I've just uploaded a new tutorial: this time it's a simple space conquest strategy game -- Betelgeuse Tutorial.
One of the things this tutorial illustrates is the use of a base class to allow comparison between various objects that belong to players.
It also provides an example of how to implement a game with each player having arbitrary number of moves per turn (sometimes you have to skip a few turns to let your space army build up, other times you may want to send multiple fleets from different stars or even from the same star system.)
Stars and fleets have a neat, consistent interface which allows convenient handling of both.
As with most other games in the guide, you can configure it to have ai vs ai play, ai vs player, or player vs player.