FantasyA is a computer game where two characters face each other in a duel where emotions are used as the driving elements in the action tendencies of the characters. In playing the game, the user influences the emotional state of his or her semi-autonomous avatar which in turn will act according to its internal emotional state. In this paper we show how we approached the problem of modelling the emotional states of the synthetic characters, and how to combine them with the perception of the emotions of the opponents in the game. This is done by simulating the opponents action tendencies in order to predict their possible actions. Our agents then act according to what is better for them to win the game. Finally, for the user to play, he or she must understand the emotional state of his opponent which is achieved through animations (featuring affective body expressions) of the character. FantasyA was evaluated with 30 subjects from different ages and the preliminary results showed that the users liked the game and were able to influence the emotional states of their characters, in particular the young users.