The first phase consists of an online survey aimed at identifying important tools and methodologies for each stage of development, as well as across all stages of development. To structure this survey the TRL model will be used as a conceptual framework (appendix 1). The different levels of the model will be used as stages of development to base the questions on. However, the aim is not to strictly adhere to this model, but to gather input on what methods should be used and what can be adjusted from existing models such as the TRL model to maximize adoption of serious games into care. Furthermore, the survey will try to identify key principles that should be taken into account across the entire developmental process of serious games for rehabilitation. These key principles, such as a user-centered approach, working evidence-based, maximizing engagement of end-users, etc., are the foundation for the developmental process and should be adhered to throughout the entire process.

The second phase consists of focus groups that will be organized to discuss the results of the online survey and add missing data if needed. The focus group discussions will also be structured based on the TRL model used during the survey and will expand on the results mentioned by the experts (appendix 2 and 3). After all focus group discussion are completed the results will be anonymized, aggregated and reported to the experts. This will provide them with the opportunity to further revise their answers based on all the results.

The third and final phase consists of consecutive online surveys in which the experts are asked to rank the different items that were mentioned in the previous phase on a five-point Likert scale (Appendix 4). Similar to the focus group discussions, the answers from these phases will be anonymized, aggregated and reported to the experts after each ranking phase. Experts will have the opportunity to revise their answers across multiple phases. This ranking process is repeated until consensus is reached for all stages. Consensus will be defined as percentage of agreement and the cut-off will be 75%, as a percentage between 70% and 80% is recommended in Delphi studies.

The first phase will consist of an online survey questionnaire aimed at identifying key development methods and tools for each stage of development. The survey will be structured using the Technology Readiness Level model and, by using open questions, experts will be asked to give their input on this model and the important items for each stage of development. Furthermore, the experts will be asked to identify the key principles that they find detrimental to the development of serious games for rehabilitation across all stages of development. Building on the results of this survey, focus group discussions will be organized.

Throughout the Delphi study, qualitative data will be collected (online surveys, focus group discussions, etc.) from experts in the field of serious games for rehabilitation on what methods and/or tools shoudl be used in the development process of serious games for rehabilitation. This data will be collected for all different stages of the development process. Furthermore, overarching key principles that span across all stages of development will also be identified based on expert opinion.