This app provides a BCI speller based on code-modulated visual evoked potential (c-VEP) under the circular-shifting paradigm that supports non-binary m-sequences.Despite their usefulness in achieving reliable, high-speed BCIs for communication and control, c-VEP paradigms using binary m-sequences often cause eyestrain for some users. This visual fatigue is likely to be caused by the high-contrast flickering (i.e., black and white) of the binary m-sequence. One of the current approaches to overcome this limitation is to use non-binary m-sequences, i.e., sequences with a higher base resulting in more values encoded with different shades of gray. However, the creation of p-ary m-sequences is not trivial, which limits its application in research studies. In this application we offer the user the possibility of using p-ary sequences of bases 2, 3, 5, 7, 11 and 13. More information can be found in: Martínez-Cagigal, Víctor, et al. "Brain–computer interfaces based on code-modulated visual evoked potentials (c-VEP): a literature review." Journal of Neural Engineering (2021).