Companion characters in are present in many video games across genres, serving the role of the player\u27s partner. Their goal is to support the player\u27s strategy and to immerse the player by providing a believable companion. These companions often only perform rigidly scripted actions and fail to adapt to an individual player\u27s play-style, detracting from their usefulness. Behavior like this can also become frustrating to the player if the companions become more of a hindrance than they are a benefit. Other work, including this project\u27s precursor, focused on building companions that mimic the player. These strategies customize the companion\u27s actions to each player, but are limited. In the same context, an ideal companion would help further the player\u27s strategy by finding complementary actions rather than blind emulation.
We propose a game-development framework that adds complementary (rather than mimicking) companions to a video game. For the purposes of this framework a complementary action is defined as any that furthers the player\u27s strategy both in the immediate future as well as in the long-term. This is determined through a combination of both player-action and game-state prediction processes, while allowing the companion to experiment with actions the player hasn\u27t tried. We used a new method to determine the location of companion actions based on a dynamic set of regions customized to the individual player. A user study of game-development students showed promising results, with a seventeen out of twenty-five participants reacting positively to the companion behavior, and nineteen saying that they would consider using the framework in future games
