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

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

To Ring :Angle :Dist :Head :Size
  # draw concentric rings of clam shapes
  Home SetH :Angle SetPW :Size/10
  Forward :Dist SetH :Head Clam :Size
  SetPC :FillCol Fill
End

To Clam :Size
  # optical clam shape drawn from centre (tp)
  SetPC White Back :Size/3 Arch 108-PW 0.6*:Size
  Forward :Size/3 Left 180
  SetPC Black Back :Size/3 Arch 108-PW 0.6*:Size
  Forward :Size/3 Left 180
End

To Arch :Angle :Radius
  # symmetrical arc drawn relative to turtle heading
  Arc :Radius Heading-:Angle/2 Heading+:Angle/2
End

To Go
  New SetPW 3
  SetSC Pick [ [102 204 51] [51 204 102] [204 204 0] ]
  Make "FillCol Pick [ [153 102 0] [128 0 255] [0 128 255] ]
  For [Angle 0 360 10] [
    Ring :Angle 180 90 30
    Ring :Angle 150 35 25
    Ring :Angle 122 325 20
    Ring :Angle 100 270 15]
End