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The rules of DNJ Dilemma  

DNJ Dilemma is a game for two players, plus a third person acting as banker. In this version the computer acts as one or both players, and also as the banker - but don't worry, it never uses its multiple roles to gain unfair advantage! 

The rules of DNJ Dilemma are very simple. Each player has two cards, marked "cooperate" and "defect". In each round of the game, each player lays one of their cards face-down on the table (it doesn't matter who goes first). When both cards have been played, the banker turns them over and calculates the scores for that round. There are four possible combinations of cards, with the following scores: 

	Player A	Player B
Both  cooperate	250	250
Both  defect	50	50
Defect/ Cooperate	400	0
Cooperate/ Defect	0	400

As you can see, when both players cooperate, they both get a good reward. When both defect, they get much smaller rewards. However when one cooperates and the other defects, it's the 'good' player who loses out, getting no points at all, while the 'cheat' gets the biggest reward of all. Such is life! 

Another factor is that players don't know how many rounds there will be in each game - it's chosen at random, and can be anything between six and 16. This makes choosing between long and short-term strategies much harder. That's a lot like life too. 

Playing modes and game strategies
DNJ Dilemma comes with four built-in game-playing strategies (called "Tit for Tat", "Random Defects", "Adaptive Defects" and "Suspicious Tit for Tat"). You can play against these strategies, either choosing which one the computer should use for each game, or allowing the computer to choose one at random (in which case it doesn't tell you which one it's been using until the game ends - this is the 'serious' way to play against the machine!)

You can also make the computer play against itself, either telling it which strategy to use for each player, or allowing it to choose its own. In this 'self-play' mode, you can tell the computer to play multiple games in a given strategy combination, for example 10 games of Tit for Tat against Adaptive Defects. 

The computer strategies don't cheat, so never 'look' at the card you've played in the current round before playing its own, and don't 'look' at the number of rounds in the game either. However they will take into account the cards you've played in previous rounds, just as you're free to analyse their previous cards.