We present a tangible programming space designed for children's collaborative construction of screen-based interactive systems. The design is based on three goals for interaction and activity: supporting co-located collaborative activity, screen-based execution, and what we call behaviour-based programming. Further, we analyse the interactions within a group of 10 year olds who used the system to create a live fantasy world together. The results show how the tangible resources shaped the activity of programming so that bodily actions and positioning became prominent. This is conceptualized through the notion of embodied programming, which highlights how programming activity must be understood through its interlinking to external resources and context.