Section 9.2 involved one real decision maker (DM), the robot, playing against a fictitious DM called nature. Now suppose that the second DM is a clever opponent that makes decisions in the same way that the robot would. This leads to a symmetric situation in which two decision makers simultaneously make a decision, without knowing how the other will act. It is assumed in this section that the DMs have diametrically opposing interests. They are two players engaged in a game in which a loss for one player is a gain for the other, and vice versa. This results in the most basic form of game theory, which is referred to as a zero-sum game.