This app implements the first P300-based BCI proposed by Farwell and Donchin. The system uses the row-column paradigm (RCP) to determine the intentions of the user. The RCP displays a matrix (i.e., speller) with several commands. The rows and columns of the matrix are randomly highlighted a predefined number of times (i.e., sequences). The user has to stare at the desired command and count the flashes (i.e., target stimuli), while ignoring the other stimuli (i.e., non-target stimuli). Target stimuli elicits visual ERPs in the EEG just after each flash. The signal processing stage detects the visual ERPs and determines the command. This BCI is also named as P300-based speller because of the P300 potential, which is the most prominent peak of visual ERPs elicited by target stimuli.