## 3 Methodology
### COGNIPLAT Platform and Data Collection
The adaptability or the ability of the system to dynamically adapt the difficulty of the game to the players is an additional important feature of the platform. An experimental evaluation study of the COGNIPLAT platform took place with the participation of 10 elderly at a daily care center (7 male and 3 female, mean \(76.1\pm 7.05\) years of age, mean \(9.60\pm 2.37\) years of education). The games were accessible as an Android application on a tablet device. Each participant had the opportunity to complete twelve game sessions during the evaluation period, which lasted for about three months. During the study, the subjects had the freedom to play any of the games for an arbitrary number of rounds and in any order. Although the main objective of the experimental study was to assess the feasibility, engagement and acceptance of serious games for the elderly people, leveraging on this evaluation our aim is to classify participants to cognitive levels by using data which were collected from the game platform and relevant questionnaires. The MoCA test was used to assess the ground truth cognitive level of the participants and their score ranged between 20 and 28 (mean 24.40 \(\pm\) 2.88). MoCA has been validated for the Greek population by providing normative data [30]. Table 3 gives the distribution of the participants according to the MoCA diagnostic classification [30] and other basic characteristics of the sample. Figure 2: Examples of COGNIPLAT game screens: (**a**) the main menu; (**b**) the sound matching game; (**c**) the maze game. MCI participants were distinguished from the \"healthy group\" with a cutoff score of 23 (2 cases) for low educational level (\(\leq\)6 years) and a cutoff score of 26 (4 cases) for middle educational level (7-12 years). The mean MoCA score for the MCI group was 22.50 \(\pm\) 1.87 and the corresponding score for the Normal group was 27.25 \(\pm\) 0.96. The morphology of the sample for the two groups has similar characteristics in terms of age and gender. The mean age is comparable between the two groups although the variance is higher in the MCI group. The mean education years of the MCI group was 8.5 \(\pm\) 2.26 and for the Normal group was 11.25 \(\pm\) 1.50. The technology familiarity (e.g., frequency of computing devices and internet usage) was assessed with relevant questionnaire items in a scale of 0 to 4 and was found to be less than average for the MCI group (1.83 \(\pm\) 0.75) and above average for the Normal group (2.50 \(\pm\) 0.58). The MoCA test can assess various cognitive domains of a subject, such as attention, concentration, executive functions, memory, language, visuospatial, as well as abstraction, delayed recall and orientation. The assessment is administered in approximately 10 min. The total points a subject can score is 30. The person who administers the assessment, sums the subtotals of each individual task that are recorded on the right-hand of the questionnaire during the MoCA process. On top of that, an additional questionnaire was administered in order to collect demographic, medical and lifestyle information. A classification of the questionnaire data is performed according to standardized categories [31], as shown in Table 4.  
The data concerning the in-game performance of each subject is contained in two tables, the _game sessions_ holding data such as which user is logged in and when, and the _game rounds_ holding data such as game type, difficulty level, game outcome (success/fail), game completion time, earned points and other details regarding a single game round. During the evaluation period, in terms of recorded data entries, there were 10 subjects, 10 different game types, 119 game sessions and 2951 game rounds in total. These data are essential for this study in order to answer the main research question.