# Main Command: Go
# Spirographs by Guy Walker
# www.logoarts.co.uk

to new
  # set default screen, pen and turtle 
  ResetAll SetScreenSize [400 400] HideTurtle 
  SetSC Black SetPC Green SetPS 1 PenUp 
end

to spir
  For [S 10 70 5] [
    PenUp SetPos XYCurve :S 0 PenDown SetPC Hue2 :S+10*:B
    For [T 1 360] [SetPos XYCurve :S :T]]
end

to xycurve :s :t
  Make "X 120 * (Sin :S+:A*:T) + :S * (Cos (:B*:T))
  Make "Y 120 * (Cos :S+:A*:T) + :S * (Sin (:B*:T))
  Output (List :X :Y)
end

to rand2
  Make "A (Pick [-1 1]) * Pick [1 2]
  Make "B (Pick [-1 1]) * Pick [2 3 4 5 6]
end

to display
  # write header title and footer values
  SetPC White
  SetPos [-190 184] Label "Spirograph
  SetPos [-190 -190] Label ( List "A\ B\ = :A :B )
end

To Hue2 :Theta
  # Output RGB hue list from angle :Theta
  Make "Red Abs 255*Sin :Theta
  Make "Green Abs 255*Sin (:Theta+120)
  Make "Blue Abs 255*Sin (:Theta+240)
  Output (List :Red :Green :Blue)
End

to go
  Repeat 12 [New Rand2 Display Spir Wait 200]
end