## 3 Practical Applications of VR in CR
### Multiplayer Immersive Systems  
Multiplayer immersive rehabilitation is an advanced cognitive rehabilitation training system that creates a fully immersive virtual environment for patients using virtual reality technology. This system supports multiple patients participating simultaneously in collaborative tasks and interactions within a shared virtual space [41], thereby promoting social interaction and cognitive function development. The advantage of the multiplayer immersive virtual reality rehabilitation therapy system is that it not only promotes social interaction in the virtual environment, which is highly beneficial for social cognitive therapy [42], but also allows for group therapy sessions, enhancing patients' motivation through social support [43]. This system is particularly suitable for the rehabilitation of patients with stroke, autism, and other diseases, providing them with a safe and controlled environment to promote the recovery of cognitive functions and enhance social skills.  
[PERSON] et al. (2017) [44] developed a multiplayer immersive virtual reality system, VR4 VR, in 2017. The system enables autism spectrum disorder (ASD) patients to master vocational skills through practice in an immersive virtual environment. VR4 VR is composed of a head-mounted display (HMD), an optical motion tracking system with multiple cameras, touch screen controls, and a remote control panel. The system provides training in six vocational skills, with three skill modules designed to be executed through the HMD and the remaining three through a 180-degree curved screen. Each skill module includes three sub-tasks of increasing difficulty, each with its own three levels. Studies have shown that trained vocational skills have improved for ASD patients, and VR4 VR can provide effective vocational training for ASD patients.  
[PERSON] et al. (2022) [45] created a novel multiplayer immersive VR system called VIRTUE. The scene construction in VIRTUE is achieved through a combination of the Unity3D game development platform and the Virtual Reality Toolkit (VRTK). VIRTUE uses a modular architecture that is divided across PC and VR headset devices, allowing for the selection of different scenes and their configuration to suit each patient. Through various tasks (e.g., making toast, paying for a meal), VIRTUE trains patients' cognitive functions such as memory and discrimination, and collects indicators to help clinical doctors assess performance. This flexible personalized medical approach, without any restrictions, also demonstrates that VR is indeed an effective measure for improving the memory and discrimination of stroke survivors. To promote the training of social skills in autistic teenagers and investigate the feasibility of virtual reality as a training environment for adolescents, [PERSON] et al. (2023) [46] developed Zentastic, an immersive multiplayer VR adventure game, in 2023. Zentastic was developed and deployed on Meta Oculus technology in Unity. The game is designed to be played by groups of teenagers under the guidance of a therapist acting as a guide in the virtual environment. Each task in Zentastic is aimed at addressing target behaviors related to social interaction, with increasing complexity. In recent studies, VR can recreate motivating environments through multisensory and interactive stimulation, allowing for interaction with scenes, thereby improving patients' cognitive abilities. VR can also be used to improve patients' balance, coordination, and muscle control, or through the simulation of activities in virtual environments, patients can engage in interactive rehabilitation training to improve motor functions.  
Multiplayer immersive rehabilitation systems also have some drawbacks: managing multiple users in a fully immersive environment is more complex. There is a risk of users being distracted by others in the virtual space.