:root {
  --ink: #172033;
  --muted: #637083;
  --panel: #ffffff;
  --bg: #f4f6fa;
  --line: #d9e0ea;
  --accent: #2639a8;
  --frontier: #f0b429;
  --explored: #8c98a8;
  --current: #e54b4b;
  --solution: #2f9e68;
  --beam: #7a4fd0;
  --board-light: #edf1f7;
  --board-dark: #8c9aaf;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  color: var(--ink);
  background: var(--bg);
}

header {
  padding: 42px max(24px, calc((100vw - 1180px) / 2));
  background: linear-gradient(120deg, #182671, #3047c5);
  color: white;
}

header h1 {
  margin: 6px 0 8px;
  font-size: clamp(28px, 4vw, 46px);
}

header p {
  margin: 0;
  max-width: 860px;
  line-height: 1.55;
}

.eyebrow {
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: .12em;
  opacity: .82;
}

main {
  max-width: 1180px;
  margin: 0 auto;
  padding: 28px 24px 48px;
}

.card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 14px;
  box-shadow: 0 8px 24px rgba(19, 34, 62, .05);
}

.controls {
  display: flex;
  gap: 18px;
  align-items: end;
  justify-content: space-between;
  padding: 18px;
  margin-bottom: 20px;
}

.algorithm-control { flex: 1; }

label {
  display: block;
  font-size: 13px;
  font-weight: 700;
  margin-bottom: 6px;
}

select,
button {
  font: inherit;
  border-radius: 9px;
  border: 1px solid #bcc6d4;
  background: white;
  padding: 10px 12px;
}

select {
  width: min(520px, 100%);
  min-width: 320px;
}

button {
  cursor: pointer;
  font-weight: 650;
}

button:hover:not(:disabled) { background: #eef1f7; }
button:disabled { opacity: .45; cursor: not-allowed; }

.buttons { display: flex; gap: 8px; }

.grid {
  display: grid;
  grid-template-columns: minmax(0, 1.65fr) minmax(300px, .85fr);
  gap: 20px;
}

.visualization-card,
.state-card,
.integrity,
.focus { padding: 20px; }

.section-title {
  display: flex;
  align-items: start;
  justify-content: space-between;
  gap: 12px;
}

.section-title h2 { margin: 5px 0 0; }

.step-counter {
  color: var(--muted);
  font-size: 13px;
  font-weight: 700;
  white-space: nowrap;
}

.badge {
  display: inline-block;
  padding: 4px 8px;
  border-radius: 999px;
  background: #edf0ff;
  color: #273b9f;
  font-size: 12px;
  font-weight: 750;
}

.muted { color: var(--muted); line-height: 1.5; }
.hidden { display: none !important; }

#graph {
  width: 100%;
  min-height: 360px;
  margin-top: 10px;
}

.edge { stroke: #aeb8c6; stroke-width: 3; }
.edge.solution-edge { stroke: var(--solution); stroke-width: 7; }

.edge-label {
  fill: #4c586b;
  font-size: 15px;
  font-weight: 700;
  paint-order: stroke;
  stroke: white;
  stroke-width: 5px;
}

.node circle { fill: white; stroke: #7c899b; stroke-width: 4; }
.node text.main { font-size: 22px; font-weight: 800; fill: var(--ink); }
.node text.h { font-size: 12px; fill: var(--muted); }
.node.frontier circle { stroke: var(--frontier); stroke-width: 7; }
.node.beam circle { stroke: var(--beam); stroke-width: 8; }
.node.explored circle { fill: #eef1f4; stroke: var(--explored); }
.node.current circle { fill: #fff1f1; stroke: var(--current); stroke-width: 8; }
.node.solution circle { fill: #e9f8ef; stroke: var(--solution); stroke-width: 8; }

.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  color: var(--muted);
  font-size: 13px;
}

.dot {
  display: inline-block;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  margin-right: 5px;
}

.dot.current { background: var(--current); }
.dot.beam { background: var(--beam); }
.dot.frontier { background: var(--frontier); }
.dot.explored { background: var(--explored); }
.dot.solution { background: var(--solution); }

.state-card h2 { margin-top: 0; }

dl {
  display: grid;
  grid-template-columns: 122px 1fr;
  gap: 8px 10px;
}

dt { font-weight: 750; color: #445066; }
dd { margin: 0; word-break: break-word; }

#scores { display: grid; gap: 6px; }

.score {
  padding: 7px 9px;
  background: #f5f7fb;
  border: 1px solid #e1e6ee;
  border-radius: 8px;
}

.note {
  margin-top: 18px;
  padding: 14px;
  border-left: 4px solid var(--accent);
  background: #f3f5ff;
  border-radius: 8px;
}

.note p { margin: 5px 0 0; line-height: 1.45; }
.focus, .integrity { margin-top: 20px; }
.focus h2, .integrity h2 { margin-top: 0; }
.focus p, .integrity p { margin-bottom: 0; line-height: 1.65; }

.boards {
  display: grid;
  grid-template-columns: repeat(2, minmax(220px, 1fr));
  gap: 22px;
  margin-top: 22px;
}

.board-panel {
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: #fafbfe;
}

.board-panel h3 { margin: 0 0 10px; font-size: 15px; }
.board-panel.accepted { border-color: #7ac59d; box-shadow: inset 0 0 0 2px #d8f0e3; }
.board-panel.rejected { border-color: #dc9c9c; box-shadow: inset 0 0 0 2px #fae2e2; }

.chessboard {
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  width: min(100%, 330px);
  aspect-ratio: 1;
  border: 2px solid #5b6575;
  border-radius: 6px;
  overflow: hidden;
  margin: 0 auto;
}

.square { display: grid; place-items: center; aspect-ratio: 1; }
.square.light { background: var(--board-light); }
.square.dark { background: var(--board-dark); }

.queen {
  font-size: clamp(20px, 4vw, 36px);
  line-height: 1;
  color: #172033;
  text-shadow: 0 1px 0 rgba(255, 255, 255, .5);
}

.board-caption {
  margin: 9px 0 0;
  color: var(--muted);
  font-size: 12px;
  text-align: center;
  line-height: 1.45;
}

.board-help {
  margin: 16px 0 0;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.55;
}

.population {
  display: grid;
  grid-template-columns: repeat(2, minmax(180px, 1fr));
  gap: 16px;
  margin-top: 22px;
}

.individual {
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: #fafbfe;
}

.individual.best { border-color: #7ac59d; box-shadow: inset 0 0 0 2px #d8f0e3; }
.individual h3 { margin: 0 0 9px; font-size: 14px; text-align: center; }
.chessboard.mini { width: min(100%, 210px); }
.chessboard.mini .queen { font-size: clamp(13px, 2.5vw, 23px); }

.load-error {
  max-width: 1180px;
  margin: 20px auto;
  padding: 14px 24px;
  color: #8d1f1f;
}

@media (max-width: 850px) {
  .grid { grid-template-columns: 1fr; }
  .controls { align-items: stretch; flex-direction: column; }
  select { width: 100%; min-width: 0; }
  .buttons { flex-wrap: wrap; }
}

@media (max-width: 620px) {
  .boards, .population { grid-template-columns: 1fr; }
  dl { grid-template-columns: 105px 1fr; }
}