CSS authoring

How to write CSS that stays legible as it grows: every colour, size, and state change flows through a small set of named channels, selectors say what they mean, and browser support is checked, not remembered.

This skill emits no values: the sizes, colours and weights come from the token skills (see Related). This is the shape the CSS that consumes them takes.

This skill targets modern, evergreen browsers. It recommends features on the basis that they are Baseline available, not that they are universally supported. Backward compatibility with older browsers is the consuming project's responsibility — section 3 is how you find out what your own target actually allows before you write the rule.

1. Channel variables — the core pattern