What design and AI lessons can we learn from Namco's seminal Pac-Man
? From history through behavior, Gamasutra presents Jamey Pittman's astounding guide to the classic game
's four brightly colored ghost antagonists -- Blinky, Pinky, Inky, and Clyde -- have three mutually-exclusive modes of behavior, each with a different objective/goal to be carried, which Pittmann details:
"Chase - A ghost's objective in chase mode is to find and capture Pac-Man by hunting him down through the maze. Each ghost exhibits unique behavior when chasing Pac-Man, giving them their different personalities: Blinky (red) is very aggressive and hard to shake once he gets behind you, Pinky (pink) tends to get in front of you and cut you off, Inky (light blue) is the least predictable of the bunch, and Clyde (orange) seems to do his own thing and stay out of the way.
Scatter - In scatter mode, the ghosts give up the chase for a few seconds and head for their respective home corners. It is a welcome but brief rest-soon enough, they will revert to chase mode and be after Pac-Man again.
Frightened - Ghosts enter frightened mode whenever Pac-Man eats one of the four energizers located in the far corners of the maze. During the early levels, the ghosts will all turn dark blue (meaning they are vulnerable) and aimlessly wander the maze for a few seconds. They will flash moments before returning to their previous mode of behavior."
Though in all modes of behavior, the ghosts are prohibited from reversing their direction while traveling down a corridor, they still manage to turn around -- this is accomplished when the system forces a ghost to change its behavior, and the reversal should be observed by players as indication of a mode switch.
"Ghosts are forced to reverse direction by the system anytime the mode changes from: chase-to-scatter, chase-to-frightened, scatter-to-chase, and scatter-to-frightened. Ghosts do not reverse direction when changing back from frightened to chase or scatter modes.
When the system forces the ghosts to reverse course, they do not necessarily change direction simultaneously; some ghosts may continue forward for a fraction of a second before turning around.
The delay between when the system signals a reversal and when a ghost actually responds depends on how long it takes the ghost to enter the next game tile along its present course after the reversal signal is given (more on tiles in Chapter 3). Once the ghost enters a new tile, it will obey the reversal signal and turn around."
You can read the full feature
, which includes more in-depth details on Pac-Man
's ghost behaviors, strategies, and the mysterious 256th level (no registration required, please feel free to link to this feature from other websites).