:root {
  --bg: #ffffff; --fg: #1a1f24; --muted: #5a6672; --line: #d8dee4;
  --accent: #3a6ea5; --ok: #2e7d46; --bad: #b3261e; --panel: #f6f8fa;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #14181c; --fg: #e6edf3; --muted: #9aa7b2; --line: #2a323a;
    --accent: #6ea3d8; --ok: #4cc46a; --bad: #f0857d; --panel: #1b2127;
  }
}
* { box-sizing: border-box; }
body {
  margin: 0; font: 15px/1.5 system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
  color: var(--fg); background: var(--bg);
}
header { padding: 1.2rem 1.5rem 0.4rem; }
h1 { margin: 0; font-size: 1.4rem; letter-spacing: -0.01em; }
.tag { margin: 0.2rem 0 0; color: var(--muted); }
main { display: grid; grid-template-columns: 320px 1fr; gap: 1rem; padding: 1rem 1.5rem; }
@media (max-width: 760px) { main { grid-template-columns: 1fr; } }
.controls { background: var(--panel); border: 1px solid var(--line); border-radius: 10px; padding: 1rem; }
.row { display: flex; flex-wrap: wrap; gap: 0.6rem; align-items: center; margin-bottom: 0.7rem; }
label { display: flex; flex-direction: column; font-size: 0.82rem; color: var(--muted); gap: 0.2rem; }
label.check { flex-direction: row; align-items: center; gap: 0.35rem; color: var(--fg); }
input[type=number] { width: 72px; }
input, button { font: inherit; padding: 0.35rem 0.5rem; border-radius: 7px;
  border: 1px solid var(--line); background: var(--bg); color: var(--fg); }
button { cursor: pointer; background: var(--accent); color: #fff; border: none; padding: 0.45rem 0.9rem; }
button:disabled { opacity: 0.5; cursor: default; }
#status { font-size: 0.82rem; color: var(--muted); }
.report { font-size: 0.82rem; color: var(--muted); min-height: 1.2em; margin: 0.3rem 0 0; }
.hint { font-size: 0.76rem; color: var(--muted); margin: 0 0 0.7rem; }
.swatch { display: inline-block; width: 0.8em; height: 0.8em; border-radius: 2px; vertical-align: middle; }
.swatch.part { background: var(--accent); opacity: 0.5; }
.swatch.hole { background: transparent; border: 1.2px dashed var(--bad); }
.stage { border: 1px solid var(--line); border-radius: 10px; overflow: hidden; background: var(--panel); }
#canvas { width: 100%; height: 68vh; display: block; }
.sheet { fill: none; stroke: var(--muted); stroke-width: 1.5; }
.part { fill: var(--accent); fill-opacity: 0.28; stroke: var(--accent); stroke-width: 1; }
.part.invalid { fill: var(--bad); stroke: var(--bad); }
.hole { fill: var(--bad); fill-opacity: 0.1; stroke: var(--bad); stroke-width: 1.2; stroke-dasharray: 5 4; }
footer { padding: 0.8rem 1.5rem 1.4rem; color: var(--muted); font-size: 0.82rem; border-top: 1px solid var(--line); }
footer a { color: var(--accent); }
code { background: var(--panel); padding: 0.05em 0.3em; border-radius: 4px; }