•critique and compare multiple design concepts  •sort out best one  •weigh concept feasibility  •prototypes: low-fidelity paper, storyboards   •&"evaluate&" via storytelling
•critique and compare multiple design concepts  •sort out best one  •weigh concept feasibility  •prototypes: low-fidelity paper, storyboards   •&"evaluate&" via storytelling
connects the designer's mental model to the user's mental model