This article examines the language and literacy practices of middle-school children as they worked toward constructing their own computer games using "Gamestar Mechanic," a game intended to teach them key ways of thinking and communicating germane to the discourse of game designers. It examines the changes that took place in what previous work with this game has called their "material dialog," a sequence of interactions with components made available by the game to make their own games. Using discourse analysis, it examines participants' conversation and think-aloud interview data to track the changes in their design and thinking strategies over time. Findings suggest that growing familiarity with the tools and components provided by the game allowed them to develop sophisticated understandings of the grammatical relationships between game elements that helped them develop a systemic perspective of their games. In doing so, this view allowed them to move from seeing game features that deviated from their intended designs as "bugs", to viewing them rather as opportunities to create features that would enrich the play experience for others. Implications of these findings for children's learning in the academic and work disciplines of the twenty-first century are discussed. (Contains 9 figures.)