## 2 Materials and Methods
### Methods  
Participants were recruited based on their expressed interest in the study. A prerequisite was that they had to be 18 years or older. Since the sample was not homogenous, in the sense that they were not all part of the same class or with the same background, it was essential to define their level using a language assessment test. To do that, the Cambridge General English Language Assessment Test [55] was chosen after taking into account specific criteria regarding accessibility, conciseness and quality. Twelve participants completed the test prior to the creation of the ER, achieving scores placing them at a B1 to B2 level. These scores determined the level for which the educational intervention was designed, with the rest of the learners being required to achieve scores within this range. Out of 26 individuals who initially expressed interest, 20 met the required proficiency level and were finally selected. The study incorporated comparative explanatory research [56] to explore and explain how two different learning approaches--collaborative and non-collaborative--impact variables like academic performance and learning experience within a distance VRER environment. The purpose of the study is to examine the differences between the two conditions and answer the question of whether working collaboratively in a VRER has more, less or equal impact on learning outcomes and experience compared to working in the same escape room individually. The 20 participants were randomly assigned to two equal-sized groups: individual players (control group) or players in pairs (experimental group), ensuring that individuals paired together were already acquainted, as is the case in typical classroom settings. The small number of participants dictated the decision to have pairs instead of larger groups in the experimental condition. Synchronous remote collaboration is the most common form of interaction in multiplayer VR games [57]. In this study, participants in pairs worked either remotely or by sharing the same space and device. A mixed-method research design was used, integrating both quantitative and qualitative data, to increase the accuracy and quality of the research findings [58]. Quantitative data included a pre- and post-test and a questionnaire, while qualitative data were gathered through focus groups. More specifically, data on learners' academic performance before the intervention were collected using a pre-test consisting of 14 multiple-choice questions. The content was determined after consulting a variety of EFL textbooks of the relevant levels. It was also evaluated and validated by three in-service EFL teachers with extensive teaching experience and diverse expertise across various educational fields, including specialisation in adult education. The final items were approved by all three of them, with comments indicating that the content is well-suited for testing learners' vocabulary knowledge. The same set of questions, but in different order, was also used as a post-test to facilitate the comparison of learners' performance (Appendix A, Table A1). To evaluate the overall learning experience, particularly the aspects related to learners' perceived learning effectiveness and cognitive benefits, motivation, satisfaction, engagement and control over the learning process, learners completed a 24-item questionnaire adapted from [59]. The particular questionnaire constitutes an adaptation from previous validated instruments and was used in this study to test how desktop virtual reality can influence learning outcomes [59]. The questionnaire was adapted by removing some parts which were not relevant to the current study's aims. Participants provided their responses on a five-point Likert scale, as follows: 1: 'Strongly disagree', 2: 'Disagree', 3: 'Neutral', 4: 'Agree', 5: 'Strongly Agree'. Before the questionnaire items, learners were also asked to fill out some demographic data (Appendix A, Table A2).