:root {
  /* Backgrounds */
  --bg-app:           #0E1014;
  --bg-surface:       #161A22;
  --bg-surface-2:     #1E2330;
  --bg-canvas:        #0A0B0F;

  /* Text */
  --text-primary:     #E6E9EF;
  --text-secondary:   #9AA3B2;
  --text-tertiary:    #5C6573;
  --text-on-hot:      #1A0E08;

  /* Borders / dividers */
  --border-subtle:    #232A38;
  --border-default:   #2E3647;
  --border-strong:    #41506A;

  /* Hot-metal accent (primary) */
  --accent-hot:       #FF7A1A;
  --accent-hot-dim:   #B9551A;
  --accent-hot-glow:  rgba(255, 122, 26, 0.18);

  /* Steel-blue accent (secondary, data/info) */
  --accent-cool:      #4FA3C7;
  --accent-cool-dim:  #346F8A;

  /* Status */
  --ok:               #4CAF82;
  --warn:             #E8A43B;
  --err:              #E5544B;

  /* IR / canvas-specific */
  --crucible-stroke:  #A89684;
  --isotherm:         rgba(255, 255, 255, 0.10);
  --flow-particle:    rgba(255, 240, 220, 0.80);
  --dim-line:         rgba(154, 163, 178, 0.40);

  /* Typography stacks (system only — no web fonts) */
  --font-sans: ui-sans-serif, -apple-system, BlinkMacSystemFont, "Inter", "Segoe UI",
               Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, "SF Mono", "JetBrains Mono", "Fira Code", "Cascadia Code",
               Menlo, Consolas, "Liberation Mono", monospace;

  /* Type scale (rem, 16px base) */
  --fs-caption: 0.75rem;
  --fs-small:   0.8125rem;
  --fs-body:    0.875rem;
  --fs-h3:      1.0rem;
  --fs-h2:      1.125rem;
  --fs-h1:      1.375rem;

  /* Spacing scale */
  --sp-1: 4px;
  --sp-2: 8px;
  --sp-3: 12px;
  --sp-4: 16px;
  --sp-5: 24px;
  --sp-6: 32px;
  --sp-7: 48px;

  /* Radii */
  --r-sm: 4px;
  --r-md: 6px;
  --r-lg: 10px;

  /* Header height */
  --header-h: 48px;
}