Augmented Reality and Gamiﬁcation in Education: A Systematic Literature Review of Research, Applications, and Empirical Studies

: This study scrutinizes the existing literature regarding the use of augmented reality and gamiﬁcation in education to establish its theoretical basis. A systematic literature review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement was conducted. To provide complete and valid information, all types of related studies for all educational stages and subjects throughout the years were investigated. In total, 670 articles from 5 databases (Scopus, Web of Science, Google Scholar, IEEE, and ERIC) were examined. Based on the results, using augmented reality and gamiﬁcation in education can yield several beneﬁts for students, assist educators, improve the educational process, and facilitate the transition toward technology-enhanced learning when used in a student-centered manner, following proper educational approaches and strategies and taking students’ knowledge, interests, unique characteristics, and personality traits into consideration. Students demonstrated positive behavioral, attitudinal, and psychological changes and increased engagement, motivation, active participation, knowledge acquisition, focus, curiosity, interest, enjoyment, academic performance, and learning outcomes. Teachers also assessed them positively. Virtual rewards were crucial for improving learning motivation. The need to develop appropriate validation tools, design techniques, and theories was apparent. Finally, their potential to create collaborative and personalized learning experiences and to promote and enhance students’ cognitive and social–emotional development was evident.


Introduction
Rapid technological advancements have drastically affected all aspects of life, including education. This fact has contributed to the development of the interdisciplinary field of educational technology, which has undoubtedly impacted the teaching and learning process, environments, approaches, and methods by integrating technological applications into the educational process [1]. The COVID-19 pandemic accelerated the integration of technologies into education [2,3].
Nowadays, students are digital natives as they have grown up in a digitalized world; as such, they can easily handle digital devices and media on a daily basis [4]. As access to information is instant from any place at any time, a student's way of acquiring knowledge and becoming informed has changed significantly [5]. Moreover, students form their personality in the light of flexible communities while requiring social interactions and prompt responses, and pursuing to be directly connected [6]. As a result, students' educational requirements have drastically shifted and so have their perspectives on what Aiming at addressing students' new and upcoming needs and requirements, education is transforming by integrating new technologies and technological paradigms into its process more actively [20]. The COVID-19 pandemic has further demonstrated the significance of incorporating new technologies and applying new approaches in education and the need to alter conventional learning environments and activities [21]. The combinational use of augmented reality and gamification has the potential to help toward the realization of this transformation, while at the same time yielding several educational merits and opportunities. Moreover, augmented reality and gamification share common attributes and both intrigue and motivate students to participate more actively and perform better in educational activities.
Although there have been several studies that examined the use of augmented reality and gamification in education separately, little is known regarding how they can affect education when used in combination. Consequently, the aim of this study was to carry out a systematic literature review to scrutinize the existing knowledge and studies concerning the use of augmented reality and gamification in education to establish its theoretical basis. In that view, this systematic literature review examines all types of related studies for all educational stages and subjects throughout the years. To guide the research, the following research questions (RQ) have been designed: 1.
RQ1: What are the benefits of combining and integrating augmented reality and gamification into the educational process? 2.
RQ2: What is the distribution among empirical studies, proposal and prototype papers, as well as review, conceptual, and theoretical papers? 3.
RQ3: In which countries have most related studies been carried out? 4. RQ4: What have been the main findings of the related studies regarding the use of augmented reality and gamification in education?

Research Design
In order to answer the above-mentioned research questions and meet the aims set, a systematic literature review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement was carried out [131]. As the topic analyzed was specific and involved empirical studies, case studies, reviews, proposals, as well as theoretical papers, the systematic literature review was deemed as an appropriate approach and the PRISMA statement was selected due to its highly strict rules and standards as well as the fact that it is a well-established method that is successfully applied in various topics, including education, offering comprehensive insights [132][133][134].
In order for a scientifically rigorous study to be conducted, 5 databases and a thorough combination of keywords were used to identify the related documents. More specifically, the databases SCOPUS, Web of Science (WoS), IEEE, Google Scholar, and ERIC were used. It is worth noting that through SCOPUS and WoS databases, the largest number of related documents and the most accurate ones were retrieved. This fact is in line with them being regarded as high-impact scientific databases [135].

Systematic Literature Review Process
Data was retrieved in January 2022. With a view to covering all the literature around this specific topic throughout all the previous years, no year limitation was set. A pertinent and thorough search equation was used to report the literature on the state-of-the-art while addressing all educational stages and topics. Consequently, and due to the interdisciplinary nature of the topic, the following query using wildcards and logical operators was used: "('augmented reality') AND ('gamif*') AND ('education' OR 'universit*' OR 'college*' OR 'school*' OR 'student*' OR 'pupil*' OR 'teach*' OR 'learn*')". In SCOPUS, WoS, IEEE, and ERIC databases, the search involved the title, abstract, and keyword parameters, while in Google Scholar the "allintitle" operator was used along with the keywords in consecutive order (e.g., 'augmented reality' AND 'gamification' AND 'education'; 'augmented reality' AND 'gamification' AND 'university', etc.).
The whole process, which is displayed in Figure 1, followed and abided by all the steps and guidelines of the PRISMA statement. Initially, 670 documents were reported in the 5 databases (314 in SCOPUS,204 in WoS, 80 in IEEE, 53 in Google Scholar, and 19 in ERIC). Of these documents, 220 were duplicates and were not included. Hence, 450 documents were screened. The main inclusion criteria were the combinational use of augmented reality and gamification elements, the reference to the educational context, and the studies involving either an empirical study, the development of an educational application, a proposal or prototype, a systematic review, or theoretical contributions. In total, 316 documents did not meet the research criteria and were excluded from the study. All of the 134 documents that were sought for retrieval were successfully retrieved. Therefore, 134 documents were examined for eligibility. In addition, 21 studies were excluded as they did not meet the necessary research criteria. Consequently, 113 studies were included and analyzed in the review. Appl. Sci. 2022, 12, x FOR PEER REVIEW 6 of 43 134 documents were examined for eligibility. In addition, 21 studies were excluded as they did not meet the necessary research criteria. Consequently, 113 studies were included and analyzed in the review. The 113 studies identified were divided into three categories; that is, (1) empirical studies (73 articles, pct. = 64.6%), (2) proposal and prototype papers (design-oriented without being applied in educational contexts) (27 articles, pct. = 23.9%), and (3) review, conceptual, and theoretical papers (13 articles, pct. = 11.5%) (RQ2). The review, conceptual, and theoretical papers were scrutinized and their main findings were identified. Regarding the proposal and prototype articles, suggestions, guidelines, practices, areas of focus, and findings were also examined and analyzed. The empirical studies were analyzed and compared according to the following variables:  The 113 studies identified were divided into three categories; that is, (1) empirical studies (73 articles, pct. = 64.6%), (2) proposal and prototype papers (design-oriented without being applied in educational contexts) (27 articles, pct. = 23.9%), and (3) review, conceptual, and theoretical papers (13 articles, pct. = 11.5%) (RQ2). The review, conceptual, and theoretical papers were scrutinized and their main findings were identified. Regarding the proposal and prototype articles, suggestions, guidelines, practices, areas of focus, and findings were also examined and analyzed. The empirical studies were analyzed and compared according to the following variables:

Results
A mixed-method research approach was adopted as both qualitative analysis and descriptive quantitative analysis were used to analyze the data [136]. The results acquired from the analysis of the articles and their variables from all three categories are presented below. Particularly, the results are categorized as those concerning the empirical studies (general information, research methods, variables and tools, application development information, and gamification elements, as well as main findings) in Tables 1-4, the proposal and prototype papers (general information, country, and aims) in Table 5 and the review, conceptual and theoretical papers (general information, aims, and main findings) in Table 6. To assess the potential of a mobile application that uses augmented reality and gamification to bridge the gap between education and gaming.
[137] Spain n/a Music Cognitive 5 teachers and 13 students from a musical school To break the initial curve of learning music by motivating students and facilitating the learning process through an augmented reality application.
[138] Indonesia Primary education Art Cognitive n/a To create an augmented reality application to introduce batik design as a form of cultural art to primary school students.
[139] Indonesia Primary education Culture Cognitive

Primary school students and teachers
To develop an application that uses augmented reality and gamification and to analyze its impact on primary school students' knowledge of Indonesian culture learning.    To propose a mobile augmented reality application that uses game elements to assist students' self-management in asthma education. To train students in all aspects of Kanji by capitalizing on the concept of flow to immerse students in a rich Japanese mythology game, which takes place in an augmented reality environment. [192] Malaysia Higher education Architecture Cognitive 87 university students To investigate how instructional design can assist in developing mobile augmented reality applications that create enjoyable learning environments, which promote students' active participation. [193] Argentina n/a General knowledge Cognitive

secondary and higher education students
To propose a framework for designing augmented reality applications and validating it by creating and assessing an application using the specific framework on a goose board game to reinforce the learning of concepts presented in a traditional classroom. [194] United Arab Emirates

Primary education
Learning to write Cognitive Primary school students To propose an augmented reality application that supports students by enabling them to learn at their own pace and to actively involve their parents. [195] Ukraine Secondary education

Physics and English Cognitive
Four groups of secondary school students To showcase the potential of using gaming elements and augmented reality to support the conduct of binary lessons, such as Physics and English, in secondary education. [196] Portugal K-12 education Interdisciplinary themes Cognitive

K-12 education students and 46 higher education ones
To analyze students' perception of the gamified augmented reality application regarding its usability and learning values, and to comprehend their viewpoints. [197] China Higher education Computer science (Web design) Cognitive 221 university students To present the benefits of using gamification and augmented reality to create personalized learning experiences in a classroom. [198] Thailand Higher education Teamwork n/a 5 specialists selected by purposive sampling To create an augmented reality application that promotes and increases students' teamwork and to evaluate its effectiveness. To present the design process of an augmented reality gamified learning experience and assess its impact on creating sustainable learning opportunities by increasing university students' sensory capacities. To investigate the potential of using augmented reality games to support the development of learning through games.       [152] n/a n/a n/a Mobile devices n/a [153] n/a n/a n/a Mobile devices Objectives, levels, points, timer, virtual rewards, collaboration, feedback, challenges, and progression [154] n   [169] n/a n/a n/a n/a Game-like features, tasks, and role-playelements [170] RoboTIC Unity Windows Holographic OS

Microsoft HoloLens
Game-like features, badges, and achievements [171,172] n/a n/a n/a n/a n/a  [176] n/a n/a n/a Mobile devices Virtual rewards and points [177] n/a n/a n/a Mobile devices Game-like features, quiz questions, and scores [178] TARGaLM n/a n/a Mobile devices Points, badges, and leaderboards [179] MRPT Unity Android HTC Vive Pro HMD Game-like features, scores, and feedback [180] n/a n/a n/a Mobile devices Game-like features [181] STEAM-GAAR n/a n/a Mobile devices Points, leaderboards, and virtual rewards [182] GARSTEM n/a n/a n/a n/a [183] n/a n/a n/a Mobile devices Game-like features, feedback, points, and virtual rewards [184] n/a n/a n/a Mobile devices Scores and mini games [185] n/a n/a n/a Leap Motion Controller Levels, tasks, and virtual rewards [186] n/a OpenCV n/a Mobile devices Game-like features [187] SolarSystemGO n/a n/a Mobile devices Game-like features, quiz questions, points, and virtual rewards [188] Hunting Game Generator n/a n/a Mobile devices Game-like features and quiz questions [189] Xplorerafe+ n/a n/a Mobile devices Game-like features and quests [190] MySpira Univty, Vuforia, ARKit and ARCore Android Mobile devices Game-like features, quiz questions, and points [191] Dragon Tale n/a n/a Mobile devices Game-like features, mini games, quiz questions, points, and puzzles [192] n/a n/a n/a Mobile devices Quiz questions and points Table 3. Cont.

Development Tools
Operating System Device Gamification Elements [193] n/a Unity and Vuforia Android Mobile devices Quiz questions and board games [194] n/a OpenCV n/a Mobile devices Game-like features [195] n/a n/a n/a Mobile devices Quests, puzzles, and levels [196] EduPARK Unity and Vuforia Android Mobile devices Quiz questions, points, and tasks [197] n/a n/a n/a Mobile devices and SmartBands Game-like features and tasks [198] AAR Book Model n/a n/a n/a n/a [199] Galaxy Shop Unity n/a Touchizer [228] Game-like features, quiz questions, scores, feedback, and levels [200] GaMbAR Node.js, MySQL and HTML5 n/a

Mobile devices and web-based environment
Game-like features, mini games, and levels [201] n/a n/a n/a n/a n/a  [205] n/a n/a n/a Mobile devices Quiz questions and levels [206] n/a n/a n/a n/a n/a [207] n/a Unity and Vuforia Android Mobile devices Game-like features and objectives [208] Ingress (Niantic) n/a Android and iOS Mobile devices Game-like features, badges, points, and tasks Table 4. Empirical studies: Main findings.

Ref. Main Findings
[81] Students found their augmented reality learning experience engaging, relevant, useful, and fun and regarded the quest completion and collaborative activities as highly motivating. [137] The overall experience was viewed as useful, motivating, and satisfactory by students. A friendly competition was created between students and teachers to see who would obtain the highest score.
[138] By promoting exploratory behaviors, the augmented reality application provided students with learning benefits, who in turn developed positive attitudes and found the application absorbing and enjoyable.
[139] Increased learning outcomes were observed for students who used the augmented reality game. [140] Students found the learning experience engaging and satisfactory; thus, the augmented reality application was characterized as a helpful learning tool.
[141] Students' learning motivation increased and the teaching process was more enjoyable.

Ref.
Main Findings [142] Although the application might not have the same outcomes in all contexts, positive learning results were observed in students with ASD.
[143] Based on the survey responses, the augmented reality application promoted self-learning, deepened students' knowledge, and increased their desire to learn. [144] The experience was intrinsically satisfactory with students showcasing positive emotions, which improved their mood and increased their involvement. Students who participated in the collaborative game demonstrated greater emotional affection, interest, and social interactions. [145] Significant differences were found between the control and experimental groups. Students who used the augmented reality application were deeply immersed in the experience and, hence, showcased improved learning outcomes, decreased negative emotions, and better flow state. [146] Students showcased a positive attitude toward using augmented reality in learning contexts as it positively impacted their engagement and motivation. Although the novelty of the activity attracts students, the challenge of designing and implementing augmented reality in the educational process effectively still remains. [147] The results indicated that the augmented reality application supported students' language learning in the affective, social, and cognitive domains, and contributed to their learning outcomes. The application was regarded as satisfactory, motivational, and enjoyable.
[148] Students found the learning experience motivating and demonstrated a high acceptance level.
[149] By incorporating audiovisual elements in real time, the augmented reality application helped students gain new experiences, acquire new knowledge, and hone their skills. [150] Students who used the augmented reality application showcased improved scores during post-tests while simultaneously the number of low performers decreased. [151] Students spent most of their time carrying out learning tasks and demonstrated higher interactivity and engagement in co-regulation activities. Opportunities to promote and increase collaborative learning were also showcased. [152] Students found the application motivating and easy to use, appreciated the fact that they could learn at their own pace, and developed a positive attitude toward language learning. Using multimodal material, students acquired new vocabulary in a playful manner while their vocabulary retention rate also improved. [153] Students found the overall activity entertaining and were motivated to play the augmented reality game. After using the application, students showcased improved learning outcomes and increased retention rate. [154] Students assessed the application as an enjoyable, intriguing, and attractive way to improve their skills at Mathematics. [155] Students actively participated in the learning process and found the immersion element beneficial to their learning. [156] Students found the experience satisfactory and engaging, viewed the application positively, and regarded it as an invaluable learning tool in flipped classroom contexts. A positive correlation between students' perceptions of the augmented reality application and their learning attitude was found.
[157] Students who used the augmented reality game were more creative and focused during the learning process. Their active participation and enthusiasm increased when they noticed the existence of rewards.
[158] Students found the experience enjoyable and interesting and were able to comprehend the concept of intelligent environments and how to program their behavior.
[159] The majority of students found the application useful as it helped them comprehend the subject taught better. They also positively valued the motivating aspects, which urged them to repeat tasks and revise the material studied. [160] Augmented reality applications can be combined with image recognition to expand their utilities, functionalities, and use cases, and to enrich the learning and teaching processes via visual objects.
[161] The gamified augmented reality application improved students' motivation and created a relaxed learning atmosphere, which fostered collaborative learning and strengthened their willingness to discuss. [162] Although major differences in terms of motivation were not observed between the gamified and non-gamified applications, students who used the gamified version demonstrated higher knowledge gain. Points were the determining gamification element that urged students to participate when compared to virtual badges and timers. [163] By providing students with interactive images and information that can easily be repeated, promising learning outcomes can be yielded.  [164] Students showcased satisfactory results and enthusiasm and highlighted that the experience stood out from conventional teaching methodologies. The system was flexible, intuitive, presented clear commands, and had acceptable latency.

Ref. Main Findings
[ 165] The application was regarded as useful to the students who acquired a better comprehension of cybersecurity and learned how to stay safe online. [166] The application performance was good and the participants showed good acceptance levels, found it useful and interesting, and quoted that it could be used as an effective supporting tool in the implementation of various teaching aims.
[167] Students demonstrated increased learning motivation and positive attitudes toward the application.
[168] Students enjoyed the overall experience while being more engaged and presenting positive emotions. [169] The results indicated higher student motivation, participation, and learning outcomes. [170] The application increased students' motivation and interest in programming. [171,172] Most university professors are acquainted with the use of augmented reality and can perform the most trivial tasks with ease. Additionally, they believe that mobile learning using augmented reality can be incorporated into education and increase students' engagement. Small differences between genders and continents were found.
[173] Students' task completion improved and teachers regarded the augmented reality game as helpful and useful.
[174] The majority of students enjoyed the augmented reality game experience and would be more than willing to participate in similar activities. Teachers confirmed that the application fulfilled the contents and aims of the syllabus.
[175] Students were really engaged and motivated during the learning activities. The size of the mobile device affected their collaboration. [176] Students who used the augmented reality application performed better, were more focused, and demonstrated more positive attitudes. Technology-enhanced contextualized learning can promote and increase students' learning attitudes and performance. [177] Students felt a sense of satisfaction, regarded the experience as suitable for their learning needs, and achieved better learning outcomes.
[178] Students found the overall approach more engaging, motivating, and interesting in comparison to traditional approaches and exhibited better learning outcomes. [179] Students felt more motivated while using the application particularly due to the positive reinforcement text and regarded it as fun, interesting, and intuitive. [180] The participants viewed the application positively as it promoted their environmental awareness and improved their language learning experience. [181] The results indicated the correlation between grit and learning achievement as well as the application positive impact on improving students' internal factors of grit-that is hope, purpose, practice, and interest. [182] Students' attitude toward the application, their intention of using it, as well as its practicability and entertainment aspects were the best predictors for its effective design. [183] The results indicated that the augmented reality game positively affected students' learning interests and motivations.
[184] The application helped students increase their spatial reasoning skills, helped narrow the gender gap in spatial reasoning, and was mostly helpful for students with lower prior spatial reasoning performance. [185] Students showcased great empathy with the augmented reality tool and demonstrated increased learning outcomes and better performance in comparison to traditional approaches.
[186] Students displayed improved writing skills and learning outcomes.
[187] The augmented reality approach managed to effectively engage students, draw their attention, and promote interdisciplinary subject matter learning. [188] Students were motivated by the augmented reality tool and regarded it as a supportive tool to traditional teaching that trigger their interest and enjoyment. [189] The augmented reality application intrigued students' motivation and excitement and increased their collaborative learning by instilling teamwork and discussions.  [190] Students who used the augmented reality application were more engaged in the learning activity and answered questions more accurately. [191] The augmented reality application improved students' learning outcomes while creating a fun and entertaining environment and integrating mini games. [192] The application supported technology-enhanced active learning and provided students with interactive visualizations in a more exciting and gratifying way. Students were more actively and passionately involved in their activities and preferred this teaching method over traditional ones as it was more efficient and intriguing. [193] Students exhibited improved knowledge retention and learning results. Better outcomes were observed for students who played the augmented reality game more times. [194] Students who used the augmented reality tool had better learning results and honed their writing skills. [195] The use of gamification and augmented reality supports binary lessons and increases students' cognitive ability. [196] The application promoted active learning in an enjoyable manner and it was assessed as interactive and easy to use. [197] The application offered students more personalized learning opportunities, freedom, and choices in their learning, and increased their active involvement, satisfaction, positive attitude toward learning, exercise completion rate, and grades. [198] The specialists regarded the application as a suitable solution to engage and motivate students and increase their teamwork and communication skills. [199] The results indicated that using augmented reality games instead of computer games engages students more effectively. [200] The gamified augmented reality application improved students' motivation and satisfaction. [201] Gamified augmented reality applications meet the essential requirements to be adopted in the educational process to better engage and motivate students. [202] Students perceived the application positively while regarding it as easy to use and enjoyable. Although negative perceptions were also found, the benefits of positive game characteristics outnumbered them. [203] Gamified augmented reality affects the educational process positively as it creates new immersive learning environments. Students' feedback regarding their overall learning experience was positive. [204] When used in conjunction with gamification, augmented reality creates new learning opportunities as it constitutes an impactful learning approach for real-world and classroom settings and it enables a preparatory transition from informal learning activities to formal design-focused ones.

Ref. Main Findings
[205] Based on teachers' viewpoints, personalized gamified augmented reality experiences enable students to form a deeper learning of the given subject while increasing their engagement and to improve their learning outcomes through real-time feedback. [206] Gamified augmented reality experiences were positively viewed by students as they provide them with a sense of independence in their learning, they create more enjoyable learning environments, and can be applied to numerous courses. [207] There are learning differences between static and dynamic augmented reality learning experiences. Although students are motivated in both cases, they perform better and achieve greater learning outcomes in dynamic augmented reality environments.
[208] Using gamified augmented reality has the potential to yield several educational benefits due to its motivational nature.
The complete results of the countries in which the studies took place are displayed in Figure 2, as a total and based on their categories. The countries (RQ3) that mostly carried out empirical study research into the use of augmented reality and gamification are: Portugal, China, Malaysia, Spain, Taiwan, and Greece. The countries that carried out proposal and suggestion papers are: Greece, the United States, Hungary, Italy, and Mexico. The countries that mostly contributed with reviews, conceptual and theoretical papers are: Spain, the United States, and Portugal. Finally, based on the total amount of articles published, the countries that examined the use of augmented reality and gamification in education more actively were: Spain, Greece, Portugal, the United States, China, Malaysia, and Taiwan.
Portugal, China, Malaysia, Spain, Taiwan, and Greece. The countries that carried out proposal and suggestion papers are: Greece, the United States, Hungary, Italy, and Mexico. The countries that mostly contributed with reviews, conceptual and theoretical papers are: Spain, the United States, and Portugal. Finally, based on the total amount of articles published, the countries that examined the use of augmented reality and gamification in education more actively were: Spain, Greece, Portugal, the United States, China, Malaysia, and Taiwan. Due to the number of variables and studies, the information is clustered and displayed accordingly on different tables to improve readability. 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). Due to the number of variables and studies, the information is clustered and displayed accordingly on different tables to improve readability. 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).
(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).   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). 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).
(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).  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 [81,232], 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. Although most of the studies (freq. = 36, pct. = 49.32%) did not specify the particular operating system on which their application was running, from the ones that did, android (freq. = 24, pct. = 32.88%) was the preferred operating system, followed by iOS (freq. = 6, pct. = 8.22%), both android and iOS (freq. = 5, pct. = 6.85%) and Windows Holographic OS (freq. = 2, pct. = 2.74%), as it can also be seen in Figure 6 (RQ11). This fact can be justified when taking into consideration the operating systems' worldwide market share [233] and the fact that the most popular augmented reality Software Development Kits (SDKs) natively support the development of applications for the Android operating system. The Unity platform (freq. = 26, pct. = 35.62%) was the most widely used development tool along with Vuforia engine and SDK (freq. = 15, pct. = 20.55%) (RQ11). It is worth noting that the majority of the studies (freq. = 34, pct. = 46.85%) did not specify which development tools were used for the creation of their application. Regarding the devices used during the experiments (Figure 7), mobile devices had the overwhelming majority as they were used in a total of 61 studies (83.56%) with only a few studies utilizing specialized equipment, such as Microsoft HoloLens (freq. = 2, pct. = 2.74%), HTC Vive Pro HMD (freq. = 1, pct. = 1.37%), Leap Motion Controller (freq. = 1, pct. = 1.37%), and Touchizer [228] (freq. = 1, pct. = 1.37%), while 7 (9.59%) studies did not specify the particular devices that were used (RQ12). As far as the gamification elements used are concerned, the applications mostly used points, scores, leaderboards, game-like features, mini games and puzzles, virtual rewards (e.g., badges, achievements, tokens, etc.), objectives, quests and tasks, quiz questions, challenges and difficulty levels, instant feedback, timer, and digital storytelling (RQ13). Moreover, studies capitalized on students' competitive spirit and collaborative learning activities. Role-play and digital storytelling were also the main aspects of certain applications while other studies used additional external material in the form of cards, board games, slides, learning sheets, etc. tions mostly used points, scores, leaderboards, game-like features, mini games and puzzles, virtual rewards (e.g., badges, achievements, tokens, etc.), objectives, quests and tasks, quiz questions, challenges and difficulty levels, instant feedback, timer, and digital storytelling (RQ13). Moreover, studies capitalized on students' competitive spirit and collaborative learning activities. Role-play and digital storytelling were also the main aspects of certain applications while other studies used additional external material in the form of cards, board games, slides, learning sheets, etc.

Ref.
Country Aims [232] Malaysia To explore how using gamification and augmented reality can engage students in language learning.
[234] Australia To examine how augmented reality and tangible user interfaces can assist in learning computer science concepts and programming skills, such as debugging.
[235] Hungary To showcase how gamified elements and augmented reality can provide immersive practicing exercises.
[236] Spain To enhance the educational process of teaching and learning mathematics through the combinational use of gamification and augmented reality.
[237] United States To showcase how the use of blockchain and augmented reality can assist in keeping track of digital assets in virtual spaces.
[238] Germany To present a gamification concept for augmented reality virtual laboratories to increase students' practical skills.
[239] Hungary To explore how augmented reality tools that utilize gamification elements can increase students' spatial skills.
[240] Greece To showcase how an extended reality platform that uses gamification can support conventional educational practices in laboratory-based training.
[241] Italy To present an augmented reality application enriched with game design elements to facilitate university students' learning about human anatomy.
[242] India To design and create an augmented reality game that promotes primary school students' programming skills development.
[243] Spain To showcase the potential of using gamified augmented reality experiences through mobile applications in educational context. [244] United States To propose an interdisciplinary approach using augmented reality and gamification elements to support students' mathematics learning.
[245] The Netherlands To present a framework for creating mixed reality gamification applications to allow students to train in immersive 3D environments. [246] Finland To show how an augmented reality application can support and guide students during their orientation week.
[247] United States To suggest how an augmented reality escape room could support and enrich a wide range of learning experiences.

Ref.
Country Aims [248] Greece To present the developmental process of creating an augmented reality application that uses gamification aspects to support learning and teaching activities.
[249] Argentina To present a gamified augmented reality application that aims at supporting collaborative learning, enriching students' learning experiences, and increasing teacher-student interaction.
[250] Thailand To propose a gamified augmented reality application to enhance students' grit.
[251] Mexico To explore how augmented reality applications that use gamification elements can support and increase students' reading abilities as a means to further strengthen their personal, work, and social relations.
[252] Greece To evaluate whether mixed reality digital games can support and enhance future learning and teaching of various educational contexts.
[253] Italy To show a prototype gamified augmented reality application that aims to improve cultural heritage learning.
[254] Romania To showcase the results of applying a gamified augmented reality application to facilitate foreign language learning while making it more enjoyable.
[255] Brazil To propose an augmented reality framework that uses gamification elements to facilitate and support the learning process of students with intellectual disabilities.
[256] Taiwan To present the benefits of using content-aware augmented reality applications in educational settings.
[257] Greece To explore how gamified augmented reality experiences can support lifelong learning and cultural education based on an augmented reality application, which focuses on the subject of science.
[258] Greece To explore how augmented reality and gamification can facilitate and support the comprehension of subject-specific matters while engaging learners in an enjoyable experience.
[259] Mexico To present the development of an augmented reality mobile application that uses gamification elements to improve students' geography knowledge.
Appl. Sci. 2022, 12, x FOR PEER REVIEW Furthermore, Table 5 depicts the basic information regarding the proposal totype studies, such as country and aims. The country, aims, and main finding review, conceptual, and theoretical papers are displayed in Table 6.

Ref.
Country Aims [232] Malaysia To explore how using gamification and augmented reality can engage students in langu  Table 6. Review, conceptual, and theoretical papers: general information.

Ref. Country Aims
Main Findings [260] United States To discuss the history of instructional design and technology field in four time periods while presenting technologies such as augmented reality, gamification, mobile learning, etc.
In order for new technologies to be adopted in education, teachers should realize their value, experience positive effects themselves, and feel confident and comfortable when using them. Learning and instructional design theories have evolved to technology-centered to address the new requirements.
[261] Philippines To propose a supplementary learning tool framework for developing educational applications using augmented reality, Unity, and Vuforia to enhance the learning process.
Augmented reality and gamification as supplementary learning tools are effective.
[262] Spain To present the key elements that must be taken into account when creating online tools that utilize gamification and augmented reality.
When combined with gamification, mixed reality applications can offer several benefits to students and the educational process. [

263] Portugal
To comprehend and analyze the gaming strategies that can be used in immersive technologies to improve foreign language learning.
Using gaming strategies along with immersive technologies, and particularly augmented reality can facilitate and enhance foreign language learning.
[264] Spain To present a research project that applies an instructional technology-based model in a bilingual education context using augmented reality and gamification.
The use of gamification and augmented reality resulted in several educational benefits, such as improved health awareness, engagement, and linguistic skills, and increased physical exercise.

[265] Portugal
To provide an overview of the concepts of immersive learning systems and gamification strategies.
n/a [266] United Kingdom To analyze the existing virtual and augmented reality taxonomies while focusing on their interconnection with gamification elements.
A proposed taxonomy and its facets were presented, which classify immersive technologies based on several attributes, including gamification.

[267] Australia
To present the advances made in the educational sector via the Unity game engine and to showcase how it can contribute to teaching students to use immersive technologies.
Practices were suggested to better implement gamification and mixed reality applications in education during the COVID-19 pandemic.

[268] China
To examine the factors of an augmented reality application design that can better support students' early language acquisition.
The main augmented reality learning activities and design strategies were presented. Specifically, the use of game mechanisms with a discovery strategy improved students' motivation.
[269] United States To showcase how gaming technology innovations in the form of digital games and augmented reality can impact education and particularly in the field of health and physical education.

n/a [270] Spain
To present and analyze some indicative applications and activities that use ICT, including games and augmented reality in teaching activities.
Augmented reality, gamification, and mobile learning have the potential to reshape educational practices and offer improved learning outcomes.
[271] India To examine how augmented reality, gamification, and adaptive learning can increase the engagement of Massive Open Online Courses (MOOCs). When adopted by MOOCs, augmented reality, gamification, and adaptive learning can lead to more interactive, pervasive, and engaging learning environments in diverse educational domains.

[272] United States
To present instructional design principles that can assist in the development of improved augmented reality learning experiences.
Fantasy, challenge, and curiosity are the main design principles that can leverage the unique affordances of augmented reality in education.
Furthermore, Table 5 depicts the basic information regarding the proposal and prototype studies, such as country and aims. The country, aims, and main findings of the review, conceptual, and theoretical papers are displayed in Table 6.

[270] Spain
To present and analyze some indicative applications and activities that use ICT, including games and augmented reality in teaching activities.
Augmented reality, gamification, and mobile learning have the potential to reshape educational practices and offer improved learning outcomes.
[271] India To examine how augmented reality, gamification, and adaptive learning can increase the engagement of Massive Open Online Courses (MOOCs).
When adopted by MOOCs, augmented reality, gamification, and adaptive learning can lead to more interactive, pervasive, and engaging learning environments in diverse educational domains. [272] United States To present instructional design principles that can assist in the development of improved augmented reality learning experiences.
Fantasy, challenge, and curiosity are the main design principles that can leverage the unique affordances of augmented reality in education.

Summary of the Results and Main Findings
To summarize the main findings and details of the above-mentioned information and studies, it can be said that the main findings of the empirical studies, proposal, and prototype papers as well as review, conceptual, and theoretical papers, all came to the same conclusion that several benefits could be yielded from the integration of augmented reality and gamification into the educational process (RQ15). To address RQ1, the main findings are summarized. Particularly, when used in a student-centered manner, following proper educational approaches and strategies and taking students' knowledge, interests, unique characteristics, and personality traits into consideration, the use of augmented reality and gamification can bring about positive outcomes, benefits for students, assist educators, improve the educational process, and facilitate the transition toward technology-enhanced learning. More specifically, increased students' engagement, motivation, active participation, knowledge acquisition, focus, curiosity, interest, enjoyment, and learning outcomes were observed. Positive behavioral and psychological changes as well as opportunities to create personalized learning experiences were also demonstrated. While being immersed in the learning activities, students could experience situations and environments that they would not have the chance to experience otherwise and found it easier to comprehend the learning material since they could acquire hands-on experience in safe virtual environments. Moreover, new opportunities to promote and adopt collaborative learning activities emerged. It is worth noting that despite the vast number of studies explored in this literature review report positive results, there are industry-focused reports and projects that failed to result in positive outcomes.
The use of gamification elements was also viewed as positive in the educational process. Specifically, it made the overall learning experience more enjoyable and intriguing, increased students' engagement, and kept them more motivated not only to stay focused and participate actively but also to perform better, which in turn led to increased academic performance. The use of virtual rewards was a significant factor, which, in several cases, further improved students' learning motivation. Students also positively regarded the use of difficulty levels, instant feedback, and the ability to review their performance. Opportunities to create collaborative learning activities and to capitalize on the spirit of friendly competition were also observed.
In addition to students' viewing the integration of augmented reality and gamification into education as positive, educators also valued it equally. The selection of the appropriate strategies and approaches was deemed as a determining factor to the successful integration. No matter how much augmented reality, gamification, and technology in general advance, educators are the ones who should familiarize themselves with the state-of-the-art technologies, applications, and approaches, and become more comfortable and confident when using them to incorporate them into their teaching process. The role of educators still remains crucial in the educational process and for students' development, and they are the ones who should strive to offer their students the best learning experiences possible while taking advantage of novel technological tools. With the aim of facilitating the adoption of augmented reality and gamification in the educational process and selecting the most suitable approach, there is a clear need for validated evaluation tools and theories to be developed to assess the applied interventions and measure their effects in a standardized and valid manner [86].
Based on the above-presented results, Spain, Greece, Portugal, the United States, China, Malaysia, and Taiwan were the countries that examined most the integration of augmented reality and gamification into education. Most studies were published in the year 2020. Higher education was the educational stage, which the majority of the studies focused on while the STEAM-related subjects, which are connected with problems that students face daily [273], and language learning, were the subjects investigated most. Assessing the impact of augmented reality and gamification in education and comprehending the participants' viewpoints were the main aims of most studies. Students were the main target sample with most of the variables analyzed being factors related to them. Ad hoc questionnaires and qualitative research approaches were mostly used. A satisfactory number of qualitative studies were also carried out, which is essential to offer more collective insights into designing better UX [274]. Although the documentation of the development process was not satisfactorily displayed and examples of the developed application were not presented in several cases, most of the studies focused on the use of mobile devices, used Unity and Vuforia as their main development platforms, and android as the operating system of their application. Not using specialized equipment to carry out the experiments showcases the potential of implementing augmented reality experiences easily and affordably in the educational process. Finally, the vast majority of the studies focused solely on students' cognitive development. As one of the main roles of education is to promote students' social-emotional development, more emphasis should also be placed on evaluating the impact of augmented reality and gamification on students' social-emotional development, and how education could contribute toward improving it.

Discussion
Along with the technological advances, the teaching and learning methodologies and approaches are also evolving to address the new and upcoming educational needs and requirements [275]. Due to this fact, technology-enhanced learning has become more essential, learning activities are progressing toward being more student-centered, and the educational content is enriched by multimedia elements to be more interactive [276]. Nonetheless, it is of great significance to take cultural, moral, and ethical factors into account when trying to adopt and implement new technologies and approaches in educational context to achieve better outcomes and facilitate the dissemination of technology [31,277].
Both augmented reality and gamification are in line with the engagement theory, which supports technology-enhanced teaching and learning [278]. Additionally, they are in accordance with the instructional theory, which supports that when students cultivate their skills in environments similar to real ones, successful learning can be attained [279,280]. Using augmented reality and gamification can enhance students' 21st-century skills, which are fundamental to the educational process [15], and help them cultivate their decisionmaking, social interaction, conflict resolution, and emotional awareness, which are essential in modern society [281]. Hence, they play a vital role in enriching the teaching and learning activities and transforming traditional education into technology-enhanced education while increasing learning outcomes. Both gamification and augmented reality are regarded as essential in developing instructional media, theories, approaches, and designs, which can be applied in several domains, including education [260]. Additionally, they promote and support ubiquitous learning and pervasive learning. Particularly, augmented reality is regarded as a significant innovation in the field of educational technology [282] and as an emerging technology, which can facilitate the creation of inclusive learning experiences [283]. On the other hand, several aspects and elements of gamification are based on educational psychology; therefore, gamification plays a significant role in the development of educational technology and the construction and transformation of education [91,284].
Through the engaging and immersive experiences that are created in safe and hybrid environments, which support guided learning, several educational benefits can be yielded and learning opportunities are brought about [285,286], such as students acquiring knowledge based on hands-on experiences [234] and the potential to apply new pedagogical approaches and methodologies [287]. Hence, experiential learning, which supports concrete experiences, reflective observation, abstract conceptualizations, and active experimentation, and in which learners personally experience and control the learning activity, is promoted [288,289].
Due to the versatility of augmented reality and gamification, both individual and collaborative hybrid learning environments can be created [290]. In particular, by participating in authentic group activities, students demonstrate increased engagement, enthusiasm, and interest in the learning activities, participate more actively, and enhance their critical thinking and problem-solving skills [291][292][293]. As gamification promotes socialization [294], it can create enjoyable social interactions among groups while promoting satisfaction, productivity, collaboration, positive behaviors, and communication [295][296][297]. Thus, gamification elements acting as motivators can positively affect performance in general, even in fields that are not directly related to education, and assist in building core career competencies [298,299], while simultaneously serving as social comparison tools [111,143].
In order to create effective gamification strategies for learning through augmented reality and digital media, thorough planning and analysis, which take learners' characteristics, learning objectives, as well as the multimedia educational content and activities into consideration must first be conducted [300]. Additionally, to achieve the desired for each case learning outcomes, it is critical to provide students with appropriate and instantaneous feedback [301], to assess their perceived enjoyment and usefulness [302], to set clear goals, instructions, and expectations [303,304], and to design and incorporate activities that stimulate students' intrinsic and extrinsic motivations [305]. Based on the motivational theory, as students' motivation increases, so do their engagement, involvement, and commitment [306]. In addition, high motivation is a significant predictor of deep immersion, which can positively affect students' academic performance [307], time spent on learning activities [308], higher-order thinking, and meaningful learning [309], as well as behaviors and attitudes toward learning [212]. As games and gamification elements are intrinsically satisfying, they can also positively impact students' emotions [144,310], which are essential aspects of education as they can either enhance or impede learning and students' attention and engagement [145,311]. Consequently, augmented reality and gamification support the constructivist learning theory and situated learning theory, which in turn assert that when students actively participate in the learning activities, they are more inclined to learn and achieve better learning outcomes [17,146,312].
Gamified augmented reality applications can impact students' social, cognitive, and emotional domains [147]. Therefore, many factors should be taken into account when designing and developing such educational applications [313,314]. Due to the multimodal nature of both gamification and augmented reality, particular attention should be paid to designing learning activities that do not overload students' cognitive capabilities [315,316]. Thus, the diverse gamification elements, which are used to provide a positive and interactive learning climate [93], and engage students more actively and for longer time periods [317], should focus on addressing specific educational contexts and activities [318].

Conclusions
The COVID-19 pandemic has made the need for technology-enhanced learning more evident. Students' educational requirements and expectations have drastically changed as they grow up in environments where technology is an essential part of everyday life. Consequently, students are seeking for more meaningful learning experiences through educational means and approaches, which are more engaging, motivating, and immersive. The application of augmented reality and gamification in education is gaining ground.
The aim of this study was to scrutinize the existing literature concerning the use of gamification and augmented reality in the educational process. Therefore, a systematic literature review was carried out. According to the results, their use in teaching and learning activities can improve the overall educational process, while also assisting educators and yielding numerous merits for students. Additionally, their integration into education facilitates the transition toward technology-enhanced learning. Nonetheless, in order for all these to be realized, their integration should follow proper educational strategies and approaches, have students at its core, and take students' knowledge, interests, unique characteristics, and personality traits into account.
In particular, the use of augmented reality applications enriched with gamification elements resulted in increasing students' engagement, motivation, active participation, knowledge acquisition, focus, curiosity, interest, enjoyment, academic performance, and learning outcomes. Furthermore, positive behavioral, attitudinal, and psychological changes were demonstrated. The overall experience and impact of their combination was positively viewed and assessed by both students and educators. Gamification elements had a significant impact on teaching and learning activities. Virtual rewards, in particular, were a vital factor in improving learning motivation and students' engagement. Their ability to create immersive environments, which promote collaborative and personalized learning experiences, was highly regarded. Finally, based on the analysis, the use of gamification elements and augmented reality technology contributed significantly to promoting and enhancing students' cognitive and social-emotional development.
The merits acquired through combining gamification with augmented reality were of great significance. Nonetheless, in order for them to be more widely accepted and adopted in education, general innovation and improvement through educational technology should be encouraged, standardized validation and evaluation tools need to be developed, more effective learning strategies and approaches need to be further explored, and cross-cultural studies that take into consideration the participants' unique characteristics should be carried out. Finally, it is of great importance not only to focus on improving students' academic performance but also to explore and enhance their social-emotional development and 21st-century skills cultivation.

Data Availability Statement:
The datasets analyzed in this study are available from the corresponding author upon reasonable request.

Conflicts of Interest:
The authors declare no conflict of interest.