# Main Command: Go
# Rainbow 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 rainbow
  SetPW 10     # big pen
  Make "Cols [1 13 3 2 4 15]
  For [N 1 6] [
    SetPC Item :N :Cols
    Arch 180 (180-12*:N) Wait 30]
end

to arch :angle :radius
  # symmetrical arc drawn relative to turtle heading
  Arc :Radius Heading-:Angle/2 Heading+:Angle/2
end

to go
  New Rainbow
end

# alternative procedure

to rainbow_alt
  SetPW 10     # big pen 
  Make "Cols [Red Orange Yellow Green Blue Purple]
  For [N 1 6] [
    SetPC Run Item :N :Cols
    Arch 180 (180-12*:N) Wait 30]
end