Figure 1. Columns show low, medium, and high levels of texture-based biofeedback. Rows show customizations of the same effect for two different games: top) Static Sprite (cracks) over Portal 2, bottom) Static Sprite (mud) over Nail'd. ABSTRACTBiofeedback games help people maintain specific mental or physical states and are useful to help children with cognitive impairments learn to self-regulate their brain function. However, biofeedback games are expensive and difficult to create and are not sufficiently appealing to hold a child's interest over the long term needed for effective biofeedback training. We present a system that turns off-the-shelf computer games into biofeedback games. Our approach uses texture-based graphical overlays that vary in their obfuscation of underlying screen elements based on the sensed physiological state of the child. The textures can be visually customized so that they appear to be integrated with the underlying game. Through a 12-week deployment, with 16 children with Fetal Alcohol Spectrum Disorder, we show that our solution can hold a child's interest over a long term, and balances the competing needs of maintaining the fun of playing, while providing effective biofeedback training.

Graphical assets in video games have become increasingly complex over the years, but little is known about their effect on player experience (PX). In this paper, we present results of a controlled study with 48 participants comparing how abstract and stylized graphics influence player experience in casual games. Our results show that high-fidelity graphics result in a more positive impression of the game. However, we also show that many effects are only present in the game with a more challenging mechanic. This shows that casual games can be compelling and enjoyable to play despite simplistic graphics, suggesting that small game developers and researchers need not focus on elaborate visuals to engage players.

In tabletop work with direct input, people avoid crossing each others' arms. This natural touch avoidance has important consequences for coordination: for example, people rarely grab the same item simultaneously, and negotiate access to the workspace via turn-taking. At digital tables, however, some situations require the use of indirect input (e.g., large tables or remote participants), and in these cases, people are often represented with virtual arm embodiments. There is little information about what happens to coordination and reaching when we move from physical to digital arm embodiments. To gather this information, we carried out a controlled study of tabletop behaviour with different embodiments. We found dramatic differences in moving to a digital embodiment: people touch and cross with virtual arms far more than they do with real arms, which removes a natural coordination mechanism in tabletop work. We also show that increasing the visual realism of the embodiment does not change behaviour, but that changing the thickness has a minor effect. Our study identifies important design principles for virtual embodiments in tabletop groupware, and adds to our understanding of embodied interaction in small groups.

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Collaborative tabletop systems can employ direct touch, where people's real arms and hands manipulate objects, or indirect input, where people are represented on the table with digital embodiments. The input type and the resulting embodiment dramatically influence tabletop interaction: in particular, the touch avoidance that naturally governs people's touching and crossing behavior with physical arms is lost with digital embodiments. One result of this loss is that people are less aware of each others' arms, and less able to coordinate actions and protect personal territories. To determine whether there are strategies that can influence group interaction on shared digital tabletops, we studied augmented digital arm embodiments that provide tactile feedback or movement alterations when people touched or crossed arms. The study showed that both augmentation types changed people's behavior (people crossed less than half as often) and also changed their perception (people felt more aware of the other person's arm, and felt more awkward when touching). This work shows how groupware designers can influence people's interaction, awareness, and coordination abilities when physical constraints are absent.