Awesome - I've been waiting for more content for ages. It's really developing quite well. I do seem to have got stuck in chapter 2 - connected three wires, but the door is still locked. Is there more, or is that the end so far?

Richard, As per my comment, to set the default world class: ... right click world class, "new XyzWorld()" ... I.e. first right-click on the world class (in the class tree) and then click "new XyzWorld()" (where "XyzWorld" is an example and will change depending on the class name). And please: (for more help, post in the discussion forum).

Jinno - post something in the discussion forum, ideally with a link to your scenario which demonstrates the problem. Richard - whichever world you interactively instantiated (right click world class, "new XyzWorld()") is the one that Greenfoot remembers as the default world. (for more help, post in the discussion forum).

This is pretty good! Though there are some clear bugs, such as the AI players fold when they could just check, and they play very conservatively - don't seem to bluff at all. I'd like to see it finished! Also would like to see the source code if you're willing to share it.

I get an exception when I try to run this: java.lang.NullPointerException at world.<init>(world.java:35)