# Main Command: Go 5
# Clover Art 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
  # global values
  Make "Board 384
  GlobalMake "CellSize :Board /:Order
  GlobalMake "OffSet (:Board -:CellSize) /2
end

to drawgrid :order
  # draw CellX x CellY array of squares
  For (List "CellY 0 :Order -1) [
    For (List "CellX 0 :Order -1) [
    SetPos GridPos :CellX :CellY SetH 0
    SetPC Shuffle [0 128 255]
    If Even :CellX +:CellY [SetPC Dark PenColor] Square :CellSize Fill
    SetPC Shuffle [0 128 255]
    If Even :CellX +:CellY [Left 180 /:Order] [SetPC Dark PenColor] 
    Clover_Rand :Order 0.9*:CellSize Fill Wait 12] ]
end

to gridpos :cellx :celly
  # return X Y screen position
  Make "PosX (:CellX*:CellSize) -:OffSet
  Make "PosY (:CellY*:CellSize) -:OffSet
  Output List :PosX :PosY
end

to clover_rand :n :size
  # draw random clover shape of total diameter Size
  Make "Dist (:Size/2)/(1+Sin (180/:N))
  PenUp Repeat :N [
    If Pick [True False] 
      [Forward :Dist Arch 180*(1+2/:N) (:Size/2)-:Dist]
      [Forward :Dist Left 180 Arch 180*(1-2/:N) (:Size/2)-:Dist Left 180]
    Back :Dist Left 360/:N] 
end

to square :side
  # square (side x side) drawn from centre (tp)
  Back :Side/2 Right 90 Back :Side/2 PenDown
  Repeat 4 [
    Forward :Side Left 90]
  PenUp Forward :Side/2 Left 90 Forward :Side/2     # return to centre
end

to even :num
  # return True if Num even, else return False 
  If (Mod :Num 2) = 0 [Output "True] [Output "False]
end

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

To Dark :Hue
  # output rgb list midway between :hue and black
  Repeat 3 [
    Make "Hue ButFirst LPut Int (First :Hue)/2 :Hue]
  Output :Hue
End

to shuffle :mylist
  # randomly shuffle list order
  LocalMake "Shuffled [ ] 
  Repeat Count :myList [
    LocalMake "Select Pick :myList
    Make "myList Remove :Select :myList
    LocalMake "Shuffled LPut :Select :Shuffled]
  Output :Shuffled
end

to go :order
  New Init :Order
  DrawGrid :Order
end