Revolve

- optical illusion

Focus your eyes on the central dot. Move your head slightly backwards and forwards, the two outer rings appear to revolve.

To New
  # set default screen, pen and turtle values
  ResetAll SetScreenSize [400 400] HideTurtle
  SetSC Black SetPC Green SetPS 1 PenUp
End

To Rhombus
  SetPC Gray Right 30 Forward 14
  Left 60 Forward 14
  SetPC White Left 120 Forward 14
  Left 60 Forward 14 Left 150
End

To Go
  New SetSC LightGray SetPC Black
  SetPW 4 Dot Pos SetPW 1
  Repeat 36 [
    Forward 180 Right 120 PenDown
    Rhombus PenUp Left 120 Back 180 Left 10]
  Repeat 30 [
    Forward 135 Left 300 PenDown
    Rhombus PenUp Right 300 Back 135 Left 12]
End

Revolve
Revolve

Procedures blue
Variables pink
Comments green
Library gray