:root {
  --bg: #f4f6f8;
  --card: #fff;
  --text: #1c2733;
  --muted: #64748b;
  --primary: #2563eb;
  --danger: #dc2626;
  --free: #e7f6ec;
  --free-text: #166534;
  --busy: #fde8e8;
  --busy-text: #991b1b;
  --border: #dbe1e8;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  padding: 16px;
  font-family: system-ui, -apple-system, 'Hiragino Sans', 'Noto Sans JP', sans-serif;
  background: var(--bg);
  color: var(--text);
}
main { max-width: 560px; margin: 0 auto; }
h1 { font-size: 1.25rem; margin: 8px 0 16px; }
h2 { font-size: 1rem; margin: 0 0 12px; }
.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px;
  margin-bottom: 16px;
}
label { display: block; font-size: 0.875rem; color: var(--muted); margin-bottom: 6px; }
input {
  width: 100%;
  padding: 12px;
  font-size: 1rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  margin-bottom: 12px;
}
button {
  width: 100%;
  padding: 14px;
  font-size: 1rem;
  font-weight: 600;
  color: #fff;
  background: var(--primary);
  border: 0;
  border-radius: 8px;
}
button.danger { background: var(--danger); }
button:disabled { opacity: 0.5; }
button + button { margin-top: 8px; }
.message { margin: 12px 0 0; font-size: 0.9rem; min-height: 1.2em; }
.message.error { color: var(--danger); }
.message.ok { color: var(--free-text); }
.muted { color: var(--muted); font-size: 0.875rem; }
.status { font-size: 1.05rem; margin: 0 0 12px; }
.seats { display: grid; grid-template-columns: repeat(auto-fill, minmax(120px, 1fr)); gap: 8px; }
.seat { border-radius: 8px; padding: 10px; background: var(--free); color: var(--free-text); }
.seat.busy { background: var(--busy); color: var(--busy-text); }
.seat.mine { outline: 2px solid var(--primary); }
.seat .label { font-weight: 600; }
.seat .who { font-size: 0.85rem; margin-top: 4px; }
[hidden] { display: none !important; }