## 4 Discussion
### Limitations  
This study was designed as a field study to ensure ecological validity, which precluded the randomization of the sample. The focus on ecological validity was prioritized over randomization.  
Due to feasibility constraints, the pre-post-intervention assessments were conducted immediately before and after the intervention. The anonymization of participants prevented a follow-up design, which would be valuable for investigating both CSE and K retainment.  
The intervention groups were designed to contrast the features AR and GAME. Substituting AR with traditional learning material is distinctive. However, eight game elements were applied or substituted for the latter feature. This approach is systematic in its design, though it does not guarantee the elimination of any playful character or feeling. Even the non-game-based interventions may have led to a playful experience, which could impair/diffuse the categorization of the result in game-based and non-game-based groups.  
Furthermore, game design and its experience is highly dependent on design details and players' attitudes. A slight variation in design may have led to a different outcome. The results of moderation model 3 could be attributed to the quality and design of the game or non-game.  
The learning environments were carried out as group work. In all intervention designs participants worked in small teams of four, sharing a tablet and working equipment. Setup into groups of four was random and consistent throughout all interventions. This organizational aspect of team-based learning may have impacted the participants' experiences and potentially affected participants' motivation, contribution, and performance [73]. This aspect was not further investigated and integrated into the data analysis due to feasibility and poses a limitation to the findings. The entire questionnaire contained additional learning variables (for different analyses, mentioned in another publication).  
Additionally, the accompanying supervisors and teachers may have impacted individual participants. This aspect was not further investigated, as the focus on ecological validity was prioritized and human interaction in the classroom remains an unforeseeable and instable factor.  
Questionnaire fatigue may have led to the notable drop-out rate (CSE: N = 217 to 177 and K: N = 217 to 196).  
The inconclusiveness of our results and previous findings of various research potentially may have arisen from the various designs of AR environments, divergent target groups, and different applied topics. Additionally, the research design may have varied, and different measuring instruments may have led to stronger or weaker effects. Furthermore, alternative underlying concepts and constructs are hard to compare. Combining different outcomes, such as \"performance\" or \"academic achievement\", under the same category \"learning gains\", may paint research findings with a broad brush. This also goes for the term self-efficacy, applied to various sub-domains of it.  
Due to this multiplicity of research design considerations (target groups, control groups design, measuring instruments, learning effect variables) as well as the specific design of AR learning scenarios (design, conceptualization, and application of AR technology), the results of this research cannot be generalized for the use of game-based AR in science education.  
Computer self-efficacy, investigated to grasp the participants' beliefs and judgments of themselves, in terms of using and handling digital media, is a subjective measure. Accordingly, the results are no unbiased entity and need to be interpreted with cautious consideration.  
Knowledge understood as the learning gained from our intervention could be realized as acquisition of specific skills in other research work or even have alternative underlying didactical principles when AR is evaluated in a different subject of science.