For the correct effect, you must edit, with notepad or wordpad, the "gpuPeteOGL2.slf" file, putting into the "screenSize" parameter the real size of your screen!!!! 

ex. 
for 1024x768 screen size, screenSize = vec2(1024.0,768.0) 
for 1280x960 screen size, screenSize = vec2(1280.0,960.0) 