Guido van Robot Worldbuilder Summary
Editing world:
    Left mouse button : Add or remove walls 
    Middle mouse button: Set arguments for the robot statement
    Right mouse button: Set arguments for the beeper statement
    
Buttons:
    Reload   : Reload the world from the editor window
               into the worldbuilder.
    Abort    : Quit the worldbuilder, *not* GvRng.
