:root {
  --bg: #f5f7fb;
  --card: #ffffff;
  --text: #1f2937;
  --muted: #6b7280;
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --border: #dbe3ef;
  --soft: #eef4ff;
  --danger: #dc2626;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans JP", sans-serif;
  background: var(--bg);
  color: var(--text);
}
.site-header {
  padding: 28px clamp(16px, 4vw, 48px);
  background: linear-gradient(135deg, #1e3a8a, #2563eb);
  color: #fff;
}
.site-header h1 { margin: 4px 0 6px; font-size: clamp(1.6rem, 3vw, 2.4rem); }
.eyebrow { margin: 0; opacity: .86; font-size: .92rem; }
.subtitle { margin: 0; opacity: .9; }
.app-shell { padding: 18px clamp(12px, 3vw, 36px) 32px; max-width: 1500px; margin: 0 auto; }
.tabs { display: flex; gap: 8px; overflow-x: auto; padding: 8px 0 14px; }
.tab-btn {
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--text);
  padding: 10px 12px;
  border-radius: 999px;
  white-space: nowrap;
  cursor: pointer;
  font-weight: 600;
}
.tab-btn.active { background: var(--primary); color: white; border-color: var(--primary); }
.panel-grid { display: grid; grid-template-columns: minmax(280px, 380px) 1fr; gap: 18px; align-items: start; }
.controls-card, .result-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 18px;
  box-shadow: 0 10px 24px rgba(15, 23, 42, .06);
  padding: 18px;
}
.controls-card { position: sticky; top: 10px; max-height: calc(100vh - 20px); overflow-y: auto; }
.controls-card h2, .result-card h2 { margin: 0 0 12px; }
.group-title {
  font-weight: 800;
  margin: 20px 0 8px;
  padding-top: 14px;
  border-top: 1px solid var(--border);
}
.input-row { margin-bottom: 12px; }
.input-row label { display: block; font-size: .92rem; font-weight: 700; margin-bottom: 5px; }
.input-row input, .input-row select {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 9px 10px;
  font-size: 1rem;
  background: #fff;
}
.radio-row { display: grid; gap: 6px; }
.radio-row label { font-weight: 500; display: flex; align-items: center; gap: 6px; }
.secondary-btn {
  border: 1px solid var(--border);
  background: var(--soft);
  color: #15316d;
  padding: 9px 12px;
  border-radius: 10px;
  cursor: pointer;
  font-weight: 700;
}
.secondary-btn:hover { background: #dfeaff; }
.plot-toolbar { display: flex; justify-content: space-between; align-items: center; gap: 12px; }
.plot { width: 100%; min-height: 460px; }
.outputs { display: grid; gap: 9px; margin-top: 10px; }
.output-line {
  border: 1px solid var(--border);
  background: #fbfdff;
  border-radius: 12px;
  padding: 10px 12px;
  line-height: 1.55;
}
.output-line.warn { border-color: #f59e0b; background: #fffbeb; }
.formula-box { margin-top: 18px; border-top: 1px solid var(--border); padding-top: 12px; }
.formula-box summary { cursor: pointer; font-weight: 800; margin-bottom: 10px; }
.formula-box h4 { margin: 16px 0 6px; }
.formula-box p { line-height: 1.7; }
.footer { max-width: 1500px; margin: 0 auto; padding: 0 clamp(12px, 3vw, 36px) 30px; color: var(--muted); }
@media (max-width: 900px) {
  .panel-grid { grid-template-columns: 1fr; }
  .controls-card { position: static; max-height: none; }
  .plot { min-height: 380px; }
}