proc DrawRect(X0, Y0, W, H, Color);
int  X0, Y0, W, H, Color, Y;
for Y:= Y0 to Y0+H-1 do
    [Move(X0, Y);  Line(X0+W-1, Y, Color)];

proc DrawEdge(PX, PY, Colors, Edge);
int  PX, PY, Colors, Edge;
int  C;
[C:= Colors(Edge);
Move(PX,    PY);
Line(PX+11, PY,    C(0));
Line(PX+11, PY+11, C(1));
Line(PX,    PY+11, C(2));
Line(PX,    PY,    C(3));
];

def ScrW=256, ScrH=256;
def LT=0, TR=1, RB=2, BL=3;     \left top, etc.
def White = $ffffff, Black = 0;
def LightOlive = $d3d004, PaleBlue = $3250ff;
int Edges, Colors, X, Y, PX, PY;
[SetFB(ScrW, ScrH, 24);
\Signifies white and black edges on the blue squares
Edges:= [
    [LT, BL, BL, RB, RB, TR, TR, LT, LT, BL, BL, RB],
    [LT, LT, BL, BL, RB, RB, TR, TR, LT, LT, BL, BL],
    [TR, LT, LT, BL, BL, RB, RB, TR, TR, LT, LT, BL],
    [TR, TR, LT, LT, BL, BL, RB, RB, TR, TR, LT, LT],
    [RB, TR, TR, LT, LT, BL, BL, RB, RB, TR, TR, LT],
    [RB, RB, TR, TR, LT, LT, BL, BL, RB, RB, TR, TR],
    [BL, RB, RB, TR, TR, LT, LT, BL, BL, RB, RB, TR],
    [BL, BL, RB, RB, TR, TR, LT, LT, BL, BL, RB, RB],
    [LT, BL, BL, RB, RB, TR, TR, LT, LT, BL, BL, RB],
    [LT, LT, BL, BL, RB, RB, TR, TR, LT, LT, BL, BL],
    [TR, LT, LT, BL, BL, RB, RB, TR, TR, LT, LT, BL],
    [TR, TR, LT, LT, BL, BL, RB, RB, TR, TR, LT, LT] ];
Colors:= [
    [White, Black, Black, White],
    [White, White, Black, Black],
    [Black, White, White, Black],
    [Black, Black, White, White] ];
DrawRect(0, 0, ScrW, ScrH, LightOlive);
for X:= 0 to 11 do
    [PX:= 27 + X*17;
    for Y:= 0 to 11 do
        [PY:= 27 + Y*17;
        DrawRect(PX, PY, 12, 12, PaleBlue);
        DrawEdge(PX, PY, Colors, Edges(Y,X));
        ];
    ];
]