*2.3.3 Inclusion and quality criteria*

Rather than distinguishing between inclusion criteria and quality criteria, this paper combines these two as IQC (see **Table 4**). This combination is because the inclusion criteria could also be qualified (totally fulfilled or partially fulfilled) and become one part of the article evaluation. We will withdraw the study if it cannot match any one of the two compulsory questions (CQs). Six main quality questions (QQs) are subsequently presented to assess the level of the selected article. If the article failed to be higher than the four scores, this work would also be rejected because of the low report quality.

QQ1 is estimated with different scores because different research aims reveal different study repeatability. For example, 5-scores are rewarding for the studies' attempt to improve the gamification outcome. These studies are probably continuous studies with a developed system under a reproducible experience. These articles might therefore be convincing for result reviewing. In contrast, if the research aims to design and test an MI-BCI game, it would be scored two since this game system might need more evidence for reproducible testing. MI-BCI applied for subjects training research will gain 3-scores. That is because a training environment is more challenging for MI-BCI robustness than just a game test. However, the lower level of challenge and number of supportive studies than the 'improvement' study positions them in 3 scores. We then divide the quality of articles into four levels: satisfactory, good, important, and excellent.
