# Main Command: Go 4
# Grid 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 "Size 378
  Make "CellSize :Size/:Order
  Make "OffSet :CellSize/2 - :Size/2
  Make "Side :CellSize/1.4
  Make "Total Power :Order 2 
end

to gridd :m :n
  # return X Y screen position
  Make "X (:N*:CellSize) + :OffSet
  Make "Y (:M*:CellSize) + :OffSet
  Output List :X :Y
end

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

To Hue2 :Theta
  # Output RGB hue list from angle :Theta
  Make "Red Abs 255*Sin :Theta
  Make "Green Abs 255*Sin (:Theta+120)
  Make "Blue Abs 255*Sin (:Theta+240)
  Output (List :Red :Green :Blue)
End

to randgrid :order
  # go to a random grid position 
  SetPos Gridd Random :Order Random :Order 
end

to drawgrid :order
  # draw M x N array of squares
  For (List "M 0 :Order-1) [
    For (List "N 0 :Order-1) [
    SetPos Gridd :M :N
    # SetH 0 Left 270*((:M+:N-2)/((2*:Order)-2))
    Square :Side] ]
end

to go :order
  # draw grid of squares
  New Init :Order
  DrawGrid :Order
end

# art procedures

to art1 :order
  # draw random array of colored squares
New Init :Order
Repeat :Total [
  RandGrid :Order
  SetPC Hue2 Random 360 Square :Side Fill]
end

to art2 :order
  # draw random lines 
New Init :Order
SetPC Purple SetPW 3 * Round :CellSize/20
For (List "M 1 :Order-2) [
  For (List "N 1 :Order-2) [
    SetPos Gridd :N :M
    SetH 90*Random 4
    PenDown Forward :CellSize PenUp] ]
end

to art3 :order
  # draw grid, random filled squares 
New Init :Order
Drawgrid :Order
SetPC DarkRed 
Repeat :Total [
  RandGrid :Order Fill]
end

to art4 :order
  # draw colour swatches
New Init :Order
Make "ColStep 255/(:Order-1)
For (List "M 0 :Order-1) [
  For (List "N 0 :Order-1) [
    SetPos Gridd :M :N
    SetPC PenCol :M :N
    Square :Side Fill] ]
end

to pencol :m :n
Make "Red Round :N*:ColStep
Make "Gre Round :M*:ColStep
Output (List :Red :Gre 0)
end

to art5 :order
New Init :Order
Make "CellList []
Repeat :Total [Make "RanSq Random :Total
If Not Member? :RanSq :CellList [
  SetPos Gridd (Modulo :RanSq :Order) (Quotient :RanSq :Order)
Square :Side SetPC DarkRed Fill SetPC Green
Make "CellList Lput :RanSq :CellList]]
SetPC Red
For (List "YY 1 :Order-2) [
  For (List "XX 1 :Order-2) [
  Make "Count :XX + :Order*:YY
  If And And And And
    (Member? :Count :CellList)
    (Member? :Count+1 :CellList)
    (Member? :Count-1 :CellList)
    (Member? :Count+:Order :CellList)
    (Member? :Count-:Order :CellList)
    [SetPos Gridd (Modulo :Count :Order) (Quotient :Count :Order) Fill] ] ]
end

to art6 :order
New Init :Order
Repeat :Total [
  RandGrid :Order
  Square :Side SetPC DarkRed Fill SetPC Green]
SetPC Red 
  For (List "M 1 :Order-2) [
    For (List "N 1 :Order-2) [
    SetPos Gridd :M :N
    If Check4 [PenDown Fill PenUp] ] ]
end

to check4
  # return true if square surrounded by 4 squares
Make "C "True
If ((First FindColor Pos)=0) [Output "False] 
Repeat 4 [
  Forward :CellSize
  If ((First FindColor Pos)=0) [Make "C "False Stop]
  Back :CellSize Right 90]
Output :C
end