*Improving the Brain-Computer Interface Learning Process with Gamification in Motor Imagery:… DOI: http://dx.doi.org/10.5772/intechopen.105715*

allowed to discover how to adjust mu rhythm, which is related to sensorimotor control by themselves. Result reveals that mu activity could be actively adjusted to control the scenery to the left or right. Researchers subsequently indicated the potential that mu rhythm becomes a binary signal for MI-BCI control. In 2013, researchers developed BrainArena, a simplified football game (2D FB, 1/18), where two users could play in a collaborative or competitive mode [47]. Eight healthy subjects in 4 pairs show an average classification accuracy of 75.4% (collaborative manner) and 74.6% (competitive manner). In 2018, a 3D ball balance game (3D BL, 1/18) was designed. Ten healthy subjects use left or right-hand MI to control the platform to slightly rotate clockwise or anti-clockwise so that the planet on the platform would not move to the low end and fall off [48]. Final accuracy could reach 70% with the concentration improvement.

#### *3.3.1 Adventure game genre*

Adventure games (2/28) are a series of a game whose target is mainly taskorientated exploration. For example, adventure gamers usually need to explore the map with specific targets, such as finding a particular non-player character (NPC) or finishing a specific mission.

We only found one type of adventure game for the MI-BCI system. Scherer et al. [49] designed a 3D first-person searching coins game (3D SC) called "freeSpace" in which two out of three healthy players succeeded in collecting all three coins in three minutes. Three out of four MI classes (right hand MI, left hand MI, tongue MI, foot MI) are used for left, right, and forward navigation to find three hidden coins on the whole map. After a few trials, two participants could see improvement in covered distance and searched coin numbers. In another report of this game experiment with a different angle, research indicates that the whole runtime would be 110s with 100% classification accuracy [27].

## *3.3.2 Puzzle game genre*

Puzzle games (7/28) usually offer enjoyable logic or cognitive training tasks. Gamers need to identify the link among the provided items, answer specific questions or find a way out of a maze in a limited duration.

*2D fix route maze games* (2D FxM, 2/7) are a group of games whose characters should walk following a pre-designed line. In 2007, a research group redesigned the 2D "Pacman" game to be compatible with MI-BCI users [50]. Users could navigate the Pacman with left hand MI or right-hand MI to finish the instructed route in the maze with the highest score. Additional credit will be rewarded if the user could pick the apple on the lane, and the game score will decline if the Pacman hits the wall. A similar maze game was designed in 2017 [51] where users could use 4-class MI (left hand, right hand, both feet, and tongue MI) to finish the instructed route. The highest gaming accuracy is 48.7% among the four subjects, while the average classification accuracy is 68.5%.

*2D Voluntary route maze games* (2D VM,3/7) are maze games without a fixed path but only a start point and an endpoint. In 2009, 2 healthy players performed well in a maze-like cursor control game [52]. Gamers are asked to move to the target area and avoid one fixed trap with left- and right-hand MI. One gamer could reach an offline classification accuracy of 73%. This game is then used among one amyotrophic lateral sclerosis (ALS) patient and one primary lateral sclerosis (PLS) [53]. ALS user presents a receiver operating characteristics (ROC) rate of 81.8%, and the ROC rate for PLS user is 86.7% in two visits. A similar game was developed in 2012, and 4-classes MI (left hand MI, right hand MI, both hand rise MI and both hand fist MI) are used for navigation in four directions [54]. Healthy gamers present an accuracy of 60%-70% in this study.

*2D Jigsaw puzzle* (2D JP) games (2/7) are a group of games where players try to finish collecting the jigsaw by specific tasks. One case study reports that Arm MIs could help play a jigsaw puzzle game [55]. The cerebral palsy (CP) participant uses left or right-arm MI to accomplish tasks and collect puzzles. The result shows that the acquired MI skill could help the participant gain additional MI-BCI skills such as choosing, playing, and pausing videos. Furthermore, the skill could last for more than six weeks, as proven by the subject's successful control of the MI-BCI virtual cube. An afterward study in 2017 with the same game but a larger number of subjects (eight patients with CP) showed the potential for CP patients to interact with this MI-BCI puzzle game [20]. However, the quantitative result in performance score for all users is relatively negative with several training issues such as head cap discomfort.
