## 3 Practical Applications of VR in CR
### Multiplayer Non-Inmersive Systems  
Multiplayer non-immersive rehabilitation typically refers to a cognitive rehabilitation training system that utilizes virtual reality technology but does not provide immersion. Instead, it allows multiple patients to participate simultaneously using other media or tools, and users can still perceive the existence of the real world during use. The advantage of this system is that it provides a relatively controlled and moderately immersive environment to support social interaction, which may be more comfortable and less frightening for users, making it ideal for group-based cognitive exercises [54; 55]. This system is particularly suitable for the cognitive rehabilitation of patients with autism, Parkinson's disease, and Alzheimer's disease. The advantages provided by VR-based systems are multifaceted. They can enhance users' positive attitudes, be attractive and encouraging, and provide information in real time [56]. However, users need to have basic knowledge of using computers, and there are significant barriers for older adults to using computers or mouse or keyboard devices. Considering these factors, [PERSON] et al. (2013) [57] developed a cognitive stimulation game system for a multi-device environment (MDE). The system is primarily aimed at Alzheimer's disease patients, providing cognitive stimulation to help with cognitive rehabilitation. The system consists of two interactive collaborative games: Co-Brain Training Tool (CBT) and AlzGame. The system integrates a tangible interface with NFC technology, mobile devices with NFC readers, and a projector displaying the main game interface. In the CBT collaborative game, multiple users can interact with each other or use the system individually. The system architecture is a co-brain training structure. The client system is a mobile device with an NFC reader that connects to the server via a wireless network and communicates with the NFC reader when the mobile device is placed near the tangible interface. The tags are integrated into each image of the tangible interface, each describing different content. When the NFC reader is close to the selected image, the tag inside is excited by the electromagnetic waves emitted by the NFC reader, and the mobile device executes the corresponding method on the server. AlzGame is a client-server combined system that executes games and stores results in the server. In this way, therapists can continuously understand the progress of the patient's rehabilitation. Remote rehabilitation balance plans based on VR have been proven to be feasible and effective in various neurological disorders. An innovative fitness training and rehabilitation method is an active electronic game that combines physical movement with gaming skills, which can be independently performed at home with minimal equipment and low cost. For example, the very popular Nintendo Wii Fit and balance board are VR fitness applications that can be used as auxiliary tools for sensory integration balance training (SIBT); SIBT is one of the most effective methods for improving the posture stability of polio patients. [PERSON] et al. (2017) [58] designed a randomized controlled trial to compare improvements in postural stability after PD patients used the Nintendo Wii Fit system (TeleWii) for VR-based home balance training and after SIBT in the clinic. The TeleWii experimental system includes the Nintendo Wii console for motion control input, the Wii Fit game system, and the balance board. Comparing the above studies, it can be found that multiplayer non-immersive rehabilitation systems also have some drawbacks [59]. For example, the benefits of VR in enhancing experiences that are similar to real life are limited, which may affect the effectiveness of applying the learned skills in real-world scenarios. Table 1 below summarizes the major studies on VR in CR.