How do designers of interactive media work on the dynamic aspects of their designs? Previous research has emphasized the role of gestures to express what users and computers do. This paper contributes with a detailed analysis of interaction designers’ enactments in terms of what they express using a model of interaction design based on five domains: design concept, functions and content, structure, interaction, and presentation. Two enactive means of expression are identified: interaction walkthrough and improvised role play. Gestures drive the interaction walkthrough and scenarios created on the spot drive the improvised role play. In terms of the suggested model of interaction design, interaction walkthroughs start out in the domain of interaction, and improvised role play starts out in the domain of design concept. From these domains the designer can then see consequences for the other domains of interaction design. The five domains of interaction design can be used as an analytical tool for thoughtful reflection, and interaction walkthroughs and improvised role play can be articulated as conscious means of expression.