:root {
  /* ─── Neutral Scale ─── (Notion warm-gray + Linear cool-gray blend) */
  --color-neutral-50:  #fafafa;
  --color-neutral-100: #f5f5f4;
  --color-neutral-150: #efefee;
  --color-neutral-200: #e5e5e4;
  --color-neutral-300: #d4d4d4;
  --color-neutral-400: #a3a3a3;
  --color-neutral-500: #737373;
  --color-neutral-600: #525252;
  --color-neutral-700: #404040;
  --color-neutral-800: #262626;
  --color-neutral-900: #171717;

  /* ─── Primary ─── (Linear-inspired indigo) */
  --color-primary-50:  #eef2ff;
  --color-primary-100: #e0e7ff;
  --color-primary-200: #c7d2fe;
  --color-primary-300: #a5b4fc;
  --color-primary-400: #818cf8;
  --color-primary-500: #6366f1;
  --color-primary-600: #4f46e5;
  --color-primary-700: #4338ca;
  --color-primary-800: #3730a3;
  --color-primary-900: #312e81;

  /* ─── Semantic ─── */
  --color-success-50:  #f0fdf4;
  --color-success-100: #dcfce7;
  --color-success-200: #bbf7d0;
  --color-success-300: #86efac;
  --color-success-400: #4ade80;
  --color-success-500: #22c55e;
  --color-success-600: #16a34a;
  --color-success-700: #15803d;
  --color-success-800: #166534;
  --color-success-900: #14532d;

  --color-warning-50:  #fffbeb;
  --color-warning-100: #fef3c7;
  --color-warning-200: #fde68a;
  --color-warning-300: #fcd34d;
  --color-warning-400: #fbbf24;
  --color-warning-500: #f59e0b;
  --color-warning-600: #d97706;
  --color-warning-700: #b45309;
  --color-warning-800: #92400e;
  --color-warning-900: #78350f;

  --color-danger-50:  #fef2f2;
  --color-danger-100: #fee2e2;
  --color-danger-200: #fecaca;
  --color-danger-300: #fca5a5;
  --color-danger-400: #f87171;
  --color-danger-500: #ef4444;
  --color-danger-600: #dc2626;
  --color-danger-700: #b91c1c;
  --color-danger-800: #991b1b;
  --color-danger-900: #7f1d1d;

  --color-info-50:  #f0f9ff;
  --color-info-100: #e0f2fe;
  --color-info-200: #bae6fd;
  --color-info-300: #7dd3fc;
  --color-info-400: #38bdf8;
  --color-info-500: #0ea5e9;
  --color-info-600: #0284c7;
  --color-info-700: #0369a1;
  --color-info-800: #075985;
  --color-info-900: #0c4a6e;

  /* ─── Priority (Todoist-inspired) ─── */
  --color-priority-high:   #dc2626;
  --color-priority-medium: #d97706;
  --color-priority-low:    #16a34a;

  /* ─── Surface / Background ─── */
  --color-bg:            var(--color-neutral-50);
  --color-bg-subtle:     var(--color-neutral-100);
  --color-surface:       #ffffff;
  --color-surface-hover: var(--color-neutral-100);
  --color-surface-active:var(--color-neutral-150);
  --color-surface-raised: #ffffff;
  --color-surface-overlay: rgba(0, 0, 0, 0.45);

  /* ─── Border ─── */
  --color-border:       var(--color-neutral-200);
  --color-border-light: var(--color-neutral-100);
  --color-border-hover: var(--color-neutral-300);
  --color-border-focus: var(--color-primary-500);
  --color-divider:      var(--color-neutral-150);

  /* ─── Text ─── */
  --color-text:           var(--color-neutral-900);
  --color-text-secondary: var(--color-neutral-600);
  --color-text-tertiary:  var(--color-neutral-400);
  --color-text-muted:     var(--color-neutral-400);
  --color-text-inverse:   #ffffff;
  --color-text-on-primary: #ffffff;
  --color-link:           var(--color-primary-600);
  --color-link-hover:     var(--color-primary-700);

  /* ─── Semantic Shortcuts ─── */
  --color-primary:   var(--color-primary-600);
  --color-primary-light:  var(--color-primary-400);
  --color-primary-dark:   var(--color-primary-800);
  --color-secondary: var(--color-info-500);
  --color-success:   var(--color-success-500);
  --color-warning:   var(--color-warning-500);
  --color-danger:    var(--color-danger-500);
  --color-info:      var(--color-info-500);

  /* ─── Typography ─── */
  --font-sans:    'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  --font-mono:    'JetBrains Mono', 'SF Mono', 'Fira Code', 'Cascadia Code', monospace;

  --text-xs:   0.75rem;     /* 12px */
  --text-sm:   0.875rem;    /* 14px */
  --text-base: 1rem;        /* 16px */
  --text-lg:   1.125rem;    /* 18px */
  --text-xl:   1.25rem;     /* 20px */
  --text-2xl:  1.5rem;      /* 24px */
  --text-3xl:  1.875rem;    /* 30px */
  --text-4xl:  2.25rem;     /* 36px */

  --leading-none:   1;
  --leading-tight:  1.25;
  --leading-normal: 1.5;
  --leading-relaxed: 1.625;

  --tracking-tight:  -0.025em;
  --tracking-normal: 0;
  --tracking-wide:   0.025em;

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

  /* ─── Spacing (4px base) ─── */
  --space-0:   0;
  --space-0_5: 0.125rem;   /* 2px */
  --space-1:   0.25rem;    /* 4px */
  --space-1_5: 0.375rem;   /* 6px */
  --space-2:   0.5rem;     /* 8px */
  --space-2_5: 0.625rem;   /* 10px */
  --space-3:   0.75rem;    /* 12px */
  --space-3_5: 0.875rem;   /* 14px */
  --space-4:   1rem;       /* 16px */
  --space-5:   1.25rem;    /* 20px */
  --space-6:   1.5rem;     /* 24px */
  --space-7:   1.75rem;    /* 28px */
  --space-8:   2rem;       /* 32px */
  --space-9:   2.25rem;    /* 36px */
  --space-10:  2.5rem;     /* 40px */
  --space-11:  2.75rem;    /* 44px */
  --space-12:  3rem;       /* 48px */
  --space-14:  3.5rem;     /* 56px */
  --space-16:  4rem;       /* 64px */
  --space-20:  5rem;       /* 80px */
  --space-24:  6rem;       /* 96px */

  /* ─── Border Radius ─── */
  --radius-none: 0;
  --radius-sm:   0.25rem;   /* 4px */
  --radius-md:   0.375rem;  /* 6px */
  --radius-lg:   0.5rem;    /* 8px */
  --radius-xl:   0.75rem;   /* 12px */
  --radius-2xl:  1rem;      /* 16px */
  --radius-3xl:  1.5rem;    /* 24px */
  --radius-full: 9999px;

  /* ─── Shadows ─── */
  --shadow-xs:   0 0 0 1px rgba(0, 0, 0, 0.03), 0 1px 2px rgba(0, 0, 0, 0.04);
  --shadow-sm:   0 1px 3px rgba(0, 0, 0, 0.05), 0 1px 2px rgba(0, 0, 0, 0.04);
  --shadow-md:   0 4px 6px -1px rgba(0, 0, 0, 0.06), 0 2px 4px -2px rgba(0, 0, 0, 0.04);
  --shadow-lg:   0 10px 15px -3px rgba(0, 0, 0, 0.06), 0 4px 6px -4px rgba(0, 0, 0, 0.04);
  --shadow-xl:   0 20px 25px -5px rgba(0, 0, 0, 0.08), 0 8px 10px -6px rgba(0, 0, 0, 0.04);
  --shadow-2xl:  0 25px 50px -12px rgba(0, 0, 0, 0.15);
  --shadow-inner: inset 0 2px 4px rgba(0, 0, 0, 0.04);
  --shadow-ring:  0 0 0 3px rgba(99, 102, 241, 0.15);

  /* ─── Focus Ring ─── */
  --focus-ring-color: var(--color-primary-500);
  --focus-ring-width: 2px;
  --focus-ring-offset: 2px;

  /* ─── Transitions ─── */
  --ease-linear:  linear;
  --ease-in:      cubic-bezier(0.4, 0, 1, 1);
  --ease-out:     cubic-bezier(0, 0, 0.2, 1);
  --ease-in-out:  cubic-bezier(0.4, 0, 0.2, 1);

  --duration-0:    0ms;
  --duration-75:   75ms;
  --duration-100:  100ms;
  --duration-150:  150ms;
  --duration-200:  200ms;
  --duration-250:  250ms;
  --duration-300:  300ms;
  --duration-500:  500ms;
  --duration-700:  700ms;

  --transition-fast:   var(--duration-150) var(--ease-out);
  --transition-normal: var(--duration-250) var(--ease-in-out);
  --transition-slow:   var(--duration-350) var(--ease-in-out);

  /* ─── Layout ─── */
  --sidebar-width:       16rem;
  --sidebar-collapsed:   4.5rem;
  --header-height:       3.5rem;
  --content-max-width:   1200px;
  --content-narrow:      720px;
  --page-padding:        var(--space-6);
  --page-padding-mobile: var(--space-4);

  /* ─── Z-Index ─── */
  --z-base:    0;
  --z-dropdown: 100;
  --z-sidebar:  200;
  --z-header:   300;
  --z-backdrop: 400;
  --z-modal:    500;
  --z-toast:    600;
  --z-tooltip:  700;

  /* ─── Avatars ─── */
  --avatar-size-sm:  1.5rem;
  --avatar-size-md:  2rem;
  --avatar-size-lg:  2.5rem;
  --avatar-size-xl:  3rem;

  /* ─── Icon ─── */
  --icon-size-xs: 0.75rem;
  --icon-size-sm: 1rem;
  --icon-size-md: 1.25rem;
  --icon-size-lg: 1.5rem;
  --icon-size-xl: 2rem;
}

/* ═══════════════════════════════════════════
   DARK MODE (Linear-inspired premium dark)
   ═══════════════════════════════════════════ */
[data-theme="dark"] {
  --color-neutral-50:  #161616;
  --color-neutral-100: #1c1c1c;
  --color-neutral-150: #222222;
  --color-neutral-200: #2a2a2a;
  --color-neutral-300: #3c3c3c;
  --color-neutral-400: #5c5c5e;
  --color-neutral-500: #86868b;
  --color-neutral-600: #a1a1a6;
  --color-neutral-700: #c7c7cc;
  --color-neutral-800: #e5e5ea;
  --color-neutral-900: #f5f5f7;

  --color-primary-50:  #1e1b4b;
  --color-primary-100: #2e2a6e;
  --color-primary-200: #3730a3;
  --color-primary-300: #4338ca;
  --color-primary-400: #4f46e5;
  --color-primary-500: #6366f1;
  --color-primary-600: #818cf8;
  --color-primary-700: #a5b4fc;
  --color-primary-800: #c7d2fe;
  --color-primary-900: #e0e7ff;

  --color-success-50:  #052e16;
  --color-success-100: #14532d;
  --color-success-200: #166534;
  --color-success-300: #15803d;
  --color-success-400: #16a34a;
  --color-success-500: #22c55e;
  --color-success-600: #4ade80;
  --color-success-700: #86efac;
  --color-success-800: #bbf7d0;
  --color-success-900: #dcfce7;

  --color-warning-50:  #451a03;
  --color-warning-100: #78350f;
  --color-warning-200: #92400e;
  --color-warning-300: #b45309;
  --color-warning-400: #d97706;
  --color-warning-500: #f59e0b;
  --color-warning-600: #fbbf24;
  --color-warning-700: #fcd34d;
  --color-warning-800: #fde68a;
  --color-warning-900: #fef3c7;

  --color-danger-50:  #450a0a;
  --color-danger-100: #7f1d1d;
  --color-danger-200: #991b1b;
  --color-danger-300: #b91c1c;
  --color-danger-400: #dc2626;
  --color-danger-500: #ef4444;
  --color-danger-600: #f87171;
  --color-danger-700: #fca5a5;
  --color-danger-800: #fecaca;
  --color-danger-900: #fee2e2;

  --color-info-50:  #082f49;
  --color-info-100: #0c4a6e;
  --color-info-200: #075985;
  --color-info-300: #0369a1;
  --color-info-400: #0284c7;
  --color-info-500: #0ea5e9;
  --color-info-600: #38bdf8;
  --color-info-700: #7dd3fc;
  --color-info-800: #bae6fd;
  --color-info-900: #e0f2fe;

  --color-priority-high:   #f87171;
  --color-priority-medium: #fbbf24;
  --color-priority-low:    #4ade80;

  --color-bg:            #0c0c0c;
  --color-bg-subtle:     #141414;
  --color-surface:       #1a1a1a;
  --color-surface-hover: #242424;
  --color-surface-active:#2e2e2e;
  --color-surface-raised: #222222;
  --color-surface-overlay: rgba(0, 0, 0, 0.7);

  --color-border:       #2e2e2e;
  --color-border-light: #242424;
  --color-border-hover: #3c3c3c;
  --color-border-focus: var(--color-primary-500);
  --color-divider:      #242424;

  --color-text:           #f5f5f7;
  --color-text-secondary: #a1a1a6;
  --color-text-tertiary:  #636366;
  --color-text-muted:     #48484a;
  --color-text-inverse:   #0c0c0c;
  --color-text-on-primary: #ffffff;
  --color-link:           var(--color-primary-400);
  --color-link-hover:     var(--color-primary-300);

  --color-primary:   var(--color-primary-500);
  --color-primary-light:  var(--color-primary-400);
  --color-primary-dark:   var(--color-primary-600);

  --shadow-xs:   0 0 0 1px rgba(255, 255, 255, 0.03), 0 1px 2px rgba(0, 0, 0, 0.3);
  --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, 0.4), 0 2px 4px -2px rgba(0, 0, 0, 0.3);
  --shadow-lg:   0 10px 15px -3px rgba(0, 0, 0, 0.4), 0 4px 6px -4px rgba(0, 0, 0, 0.3);
  --shadow-xl:   0 20px 25px -5px rgba(0, 0, 0, 0.5), 0 8px 10px -6px rgba(0, 0, 0, 0.3);
  --shadow-2xl:  0 25px 50px -12px rgba(0, 0, 0, 0.5);
  --shadow-inner: inset 0 2px 4px rgba(0, 0, 0, 0.2);
  --shadow-ring:  0 0 0 3px rgba(129, 140, 248, 0.3);
}

/* ─── Reduced Motion ─── */
@media (prefers-reduced-motion: reduce) {
  :root {
    --duration-0:    0ms;
    --duration-75:   0ms;
    --duration-100:  0ms;
    --duration-150:  0ms;
    --duration-200:  0ms;
    --duration-250:  0ms;
    --duration-300:  0ms;
    --duration-500:  0ms;
    --duration-700:  0ms;
  }
}