Source code in the freebasic programming language

' version 16-03-2017
' compile with: fbc -s gui

Const As ULong w = 400
Const As ULong w1 = w -1

Dim As Long x, y, lastx, lasty
Dim As Long count, max = w * w \ 4

ScreenRes w, w, 8 ' windowsize 400 * 400, 8bit
' hit any key to stop or mouseclick on close window [X]
WindowTitle "hit any key to stop and close the window"

Palette 0, 0                   ' black
Palette 1, RGB(  1,   1,   1)  ' almost black
Palette 2, RGB(255, 255, 255)  ' white
Palette 3, RGB(  0, 255,   0)  ' green

Line (0, 0) - (w1, w1), 0, BF  ' make field black
Line (0, 0) - (w1, w1), 1, B   ' draw border in almost black color

Randomize Timer
x = Int(Rnd * 11) - 5
y = Int(Rnd * 11) - 5

PSet(w \ 2 + x, w \ 2 + y), 3 ' place seed near center

Do
    Do  ' create new particle
        x = Int(Rnd * w1) + 1
        y = Int(Rnd * w1) + 1
    Loop Until Point(x, y) = 0 ' black
    PSet(x, y), 2

    Do
        lastx = x
        lasty = y
        Do
            x = lastx + Int(Rnd * 3) -1
            y = lasty + Int(Rnd * 3) -1
        Loop Until Point(x, y) <> 1

        If Point(x, y) = 3 Then
            PSet(lastx, lasty), 3
            Exit Do ' exit do loop and create new particle
        End If

        PSet(lastx, lasty), 0
        PSet(x,y), 2

        If Inkey <> "" Or Inkey = Chr(255) + "k" Then
            End
        End If
    Loop

    count += 1
Loop Until count > max

Beep : Sleep 5000
End