:root {
  /* Typography */
  --font-sans: ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, "Apple Color Emoji", Arial, sans-serif, "Segoe UI Emoji", "Segoe UI Symbol";
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
  --font-serif: Lyon-Text, Georgia, ui-serif, serif;

  /* Font sizes */
  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.25rem;
  --text-2xl: 1.5rem;
  --text-3xl: 1.875rem;
  --text-4xl: 2.25rem;

  /* Spacing (4px grid) */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 24px;
  --space-6: 32px;
  --space-7: 48px;
  --space-8: 64px;

  /* Layout */
  --sidebar-width: 240px;
  --content-max-width: 720px;
  --toc-width: 200px;

  /* Borders */
  --radius-sm: 3px;
  --radius-md: 6px;
  --radius-lg: 8px;

  /* Transitions */
  --transition-fast: 120ms ease;
  --transition-base: 200ms ease;
  --transition-slow: 300ms ease;

  /* Light theme (default) */
  --color-bg: #ffffff;
  --color-bg-secondary: #f7f6f3;
  --color-bg-hover: rgba(55, 53, 47, 0.08);
  --color-bg-active: rgba(55, 53, 47, 0.16);
  --color-text: #37352f;
  --color-text-secondary: rgba(55, 53, 47, 0.65);
  --color-text-tertiary: rgba(55, 53, 47, 0.45);
  --color-border: rgba(55, 53, 47, 0.09);
  --color-border-strong: rgba(55, 53, 47, 0.16);
  --color-accent: #2eaadc;
  --color-accent-hover: #298ab8;
  --color-sidebar-bg: #f7f6f3;
  --color-sidebar-hover: rgba(55, 53, 47, 0.08);
  --color-card-bg: #ffffff;
  --color-card-shadow: rgba(15, 15, 15, 0.1);
  --color-code-bg: rgba(135, 131, 120, 0.15);
  --color-code-text: #eb5757;
  --color-tag-bg: rgba(55, 53, 47, 0.06);
  --color-tag-text: rgba(55, 53, 47, 0.65);
  --color-overlay: rgba(0, 0, 0, 0.4);
}

[data-theme="dark"] {
  --color-bg: #191919;
  --color-bg-secondary: #202020;
  --color-bg-hover: rgba(255, 255, 255, 0.08);
  --color-bg-active: rgba(255, 255, 255, 0.16);
  --color-text: rgba(255, 255, 255, 0.9);
  --color-text-secondary: rgba(255, 255, 255, 0.6);
  --color-text-tertiary: rgba(255, 255, 255, 0.4);
  --color-border: rgba(255, 255, 255, 0.09);
  --color-border-strong: rgba(255, 255, 255, 0.16);
  --color-accent: #529cca;
  --color-accent-hover: #4a8ab4;
  --color-sidebar-bg: #202020;
  --color-sidebar-hover: rgba(255, 255, 255, 0.08);
  --color-card-bg: #252525;
  --color-card-shadow: rgba(0, 0, 0, 0.3);
  --color-code-bg: rgba(135, 131, 120, 0.15);
  --color-code-text: #ff7b72;
  --color-tag-bg: rgba(255, 255, 255, 0.08);
  --color-tag-text: rgba(255, 255, 255, 0.6);
  --color-overlay: rgba(0, 0, 0, 0.6);
}