Existing theories of how game use relates to mental health have important limitations: few account for both quantity and quality of use, differentiate components of mental health (hedonic wellbe- ing, eudaimonic wellbeing, and illbeing), provide an explanation for both positive and negative outcomes, or readily explain the well-evidenced absence of playtime effects on mental health. Many also lack the specificity to be readily falsifiable. In response, we present the Basic Needs in Games (BANG) model. Grounded in self- determination theory, BANG proposes that mental health outcomes of game use are in large part mediated by the motivational quality of play and the extent to which play quantity and quality lead to need satisfaction or frustration. We show how BANG addresses the limitations of current theories and aligns with emerging evidence on the etiologies of disordered play. Thus, BANG advances HCI theory on the impact of games and other interactive technologies on mental health.