# Main Command: Go
# Arc Step 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 onstage?
  # check turtle within window edges
  If (Or X<-190 X>190 Y<-190 Y>190) [Output False] [Output True]
end

to rightarc :angle :radius
  # arc drawn relative to turtle position
  PenUp If :Angle <0
    [Right 90 Back :Radius Right :Angle Arc :Radius Heading Heading-:Angle 
      Forward :Radius Left 90]
    [Left 90 Back :Radius Arc :Radius Heading Heading+:Angle 
      Right :Angle Forward :Radius Right 90]
  PenDown
end

to go
  New 
  Repeat 4 [
    PenUp Home SetH RepCount*90 SetPC RepCount PenDown
    While [OnStage?] [
      Make "Parity Pick [-1 1]
      RightArc :Parity*90 12 Wait 2] ]
end