**2. Design Principles for the Gamification Platform**

The design of the gamification and coaching platform adheres to basic principles of healthcare, design principles for serious gaming as well as design principles for behaviour change support systems. Care values were considered in determining design, especially regarding what techniques and content the system implements, how the system communicates with the user, and how the system treats personal information, regarding security and privacy issues. The gamified platform involved introducing intelligent systems to users that could to some extent take over the role of human

caregivers. This raised issues of responsibility for protecting care values [50]. In our view, a system can never take away the responsibility from the human user (e.g., the care provider, or the patient). On the contrary, the design should aim at supporting the patient in becoming a responsible person in their self-care by providing the patient the means, along with supportive motivation, to make a well-informed decision. Tailoring to the individual user and his or her social and intellectual abilities was therefore an important requirement for the design. The aim of technology for self-management in healthcare is not to completely replace the human care system but to support and enhance it. The PERGAMON system was designed to be integrated in the care and treatment of young patients by the medical caregivers, e.g., pediatricians, diabetes nurses, and informal carers. Patient's credibility rating of the system depends on how trustworthy the medical experts are that provide input into the design of the system. Educational goals and targets of diabetes self-management formulated by diabetes care organizations were used to drive the content and design of the system as a whole as well as for the specific themes of the games in the system. Specifically, these goals (diabetes educators) were balancing energy through medication intake, healthy eating, being physically active, learning how to monitor blood sugar levels, coping with high and lows of BG and how to reduce risks associated with BGM. The system guides the individual and establishes together with the user specific, measurable, attainable, realistic, and timely (SMART) goals [51].

The design of a behaviour change support system for health interventions [52] involves the implementation of several behaviour change techniques, such as feedback and monitoring, reward and threat, and social support. A behaviour change technique is a component of an intervention designed to alter or redirect causal processes that regulate behaviour [53]. They are based on socio–psychological behaviour theories, e.g., Goal-Setting [54], Self-Determination Theory [55]. Behavior change techniques (BCTs) were integrated into the Persuasive System Design Model (PSD) for behaviour change support systems [52] that we use to describe the system's design. The PSD model has four categories: primary task support, dialogue support, system credibility support and social support, each with a number of design principles (to be distinguished from the moral principles of health care). Key aspects of BCTs were integrated, e.g., self-monitoring, rewards or provide information about others approval. Although Abraham et al. [53] presents 26 BCTs, the principles in the category of System Credibility Support in the PSD model do not occur in the BCTs listed. This is understandable because the PSD is intended for the design and evaluation of a technical system, not human beings per se. These systems function as more or less autonomous entities in situations where the medical care giver is not immediately present for the user. Also, by their very nature, technical systems have —seen from a design perspective abstract users so that for the system designer tailoring and personalisation become a concern (partly solved by explicit user models and use of persona in the design process) where treatments by human caregivers and coaches (different from rule following machines) are tacitly assumed to tailor their treatment to the individual patient.

Some of the design principles of the PSD model are implemented in our system by means of specific game elements (which encompass game mechanics, themes, game characters, challenges, rewards) from game design [28]. For example, the principles of reduction and tunneling in the PSD model are materialized by dedicated learning tasks in different mini games and by distinguishing different reachable goal levels. Other principles are implemented in actions of the virtual coach: praise, rewards, reminders, suggestions as well as by various game elements. Similarity and social role are materialized by game elements that aim at identification with the main character in the game as well as by the use of a similar character for the virtual coach.

The educational goals for diabetes care (e.g., the BCT provide information on consequences [53]) are implemented in the adventure game, called the Tako Game, in particular in a number of integrated educational mini games and by educational elements such as videos. The Tako Game is a "pervasive" game in the sense that it expands the "magic circle" of play [24,28]: the border between game world and reality is blurred by making daily self-management activities relevant in the game.
