Simon followed Daniel Shiffman’s Fractal Recursion tutorial on how to write functions in Processing that call themselves (recursion) for the purpose of drawing fractals.
Later he programmed a Sierpinski triangle from memory, using circles. A Sierpinski triangle is a fractal set with the overall shape of an equilateral triangle, subdivided recursively into smaller equilateral triangles. Originally constructed as a curve, this is one of the basic examples of self-similar sets, i.e., it is a mathematically generated pattern that can be reproducible at any magnification or reduction. It is named after the Polish mathematician Wacław Sierpiński, but is actually a reincarnation of Pascal’s triangle.