# Evaluation of the User Adaptation in a BCI Game Environment +
## 2 Related Work  
Several papers were published in the last few years that intend to connect BCIs with video games. The main target of these studies is to develop games that can be played by brain signal commands. In the following papers from the literature, the main technique that was used is attention and meditation levels to control the BCI and play the games. In the works of [16; 17; 18], the authors chose Neurosky devices with one sensor to acquire the EEG data, while [19; 20; 21] chose headsets with more EEG sensors, including the Emotiv Insight \begin{table}
\begin{tabular}{l l c c} \hline \hline
**Device** & **EEG Electrodes** & **Sampling Rate** & **Price** \\ \hline Muse 2 & 4 (AF7, AF8, TP9, TP10) & 256 Hz & 2505 \\ Neurosky MindWave & 1 (FP1) & 512 Hz & 100€ \\ Emotiv Insight & 5 (AF3, AF4, T7, T8) & 128 Hz & 4995 \\ Unicorn Hybrid Black & 8 (Fz, C3, Cz, C4, Pz, PO7, Oz, PO8) & 250 Hz & 9905 \\ Emotiv EPOC+ & 14 (AF3, F7, F3, FC5, T7, P7, O1, O2, P8, T8, FC6, F4, F8, AF4) & 128 Hz & 8495 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Commercially available non-invasive EEG devices. Figure 1: Major components of a BCI system. headset with 5 sensors, the EMOTIV EPOC+ headset with 14 sensors, and the Muse 2 headband with 4 sensors, respectively. [PERSON] et al. [16] developed an android racing BCI game controlled by Mindset, a commercially available EEG headset. NeuroSky Mindset is an EEG headband with only 1 sensor, and it is mostly used for attention-meditation values. The employed racing game is controlled by the user's neural mind states. The user can alter the speed of the car and the map of the game with his attention and meditation level. To finish the game, the user must complete 2 map circles, and the map can dynamically change depending on the mean meditation level. For a mean meditation between 0 and 35, the most difficult map is loaded; for mean meditation values between 36 and 70, the intermediate one is loaded, and for 71 to 100, the easiest one is loaded. If the mean meditation level is high, then the user is nervous. The car's speed is proportional to the attention level, so the higher the attention level of the player, the faster he can finish the game. For the testing phase, 5 subjects played the game; 1 of them managed to load the difficult map, 3 managed to load the intermediate map, and 1 loaded the easiest map. Their mean meditation scores were 27, 39, 47, 55, and 79. [PERSON] et al. [17] designed the Mental War game controlled by the NeuroSky MindWave headset, which has 1 electrode. The developed game is a tug-of-war game based on the user's attention level. The game has 3 different modes: single player, competitive and collaborative. In single-player mode, the user competes against the computer, and there are 3 difficulty levels: easy, medium and hard. In competitive mode, which is multiplayer, users battle against each other, and the player with the greater attention level will pull the others to his side. In collaborative mode, users can team up and battle against the computer or a different team of players. The team's attention level is the mean of the sum of each individual's attention level. Therefore, if a team member has a low attention score, the others should score very high for their team to win. In the testing phase, 24 subjects participated in several scenarios to improve and evaluate the game. Attention levels and the duration of the game were the two evaluation metrics. The average attention score for the single-player mode was 53.49%, while for the multiplayer (competitive and collaborative) modes, the average score was 52.42%. The average duration of the single player mode was 90.99 s, and for the multiplayer mode, the average duration was 56.22 s.  
[PERSON] et al. [19] developed a game called Mental Pool Game powered by the Unity engine and controlled by an Emotiv Insight headset with 5 EEG sensors. In this work, neutral state and attention level are used for playing the game. The user can control the speed and strength of a white ball with his attention level.