# Main Command: Go 5
# Dragon Curve (Round Corner) 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 init :order
  # make Size and Angle global values
  Make "Size 11*Power (SqRt 2) (9-:Order)
  Make "Angle 90
  Make "Step 0.025*Pi * :Size Make "Ang :Angle/10 
end

to display :order
  # write header title and curve level
  SetPC White
  SetPos [-190 184] Label Sentence [Dragon Curve Order] :Order
end

to dragon :order :parity
  If :Order < 1 [Stop]     # ie if = 0
  Dragon :Order-1 1
  Turn :Parity*:Ang     # turn left or right :Angle degrees
  Dragon :Order-1 Minus 1
end

to go :order
  New
  Init :Order Display :Order
  SetPos [-108 0] SetPC Green PenDown
  Right (45 *:Order)+90     # similar orientations of curves
  Forward :Size/2 Dragon :Order 1 Forward :Size/2
end

to turn :a
  Left :A/2
  Repeat 9 [Forward :Step Left :A]
  Forward :Step Left :A/2
end