Gerstner’s Tangential Eccentric (2018)
Animation of Karl Gerstner’s interactive/viewer-changeable Tangential Eccentric (1956/57). 

‘A good picture always gives back more than the designer could ever put into it; the longer its life, the more it gives. It is indeed created by the designer’s intention, but it lives on in the onlooker’s sympathy. ¶To take this fact as a working hypothesis means: to have the onlooker participate in the process of design. For instance the “tangential eccentric” is an intentionally unfinished picture; the intention has to be understood as part of the design. I make the choice of the elements and determine the laws of their grouping. The grouping itself, the constellation is “found” by the onlooker. What is important is that is if he follows the rules he finds not merely one but x possible completions of the picture, constellations of the same structure which are equal in value, as original as the basic law. ¶The onlooker changes the picture according to his disposition and his mood. In addition to my intentions—and perhaps also in spite of them—he invests ideas of his own. He shares the fun and also the responsibility. He is not a passive admirer but an active partner.’ —Karl Gerstner, Designing Programmes, pp 78–9.

Of course, animating it myself and showing it to you contradicts the spirit of the piece; perhaps I’d better get around to sharing the code?

Made in Python with DrawBot.