:root {
  /* Colors — Indigo accent palette */
  --color-primary: #4f46e5;
  --color-primary-hover: #4338ca;
  --color-primary-active: #3730a3;
  --color-primary-subtle: #eef2ff;

  --color-surface: #ffffff;
  --color-surface-raised: #ffffff;
  --color-surface-overlay: rgba(0, 0, 0, 0.5);
  --color-background: #f8fafc;

  --color-border: #e2e8f0;
  --color-border-hover: #cbd5e1;

  --color-text: #0f172a;
  --color-text-secondary: #475569;
  --color-text-tertiary: #94a3b8;
  --color-text-inverse: #ffffff;

  --color-success: #16a34a;
  --color-success-subtle: #f0fdf4;
  --color-warning: #d97706;
  --color-warning-subtle: #fffbeb;
  --color-error: #dc2626;
  --color-error-subtle: #fef2f2;
  --color-info: #2563eb;
  --color-info-subtle: #eff6ff;

  --color-drop-zone: #eef2ff;
  --color-drop-zone-active: #e0e7ff;
  --color-drop-zone-border: #a5b4fc;

  /* Spacing scale (4px base) */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;

  /* Typography — system font stack */
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --font-mono: 'SF Mono', 'Fira Code', 'Fira Mono', 'Roboto Mono', monospace;

  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.25rem;
  --text-2xl: 1.5rem;

  --leading-tight: 1.25;
  --leading-normal: 1.5;
  --leading-relaxed: 1.625;

  --weight-normal: 400;
  --weight-medium: 500;
  --weight-semibold: 600;
  --weight-bold: 700;

  /* Shadows */
  --shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1), 0 1px 2px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 8px 10px -6px rgba(0, 0, 0, 0.1);

  /* Radii */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 200ms ease;
  --transition-slow: 300ms ease;

  /* Z-index scale */
  --z-base: 0;
  --z-dropdown: 100;
  --z-sticky: 200;
  --z-modal-backdrop: 300;
  --z-modal: 400;
  --z-toast: 500;

  /* Layout */
  --header-height: 56px;
  --footer-height: 40px;
}

[data-theme="dark"] {
  --color-primary: #818cf8;
  --color-primary-hover: #a5b4fc;
  --color-primary-active: #6366f1;
  --color-primary-subtle: rgba(99, 102, 241, 0.15);

  --color-surface: #1e293b;
  --color-surface-raised: #273548;
  --color-surface-overlay: rgba(0, 0, 0, 0.7);
  --color-background: #0f172a;

  --color-border: #334155;
  --color-border-hover: #475569;

  --color-text: #f1f5f9;
  --color-text-secondary: #94a3b8;
  --color-text-tertiary: #64748b;
  --color-text-inverse: #0f172a;

  --color-success: #4ade80;
  --color-success-subtle: rgba(74, 222, 128, 0.1);
  --color-warning: #fbbf24;
  --color-warning-subtle: rgba(251, 191, 36, 0.1);
  --color-error: #f87171;
  --color-error-subtle: rgba(248, 113, 113, 0.1);
  --color-info: #60a5fa;
  --color-info-subtle: rgba(96, 165, 250, 0.1);

  --color-drop-zone: rgba(99, 102, 241, 0.08);
  --color-drop-zone-active: rgba(99, 102, 241, 0.15);
  --color-drop-zone-border: #6366f1;

  --shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.2);
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3), 0 1px 2px rgba(0, 0, 0, 0.2);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.3), 0 2px 4px -2px rgba(0, 0, 0, 0.2);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.3), 0 4px 6px -4px rgba(0, 0, 0, 0.2);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.3), 0 8px 10px -6px rgba(0, 0, 0, 0.2);
}