state-machine
The state-machine skill models complex UI behavior using finite state machines, defining distinct states, events triggering transitions between them, and conditional guards or actions that execute during changes. Use this when designing forms, data fetches, authentication flows, or multi-step wizards to eliminate impossible states, prevent edge case bugs, and create predictable, testable UI behavior specifications shared across design and engineering teams.
git clone --depth 1 https://github.com/Owl-Listener/designer-skills /tmp/state-machine && cp -r /tmp/state-machine/interaction-design/skills/state-machine ~/.claude/skills/state-machineSKILL.md
# State Machine You are an expert in modeling complex UI behavior as finite state machines. ## What You Do You model UI components and flows as state machines to eliminate impossible states and make behavior predictable. ## State Machine Components - **States**: Distinct modes the UI can be in (idle, loading, success, error) - **Events**: Things that cause transitions (click, submit, timeout, response) - **Transitions**: Rules for moving between states (on event X in state A, go to state B) - **Actions**: Side effects during transitions (fetch data, show toast, log event) - **Guards**: Conditions that must be true for a transition (isValid, hasPermission) ## Common UI State Machines ### Form idle -> editing -> validating -> submitting -> success/error -> idle ### Data Fetching idle -> loading -> success/error, error -> retrying -> success/error ### Authentication logged-out -> authenticating -> logged-in -> logging-out -> logged-out ### Multi-Step Wizard step1 -> step2 -> step3 -> review -> submitting -> complete ## Modeling Approach 1. List all possible states 2. List all events/triggers 3. Define valid transitions 4. Identify impossible states to prevent 5. Add guards for conditional transitions 6. Define entry/exit actions per state ## Benefits - Eliminates impossible states (no loading + error simultaneously) - Makes edge cases visible - Shared language between design and engineering - Testable behavior specification ## Best Practices - Start with the happy path, then add error states - Every state should have a way out (no dead ends) - Keep state machines focused (one per concern) - Document with visual diagrams - Map each state to a UI representation
Design an A/B experiment — hypothesis, variants, primary metric, and sample size. Use when a change can be measured quantitatively at scale. For observing behaviour qualitatively, use `test-scenario`.
Audit an existing interface against WCAG, producing findings with severity ratings and remediation steps. Use when you have a design or build to assess now. Not for planning future sessions with assistive-technology users — use `accessibility-test-plan` (prototyping-testing).
Plan accessibility testing — assistive technologies, participant criteria, WCAG coverage, and session protocol. Use when scheduling testing with real AT users. Not for evaluating a design yourself — use `accessibility-audit` (design-systems).
Apply the Aesthetic-Usability Effect — polished, consistent interfaces are perceived as more usable and forgive minor friction. Use when justifying visual polish or diagnosing why a functional design tests badly. For emotional resonance specifically, use `interfaces-that-feel` (interaction-design).
Cluster many qualitative data points into themes and insight statements. Use when synthesising across multiple sessions or sources. For a single transcript use `summarize-interview`; for one segment's inner state use `empathy-map`.
Apply animation principles — easing, staging, follow-through — to one specific UI motion. Use when tuning how an animation feels. For product-wide duration and easing tokens use `motion-system` (design-systems); for a full interaction spec use `micro-interaction-spec`.
A practitioner's toolkit for thinking and communicating as a designer in a business context — reading financials, mapping competitive landscapes, and defending design decisions in the language of value.
Analyse open or closed card sort results into a proposed grouping and label set. Use after running a sort study. For turning that evidence into a full structure, use `information-architecture` (ux-strategy).