Using game balancing techniques can provide the right level of challenge and hence enhance player engagement for sport players with different skill levels. Digital technology can support and enhance balancing techniques in sports, for example, by adjusting players' level of intensity based on their heart rate. However, there is limited knowledge on how to design such balancing and its impact on the user experience. To address this we created two novel balancing techniques enabled by digitally augmenting a table tennis table. We adjusted the more skilled player's performance by inducing two different styles of play and studied the effects on game balancing and player engagement. We showed that by altering the more skilled player's performance we can balance the game through: (i) encouraging game mistakes, and (ii) changing the style of play to one that is easier for the opponent to counteract. We outline the advantages and disadvantages of each approach, extending our understanding of game balancing design. We also show that digitally augmenting sports offers opportunities for novel balancing techniques while facilitating engaging experiences, guiding those interested in HCI and sports.

Playing exertion games with others can be engaging. However, players with different physical skill levels competing against each other can experience reduced engagement because they are either not challenged enough, or challenged too much. Balancing methods can address this; however, there is only limited understanding of balancing in exertion games. In this paper, we identify two distinct dimensional balancing techniques: "internal adjustment" and "external adjustment". We report results from a study where we measured player engagement after applying these adjustments to a digital table tennis game and the traditional table tennis game, finding two disengagement factors: "unexpected physical challenges" and "unacceptable competitive advantage". Based on these factors we derived a set of exertion game design considerations. We conclude that applying digital technology to a physical game can change the required skill level to play the game, and this can affect the impact of these adjustments on player engagement. These results enhances our understanding of balancing in exertion games, supporting the benefits of playing exertion games with others.

Digital games are increasingly profiting from sensing technologies. However, their focus is mostly on sensing limb movements. We propose that sensing capabilities could also be used to engage players with proxemics: the interpersonal distance between players. We further add that wireless networks offer complementary distance zones for designers, offering novel design resources for digital play. We use our own as well as other games to articulate a set of strategies on how designers can utilize both proxemics and the new wireless proxemics to facilitate novel play experiences. Ultimately, with our work, we aim to expand the range of digital play.

In order for natural interaction in Augmented Reality (AR) to become widely adopted, the techniques used need to be shown to support precise interaction, and the gestures used proven to be easy to understand and perform. Recent research has explored free-hand gesture interaction with AR interfaces, but there have been few formal evaluations conducted with such systems. In this paper we introduce and evaluate two natural interaction techniques: the free-hand gesture based Grasp-Shell, which provides direct physical manipulation of virtual content; and the multi-modal Gesture-Speech, which combines speech and gesture for indirect natural interaction. These techniques support object selection, 6 degree of freedom movement, uniform scaling, as well as physics-based interaction such as pushing and flinging. We conducted a study evaluating and comparing Grasp-Shell and Gesture-Speech for fundamental manipulation tasks. The results show that Grasp-Shell outperforms Gesture-Speech in both efficiency and user preference for translation and rotation tasks, while Gesture-Speech is better for uniform scaling. They could be good complementary interaction methods in a physics-enabled AR environment, as this combination potentially provides both control and interactivity in one interface. We conclude by discussing implications and future directions of this research.

In Artificial Reality experiences, that is, interactive, unencumbered, full-body, 2D vision-based virtual reality (VR) experiences (heirs of the seminal Videoplace by Myron Krueger), there are two possible interaction paradigms, namely, first-person and third-person—which differ significantly from the classic VR first- and third-person notions. Up until now, these two paradigms had not been compared or objectively analyzed in such systems. Moreover, most systems are based on the third-person paradigm without a specific justification, most probably due to the influence of the original Videoplace system and because it is the only paradigm available in commercial development tools and leisure systems. For example, many rehabilitation projects have chosen to use these VR systems because of their many advantages. However, most of these projects and research have blindly adopted the third-person paradigm. Hence, the field of virtual rehabilitation has analyzed the beneficial properties of these systems without considering the first-person paradigm that could potentially present better adequacy. To find and understand potential differences between the two paradigms, we have defined an application categorization from which we developed two full-body interactive games and set up an experiment to analyze each game in both paradigms. We studied how 39 participants played these games and we quantitatively and qualitatively analyzed how each paradigm influenced the experience, the activity and the behavior of the users and the efficiency in accomplishing the required goals. We present the results of these experiments and their general implications, and especially for virtual rehabilitation due to the potential impact these systems may have in the well-being of many people.