A practical reference when you're building apps that need to look native on iOS, Android, and web without maintaining three separate design systems. It bundles 300+ rules extracted from Apple's Human Interface Guidelines, Material Design 3, and WCAG 2.2 accessibility standards. The value here is consolidation: instead of context-switching between official docs while designing buttons, spacing, or touch targets, you get cross-platform guidance in one place. Most useful during early design phases when you're establishing patterns, less so if you're already deep in platform-specific polish. The upstream repo from @ehmo suggests this is actively maintained, though you'll want to verify the rule coverage matches your specific platform targets before committing to it as your primary reference.
npx skills add https://github.com/nexu-io/open-design --skill platform-design