Layers Intro

# /layers-intro

Load this skill at the start of any design session. It provides the framework context that all other `/layers-*` skills depend on.

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## The framework

**Layers of Product Design** organises design work into seven layers across three zones. Layers have *logical dependency*: lower layers are foundations for upper ones. Weak lower layers create UX debt that propagates upward.

**Reality** — complex, contradictory, evolving. Source of all learning.

**Problem space** — knowledge gathered from reality:
1. **Observed behaviour** — what users actually do
2. **The domain** — concepts, terminology, and mental models that exist independently of any product
3. **User needs** — what we think users are trying to achieve, and why

**Solution space** — deliberate decisions about what to build:
4. **Product & service strategy** — which needs to serve, and what business outcomes to target
5. **Conceptual model** — objects, relationships, states, vocabulary — independent of any interface
6. **Interaction structure and flow** — places, affordances, connections, and flow logic
7. **Surface** — words, visuals, feedback, hierarchy — what users actually encounter

The layers are not a linear process. Enter anywhere — but always check whether the foundations below are sound.

*Inspired by Jesse James Garrett's* The Elements of User Experience *(2000).*

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## Design is decision-making

Design = making decisions about the form of a solution (Christopher Alexander). Form is the solution; context is the requirements, constraints, and environment it must fit. Good design is good fit.

**Four kinds of progress:**
1. **Making decisions** — resolving something undecided
2. **Uncovering unmade decisions** — discovering what hasn't been decided yet (often more valuable than 1)
3. **Evaluating decisions** — identifying decisions already made that are risky, inconsistent, or wrong
4. **Prioritising decisions** — lower layers are more foundational and carry more risk if wrong

The job of every skill is to help the designer make better decisions — not to make decisions for them.

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## How to use these skills

Each `/layers-*` skill is a **library of techniques for one layer — not a script to run start to finish.** Don't march through every step and emit a stack of artefacts. Instead:

1. **Find the live decisions.** What at this layer is genuinely undecided, risky, or worth surfacing? (`/layers-orient` finds these across all layers if you're not sure.) If nothing here is live, say so and move on — don't manufacture work to fill the structure.
2. **Offer a technique that fits the decision.** Each skill lists techniques with the situations they suit. Suggest one or two and let the designer choose. A technique is a way to make a specific decision, not a box to fill.
3. **Work the decision; capture only the residue.** Produce what the decision needs — usually a few lines, sometimes a diagram — not a full report. The conversation is the working surface; the capture is what survives it.

Each skill names **the decisions that layer makes** and the **disciplines** that keep it honest. Those are the spine. The wording of any individual prompt is disposable; the decision it serves is not.

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## Principles — apply across all sessions

1. **Decisions, not outputs.** Artefacts are useful only insofar as they represent decisions made or surfaced. Name the decision, not just the diagram.
2. **Uncover before you resolve.** Surfacing decisions the designer didn't know they needed to make is often more valuable than answering the ones they did.
3. **Work at one layer at a time.** Conflating problem space and solution space, or surface and conceptual model, produces confused outputs.
4. **Check foundations before building upward.** Before working on an upper layer, audit the layer below. Flag inst