This is the foundation skill for a seven-layer product design framework that separates problem space (observed behavior, domain, user needs) from solution space (strategy, conceptual model, interaction flow, surface). You load it first because all the other `/layers-*` skills depend on its vocabulary and structure. The framework treats design as decision-making, not artifact production, which means each layer skill is a library of techniques to surface and resolve live decisions rather than a checklist to march through. The most useful bit is probably the emphasis on working one layer at a time and checking foundations before building up, especially the conceptual model layer which it calls the most neglected load-bearing part of the stack.
npx skills add https://github.com/jamiemill/layers-skills --skill layers-intro