## 5 Conclusions and Future Work  
During the literature review, we found that there is no solid work focused on accessibility with WCAG 2.1. Therefore, this work proposes the application of a combined method of evaluating accessibility in serious games and establishes 29 guidelines based on WCAG. From the case study, we can conclude that the most neglected accessibility principles are operable and robust; the operable principle refers to how people interact and have control during interaction with serious games. On the other hand, \"robust\" barriers related to related ones can be addressed by including assistive technology that allows better compatibility with current and future tools.  
This combined approach can be replicated for other serious games that include users with different types of disabilities. To improve accessibility in serious gaming, we propose to include (1) automatic transcriptions or a bot to transcribe the audio or video to text without human intervention, so that the user can review the transcriptions while playing; (2) sign language to establish a communication channel with the social environment, this option is useful for users with hearing disabilities; (3) photosensitivity control, to configure the excess of light and brightness useful in users with epilepsy problems;  
Figure 6: Success criteria in manual evaluation that exceed the barriers.  
Figure 7: WCAG levels in manual evaluation that exceed the barriers.  
(4) external devices to allow virtual and augmented reality, for example, with the oculus quest the user can achieve greater immersion in the learning process; and (5) a contextual help option so that users can operate without losing sight of what they are doing. The authors can conclude that no serious games among those selected have reached an acceptable level of accessibility. Therefore, serious game developers should make significant efforts to improve accessibility.  
This study has its limitations because it is a combined method that includes a manual part where accessibility experts intervene; the evaluation results depend on the experience and ability to evaluate serious games. From the theoretical point of view, we present a new method to evaluate accessibility in serious games based on a combined method. On the other hand, in practical terms, this study tries to wake up and motivate serious game developers to apply WCAG 2.1 guidelines to make serious games more accessible and inclusive that consider diversity. Additionally, this method can serve as a reference for future studies related to accessibility in simulations and serious games.  
As future work, we suggest (1) testing this method with users with different types of disabilities and applying the corresponding disability-related guidelines; (2) generating a heuristic accessibility evaluation focused on serious games, based on the accessibility issues identified in WCAG 2.1; (3) expanding the serious games database with some applications other than serious games to deepen the analysis and evaluation, and (4) developing a software application that includes the WCAG 2.1 guidelines to assist in the evaluation of serious games.  
Conceptualization, L.S.-U. and P.A.-V.; methodology, L.S.-U.; investigation, L.S.-U.; M.G. and P.A.-V.; writing--original draft preparation, L.S.-U. and P.A.-V.; writing--review and editing L.S.-U., S.L.-M., M.G. and P.A.-V.; supervision, S.L.-M.; project administration, P.A.-V. and L.S.-U. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Universidad de Las Americas-Ecuador, as part of an internal research project FGE.PAV.19.11.  
The authors declare no conflict of interest.