These BCI games are based on different BCI protocols, from spontaneous EEG (Millán, 2003; Krepki et al., 2007; Tangermann et al., 2008) to evoked EEG potentials (Lalor et al., 2005; Finke et al., 2009), where the user delivers (as usual for a BCI) mental commands to control some aspect of the game. Another alternative is to determine the user's mental or affective state from their EEG and to use this information to adapt the dynamics of the game to the user's affective state (Nijholt et al., 2008b). As stated in Nijholt et al. (2008a), “Measuring brain activity for gamers can be used so that the game environment (1) knows what a subject experiences and can adapt game and interface in order to keep the gamer “in the flow” of the game, and (2) allows the gamer to add brain control commands to the already available control commands for the game.” This perspective matches well that described in Williamson (2006) when discussing a general framework for interaction design.