[Lab] strange visual effect trying to create a radial blur

[Phuket2]

I got a very strange optical illusion with the code below. Was trying to make a radial blur effect. Is interesting.

'''
	Pythonista Forum - @Phuket2
'''
import ui

class MyClass(ui.View):
	def __init__(self, *args, **kwargs):
		super().__init__(*args, **kwargs)
	
	def draw(self):
		wh = 100
		r = ui.Rect(0, 0, wh, wh)
		r.center(self.bounds.center())
		s = ui.Path.oval(*r)
		rd = 1
		for i in range(int(r.width)):
			s = ui.Path.oval(*r)
			s.line_width = 1
			c = (0,  rd, 0, 1)
			ui.set_color( c)
			s.stroke()
			r = r.inset(.5, .5)
			rd -=.01
		

if __name__ == '__main__':
	w, h = 320, 480
	f = (0, 0, w, h)
	
	mc = MyClass(frame=f, bg_color='white')
	mc.present('sheet', animated=False)

If you change rd -= .01, to rd -= .02 then you get the below

Sort of looks like a radial blur. But with rd-=.01 you get a wacky illusion. Just for fun