Maintaining balance between challenge and skills in games is critical for enjoyment, and can be applied to accommodate player performance as well as system performance for low accuracy input devices. Previous work has explored different performance-accommodation mechanisms (PAMs) for balancing, but studies have focused mainly on variables not directly related to how the PAMs lower challenge level. This paper identifies different levels of PAMs, then offers a first attempt at a coherent framework of action-level PAMs based on how they modify the mapping from player input to output.CCS Concepts: • Human-centered computing → HCI theory, concepts and models.

To reduce frustration while performing no-risk tasks (e.g. in training and games) for BCI users, we propose increasing their perceived level of control through fabricated input - system-generated positive task outcomes. Two surrogate BCI studies injected fabricated input creating additional positive task outcomes to a 50% baseline. Users' perceived control increased significantly compared to the 50% baseline. In turn, frustration levels decreased. Fabricated input worked equally well in a game story context that provided an emotional stake in the protagonist's success and a simpler task lacking such incentives. People's number of input attempts during the tasks determined perceived control more than our controlled ratios of positive to negative task outcomes. Delays between users' input attempts and subsequent fabricated inputs further moderated their perceived control.