:root {
  --bg: #f6f4ef; --panel: #fffdf8; --ink: #1c1b19; --muted: #5d5a53; --line: #d9d4c8;
  --accent: #b3440e; --good: #1b7a43; --bad: #b3261e; --hidden: #b9b5ab; --cubeline: #1c1b19;
  color-scheme: light;
}
:root[data-theme="dark"] {
  --bg: #121210; --panel: #1b1b18; --ink: #efece4; --muted: #aaa69c; --line: #38372f;
  --accent: #f0914f; --good: #5fce8d; --bad: #f28b82; --hidden: #4b4a44; --cubeline: #000;
  color-scheme: dark;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #121210; --panel: #1b1b18; --ink: #efece4; --muted: #aaa69c; --line: #38372f;
    --accent: #f0914f; --good: #5fce8d; --bad: #f28b82; --hidden: #4b4a44; --cubeline: #000;
    color-scheme: dark;
  }
}
* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--ink); font: 16px/1.55 Charter, "Iowan Old Style", Georgia, serif; }
main, header.top { max-width: 1040px; margin: 0 auto; padding-inline: 16px; }
header.top { padding-block: 36px 8px; display: flex; gap: 16px; justify-content: space-between; align-items: flex-start; }
h1 { font-size: clamp(30px, 6vw, 46px); line-height: 1.08; margin: 0 0 10px; letter-spacing: -0.01em; }
h2 { font-size: 25px; margin: 0 0 10px; }
h3 { font-size: 18px; margin: 0 0 4px; }
p { margin: 0 0 12px; }
.lede { font-size: 19px; max-width: 62ch; }
section { padding-block: 26px; border-top: 1px solid var(--line); }
header.top + main > section:first-child { border-top: 0; }
code, .alg { font-family: ui-monospace, Menlo, Consolas, monospace; font-size: .92em; }
.muted { color: var(--muted); }
.small { font-size: 14px; }
a { color: var(--accent); }
button, select { font: 15px/1.2 ui-sans-serif, -apple-system, "Segoe UI", sans-serif; color: var(--ink); background: var(--panel); border: 1px solid var(--line); border-radius: 6px; min-height: 44px; padding: 8px 12px; }
button { cursor: pointer; }
button:hover { border-color: var(--ink); }
button:disabled { opacity: .5; cursor: default; }
:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }
button.primary { background: var(--accent); border-color: var(--accent); color: #fff; font-weight: 600; }
:root[data-theme="dark"] button.primary { color: #1b1208; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) button.primary { color: #1b1208; } }

.shapes { display: grid; grid-template-columns: repeat(auto-fit, minmax(210px, 1fr)); gap: 18px; margin-top: 14px; }
.shape svg { width: 100%; max-width: 190px; display: block; }
.shape h3 .alg { font-weight: 400; }

.flow { overflow-x: auto; }
.flow svg { min-width: 640px; width: 100%; height: auto; display: block; }
.flow text { font: 14px ui-sans-serif, -apple-system, "Segoe UI", sans-serif; fill: var(--ink); }
.flow .box { fill: var(--panel); stroke: var(--line); stroke-width: 1.5; }
.flow .ask { stroke: var(--accent); stroke-width: 2; }
.flow .end { fill: #1b7a43; stroke: none; }
.flow .end + text, .flow text.onend { fill: #fff; }
.flow path { fill: none; stroke: var(--muted); stroke-width: 1.6; }
.flow .lab { font-size: 13px; fill: var(--muted); }

.lab { display: grid; grid-template-columns: minmax(0, 300px) minmax(0, 1fr); gap: 22px; align-items: start; }
@media (max-width: 760px) { .lab { grid-template-columns: minmax(0, 1fr); } }
.views { display: grid; gap: 10px; }
.views svg { width: 100%; max-width: 280px; display: block; margin-inline: auto; }
.controls { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; margin-bottom: 12px; }
.controls label { display: inline-flex; gap: 6px; align-items: center; min-height: 44px; font: 14px ui-sans-serif, -apple-system, sans-serif; }
.algs { display: grid; gap: 6px; }
.algrow { display: flex; gap: 6px; }
.algrow .pick { flex: 1; min-width: 0; text-align: left; font-family: ui-monospace, Menlo, Consolas, monospace; font-size: 14px; overflow-wrap: anywhere; }
.algrow .pick b { color: var(--muted); font-weight: 400; margin-right: 6px; }
.algrow .pick.right { border: 2px solid var(--good); }
.algrow .pick.wrong { border: 2px solid var(--bad); }
.algrow .replay { flex: none; }
.verdict { min-height: 26px; font-weight: 600; margin: 10px 0; }
.verdict.ok { color: var(--good); }
.verdict.no { color: var(--bad); }
.stepper { margin-top: 12px; padding-top: 12px; border-top: 1px solid var(--line); }
.tokens { display: flex; flex-wrap: wrap; gap: 4px; margin: 6px 0; font-family: ui-monospace, Menlo, monospace; }
.tokens span { padding: 2px 6px; border-radius: 4px; }
.tokens span.cur { background: var(--accent); color: #fff; }
.tokens span.touch { text-decoration: underline; text-decoration-thickness: 2px; }
.score { font: 15px ui-sans-serif, -apple-system, sans-serif; }

ol.rules { padding-left: 22px; }
ol.rules li { margin-bottom: 12px; }
table { border-collapse: collapse; width: 100%; font-size: 14px; }
th, td { text-align: left; padding: 7px 10px 7px 0; border-bottom: 1px solid var(--line); vertical-align: top; }
td.num, th.num { text-align: right; font-variant-numeric: tabular-nums; }
.scroll { overflow-x: auto; }
details > summary { cursor: pointer; min-height: 44px; display: flex; align-items: center; font-weight: 600; }
footer { max-width: 1040px; margin: 0 auto; padding: 26px 16px 48px; border-top: 1px solid var(--line); }

.zgrid { display: grid; grid-template-columns: repeat(auto-fill, minmax(190px, 1fr)); gap: 18px 16px; margin-block: 10px 18px; }
.zgrid.three { grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); }
.zcard h3 { font-size: 14px; font-weight: 600; min-height: 2.5em; margin-bottom: 6px; overflow-wrap: anywhere; }
.zcard.big h3 { font-size: 18px; min-height: 0; }
.zcard p { margin: 6px 0 0; font-size: 13px; line-height: 1.4; }
.zcard.big p { font-size: 14px; }
svg.zone { width: 100%; max-width: 180px; display: block; }
.zcard.big svg.zone { max-width: 260px; }
.zone .strip { fill: var(--hidden); opacity: .35; }
.zone .hub { fill: var(--hidden); opacity: .6; }
.zone .still, .swatch.still { fill: #2ea868; background: #2ea868; }
.zone .moved, .swatch.moved { fill: #e0a437; background: #e0a437; }
.zone .fr, .swatch.fr { fill: var(--hidden); background: var(--hidden); }
.zone .lit, .swatch.lit { fill: var(--accent); background: var(--accent); }
.zone .casing { fill: none; stroke: #fff; stroke-width: 4; }
.zone .route { fill: none; stroke: #16140f; stroke-width: 1.8; }
.route-head { fill: #16140f; stroke: #fff; stroke-width: 1; }
.zone .badge { fill: #16140f; stroke: #fff; stroke-width: 1; }
.zone .badge-text { fill: #fff; font: 700 10px ui-sans-serif, -apple-system, sans-serif; }
.zread { display: grid; grid-template-columns: minmax(0, 280px) minmax(0, 1fr); gap: 24px; align-items: start; }
@media (max-width: 760px) { .zread { grid-template-columns: minmax(0, 1fr); } }
.zkey { list-style: none; margin: 0; padding: 0; display: grid; gap: 10px; }
.zkey li { display: block; padding-left: 32px; position: relative; }
.swatch { position: absolute; left: 0; top: 4px; width: 20px; height: 20px; border-radius: 4px; display: block; }
.swatch.badge-key { background: #16140f; color: #fff; border: 1px solid #fff; border-radius: 50%; font: 700 11px/20px ui-sans-serif, -apple-system, sans-serif; text-align: center; }
ul.plain { padding-left: 20px; }
ul.plain li { margin-bottom: 8px; }
.zcase { padding-block: 14px 0; border-top: 1px solid var(--line); }
.zcase[hidden] { display: none; }