Sub pythagoras_tree(x1, y1, x2, y2, depth)
    local dx, dy, x3, y3, x4, y4, x5, y5

    If depth > limit Return

    dx = x2 - x1 : dy = y1 - y2
    x3 = x2 - dy : y3 = y2 - dx
    x4 = x1 - dy : y4 = y1 - dx
    x5 = x4 + (dx - dy) / 2
    y5 = y4 - (dx + dy) / 2
    //draw the box
    color 255 - depth * 20, 255, 0
    fill triangle x1, y1, x2, y2, x3, y3
    fill triangle x3, y3, x4, y4, x1, y1
    fill triangle x4, y4, x5, y5, x3, y3

    pythagoras_tree(x4, y4, x5, y5, depth +1)
    pythagoras_tree(x5, y5, x3, y3, depth +1)

End Sub

// ------=< MAIN >=------
w = 800 : h = int(w * 11 / 16)
w2 = int(w / 2) : diff = int(w / 12)
limit = 12

open window w, h
//backcolor 0, 0, 0
clear window

pythagoras_tree(w2 - diff, h -10 , w2 + diff , h -10 , 1)