For using the Prolog reasoner instead of JavaProver or Jocular you need to do the following: - install Eclipse-Prolog (http://www.eclipse-clp.org) - set the ECLIPSE_DIR environment variable to the Eclipse-Prolog installation directory - use GameFactory.PROLOG in MyPlayer.commandStart(Message msg) instead of GameFactory.JAVAPROVER It shouldn't be necessary to change any other part of your program.