## 5 Results
Specifically, Table 1 depicts the main information of the empirical studies, Table 2 showcases their research methods, variables, and tools, Table 3 presents their application development information and gamification elements, while Table 4 quotes their main findings (RQ4). Based on the above-presented information, several observations can be made. Figure 3 depicts the results regarding the educational stage, which the articles emphasized. Most of the studies focused on higher education (freq. = 31, pct. = 42.47%), followed by primary education (freq. = 20, pct. = 27.4%), secondary education (freq. = 11, pct. = 15.07%), and K-12 education (freq. = 7, pct. = 9.59%) (RQ5). In total, 4 (5.48%) studies did not specify the educational stage or age of the participants. As it can be seen in Figure 4, the majority of studies focused on students' cognitive development (freq. = 63, pct. = 86.30%), 2 (2.74%) studies focused on students' social-emotional development, 3 (4.11%) studies emphasize both students' cognitive and social-emotional development, while 5 (6.85%) studies did not give any specification (RQ6). Although some studies analyze and take teachers' viewpoints into account, the majority of the studies use students as the main participants (RQ7). Despite the fact that the goals of the studies are diverse, most of them aim at improving students' learning experience and academic performance while increasing their motivation and engagement and providing them with an intriguing and enjoyable learning environment (RQ8). When clustering the main areas of focus of the given studies, the majority of them focused on STEAM-related fields, particularly computer science and mathematics, followed by language learning, medical and healthcare education, culture and history, as well as literacy skills (RQ9). Figure 2: Countries in which the experiments/studies were carried out. Moreover, the research methods that the studies of this category used are displayed in Figure 5. The majority of the studies used quantitative approaches (freq. = 45, pct. = 61.64%) followed by qualitative (freq. = 14, pct. = 19.18%) and mixed (freq. = 14, pct. = 19.18%) methods (RQ10). Although most of the questionnaires and surveys used were ad hoc, popular, and validated in the field of education questionnaires, such as the Technology Acceptance Model (TAM) [209, 215], Instructional Material Motivation Survey (IMMS) [214], Presence Questionnaire [216], Motivated Strategies for Learning Questionnaire (MSLQ) [227], Intrinsic Motivation Inventory (IMI) [225], Achievement Emotions Questionnaire (AEQ) [211], System Usability Scale (SUS) [222], Goal-Question-Metric (GQM) [229], and the Flow Experience Questionnaire [212] were also used. Some studies followed guidelines and adopted items in their survey from questionnaires, such as those presented in [210, 215, 218, 220, 221, 223, 224, 226, 230, 231] (RQ10). The main variables used were related to students' motivation, viewpoints, and learning outcomes (RQ10). Figure 4: Empirical studies: developmental categories. Figure 3: Empirical studies: educational stages. Furthermore, a lack of a thorough display of examples of the developed applications, a detailed description of the methods, tools, and particularly of the approaches used for their development, technical, as well as provision of resources and repositories for readers to use and test the applications themselves was evident. Some examples of development methodologies, models, and approaches used during the Software Development Life Cycle (SDLC) were: Analysis, Design, Development, Implementation, and Evaluation (ADDIE) model [81; 322], incremental development [138], waterfall model [138; 139], agile methodology [140], quasi-experimental design [141], and the octalysis framework [142] (RQ11). Future studies should provide such information so that it would be possible to answer key research questions, such as how specific development methodologies and approaches affect the success of adopting and using technologies and applications in education.