'[RC]Brownian motion tree
    nomainwin
    dim screen(600,600)
    WindowWidth = 600
    WindowHeight = 600
    open "Brownian" for graphics_nsb_nf as #1
    #1 "trapclose [quit]"
    #1 "down ; fill blue"
    rad=57.29577951
    particles=500

    'draw starting circle and mid point
    for n= 1 to 360
            x=300-(200*sin(n/rad))
            y=300-(200*cos(n/rad))
            #1, "color white ; set ";x;" ";y
            screen(x,y)=1
    next n
    #1, "color white ; set 300 300"
    screen(300,300)=1

    'set up initial particles
    dim particle(particles,9)'x y deltax deltay rotx roty
    for n = 1 to particles
        gosub [randomparticle]
    next

    'start timed drawing loop
    timer 17, [draw]
    wait


    [draw]
    #1 "discard"
    scan
    for n = 1 to particles
        oldx=particle(n,1)
        oldy=particle(n,2)

        'erase particle
        if not(screen(oldx,oldy)) then
            #1 "color blue ; set ";oldx;" ";oldy
        end if

        'move particle x
        particle(n,1)=particle(n,1)+int((sin(particle(n,6)/rad)*10)+particle(n,3))
        particle(n,5)=particle(n,5)+6 mod 360
        if particle(n,1)>599 or particle(n,1)<1 then gosub [randomparticle]

        'move particle y
        particle(n,2)=particle(n,2)+int((sin(particle(n,5)/rad)*10)+particle(n,4))
        particle(n,6)=particle(n,6)+6 mod 360
        if particle(n,2)>599 or particle(n,2)<1 then gosub [randomparticle]

        'checkhit
        x=particle(n,1)
        y=particle(n,2)
        if screen(x-1,y-1) or screen(x-1,y) or screen(x-1,y+1)_
        or screen(x,y-1) or screen(x,y) or screen(x,y+1)_
        or screen(x+1,y-1) or screen(x+1,y) or screen(x+1,y+1) then
            #1 "color white ; set ";particle(n,1);" ";particle(n,2)
            screen(particle(n,1),particle(n,2))=1
        else
            #1 "color red ; set ";particle(n,1);" ";particle(n,2)
        end if
    next
    wait



    [randomparticle]
    particle(n,1)=int(rnd(0)*599)+1
    particle(n,2)=int(rnd(0)*599)+1
    particle(n,3)=int(2-rnd(0)*4)
    particle(n,4)=int(2-rnd(0)*4)
    particle(n,5)=int(rnd(0)*360)
    particle(n,6)=int(rnd(0)*360)
    return

    [quit]
    timer 0
    close #1
    end