In the last years, there has been an increasing interest in the design of video games as a tool for education, training, health promotion, socialization, etc. Usability, which is a key factor in any video game, becomes even more important in these so-called Bserious games^, where the users' special characteristics should be considered, and the game efficacy depends on the users' adherence and engagement. However, evaluation of the usability of this kind of games requires a redefinition of techniques, methods and even terminology. In this paper, we elicit six research questions and conduct a systematic review of the scientific literature, which resulted in the selection of 187 papers that contained the most relevant responses. The conclusions of this systematic review illustrate the general status of current academic usability evaluations of these games and the main trends in the selection of methodologies and how are they applied. This view may be a very valuable foundation for future research.

Heuristic evaluation is the preferred method to assess usability in games when experts conduct this evaluation. Many heuristics guidelines have been proposed attending to specificities of games but they only focus on specific subsets of games or platforms. In fact, to date the most used guideline to evaluate games usability is still Nielsen's proposal, which is focused on generic software. As a result, most evaluations do not cover important aspects in games such as mobility, multiplayer interactions, enjoyability and playability, etc. To promote the usage of new heuristics adapted to different game and platform aspects we propose a modular approach based on the classification of existing game heuristics using metadata and a tool, MUSE (Meta-heUristics uSability Evaluation tool) for games, which allows a rebuild of heuristic guidelines based on metadata selection in order to obtain a customized list for every real evaluation case. The usage of these new rebuilt heuristic guidelines allows an explicit attendance to a wide range of usability aspects in games and a better detection of usability issues. We preliminarily evaluate MUSE with an analysis of two different games, using both the Nielsen's heuristics and the customized heuristic lists generated by our tool.