Functional foundation · Field guide
Interaction design
Design the dialogue between people and products across actions, states, feedback, and time.
Interaction design defines what people can do, how the system responds, and how both sides understand what happens next. It includes flow, state, language, feedback, error prevention, recovery, accessibility, and technical constraints.
Ways to practise the skill.
Choose methods because they reduce the uncertainty in front of the team—not because a template says they belong in the process.
Task and flow modelling
Map goals, entry points, decisions, system actions, interruptions, and completion.
Helpful whenA journey crosses several screens, actors, or services.State modelling
List loading, empty, partial, success, error, permission, and return states.
Helpful whenHappy-path screens hide consequential behaviour.Interaction prototype
Represent enough behaviour to test timing, sequence, control, and feedback.
Helpful whenStatic screens cannot answer the key design question.Heuristic review
Inspect an experience against recognised usability principles and document evidence and severity.
Helpful whenFinding likely issues before or alongside user testing.Continue into the field.
Practical standards and method guidance from established sources.