*, *::before, *::after { box-sizing: border-box; }
  [hidden] { display: none !important; }
  body {
    margin: 0;
    padding: 16px;
    font-family: var(--font-sans, system-ui, -apple-system, sans-serif);
    color: var(--color-text-primary, #111827);
    background: var(--color-background-primary, #ffffff);
    line-height: 1.5;
  }
  main {
    display: flex;
    flex-direction: column;
    gap: 16px;
    max-width: 1080px;
    margin: 0 auto;
  }
  header {
    display: flex;
    flex-direction: column;
    gap: 6px;
  }
  .back-link {
    font-size: 13px;
    color: var(--color-text-info, #2563eb);
    text-decoration: none;
    align-self: flex-start;
  }
  .back-link:hover { text-decoration: underline; }
  h1 { font-size: 20px; margin: 0; font-weight: 600; }
  h2 { font-size: 15px; margin: 0; font-weight: 600; }
  p { margin: 0; color: var(--color-text-secondary, #4b5563); font-size: 14px; }
  .toolbar {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    align-items: center;
    justify-content: space-between;
    padding: 10px 12px;
    background: var(--color-background-secondary, #f3f4f6);
    border: 1px solid var(--color-border-primary, #e5e7eb);
    border-radius: var(--border-radius-md, 8px);
  }
  .btn-group {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
    align-items: center;
  }
  .group-label {
    font-size: 12px;
    font-weight: 600;
    color: var(--color-text-secondary, #4b5563);
    margin-right: 4px;
  }
  button {
    font-family: inherit;
    font-size: 12.5px;
    font-weight: 500;
    padding: 6px 10px;
    border-radius: var(--border-radius-sm, 6px);
    border: 1px solid var(--color-border-primary, #d1d5db);
    background: var(--color-background-primary, #ffffff);
    color: var(--color-text-primary, #111827);
    cursor: pointer;
  }
  button[aria-pressed="true"] {
    background: var(--color-background-info, #dbeafe);
    color: var(--color-text-info, #1d4ed8);
    border-color: var(--color-text-info, #1d4ed8);
    font-weight: 600;
  }
  .workspace {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(310px, 1fr));
    gap: 16px;
    align-items: start;
  }
  .card {
    min-width: 0;
    background: var(--color-background-primary, #ffffff);
    border: 1px solid var(--color-border-primary, #e5e7eb);
    border-radius: var(--border-radius-md, 8px);
    padding: 12px;
    display: flex;
    flex-direction: column;
    gap: 12px;
  }
  .svg-wrap {
    width: 100%;
    border: 1px solid var(--color-border-secondary, #e5e7eb);
    border-radius: var(--border-radius-sm, 6px);
    background: var(--color-background-secondary, #f9fafb);
    overflow: hidden;
  }
  svg {
    display: block;
    width: 100%;
    height: auto;
    user-select: none;
  }
  .legend {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    font-size: 12px;
    color: var(--color-text-secondary, #4b5563);
  }
  .legend-item {
    display: inline-flex;
    align-items: center;
    gap: 6px;
  }
  .swatch {
    width: 14px;
    height: 3px;
    border-radius: 2px;
    display: inline-block;
  }
  .stat-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 8px;
  }
  .stat {
    padding: 8px 10px;
    border: 1px solid var(--color-border-primary, #e5e7eb);
    border-radius: var(--border-radius-sm, 6px);
    display: flex;
    flex-direction: column;
    gap: 2px;
  }
  .stat-label {
    font-size: 12px;
    color: var(--color-text-secondary, #4b5563);
  }
  .stat-val {
    font-family: var(--font-mono, ui-monospace, SFMono-Regular, Menlo, monospace);
    font-size: 13.5px;
    font-weight: 600;
  }
  .control-grid {
    display: flex;
    flex-direction: column;
    gap: 8px;
  }
  .control-row {
    display: flex;
    flex-direction: column;
    gap: 3px;
  }
  .control-header {
    display: flex;
    justify-content: space-between;
    align-items: baseline;
    font-size: 12.5px;
    font-weight: 500;
  }
  .mono {
    font-family: var(--font-mono, ui-monospace, SFMono-Regular, Menlo, monospace);
    font-size: 12.5px;
  }
  input[type="range"] {
    width: 100%;
    margin: 0;
    accent-color: var(--color-text-info, #2563eb);
  }
  .formula-box {
    background: var(--color-background-secondary, #f3f4f6);
    border: 1px solid var(--color-border-primary, #e5e7eb);
    border-radius: var(--border-radius-sm, 6px);
    padding: 10px 12px;
    display: flex;
    flex-direction: column;
    gap: 6px;
    font-size: 13px;
  }
  .formula-line {
    font-family: var(--font-mono, ui-monospace, SFMono-Regular, Menlo, monospace);
    font-size: 12.5px;
    overflow-x: auto;
  }
  .table-wrap {
    overflow-x: auto;
  }
  table {
    width: 100%;
    border-collapse: collapse;
    font-size: 12px;
  }
  th, td {
    text-align: left;
    padding: 6px 8px;
    border-bottom: 1px solid var(--color-border-primary, #e5e7eb);
    font-family: var(--font-mono, ui-monospace, SFMono-Regular, Menlo, monospace);
  }
  th {
    font-family: var(--font-sans, system-ui, sans-serif);
    font-weight: 600;
    color: var(--color-text-secondary, #4b5563);
  }