MODULE Pythagoras_tree {
    CLS 5, 0  ' MAGENTA, NO SPLIT SCREEN
    PEN 14   ' YELLOW
    \\ code from zkl/Free Basic
    LET w = scale.x, h = w * 11 div 16
    LET w2 = w div 2, diff = w div 12
    LET TreeOrder = 6
    pythagoras_tree(w2 - diff, h -10, w2 + diff, h -10, 0)

    SUB pythagoras_tree(x1, y1, x2, y2, depth)

        IF depth > TreeOrder THEN EXIT SUB

        LOCAL dx = x2 - x1, dy = y1 - y2
        LOCAL x3 = x2 - dy, y3 = y2 - dx
        LOCAL x4 = x1 - dy, y4 = y1 - dx
        LOCAL x5 = x4 + (dx - dy) / 2
        LOCAL y5 = y4 - (dx + dy) / 2
        MOVE x1, y1
        DRAW TO x2, y2
        DRAW TO x3, y3
        DRAW TO x4, y4
        DRAW TO x1, y1
        pythagoras_tree(x4, y4, x5, y5, depth +1)
        pythagoras_tree(x5, y5, x3, y3, depth +1)

    END SUB
}
Pythagoras_tree