FUNDAMENTALS OF GAME DESIGN, SECOND EDITION

PERSONALITIES

Unlike almost every other computer game, The Sims tries to simulate relationships among individual people. These relationships are not terribly sophisticated, but they do include such emotions as jealousy, anger, and love. In the first The Sims game, five key characterization attributes define each sim's personality: neat, outgo­ing, active, playful, and nice. (In The Sims 3, the number of personality traits has gone up to 63!) These determine how sims react to one another and whether they're likely to get along. Sims become closer to each other if the player actively stimulates interactions by making them talk to each other, give each other gifts, and so on. The Sims encourages the player to develop friendships among his sims because career advancement depends upon having a certain number of friends.

To construct a mechanism for computing the affinity between two characters, con­sider implementing three rules that each character might have, but which apply to different attributes:

■ The "I Can't Stand..." Rule. A character can have an attribute that designates a quality that she cannot tolerate in others. For example, if character A can't stand talkative people, and character B has a talkativeness attribute above a given thresh­old, then A will never make friends with B. Another character might have the same rule, but about a different attribute such as cleanliness. (You can even create hypo­critical characters, if a character dislikes a quality in others that he himself possesses!) This rule would override the next two.

■ The Birds of a Feather Rule. Characters with high levels of particular attributes are attracted to other characters who have high levels of the same attribute; that is, studious people are inclined to be attracted to other studious people. Again, each character might apply the rule to a different attribute, so A tends to be friends with similarly generous people, while B tends to be friends with similarly spontaneous people.

■ The Opposites Attract Rule. Characters with high levels of particular attributes are attracted to other characters with low levels of the same attribute, and vice versa. For example, a non-musical person might be attracted to a musically talented person (perhaps out of respect for a talent that the former lacks).

While the Birds of a Feather and Opposites Attract rules seem to be mutually exclu­sive, they aren't if they apply to different attributes. One character might prefer the friendship of others who are similarly well organized (the Birds of a Feather Rule, applied to organizational ability), but also enjoy the company of people who have quite different talents from their own (the Opposites Attract Rule, applied to talent).