This article investigates the use and effect of optimizing strategies in the online game World of Warcraft. Specifically, it looks at the phenomenon known as “theorycrafting,” wherein expert players reverse engineer the game and use its underlying algorithms to calculate maximized play strategies. Play from a theorycrafting perspective is about the correct input and output of numbers, challenging the narrative of play as something free and frivolous. Seeking to understand how play and knowledge relate to each other, the article discusses (...) how theorycrafting’s seemingly abstract, objective, and neutral information about the game is also embedded with values, ideas, and norms. Based on a 1-year ethnographic study, the article uses Jasanoff’s idiom of coproduction to discuss how abstract calculations are rendered meaningful and valuable by players, and the consequences of this in stabilizing particular ways of playing World of Warcraft. (shrink)