@import url('https://fonts.googleapis.com/css2?family=Source+Sans+3:wght@300;400;600;700&family=Merriweather:wght@400;700&display=swap');
 
  /* ── USWDS-inspired tokens ── */
  :root {
    --usa-blue-warm-70: #162e51;
    --usa-blue-warm-60: #2e4a72;
    --usa-blue-warm-50: #2c608a;
    --usa-blue-vivid-30: #2491ff;
    --usa-blue-vivid-20: #58b4ff;
    --usa-gold-20: #ffbc78;
    --usa-gold-10: #ffe396;
    --usa-red-warm-50: #d54309;
    --usa-green-cool-50: #21827f;
    --usa-gray-cool-2: #f5f6f7;
    --usa-gray-cool-5: #edeff0;
    --usa-gray-cool-10: #dfe1e2;
    --usa-gray-cool-30: #a9aeb1;
    --usa-gray-cool-50: #71767a;
    --usa-gray-cool-70: #3d4551;
    --usa-gray-cool-90: #1b1b1b;
    --usa-white: #ffffff;
    --font-body: 'Source Sans 3', 'Helvetica Neue', Helvetica, Arial, sans-serif;
    --font-heading: 'Merriweather', Georgia, 'Times New Roman', serif;
    --line-height: 1.625;
    --radius: 0;
    --shadow-card: 0 1px 4px rgba(0,0,0,0.08), 0 2px 8px rgba(0,0,0,0.04);
    --shadow-card-hover: 0 2px 8px rgba(0,0,0,0.12), 0 4px 16px rgba(0,0,0,0.06);
  }
 
  *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
 
  body {
    font-family: var(--font-body);
    font-size: 16px;
    color: var(--usa-gray-cool-90);
    background: var(--usa-gray-cool-2);
    -webkit-font-smoothing: antialiased;
  }
 
  /* ── Official banner bar ── */
  .usa-banner {
    background: var(--usa-blue-warm-70);
    color: var(--usa-white);
    font-size: 13px;
    font-weight: 600;
    letter-spacing: 0.02em;
    padding: 6px 24px;
    display: flex;
    align-items: center;
    gap: 8px;
  }
  .usa-banner .tag {
    background: var(--usa-blue-vivid-30);
    color: var(--usa-white);
    font-size: 10px;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    padding: 2px 8px;
    border-radius: 2px;
  }
 
  /* ── Page header ── */
  .page-header {
    background: var(--usa-white);
    border-bottom: 4px solid var(--usa-blue-vivid-30);
    padding: 32px 24px 28px;
    max-width: 1200px;
    margin: 0 auto;
  }
  .page-header h1 {
    font-family: var(--font-heading);
    font-size: clamp(24px, 4vw, 34px);
    font-weight: 700;
    color: var(--usa-blue-warm-70);
    margin-bottom: 8px;
  }
  .page-header p {
    color: var(--usa-gray-cool-50);
    font-size: 16px;
    line-height: 1.5;
    max-width: 680px;
  }
  .page-header a {
    color: var(--usa-blue-vivid-30);
    text-decoration: underline;
    text-underline-offset: 2px;
  }
 
  /* ── Sections ── */
  .container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
  }
 
  section {
    margin: 32px 0;
  }
 
  .section-label {
    font-size: 12px;
    font-weight: 700;
    letter-spacing: 0.1em;
    text-transform: uppercase;
    color: var(--usa-blue-warm-60);
    margin-bottom: 4px;
  }
  .section-title {
    font-family: var(--font-heading);
    font-size: 22px;
    font-weight: 700;
    color: var(--usa-blue-warm-70);
    margin-bottom: 6px;
  }
  .section-desc {
    color: var(--usa-gray-cool-50);
    font-size: 14px;
    margin-bottom: 20px;
    max-width: 640px;
  }
 
  /* ── Height Predictor Panel ── */
  .predictor-panel {
    background: var(--usa-white);
    border: 1px solid var(--usa-gray-cool-10);
    box-shadow: var(--shadow-card);
    padding: 24px;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 24px;
  }
  @media (max-width: 720px) {
    .predictor-panel { grid-template-columns: 1fr; }
  }
 
  .predictor-controls label {
    display: block;
    font-size: 13px;
    font-weight: 600;
    color: var(--usa-gray-cool-70);
    margin-bottom: 4px;
    letter-spacing: 0.01em;
  }
  .predictor-controls textarea {
    width: 100%;
    min-height: 120px;
    padding: 10px 12px;
    font-family: var(--font-body);
    font-size: 16px;
    line-height: var(--line-height);
    color: var(--usa-gray-cool-90);
    border: 1px solid var(--usa-gray-cool-30);
    border-radius: var(--radius);
    resize: vertical;
    outline: none;
    transition: border-color 0.15s;
  }
  .predictor-controls textarea:focus {
    border-color: var(--usa-blue-vivid-30);
    box-shadow: 0 0 0 2px rgba(36, 145, 255, 0.25);
  }
 
  .slider-group {
    margin-top: 16px;
  }
  .slider-group .slider-header {
    display: flex;
    justify-content: space-between;
    align-items: baseline;
  }
  .slider-group .slider-value {
    font-size: 14px;
    font-weight: 700;
    color: var(--usa-blue-vivid-30);
    font-variant-numeric: tabular-nums;
  }
  .slider-group input[type="range"] {
    width: 100%;
    margin-top: 4px;
    accent-color: var(--usa-blue-vivid-30);
    cursor: pointer;
  }
  .font-select-group {
    margin-top: 16px;
  }
  .font-select-group select {
    width: 100%;
    padding: 8px 10px;
    font-family: var(--font-body);
    font-size: 14px;
    border: 1px solid var(--usa-gray-cool-30);
    border-radius: var(--radius);
    background: var(--usa-white);
    color: var(--usa-gray-cool-90);
    cursor: pointer;
  }
 
  /* ── Results readout ── */
  .predictor-results {
    display: flex;
    flex-direction: column;
    gap: 16px;
  }
  .result-box {
    background: var(--usa-gray-cool-2);
    border: 1px solid var(--usa-gray-cool-10);
    padding: 16px;
    flex: 1;
  }
  .result-box h3 {
    font-size: 12px;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--usa-gray-cool-50);
    margin-bottom: 10px;
    display: flex;
    align-items: center;
    gap: 6px;
  }
  .result-box h3 .dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    display: inline-block;
  }
  .dot-pretext { background: var(--usa-blue-vivid-30); }
  .dot-dom { background: var(--usa-red-warm-50); }
 
  .metrics-grid {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
    gap: 12px;
  }
  .metric {
    text-align: center;
  }
  .metric .metric-value {
    font-size: 28px;
    font-weight: 700;
    font-variant-numeric: tabular-nums;
    line-height: 1.1;
  }
  .metric-pretext .metric-value { color: var(--usa-blue-vivid-30); }
  .metric-dom .metric-value { color: var(--usa-red-warm-50); }
  .metric .metric-label {
    font-size: 11px;
    font-weight: 600;
    color: var(--usa-gray-cool-50);
    text-transform: uppercase;
    letter-spacing: 0.06em;
    margin-top: 2px;
  }
 
  .speedup-bar {
    margin-top: 16px;
    padding: 12px 16px;
    background: var(--usa-blue-warm-70);
    color: var(--usa-white);
    font-size: 14px;
    font-weight: 600;
    display: flex;
    justify-content: space-between;
    align-items: center;
  }
  .speedup-bar .speedup-value {
    font-size: 22px;
    font-weight: 700;
    color: var(--usa-gold-20);
    font-variant-numeric: tabular-nums;
  }
 
  /* ── Live preview stripe ── */
  .live-preview-wrap {
    margin-top: 16px;
    border: 2px dashed var(--usa-gray-cool-10);
    padding: 12px;
    position: relative;
    overflow: hidden;
    background: repeating-linear-gradient(
      90deg,
      transparent,
      transparent 19px,
      rgba(0,0,0,0.02) 19px,
      rgba(0,0,0,0.02) 20px
    );
  }
  .live-preview-wrap .preview-text {
    font-family: var(--font-body);
    line-height: var(--line-height);
    color: var(--usa-gray-cool-90);
    word-wrap: break-word;
    overflow-wrap: break-word;
  }
  .height-indicator {
    position: absolute;
    right: 0;
    top: 0;
    width: 3px;
    background: var(--usa-blue-vivid-30);
    transition: height 0.15s ease;
    opacity: 0.6;
  }
 
  /* ── Masonry Grid ── */
  .masonry-controls {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
    align-items: flex-end;
    margin-bottom: 16px;
  }
  .masonry-controls .control-group {
    display: flex;
    flex-direction: column;
    gap: 4px;
  }
  .masonry-controls label {
    font-size: 12px;
    font-weight: 600;
    color: var(--usa-gray-cool-70);
    text-transform: uppercase;
    letter-spacing: 0.06em;
  }
  .masonry-controls select,
  .masonry-controls input[type="range"] {
    font-family: var(--font-body);
    font-size: 14px;
  }
  .masonry-controls select {
    padding: 6px 8px;
    border: 1px solid var(--usa-gray-cool-30);
    border-radius: var(--radius);
    background: var(--usa-white);
    cursor: pointer;
  }
  .masonry-controls input[type="range"] {
    width: 140px;
    accent-color: var(--usa-blue-vivid-30);
    cursor: pointer;
  }
  .masonry-timing {
    font-size: 12px;
    font-weight: 600;
    color: var(--usa-green-cool-50);
    background: rgba(33,130,127,0.08);
    padding: 6px 12px;
    border: 1px solid rgba(33,130,127,0.2);
    margin-left: auto;
    font-variant-numeric: tabular-nums;
    white-space: nowrap;
  }
 
  .masonry-grid {
    display: flex;
    gap: 16px;
    align-items: flex-start;
  }
  .masonry-column {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 16px;
  }
  .masonry-card {
    background: var(--usa-white);
    border: 1px solid var(--usa-gray-cool-10);
    box-shadow: var(--shadow-card);
    padding: 20px;
    transition: box-shadow 0.2s, transform 0.2s;
    position: relative;
    overflow: hidden;
  }
  .masonry-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
  }
  .masonry-card:nth-child(4n+1)::before { background: var(--usa-blue-vivid-30); }
  .masonry-card:nth-child(4n+2)::before { background: var(--usa-red-warm-50); }
  .masonry-card:nth-child(4n+3)::before { background: var(--usa-green-cool-50); }
  .masonry-card:nth-child(4n)::before { background: var(--usa-gold-20); }
 
  .masonry-card:hover {
    box-shadow: var(--shadow-card-hover);
    transform: translateY(-1px);
  }
 
  .card-tag {
    font-size: 11px;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    margin-bottom: 6px;
    color: var(--usa-blue-warm-60);
  }
  .card-title {
    font-family: var(--font-heading);
    font-size: 16px;
    font-weight: 700;
    line-height: 1.35;
    color: var(--usa-blue-warm-70);
    margin-bottom: 8px;
  }
  .card-body {
    font-size: 14px;
    line-height: var(--line-height);
    color: var(--usa-gray-cool-70);
  }
  .card-meta {
    margin-top: 12px;
    padding-top: 10px;
    border-top: 1px solid var(--usa-gray-cool-5);
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 11px;
    color: var(--usa-gray-cool-30);
    font-variant-numeric: tabular-nums;
  }
  .card-meta .predicted {
    color: var(--usa-blue-vivid-30);
    font-weight: 600;
  }
 
  /* ── Footer ── */
  .demo-footer {
    margin-top: 48px;
    padding: 20px 24px;
    background: var(--usa-blue-warm-70);
    color: rgba(255,255,255,0.6);
    font-size: 13px;
    text-align: center;
  }
  .demo-footer a {
    color: var(--usa-blue-vivid-20);
    text-decoration: underline;
    text-underline-offset: 2px;
  }
 
  /* ── Loading state ── */
  .loading-overlay {
    position: fixed;
    inset: 0;
    background: var(--usa-white);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 999;
    transition: opacity 0.3s;
  }
  .loading-overlay.hidden {
    opacity: 0;
    pointer-events: none;
  }
  .loading-spinner {
    width: 32px;
    height: 32px;
    border: 3px solid var(--usa-gray-cool-10);
    border-top-color: var(--usa-blue-vivid-30);
    border-radius: 50%;
    animation: spin 0.7s linear infinite;
  }
  @keyframes spin { to { transform: rotate(360deg); } }