I started with a full audit of the product's design files and live site, cataloging every UI pattern, color, type style, and spacing value. From there I defined the design tokens — color, typography, spacing, elevation — structured in two layers: a global foundation, plus an alias layer that could be re-themed without touching the components. Components were built collaboratively, starting with the highest-frequency patterns and involving PMs and engineers early so naming and structure matched how the code was actually written.