Define constraints together
Screen sizes, data structures, access rules and state changes all affect user experience. Discussing these constraints together early helps designers and engineers avoid rework later.
Design systems connect design and code
Shared colors, spacing, typography and components let design specifications map to real code. Components need loading, empty, error and disabled states as well as their default appearance.
Validate the experience in a working interface
Static mockups cannot show network delays, long text or keyboard navigation. Trying the real interface throughout development reveals problems earlier than a single final handover.