Sigma motion visual illusion in R

Michael Bach, who is a professor and vision scientist at the University of Freiburg, maintains a fascinating site about visual illusions. One visual illusion really surprised me: the sigma motion.

The sigma motion displays a flickering figure of black and white columns. Actually it is just a chart, as displayed below, with the columns changing backwards and forwards from black to white at a rate of about 30 transitions per second.

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