This JSL is a result of watching a mathologer video. Usually pictures of the mandelbrot set are pictures of points just outside the set, colored based on how hard it was to decide the point really was outside the set. Usually the interior points are all dark because they are all boring; they take forever to determine they are really inside the set. But the orbits of those points are different and can be plotted, which is what this JSL does.
This video uses a small sample of initial points and follows their orbit for 1500 steps, adding a point to the bitmap at each step.