Proactive Measures

Pac-Man's performance will be measured to evaluate the level of diculty each Pac- Man strategy is having with the adaptations to game factors. Proactive heuristics identify situations where Pac-Man is struggling to progress in the game prior to failure. In the rst part of our experiment all analysis of the proactive heuristics will be performed retroactively, after the games have been simulated to calculate eects of factors. During our experiment and analysis phases we will use the statistical analysis terminology response variables when referring to the collected results of either proactive or reactive measures. During the development of the adaptive game in the second part of the experiment we will reuse a selection of these retroactive measurements to proactively estimate the future performance of the player. In this section we preview several measures which could contribute to the modeling of the level of diculty for the player. Our focus in this section is to highlight factors which potentially aect score. We feel score is one of the most important response variables in the experiment and is the easiest to discuss in relation to actions and consequence. This experiment will investigate the following proactive measures:

• Close calls occur when a ghost has come within 2 squares of Pac-Man. • The repetition of squares by Pac-Man that contain no point value.

• The number of steps since Pac-Man has collected an object, such as a token, a

power pellet, a fruit or a ghost.

• The number of power pellets remaining on the board.

The number of close calls measure identies situations in which ghosts are close to catching Pac-Man but have not been able to accomplish the task. This variable could provide insight on how to adapt gameplay when the player has produced a high score. A high score indicates a situation in which the level of challenge should be altered. If the number of close calls is low, the player is likely feeling unchallenged and a larger alteration could be made, whereas a high close calls value, indicates the level of challenge may not need to be changed or only slightly increased due to the potential contribution of luck. The number of close calls will be normalized via the number of steps per life to avoid situations where one player would have played longer than another. A summary of the expected eects for the close calls measure is listed in Table 4.10. When combined with player score, it should provide a reasonable base estimation for the perceived level of challenge and player's experience.

Tables presented in this section demonstrate the possible extreme values of the proactive measures, and the player's score. Although the player's excitement would be distinct for each player, and cannot be accurately assessed given only these measures, we have included the level of excitement as a likely base emotional state towards which the player's experience is being directed by the current level of diculty. An impor- tant note in terms of situations for adaptation is that providing a medium challenge or matching challenge and excitement states may require additional observations before adapting the game to account for the possibility of luck within the game.

Close Calls

Low High Score Low High Challenge High Challenge

High Frustration Possible Frustration High Low Challenge High Challenge

Medium Excitement High Excitement

Table 4.10: Potential player experiences relating to the response variable close calls and score

The repetition of squares which contain no point value and the number of steps since Pac-Man collected an object indicate situations where Pac-Man is failing to progress in the game. The repetition of squares which contain no point value indicates that the player either does not understand how to accomplish the goals in the game or is struggling to get to the desired location as a result of being chased by ghosts.

Repetition of Squares Low High Score Low High Challenge High Challenge

Possible Frustration Possible Frustration High Low Challenge High Challenge

Medium Excitement High Excitement

Table 4.11: Potential player experience comparing the response variables repeated number of squares and score

Likewise the number of steps since Pac-Man has collected an object indicates a failure to obtain points during the limited number of moves. This can caused by Pac-Man being redirected from goals via ghosts' actions or failed attempts to obtain bonus items. As the level progresses, a greater number of squares which have no point value will become available, as Pac-Man has already obtained the points from those squares. Thus Pac-Man will have to traverse a larger number of squares to obtain the remaining tokens. This will increase both the repetition of squares and the number

of steps since the last completed task. The two measures, repetition of squares and moves without eating, were selected because they both directly aect the player's overall score and the number of tokens collected.

Time since goal accomplished

Low High

Score Low Medium-High Challenge High Challenge Possible Frustration High Low Challenge High Challenge

Medium Excitement High Excitement

Table 4.12: Potential player experience reviewing time since goal accomplished and score.

The number of remaining power-pellets could be an important measure due to the fact that eating a power-pellet alters the ghost strategies. The presence of power- pellets allows Pac-Man to turn the ghosts into prey which allows the player to obtain more points for eating the ghosts. In addition, it allows Pac-Man to protected for a short period of time and get out of dangerous positions. The presence of power- pellets alters the optimal strategy of the ghosts, in that the ghosts should not converge when Pac-Man is closer to a power-pellet. Likewise they should disperse as quickly as possible as prey when in close proximity to Pac-Man to avoid being collectively eaten. The presence of power-pellets allows Pac-Man to use a wider set of skills when no power-pellets are present. If no power-pellets remain on the board Pac-Man must avoid ghosts purely on skill, but when present, power-pellets oer the opportunity to be more strategic by setting traps or attacking dangerous areas of the board.