Directly Controlling the Perceived Difficulty of a Shooting Game by the Addition of Fake Enemy Bullets

Adjusting the balance between the player’s game skill and the difficulty level is one of the most important factors to improve the player’s engagement. However, it is still quite rare to find works that aim to straightly control the subjective difficulty perceived by the player. Our research question is whether or not it is possible to control the perceived difficulty just by adding enemy objects that do not raise the actual difficulty level. To investigate this issue, we designed a simple shooting game with two ‘fake enemy bullets’: Unreachable Bullets and Non-collisionable Bullets, which do not damage the player character. The experiment suggests that the non-collisionable bullet can efficiently increase the perceived difficulty level but the unreachable bullet does not. Such a study in novel techniques that can control the perceived difficulty without changing the actual difficulty could contribute to both research and practices in game design.