:root {
  --bg: #0d1117; --panel: #161b22; --line: #30363d;
  --fg: #e6edf3; --muted: #8b949e; --accent: #2f81f7; --good: #3fb950;
}
* { box-sizing: border-box; }
body {
  margin: 0; background: var(--bg); color: var(--fg);
  font: 14px/1.45 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}
header {
  display: flex; align-items: center; justify-content: space-between;
  padding: 12px 18px; border-bottom: 1px solid var(--line);
}
header h1 { font-size: 18px; margin: 0; }
.router-pill {
  font-size: 12px; color: var(--muted); background: #21262d;
  border: 1px solid var(--line); border-radius: 999px; padding: 6px 12px;
}
.router-pill.live { color: var(--good); border-color: var(--good); }
.layout { display: flex; gap: 18px; padding: 18px; align-items: flex-start; }
.panel { width: 290px; flex: none; display: flex; flex-direction: column; gap: 16px; }
.panel section {
  background: var(--panel); border: 1px solid var(--line);
  border-radius: 10px; padding: 14px;
}
.panel h2 { font-size: 12px; text-transform: uppercase; letter-spacing: .06em;
  color: var(--muted); margin: 0 0 10px; }
h2.toggle { cursor: pointer; display: flex; justify-content: space-between; align-items: center;
  user-select: none; margin-bottom: 0; }
h2.toggle:hover { color: var(--fg); }
h2.toggle .caret { transition: transform .15s; font-size: 10px; }
h2.toggle.open .caret { transform: rotate(90deg); }
h2.toggle.open { margin-bottom: 10px; }
#txSummary { margin-top: 8px; }
.help { font-size: 12.5px; color: var(--fg); line-height: 1.5; }
.help p { margin: 8px 0; }
.help ul { margin: 6px 0; padding-left: 18px; }
.help li { margin: 2px 0; }
.help .formula { background: #0a0d12; border: 1px solid var(--line); border-radius: 6px;
  padding: 8px; font-size: 12px; color: var(--accent); }
label.row { display: flex; flex-direction: column; gap: 6px; margin: 10px 0; font-size: 13px; }
input[type=range] { width: 100%; accent-color: var(--accent); }
select, button {
  background: #21262d; color: var(--fg); border: 1px solid var(--line);
  border-radius: 7px; padding: 8px 10px; font-size: 13px; cursor: pointer;
}
button:hover { border-color: var(--accent); }
button:disabled { opacity: .45; cursor: not-allowed; }
button.primary { background: var(--accent); border-color: var(--accent); color: #fff; width: 100%; }
.tools { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 8px; }
.tools button { flex: 1 1 calc(50% - 6px); }
.tool.active, .mode.active { border-color: var(--accent); background: #1f6feb33; color: #fff; }
#clearWalls, #resetRoom, #calibrate { width: 100%; margin-top: 6px; }
.kv { font-size: 12px; margin-top: 10px; white-space: pre-wrap; }
.muted { color: var(--muted); }
.kv b { color: var(--fg); }
.legend { display: flex; align-items: center; gap: 8px; font-size: 11px; color: var(--muted); margin-top: 6px; }
#legendBar { flex: 1; height: 12px; border-radius: 4px;
  background: linear-gradient(90deg,#1a9850,#a6d96a,#fee08b,#fdae61,#d73027,#4a0c0c); }
main { flex: 1; }
canvas { background: #0a0d12; border: 1px solid var(--line); border-radius: 10px;
  width: 100%; height: auto; cursor: crosshair; display: block; }
.hint { color: var(--muted); font-size: 12px; margin: 10px 2px; }