:root {
  /* ============================================
     COLOR SYSTEM - Warm neutrals inspired by Anthropic
     ============================================ */

  /* Neutral palette with warm undertones */
  --color-gray-50: #faf9f7;
  --color-gray-100: #f5f4f1;
  --color-gray-200: #e8e6e1;
  --color-gray-300: #d4d2cc;
  --color-gray-400: #a8a5a0;
  --color-gray-500: #7c7872;
  --color-gray-600: #5c5955;
  --color-gray-700: #3d3b38;
  --color-gray-800: #262523;
  --color-gray-900: #131312;

  /* Accent colors */
  --color-accent-primary: #d97757;
  --color-accent-primary-hover: #c4684a;
  --color-accent-primary-subtle: rgba(217, 119, 87, 0.12);
  --color-accent-secondary: #3b82f6;
  --color-accent-bike: #d97757;
  --color-accent-run: var(--color-gray-900);
  --color-success: #22c55e;
  --color-danger: #ef4444;
  --color-warning: #f59e0b;

  /* Semantic colors - Light mode defaults */
  --color-bg: var(--color-gray-50);
  --color-bg-elevated: #ffffff;
  --color-panel: #ffffff;
  --color-panel-hover: var(--color-gray-100);
  --color-panel-stroke: transparent;
  --color-text-primary: var(--color-gray-900);
  --color-text-secondary: var(--color-gray-600);
  --color-text-tertiary: var(--color-gray-400);
  --color-border: var(--color-gray-200);
  --color-border-subtle: var(--color-gray-100);

  /* ============================================
     SPACING SCALE - 4px base unit
     ============================================ */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 24px;
  --space-6: 32px;
  --space-7: 48px;
  --space-8: 64px;
  --space-9: 96px;
  --space-10: 128px;

  /* Legacy aliases */
  --space-xs: var(--space-1);
  --space-sm: var(--space-2);
  --space-md: var(--space-4);
  --space-lg: var(--space-5);
  --space-xl: var(--space-6);

  /* Density-aware spacing */
  --density-card-padding: var(--space-5);
  --density-item-gap: var(--space-3);
  --density-section-gap: var(--space-7);

  /* ============================================
     TYPOGRAPHY - Fluid scale with clamp()
     ============================================ */
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, monospace;

  /* Fluid type scale */
  --text-xs: clamp(0.6875rem, 0.65rem + 0.1vw, 0.75rem);
  --text-sm: clamp(0.8125rem, 0.78rem + 0.1vw, 0.875rem);
  --text-base: clamp(0.9375rem, 0.9rem + 0.1vw, 1rem);
  --text-lg: clamp(1.0625rem, 1rem + 0.2vw, 1.125rem);
  --text-xl: clamp(1.1875rem, 1.1rem + 0.3vw, 1.25rem);
  --text-2xl: clamp(1.375rem, 1.2rem + 0.5vw, 1.5rem);
  --text-3xl: clamp(1.625rem, 1.4rem + 0.8vw, 1.875rem);
  --text-4xl: clamp(2rem, 1.7rem + 1vw, 2.5rem);

  /* Font weights */
  --font-normal: 400;
  --font-medium: 500;
  --font-semibold: 600;
  --font-bold: 700;

  /* Line heights */
  --leading-tight: 1.25;
  --leading-snug: 1.375;
  --leading-normal: 1.5;
  --leading-relaxed: 1.625;

  /* Letter spacing */
  --tracking-tight: -0.02em;
  --tracking-normal: 0;
  --tracking-wide: 0.04em;

  /* ============================================
     BORDER RADIUS
     ============================================ */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --radius-xl: 20px;
  --radius-full: 9999px;

  /* ============================================
     SHADOWS - Elevation system
     ============================================ */
  --shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.03);
  --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.08);
  --shadow-xl: 0 16px 48px rgba(0, 0, 0, 0.1);
  --shadow-lifted: 0 8px 30px rgba(0, 0, 0, 0.12);

  /* ============================================
     ANIMATION TOKENS
     ============================================ */
  --duration-instant: 50ms;
  --duration-fast: 150ms;
  --duration-normal: 200ms;
  --duration-slow: 300ms;
  --duration-slower: 500ms;

  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --ease-in-out: cubic-bezier(0.65, 0, 0.35, 1);
  --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
  --ease-bounce: cubic-bezier(0.68, -0.55, 0.265, 1.55);
}

/* ============================================
   DARK MODE - System preference
   ============================================ */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --color-bg: var(--color-gray-900);
    --color-bg-elevated: var(--color-gray-800);
    --color-panel: var(--color-gray-800);
    --color-panel-hover: var(--color-gray-700);
    --color-panel-stroke: transparent;
    --color-text-primary: var(--color-gray-50);
    --color-text-secondary: var(--color-gray-400);
    --color-text-tertiary: var(--color-gray-500);
    --color-border: var(--color-gray-700);
    --color-border-subtle: var(--color-gray-800);
    --color-accent-run: var(--color-gray-50);

    /* Dark mode shadows */
    --shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.15);
    --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.2);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.25);
    --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.3);
    --shadow-xl: 0 16px 48px rgba(0, 0, 0, 0.35);
    --shadow-lifted: 0 8px 30px rgba(0, 0, 0, 0.4);
  }
}

/* ============================================
   MANUAL THEME OVERRIDES via data-theme
   ============================================ */
[data-theme="dark"] {
  --color-bg: var(--color-gray-900);
  --color-bg-elevated: var(--color-gray-800);
  --color-panel: var(--color-gray-800);
  --color-panel-hover: var(--color-gray-700);
  --color-panel-stroke: transparent;
  --color-text-primary: var(--color-gray-50);
  --color-text-secondary: var(--color-gray-400);
  --color-text-tertiary: var(--color-gray-500);
  --color-border: var(--color-gray-700);
  --color-border-subtle: var(--color-gray-800);
  --color-accent-run: var(--color-gray-50);

  --shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.15);
  --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.2);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.25);
  --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.3);
  --shadow-xl: 0 16px 48px rgba(0, 0, 0, 0.35);
  --shadow-lifted: 0 8px 30px rgba(0, 0, 0, 0.4);
}

[data-theme="light"] {
  --color-bg: var(--color-gray-50);
  --color-bg-elevated: #ffffff;
  --color-panel: #ffffff;
  --color-panel-hover: var(--color-gray-100);
  --color-panel-stroke: transparent;
  --color-text-primary: var(--color-gray-900);
  --color-text-secondary: var(--color-gray-600);
  --color-text-tertiary: var(--color-gray-400);
  --color-border: var(--color-gray-200);
  --color-border-subtle: var(--color-gray-100);
  --color-accent-run: var(--color-gray-900);
}

/* ============================================
   DENSITY MODES
   ============================================ */
[data-density="compact"] {
  --density-card-padding: var(--space-3);
  --density-item-gap: var(--space-2);
  --density-section-gap: var(--space-5);
}

[data-density="comfortable"] {
  --density-card-padding: var(--space-5);
  --density-item-gap: var(--space-3);
  --density-section-gap: var(--space-7);
}