## 1 Introduction
Previous research investigated the development and assessment of a temporalis EMG wheelchair interface that was evaluated with ALS patients for hands-free control [6]. The temporalis muscle is responsible for the elevation of the mandible and is located laterally on the head [15]. Despite the motor neuron degeneration that occurs in ALS progression, the temporalis muscle has a lesser decrease in its contraction force over time than the muscles of the digits [16]. The wheelchair interface uses signal discretization of muscle contraction magnitude to control steering and movement. For instance, a calibrated\"hard\" flex corresponds to a forward movement, \"medium\" flex to a right turn, and a \"light\" flex to a left turn [6]. This interface was tested among ALS patients in a clinical setting, and although independent control was established, patients found reliable discretization of temporalis flexions difficult [6]. In contrast to other wheelchair control systems, the utilization of EMG technology allows a high degree of modulation. Though the temporalis muscle was selected because of the ease of electrode placement alongside a lessened impact on contraction force, other muscles could be also used. Because surface electromyography is utilized, individuals with ALS or other disorders may benefit from the selection of other muscle groups. Additionally, the EMG-wheelchair interface can be attached to any power wheelchair system, as a housing is placed over the traditional joystick in order to provide navigational control. Training prior to real-world implementation of the interface could reduce this initial barrier to using the wheelchair [17]. As training with the hands-free wheelchair can be challenging, serious training games were explored to support patients in learning how to control the electromyography-actuated system [6]. Serious games are video games used for a purpose in addition to entertainment [18]. There have been many recent advancements in gamified trainingand it has been increasingly implemented in clinical settings. Most recently, PhantomAR was developed to improve rehabilitation outcomes for patients with phantom limb pain [19]. This platform allowed users to immerse themselves in a task-based mixed reality environment. A systematic study of motorized, virtual reality, and electrical simulation games shows how these platforms can be useful for stroke rehabilitation [20], specifically in improving cognitive, emotional, and social outcomes. One study tested racing, dexterity, and rhythm-based video games against a standardized EMG training tool (MyoBoy) [21]. Users expressed more motivation and engagement playing through the gamified training games [21]. In an analysis comparing equivalent gamified learning and traditional learning methods, gamified methods promoted more learning, and this difference was attributed to higher engagement and flow levels [22]. The authors' prior research has focused on using gamified training to improve training efficacy for electromyography-controlled accessibility devices, including pediatric prostheses [23]. Early evaluations of EMG control mechanisms led to a variety of gamified control training schemes, which were created to improve usability and reduce rejection rates among the patients [24]. Early games such as \"Sushi Slap\", \"Crazy Meteor Cleaner\", and \"Beeline Border Collie\" utilized a flex threshold for gameplay [23]. For more complex hands-free wheelchair controls to steer the device, a new training platform was created. _Limbitless Journey_ is a serious game designed to practice flexion control of the temporalis muscles in an engaging but low-stress environment. This virtual environment is controlled by muscle flexions that parallel the controls required to operate the wheelchair. Muscle activity is read by a novel EMG video game \"flex controller\" placed on the temporalis muscle that controls in-game character movements.