nomainwin

WindowWidth  =440
WindowHeight =460

open "Mandelbrot Set" for graphics_nsb_nf as #w

#w "trapclose [quit]"
#w "down"

for x0 = -2 to 1 step .0033
    for y0 = -1.5 to 1.5 step .0075
        x = 0
        y = 0

        iteration    =   0
        maxIteration = 255

        while ( ( x *x +y *y) <=4) and ( iteration <maxIteration)
            xtemp      =x *x -y *y +x0
            y          =2 *x *y +y0
            x          = xtemp
            iteration  = iteration + 1
        wend

        if iteration <>maxIteration then
            c =iteration
        else
            c =0
        end if

        call pSet x0, y0, c
        scan
    next
next

#w "flush"

wait

sub pSet x, y, c
    xScreen = 10 +( x +2)   /3 *400
    yScreen = 10 +( y +1.5) /3 *400
    if c =0 then
        col$ ="red"
    else
        if c mod 2 =1 then col$ ="lightgray" else col$ ="white"
    end if
    #w "color "; col$
    #w "set "; xScreen; " "; yScreen
end sub

[quit]
close #w
end