Mindball is a concept mentioned in a book I read in 2013 called Trying Not to Try. The game is usually played by two players. The players sit on either end of a table and a ball in the middle rolls away from the player who is more relaxed, focused, and meditative. If the ball reaches your end of the table, you lose.
I wanted to create a single player version of the game that included optical biofeedback, so that someone could play it alone as a way to train themselves to calm their mind. The ball starts away from the player and rolls towards them. The ball reaching the player gives a sense of acheivement rather than anxiety.
This was a personal project, and I did all of the electrical hardware, mechanical design, and coding. The ball is a 2" steel ball that rides on a magnetic track driven by a stepper motor. The game receives EEG data from a MindWave Mobile over bluetooth, parses it, computes the game math and translates it into a color that the player sees, and if above a certain threshold, the ball moves towards the player (and away if below).