February 19, 2009 5:15 PM   Subscribe

The Pac-Man Dossier is an extremely detailed description of the game logic of arcade Pac-Man. It explains why, once in a while, monsters will harmlessly pass through Pac-Man. It explains why they won't go up through the tunnels above the monster box. It explains why occasionally, after losing a life, monsters will refuse to leave the box. It explains when and why Blinky becomes Cruise Elroy, and why sometimes Pinky gets confused and loses track of Pac-Man. It even explains, as far as the player can continue to play, what to do on the kill screen. It is awesome. Previously....
posted by JHarris (34 comments total) 60 users marked this as a favorite
1. Awesome.
2. Didn't Billy Mitchell offer a million dollars to anyone who could figure out how to play through the kill screen?
posted by roll truck roll at 5:36 PM on February 19, 2009

Whoa, this is awesome!

And, roll truck roll, from the very end of the dossier:

For decades, Pac-Man enthusiasts worldwide have heard the whispers about a “secret trick” allowing a player to get past level 256 and continue playing without using the aforementioned rack test. Several players have boasted having acquired this holy grail of Pac-Man knowledge over the years, but no one has been able to make good on their claims by actually proving it. This topic became so hotly debated in the upper echelons of the arcade gaming community that Billy Mitchell—who was convinced it was impossible—offered a $100,000 cash prize to the first player to prove they could legitimately get past level 256, leaving the challenge open for a full year. The prize money went unclaimed.

In spite of the evidence against there being a way to get past level 256, rumors still persist and can occasionally be found in classic gaming forums online, yet no one has been able to back up their words with indisputable proof. It's hard to imagine why anyone who could legitimately get past the level did not collect Mr. Mitchell's prize money to be sure. Still the occasional whispers can be heard. Perhaps it is simply natural for people to want to believe in the possibility as opposed to not—like Santa Claus or the Easter Bunny. Then again, maybe there is some middle-aged Pac-Man junkie out there who is withholding secrets to a 30 year-old amusement device for his or her own unfathomable reasons. Stranger things have happened. You be the judge.
posted by barnacles at 5:37 PM on February 19, 2009

This is extremely cool. I love this for the same reason I love tool-assisted speedruns -- all the programming hacks and compromises and workarounds, laid bare. It's fun to see the reactions of oldschool developers when they find out that future nerds have spent hundreds of hours reverse-engineering stuff they haven't even thought about in decades. This interview with the composer of NES Contra is particularly amazing.
posted by jake at 5:47 PM on February 19, 2009 [2 favorites]

When I was a kid, some time in the early-to-mid 80s, I had a great idea for a video game. I was going to clean. up. It was going to be exactly like Pac-Man but with a different maze. Incredible, I know. I should have first warned you to sit down.
posted by DU at 5:48 PM on February 19, 2009 [6 favorites]

Yes. This is indeed awesome.
posted by jquinby at 5:51 PM on February 19, 2009

I was wondering why all these people suddenly started Googling for Cruise Elroy.
posted by danb at 6:01 PM on February 19, 2009

Scarily impressive! As is this.
posted by tellurian at 6:02 PM on February 19, 2009 [1 favorite]

all the programming hacks and compromises and workarounds, laid bare. It's fun to see the reactions of oldschool developers when they find out that future nerds have spent hundreds of hours reverse-engineering stuff they haven't even thought about in decades.

It was only recently, for example, that the "NARPASSWORD" cheat code for Metroid NES was discovered, through reverse engineering of the code.

All I had in my day was JUSTIN BAILEY. Damn kids and their new fangled 6502 disassemblers.
posted by blenderfish at 6:13 PM on February 19, 2009 [1 favorite]

the madness of mission 6. A better adaptation than the forthcoming Watchmen flick, I'll, uh, warrant. Er, I mean speculate.
posted by mwhybark at 6:25 PM on February 19, 2009 [1 favorite]

Where was this 28 years ago when I really needed it?
posted by Joey Michaels at 6:54 PM on February 19, 2009

Today metafilter provided a nice encapsulation of a computerized youth in three posts: first the Commodore 64 post, then Street Fighter, now this Pac-Man post.
posted by exogenous at 7:00 PM on February 19, 2009

The movie adaptation better kick ass!
posted by humannaire at 7:09 PM on February 19, 2009

Although Pac-Man was arguably more popular because of the cute graphics, the ghost AI was actually really impressive for such an early game. It's one of the few games that are extremely hard to replicate in fan-made clones, because inevitably the remakes never capture the details that make the original so complex. And I still refuse to acknowledge that the Atari 2600 version exists at all.
posted by burnmp3s at 7:09 PM on February 19, 2009 [1 favorite]

Wakka. Wakka. Wakka.. Wakka. Wakka. DOOM
posted by The Whelk at 7:32 PM on February 19, 2009

And here is the Z80 assembly code demonstrating why the ghosts fuck up.

Seriously, seriously awesome.
posted by localroger at 7:37 PM on February 19, 2009

Awesome webpage, pulled me right in even though some of the logic was over my head.
and now the "Cruise Elroy" enigma will haunt me forever . . . pun not intended.
posted by arcanecrowbar at 8:25 PM on February 19, 2009

posted by zap rowsdower at 8:43 PM on February 19, 2009

I'm really pissed that I only just heard about this t-shirt a couple of days ago.
posted by middleclasstool at 8:50 PM on February 19, 2009

middlecalsstool, it's been reprinted a couple of times. however, until they re-up, allow me to say gloatingly: I have one!

I'm sure that the arts funding in the stim-pill bill will fund Madness of Mission Six tees for all.
posted by mwhybark at 9:39 PM on February 19, 2009

And I thought the amount of time I spent playing and studying Counter-Strike was nerdy...now I feel better about myself. Awesome post.
posted by Chan at 9:44 PM on February 19, 2009

Is this something I'd have to have spent time in an arcade in the 1980's to understand?

Awww, I'm just otoboke.
posted by Ambrosia Voyeur at 1:20 AM on February 20, 2009

I refuse to read any of this. As far as I am concerned, Pac-Man and the ghosts are controlled by a life force which we can never hope to understand.
posted by orme at 5:02 AM on February 20, 2009 [3 favorites]

This sort of thing is fascinating to me. It is a world which is completely and forever out of my grasp. I am amazed at the care and attention to detail on all sides of this, and sometimes I regret my pathetic math skills and general impatience with lists and numbers.
posted by Scattercat at 5:30 AM on February 20, 2009

Strangely, I'm actually wearing a Pac-Man shirt at this very moment.
posted by zengargoyle at 7:32 AM on February 20, 2009

What a fantastic post. This is what the internet is for.
posted by Kwine at 9:35 AM on February 20, 2009

The major realization here, I think, is that while the ghosts and Pac-Man appear to be moving smoothly through the level, behind the scenes they actually jerk along in eight pixel units, tied to the hardware tile system. It's really amazing that this fact is so little-known, as a lot of Pac-Man's design decisions are based off of it. It's effectively a spriteless game!

It greatly reduces the complexity of the design, but also means Pac-Man can move through monsters occasionally. If you've ever wondered why sometimes a monster will kill Pac-Man on the merest touch, yet other times must completely engulf him, here's your answer.

Also, the bug in Pinky's chase algorithm that causes it to home in on Pac-Man incorrectly when he's facing up seems like it must have some clever applications.
posted by JHarris at 9:55 AM on February 20, 2009

Really great reading! Thanks so much for the post, JHarris!
posted by vacapinta at 9:56 AM on February 20, 2009

this is the best fpp ever.
posted by shmegegge at 10:45 AM on February 20, 2009

Anybody want to update the Wikipedia article for Pac-Man? It currently states:

"However, while players generally agree that the behaviors of each ghost add depth and challenge to the game, no consensus has been reached on exactly how to describe those behaviors."

This article seems to describe the ghosts' behaviours pretty exactly.
posted by obiwanwasabi at 12:41 AM on February 21, 2009

Funny, I just found the Dossier a couple weeks ago myself, while doing research on the ghost AI. I found it to be by far the most informative Pac-Man resource I have seen. One could make a great clone using just this text and nothing else.
posted by mysterpigg at 6:43 PM on February 21, 2009

After years of telling my kids about the thrill of hours of pacman (and the sore arm) they finally decided to plug a PacMan cartridge into the Nintendo. They loved it. Unfortunately, age had taken a toll on me. In my prime, I could go 30 minutes on a quarter.
posted by ejc123 at 9:47 AM on February 22, 2009

ejc123, there are aspects of arcade Pac-Man, this article reveals, that are obscure enough that they likely aren't emulated properly. In fact, the directions that monsters go when they are vulnerable is pseudo-random and routed through random memory addresses, so it's impossible to recreate Pac-Man accurately without the memory map of the arcade game at hand, and if you've got than then you might as well emulate it anyway!

I guess what I'm saying is: MAME rocks.
posted by JHarris at 11:41 AM on February 22, 2009

(Er, lost my point again...)

So, the game you're playing on the NES is not the same as the arcade game. Which could well explain your underperformance.
posted by JHarris at 11:42 AM on February 22, 2009

Very cool! And thank you for resurrecting (and putting to rest) a memory I had of playing, and having Pacman pass right through Blinky!!! No one believed me. Vindication is mine.
posted by ObscureReferenceMan at 10:10 AM on February 23, 2009 [1 favorite]

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