## 4 Method
### Procedure
Participants were instructed to hold both controllers in their hands, using one or both as preferred by them. Input controls were mirrored on both controllers, so moving and interactions were comfortable right-handed or left-handed. Participants could interact through the HMD by looking in any direction they wanted to explore the given scene. After they completed the entry level, they were directed to complete the second questionnaire. They were asked about their wellness, previous usage of VR technology, physical activity level (International Physical Activity Questionnaire), and emotional state. All questionnaires at the Multimedia Laboratory were filled out online via a web browser on a notebook PC with a touch display. Having done this, participants began to play all six levels. To account for potential order effects, conditions were counterbalanced across participants (Latin square method). Before the gameplay, the participants were not informed which level they would play (modeof the game), neither were they informed about the rest-frames, so they would not pay attention and be aware of the rest-frames (the instruction did not manipulate the awareness and salience of the rest-frames). Based on the post-semi-structured questionnaire, most of them noticed the glasses and only some the baseball hat. Average playtime for all three rest-frame conditions (NORF, RFG, and RFH) in HA mode of the game was 2 min and 19 s, while, in the LA, it was 3 min and 22 s, so the playtime in LA was 44.88% longer. Immediately after each gameplay, participants' feedback was collected with a third set of questionnaires. We asked participants to complete the SSQ, SPES, UEQ-S, and VRNQ Questionnaire (user experience and VRISE section of the questionnaire). All those questionnaires were completed on a computer on the other side of the Multimedia Laboratory, so the participants needed to stand up and walk to the computer, assuming that would help lessen the VRISE and be more precisely able to determine them (especially postural instability and disorientation). We also collected the FMS score six times, before and during the game. The first FMS score was collected before the participant put on the HMD, while the other FMS scores were collected during the gameplay, and the last one at the end of the gameplay, still with an HMD placed on the head. During gameplay, there were specific places in VE where FMS scores needed to be given. This was done using giant billboards in VE (Figure 4), which displayed the text \"Kako se povtite?\" (How do you feel?) when the player came near the billboard. FMS score was given verbally and recorded by the researcher. Before the first gameplay, the participants were instructed how to give FMS scores correctly. To continue with the next level, we gave participants enough time to recover from possible VRISE before proceeding with the next level. The minimum time to proceed with another level/condition was five minutes, but we gave them more time when needed. We took care that participants did not continue with the next level if the FMS took before gameplay was more than 1 (negligible VRISE effects). After completing the experiment, participants were instructed to complete the fourth set of questionnaires. They were asked to fulfil a VRNQ Questionnaire (Game Mechanics and In-Game Assistance section) and NASA Task Load Index (NASA-TLX) to determine the task load of the experiment. Qualitative data was collected by a semi-structured interview  
Figure 4: Screenshot from the LA game without rest-frames in front of the table for collecting the Fast Motion Sickness (FMS) score. There are visible doors in the background, which were needed to be opened to continue onto the next scene. after the experiment's competition and analyzed to investigate the potential factors causing VRISE and affecting the user experience and presence. One week's time after the experiment, to summarize the experience with the experiment, one last questionnaire was fulfilled by the participants (2 of them did not complete it).