This article focuses on the concept of labor in co-creation, arguing that its definition needs to be expanded to include a process of intensity. Intensity foregrounds the different degrees in which participants involve themselves in a craft, and also the elements of time, effort, and affectivity. Using game modification as a case study, the article analyzes how automated, computerized systems of evaluations, embedded into webpages, can create grounds for a self-understanding of productive abilities. Maneuvering through the three registers of industry, websites, and game modders, it examines the discourses of evaluative systems and details how participants use these technologies to self-manage and calibrate their labor. Interviews showed that the increasingly competitive drive for optimal standards of production comes at a cost to the well-being of participants. Studies of labor therefore need to consider the "intense" aspect of participatory production, and the impact it may have on its participants.