Back in college, I had a roommate who was obsessed with Pac Man. He’d study the ghosts, looking for patterns and do research on the net. If this was available then, he wouldn’t have to look anywhere else. The Pac Man Dossier goes into such incredible depth, even reviewing code from the game to figure out exactly how the game works. Here’s an excerpt:

Pinky: Nicknamed “Pinky”, the pink ghost’s character is described as one who isspeedy. In Japan, he is characterized as machibuse, meaning “to perform an ambush”,perhaps because Pinky always seems to be able to get ahead of you and cut you off when you least expect it. He always moves at the same speed as Inky and Clyde, however, which suggests speedy is a poor translation of the more appropriatemachibuse. Pinky and Blinky often seem to be working in concert to box Pac-Man in, leaving him with nowhere to run.

In chase mode, Pinky behaves as he does because he does not target Pac-Man’s tile directly. Instead, he selects an offset four tiles away from Pac-Man in the direction Pac-Man is currently moving (with one exception). The pictures below illustrate the four possible offsets Pinky will use to determine his target tile based on Pac-Man’s orientation:

If Pac-Man is moving left, Pinky’s target tile will be four game tiles to the left of Pac-Man’s current tile. If Pac-Man is moving right, Pinky’s tile will be four tiles to the right. If Pac-Man is moving down, Pinky’s target is four tiles below. Finally, if Pac-Man is moving up, Pinky’s target tile will be four tiles up and four tiles to the left. This interesting outcome is due to a subtle error in the logic code that calculates Pinky’s offset from Pac-Man. This piece of code works properly for the other three cases but, when Pac-Man is moving upwards, triggers an overflow bug that mistakenly includes a left offset equal in distance to the expected up offset (we will see this same issue in Inky’s logic later). Don Hodges’ website has an excellent article giving a thorough, code-level analysis of this bug, including the source code and a proposed fix—click here to go there now.