:root {
  --color-paper: oklch(98% 0.008 248);
  --color-paper-2: oklch(95% 0.014 248);
  --color-paper-3: oklch(91% 0.022 248);
  --color-ink: oklch(19% 0.032 252);
  --color-ink-2: oklch(36% 0.032 252);
  --color-muted: oklch(49% 0.025 252);
  --color-rule: oklch(82% 0.025 248);
  --color-rule-2: oklch(90% 0.018 248);
  --color-accent: oklch(54% 0.2 258);
  --color-accent-ink: oklch(98% 0.008 248);
  --color-focus: oklch(68% 0.2 235);
  --color-deep: oklch(16% 0.055 252);
  --color-deep-2: oklch(23% 0.07 252);
  --color-on-dark: oklch(96% 0.012 248);
  --color-on-dark-muted: oklch(82% 0.035 244);
  --color-overlay: oklch(11% 0.05 252 / 0.82);
  --color-overlay-soft: oklch(11% 0.05 252 / 0.42);

  --font-display: "Bricolage Grotesque", "Noto Sans TC", sans-serif;
  --font-body: "Noto Sans TC", sans-serif;

  --space-3xs: 0.125rem;
  --space-2xs: 0.25rem;
  --space-xs: 0.5rem;
  --space-sm: 0.75rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  /* Unified page rhythm: content chapters should feel connected, not isolated. */
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4.5rem;
  --space-4xl: 6.5rem;

  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-md: 1.25rem;
  --text-lg: 1.5625rem;
  --text-xl: 1.953rem;
  --text-2xl: 2.441rem;
  --text-3xl: 3.052rem;
  --text-display: clamp(2.75rem, 5vw + 1rem, 5.25rem);

  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --ease-in: cubic-bezier(0.7, 0, 0.84, 0);
  --ease-in-out: cubic-bezier(0.65, 0, 0.35, 1);
  --dur-micro: 120ms;
  --dur-short: 220ms;
  --dur-long: 420ms;

  --rule-thin: 1px;
  --rule-medium: 2px;
  --radius-sm: 0.375rem;
  --radius-card: 0.75rem;
  --radius-button: 999px;
  --shadow-whisper: 0 1px 2px oklch(18% 0.02 252 / 0.08);
  --z-base: 1;
  --z-raised: 10;
}