This applies Feature-Sliced Design v2.1 methodology to your frontend codebase, organizing it into six layers from app down through pages, widgets, features, entities, and shared. The big shift in v2.1 is "pages first," keeping code in pages and widgets until you actually need to reuse it elsewhere, rather than prematurely extracting everything into features and entities. It enforces strict import rules so higher layers can't import from lower ones, and slices on the same layer stay independent except through explicit @x cross-imports for legitimate business relationships. Use it when setting up a new project structure or refactoring an existing one that's become hard to navigate. The methodology is opinionated but solves real problems around where code lives and how pieces connect.
npx skills add https://github.com/aiko-atami/fsd --skill feature-sliced-design