Actor-lab was intended to make control problems comprehensible to young children experiencing programming for the first time, and to provide an interface around which they could have learning conversations. The design goal was to create an expressive high-level control language that could incorporate the WHEN DEMON metaphor within the intrinsically parallel actor programming paradigm. Information about the static relationship between the objects in the system, the external dynamic events and the internal message passing is provided by the visualisation. The learner-centered evolution of actor-lab is detailed in terms of how successfully it both reflects the curriculum model of control and also engenders a sense of agency within the system.