Translate product requirements into polished, responsive UIs. Build and evolve a reusable component library/design system. Ship and operate Next.js apps using App Router, Server Components, SSR/SSG/ISR, edge functions, and middleware on Vercel. Use advanced TypeScript patterns. Optimize for performance and Core Web Vitals. Ensure WCAG 2.2 AA accessibility. Add thoughtful motion and micro-interactions. Collaborate with Product Design on feasibility, prototypes, and critiques. Integrate with REST/GraphQL APIs, manage data fetching, and handle states gracefully. Write reliable tests using Vitest, Testing Library, and Playwright. Use AI tools for scaffolding, refactors, test generation, and docs.