Theme DNA is the single source of truth for how this site looks. Colour, typography, radii, spacing and layout width are stored as CMS settings and injected as CSS custom properties at the document root, so every page and template reads from those tokens instead of hardcoded values. Restyling the entire site is a settings change, not a code change.
The rule is enforced rather than suggested: templates may not hardcode brand colours, radii, fonts or layout widths, and the only fixed colours allowed are neutral overlays that must deliberately not shift with the theme — a glass highlight and image-legibility scrims. Pages can additionally re-declare tokens in their own scope, which is how individual pages carry their own art direction without leaving the system.