const boxSize := 50
for i : 1 .. 3
    for j : 1 .. 3
        drawfillbox (i * boxSize, j * boxSize, (i + 1) * boxSize - 1, (j + 1) * boxSize - 1, i + j * 3)
    end for
end for

var mx, my, button, squareOn, i, j, turnOn : int
turnOn := 0
loop
    mousewhere (mx, my, button)
if button = 1 and View.WhatDotColour (mx, my) not= white and View.WhatDotColour(mx,my) not= 33 and View.WhatDotColour(mx,my) not= 35 then
        squareOn := View.WhatDotColour (mx, my)
        i := (squareOn - 1) mod 3 + 1
        j := (squareOn - 1) div 3
        drawfillbox (i * boxSize, j * boxSize, (i + 1) * boxSize - 1, (j + 1) * boxSize - 1, white)
        if turnOn mod 2 = 0 then
            Draw.ThickLine (i * boxSize, j * boxSize, (i + 1) * boxSize - 1, (j + 1) * boxSize - 1, 3, 35)
            Draw.ThickLine (i * boxSize, (j + 1) * boxSize - 1, (i + 1) * boxSize - 1, j * boxSize, 3, 35)
        else
            drawfilloval (i * boxSize + boxSize div 2, j * boxSize + boxSize div 2, boxSize div 2, boxSize div 2, 33)
            drawfilloval (i * boxSize + boxSize div 2, j * boxSize + boxSize div 2, boxSize div 2 - 5, boxSize div 2 - 5, white)
        end if
        turnOn += 1
    end if
end loop