The Pac-Man Dossier

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"Ghosts use a pseudo-random number generator (PRNG) to pick a way to turn at each intersection when frightened. The PRNG generates an pseudo-random memory address to read the last few bits from. These bits are translated into the direction a frightened ghost must first try. If a wall blocks the chosen direction, the ghost then attempts the remaining directions in this order: up, left, down, and right, until a passable direction is found. The PRNG gets reset with an identical seed value every new level and every new life, causing predictable results." - Jamey Pittman

When I first played the NES port of Pac-Man many years ago, I thought the ghosts, Blinky, Pinky, Inky, and Clyde, were pretty smart. Now, many years later, I think the code behind the ghosts is pretty smart. The careful analyzing that Jamey Pittman presents on the Pac-Man Dossier is well worth a look. Interesting facts that caught my eye:

  •   Puck-Man's creation was a year and five months in the making--the longest ever for a video game to that point.
  • The game starts with Pac-Man at 80% of his maximum speed.
  • Billy Mitchell offered a $100,000 cash prize to the first player to prove they could legitimately get past level 256.



Jessie Krehlik said:

I had a very similar reaction to the Pac-Man Dossier. I used to think the four ghosts were pretty smart too--it was one of the reasons I hated the game, because I hated being chased and feeling like I was surrounded. I had no clue that the ghosts had different behaviors/patterns, and I don't think I would've ever picked up on these patterns by myself.

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