The Hopalong Attractor is defined by these two equations:
x_n+1 = y - 1 - sqrt(abs(b*x - 1 - c))*Math.sign(x - 1)
y_n+1 = a - x - 1
Change the values of the parameters a, b, c, and d by using the sliders.
Key 'r': Redraw with a random set of parameters.
LEFT_ARROW: Draw with few points (faster).
RIGHT_ARROW: Draw with many more points (slower).
Key 'e': Save a high-resolution PNG of the current image.
Key 'a': Increment the number of points.
Key 's': Decrement the number of points.
This p5js code is scrollable.