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Pac-Man's Ghost Behavior Algorithms
An anonymous reader writes "This article has a very interesting description of the algorithms behind the ghosts in Pac-Man. I had no idea about most of this information, but that's probably because it's difficult to study the ghosts when I die every 30 seconds. Quoting: 'The ghosts are always in one of three possible modes: Chase, Scatter, or Frightened. The "normal" mode with the ghosts pursuing Pac-Man is Chase, and this is the one that they spend most of their time in. While in Chase mode, all of the ghosts use Pac-Man's position as a factor in selecting their target tile, though it is more significant to some ghosts than others. In Scatter mode, each ghost has a fixed target tile, each of which is located just outside a different corner of the maze. This causes the four ghosts to disperse to the corners whenever they are in this mode. Frightened mode is unique because the ghosts do not have a specific target tile while in this mode. Instead, they pseudorandomly decide which turns to make at every intersection.'"
I read somewhere If pac-man leaves tile A entering tile B on the same clock pulse as a ghost leaving tile B enters tile A, the machine will switch their positions on that pulse; they never occupy the same tile.
Yawn... This stuff that already been posted on the Pacman Dossier for years. Not really "news for nerds".
Now, what would really be "news for nerds" is the analysis of the ghosts' behavior in Google Pacman, which is very similar, but subtly different.
Of course, since Google Pacman's source is available, this can theoretically be deduced straight from the source, but it's more fun to figure it out by trial and error. Great timekiller. There are definitely notable differences -- like certain directions the ghosts will never turn to if they enter the intersection from one direction, but will if they enter the same intersection from the opposite direction.
Following exact patterns work because that generates the same exact pseudo-random number pool that the ghosts use to pick directions.