Electroencephalogramm (EEG) — is a recording of electrical activity of brain. Different part of the brain specialize on different tasks, e.g. frontal cortex is responsible for cognitive and memory processes, parietal for sound processing. The more neurons currently work — the more electrical activity they create.

Despite the fact that the signal is blurred by brain’s covers and skull there are stable working patterns which could be used to judge on the current specific brain activity. E.g. the frontal cortex produces more signals within 14-30 Hz range while the brain’s owner is concentating on conginitive tasks. This particular brain rhythm is called the "beta-rhythm". In the occipital (rear) lobes which specialize on visual processing one can produce "alpha-rhythm" — a high amplitude brain rhythm in 8-14 Hz range. Specifically, while closing one’s eyes or relaxing.

The NeuroPlaydevices are encephalographers, that allow to acquire medical grade EEG through Bluetooth. The software calculates the following parameters of brain activity:

• Rhythms — percentage ratio of different rhythms (alpha, beta, gamma, delta, theta) on each channel
• "Meditation" and "concentration" — normalized meta-indexes (0-100%), that show how much the user is relaxed or mentally loaded at the moment
• Mental states — steady mental patterns that can be generated by users on their free will. This technique requires a bit of training. A begginer can produce 2-3 states after 30 minutes. For a more stable and robust experience one must continuously train (something like "brain-yoga").