'Run' Problem

Do you mean letting Greenfoot start running the scenario automatically? In that case, after you're done creating the world (in this case, the start screen), you run this: Although I don't know about your implementation, I would expect you to have to place this at the end of the constructor of your start screen world.

Some things you could do: (1) add a 'Greenfoot.start();' line in your initial world constructor so the user does not have to press the 'Run' button at all; (2) add a 'public void started()' method to your initial world class and remove the button so that pressing 'Run' starts the first level; This is what you should already have. Unless you have a 'Greenfoot.stop();' line in one of your world class constructors, you should not have this behavior. If you cannot resolve this, you will need to show your world class codes.