/* Sliding puzzle. The top part is the shared paper-and-ink look of the other sections (copied from
   ../hangman/styles.css: header, intro, tabs, buttons, article, footer); the puzzle and the diagrams are at the bottom. */
:root {
  --paper: #faf8f2;
  --ink: #292d28;
  --muted: #697064;
  --line: #dfdfd3;
  --accent: #bd5f3e;
  --teal: #24878b;
  --pad: #fffdf8;
  --dot: #d5d3c4;
  --ink-mark: #bd5f3e;
  --display: ui-rounded, "SF Pro Rounded", "Hiragino Maru Gothic ProN", "Arial Rounded MT Bold", system-ui, sans-serif;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper: #1b1d1a; --ink: #ecebe3; --muted: #a3a898; --line: #3a3d36;
    --accent: #e27f5a; --teal: #58b9bd; --pad: #232621; --dot: #3d4138; --ink-mark: #e27f5a;
  }
}
:root[data-theme="dark"] {
  --paper: #1b1d1a; --ink: #ecebe3; --muted: #a3a898; --line: #3a3d36;
  --accent: #e27f5a; --teal: #58b9bd; --pad: #232621; --dot: #3d4138; --ink-mark: #e27f5a;
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }
body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font: 16px/1.6 system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  -webkit-tap-highlight-color: transparent;
}
a { color: inherit; }
button { font: inherit; color: inherit; }
a:focus-visible, button:focus-visible, summary:focus-visible { outline: 3px solid var(--teal); outline-offset: 4px; }
.wrap { width: min(1120px, calc(100% - 48px)); margin: 0 auto; }

/* ---------- header ---------- */
.site-header {
  display: flex; align-items: center; gap: 20px;
  padding: 20px 0; border-bottom: 1px solid var(--line);
}
.brand { display: inline-flex; align-items: center; gap: 10px; font-weight: 800; text-decoration: none; white-space: nowrap; }
.crumbs { flex: 1; color: var(--muted); font-size: 15px; min-width: 0; }
.crumbs a { text-decoration: none; }
.crumbs a:hover { color: var(--accent); }
.crumbs .sep { margin: 0 8px; color: var(--line); }
.crumbs [aria-current] { color: var(--ink); }
.theme-btn {
  width: 40px; height: 40px; border-radius: 50%; border: 1px solid var(--line);
  background: transparent; display: grid; place-items: center; cursor: pointer;
}
.theme-btn:hover { border-color: var(--ink); }
.theme-btn svg { width: 20px; height: 20px; fill: none; stroke: currentColor; stroke-width: 2; stroke-linejoin: round; }
.langs { display: flex; gap: 2px; }
.langs a { padding: 5px 8px; border-radius: 999px; font-size: 13px; font-weight: 700; letter-spacing: .03em; color: var(--muted); text-decoration: none; }
.langs a:hover { color: var(--ink); }
.langs a[aria-current] { color: var(--ink); background: var(--line); }

/* ---------- intro ---------- */
.intro { padding: 34px 0 22px; }
.intro h1 {
  margin: 0; font-family: var(--display); font-weight: 800;
  font-size: clamp(40px, 6.4vw, 68px); line-height: 1.02; letter-spacing: -0.02em;
}
.lede { margin: 12px 0 0; font-size: 18px; color: var(--muted); max-width: 58ch; }

.durations { display: flex; flex-wrap: wrap; gap: 8px; margin: 0 0 20px; }
.durations a {
  padding: 7px 16px; border: 1.5px solid var(--line); border-radius: 999px;
  text-decoration: none; font-size: 15px; color: var(--muted);
}
.durations a:hover { border-color: var(--ink); color: var(--ink); }
.durations a[aria-current] { background: var(--ink); border-color: var(--ink); color: var(--paper); font-weight: 600; }

.mode-switch { display: inline-flex; margin: 0 0 18px; border: 1.5px solid var(--ink); border-radius: 999px; overflow: hidden; }
.mode-switch button { border: 0; background: transparent; padding: 8px 18px; cursor: pointer; font-weight: 600; }
.mode-switch button[aria-pressed="true"] { background: var(--ink); color: var(--paper); }
.stop-row { margin: 14px 0 0; min-height: 0; }
.stop-row:has([hidden]) { margin: 0; }

.challenge {
  margin: 0 0 20px; padding: 12px 16px; border-left: 4px solid var(--accent);
  background: var(--pad); font-weight: 600;
}

.actions { grid-column: 1 / -1; display: flex; flex-wrap: wrap; align-items: center; gap: 12px; margin-top: 22px; }
.btn {
  padding: 11px 22px; border-radius: 999px; border: 1.5px solid var(--ink);
  background: transparent; cursor: pointer; font-weight: 600;
}
.btn:hover { border-color: var(--accent); color: var(--accent); }
.btn.primary { background: var(--ink); color: var(--paper); }
.btn.primary:hover { background: var(--accent); border-color: var(--accent); color: #fff; }
/* ---------- article ---------- */
.prose { max-width: 70ch; margin: 56px 0 0; font-size: 17px; line-height: 1.7; }
.prose h2 { font-family: var(--display); font-weight: 800; font-size: 28px; line-height: 1.2; margin: 44px 0 10px; letter-spacing: -0.01em; }
.prose h3 { font-size: 19px; margin: 26px 0 6px; }
.prose p { margin: 0 0 14px; }
.prose ul, .prose ol { padding-left: 22px; margin: 0 0 14px; }
.prose li { margin-bottom: 6px; }
.prose a { color: var(--accent); }
.prose table { width: 100%; border-collapse: collapse; font-size: 16px; margin: 0 0 16px; }
.prose th, .prose td { border-bottom: 1px solid var(--line); padding: 9px 12px 9px 0; text-align: left; vertical-align: top; }
.prose th { border-bottom: 2px solid var(--ink); font-weight: 700; }
.prose td:first-child { font-weight: 700; white-space: nowrap; }
.faq details { border-bottom: 1px solid var(--line); padding: 12px 0; }
.faq summary { cursor: pointer; font-weight: 600; }
.faq-answer { padding: 8px 0 0; color: var(--muted); }

/* ---------- footer ---------- */
.site-footer { margin-top: 64px; padding: 22px 0 40px; border-top: 1px solid var(--line); color: var(--muted); font-size: 15px; }
.site-footer nav { display: flex; flex-wrap: wrap; gap: 6px 22px; }
.site-footer a { text-decoration: none; color: var(--ink); }
.site-footer a:hover { color: var(--accent); }
.site-footer a[aria-current] { color: var(--muted); }
.site-footer .footer-site { margin-top: 10px; padding-top: 10px; border-top: 1px solid var(--line); }
.site-footer p { margin: 10px 0 0; }

.toolbar { display: flex; flex-wrap: wrap; align-items: center; gap: 10px 14px; margin: 18px 0 0; }
.toolbar .label { color: var(--muted); font-size: 15px; }
.seg { display: inline-flex; border: 1.5px solid var(--ink); border-radius: 999px; overflow: hidden; }
.seg button { border: 0; background: transparent; padding: 7px 14px; cursor: pointer; font-weight: 600; font-variant-numeric: tabular-nums; }
.seg button[aria-pressed="true"] { background: var(--ink); color: var(--paper); }


/* ---------- small screens (shared) ---------- */
@media (max-width: 760px) {
  .wrap { width: calc(100% - 32px); }
  .site-header { gap: 12px; padding: 14px 0; }
  .crumbs { display: none; }
  .brand { flex: 1; }
  .intro { padding: 24px 0 16px; }
  .lede { font-size: 16px; }
  .durations { flex-wrap: nowrap; overflow-x: auto; margin: 0 -16px 14px; padding: 2px 16px 6px; scrollbar-width: none; }
  .durations::-webkit-scrollbar { display: none; }
  .durations a { white-space: nowrap; flex: none; }
  .prose { font-size: 16px; margin-top: 40px; }
  .prose h2 { font-size: 23px; }
  .prose table { display: block; overflow-x: auto; }
}

/* ---------- sliding puzzle ---------- */
.sp-game { max-width: 520px; }
.sp-stats { display: grid; grid-template-columns: 1fr 1fr 1.4fr; gap: 10px; margin: 0 0 12px; }
.sp-stats span { display: flex; flex-direction: column; gap: 2px; padding: 8px 12px; border: 1.5px solid var(--line); border-radius: 14px; background: var(--pad); min-width: 0; }
.sp-stats small { color: var(--muted); font-size: 13px; }
.sp-stats b { font: 800 22px/1.1 var(--display); font-variant-numeric: tabular-nums; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.sp-frame { padding: 8px; border-radius: 18px; background: #6f4a2c; border: 3px solid var(--ink); }
.sp-board {
  --n: 4; position: relative; width: 100%; aspect-ratio: 1; border-radius: 10px; background: #4b3120;
  touch-action: none; user-select: none; -webkit-user-select: none; outline: none; container-type: inline-size;
}
.sp-board:focus-visible { box-shadow: 0 0 0 3px var(--teal); }
.sp-tile {
  position: absolute; left: 0; top: 0; width: calc(100% / var(--n)); height: calc(100% / var(--n)); padding: 3px; border: 0; margin: 0;
  background: transparent; cursor: pointer; transform: translate(calc(var(--c) * 100%), calc(var(--r) * 100%));
  transition: transform .12s ease-out; color: var(--ink);
}
.sp-tile span {
  display: grid; place-items: center; width: 100%; height: 100%; border-radius: 9px; background: #fff6e6;
  box-shadow: inset 0 -4px 0 rgba(0, 0, 0, .18), 0 2px 3px rgba(0, 0, 0, .25);
  font: 800 calc(100cqw / var(--n) * .38) / 1 var(--display); font-variant-numeric: tabular-nums;
}
.sp-tile.is-home span { background: #fffdf8; }
.sp-board[data-style="colours"] .sp-tile span { background: var(--tc); color: #1d1f1c; }
.sp-board[data-style="colours"] .sp-tile span { font-size: calc(100cqw / var(--n) * .26); }
.sp-tile.is-hint span { box-shadow: inset 0 0 0 4px #f2b400, 0 2px 3px rgba(0, 0, 0, .25); }
.sp-board.is-done .sp-tile { cursor: default; }
.sp-board.is-done .sp-tile span { animation: sp-pop .5s ease-out; }
@keyframes sp-pop { 50% { transform: scale(.9); } }
.sp-status { margin: 12px 0 0; min-height: 1.6em; font-weight: 600; }
.sp-actions { display: flex; flex-wrap: wrap; gap: 10px; margin: 10px 0 0; }
.sp-result { margin: 18px 0 0; padding: 16px 18px; border-left: 4px solid var(--teal); background: var(--pad); }
.sp-result-head { margin: 0; font: 800 26px/1.2 var(--display); }
.sp-result-sub { margin: 6px 0 12px; color: var(--muted); }
.sp-bar { margin: 22px 0 0; padding-top: 16px; border-top: 1px solid var(--line); }
.sp-group { display: inline-flex; flex-wrap: wrap; align-items: center; gap: 8px 10px; }
.sp-note { margin: 12px 0 0; color: var(--muted); font-size: 15px; }

/* ---------- diagrams in the articles ---------- */
.sp-fig { margin: 22px 0; }
.sp-fig-row { display: flex; flex-wrap: wrap; gap: 14px 22px; align-items: flex-end; }
.sp-fig-item { display: flex; flex-direction: column; gap: 4px; min-width: 0; }
.sp-fig-item span { color: var(--muted); font-size: 14px; font-weight: 600; }
.sp-fig svg { display: block; max-width: 100%; height: auto; }
.sp-fig figcaption { margin: 8px 0 0; color: var(--muted); font-size: 15px; }
.sp-fig .fr { fill: #6f4a2c; } .sp-fig .bg { fill: #4b3120; }
.sp-fig .tl { fill: #fff6e6; } .sp-fig .dn { fill: #cfe7d9; } .sp-fig .hl { fill: #f7d488; } .sp-fig .ar { fill: none; stroke: #bd5f3e; stroke-width: 3; stroke-linecap: round; }
.sp-fig .ah { fill: #bd5f3e; }
.sp-fig .nm { fill: #1d1f1c; font: 800 16px system-ui, sans-serif; }

@media (max-width: 760px) {
  .sp-stats b { font-size: 18px; }
  .sp-actions .btn { padding: 8px 14px; font-size: 15px; }
  .sp-bar { gap: 8px 10px; }
  .sp-bar .label { font-size: 13px; }
  .sp-bar .seg button { padding: 5px 10px; font-size: 14px; }
}
@media (prefers-reduced-motion: reduce) { .sp-tile { transition: none; } .sp-board.is-done .sp-tile span { animation: none; } }