- optical illusion
A series of concentric circles appear as a spiral with the added black and white markers.
To New
# set default screen, pen and turtle values
ResetAll SetScreenSize [400 400] HideTurtle
SetSC Black SetPC Green SetPS 1 PenUp
End
To Go
New SetSC LightGray
For [X 5 175 15] [
Make "NewRadius 10+90*(1+Cos :X)
SetPC White SetPW 1 Circle :NewRadius FillZone
SetPC Black Right 6*PenWidth SetPW (:NewRadius/7)-2
Repeat 18 [
PenDown Forward :NewRadius-(PenWidth/2)
PenUp Back :NewRadius-(PenWidth/2) Left 20]
SetPC Gray SetPW 1 Circle :NewRadius ]
End