35in; row-gap: 0.18in; }
  .pq { break-inside: avoid; }
  .pq h4 { margin: 0 0 4pt; font-size: 10.5pt; text-align: center; }
  .pq .board { width: 2.85in; margin: 0 auto; }
  /* the first tiebreaker page also carries a title: slightly smaller diagrams keep its four questions on one Letter page */
  .pg.has-title .pq .board { width: 2.55in; }
  .pq .board .l { fill: #ffffff; }
  .pq .board .d { fill: #c2c2c2; }
  .pq .board .fr { fill: #333333; }
  .pq .board text { fill: #ffffff; font-size: 8.5px; }
  .pq .ask { margin: 6pt 0 3pt; font-weight: 600; font-size: 10.5pt; }
  .pq ol { margin: 0; padding-left: 0; list-style: none; font-size: 10.5pt; }
  .pq li { margin: 1pt 0; }
  .fig { width: 1.15em; height: 1.15em; vertical-align: -0.25em; }
  .ptitle { font-size: 16pt; margin: 0 0 4pt; }
  .psub { margin: 0 0 10pt; font-size: 10.5pt; }
  .instr { border: 1.5pt solid #000; padding: 8pt 12pt; margin: 0 0 12pt; font-size: 10.5pt; }
  .instr p { margin: 0 0 5pt; }
  .figkey { display: flex; flex-wrap: wrap; gap: 4pt 16pt; margin-top: 4pt; }
  /* answer sheet */
  .as-top { display: grid; grid-template-columns: 1fr 1.25fr; border: 1.2pt solid #000; margin-bottom: 10pt; }
  .as-grader { padding: 6pt 8pt; border-right: 1.2pt solid #000; font-size: 9.5pt; }
  .as-grader p { margin: 0 0 7pt; }
  .as-name { padding: 6pt 8pt; text-align: center; }
  .as-name .cn { text-align: right; font-weight: 700; font-size: 10pt; margin: 0 0 14pt; }
  .as-name h2 { font-size: 13pt; margin: 0; }
  .as-hint { text-align: center; font-style: italic; font-weight: 700; margin: 4pt 0 8pt; }
  .as-grades { text-align: center; font-weight: 700; margin: 0 0 10pt; word-spacing: 10pt; }
  .as-sec { font-weight: 700; margin: 8pt 0 4pt; font-size: 11pt; }
  .as-sec small { font-weight: 400; font-style: italic; font-size: 9pt; }
  .as-grid { display: grid; grid-template-columns: 1fr 1fr; column-gap: 0.4in; }
  .as-row { display: flex; align-items: center; height: 0.34in; font-size: 11pt; }
  .as-row b { width: 0.42in; }
  .as-row span { width: 0.42in; text-align: center; }
  .as-box { border: 1pt dashed #000; margin-left: -4pt; padding-left: 4pt; position: relative; }
  .as-side { position: absolute; right: 8pt; top: 50%; transform: translateY(-50%); width: 1.05in; font-size: 9pt; font-style: italic; line-height: 1.3; }
  .as-foot { margin-top: 12pt; font-size: 9pt; }
  /* key */
  .key-grid { display: grid; grid-template-columns: 1fr 1fr; column-gap: 0.5in; font-size: 12pt; max-width: 4in; }
  .key-grid div { padding: 2pt 0; }
  .whys { font-size: 9.5pt; columns: 2; column-gap: 0.35in; padding-left: 1.6em; margin: 6pt 0 0; }
  .whys li { break-inside: avoid; margin: 0 0 5pt; }
  h3.ksec { font-size: 12pt; margin: 12pt 0 4pt; }
}
/* figurines are drawn for light paper: in dark mode they sit on a light square so outlines and Black pieces show */
@media (prefers-color-scheme: dark) { .fig { background: var(--sq-light); border-radius: 3px; } }