6 ms·

Some of the games appeared to not have randomness (eg PacMan ghost patterns). Was this an intentional gameplay feature, or did the hardware lack a suitable sour

Some of the games appeared to not have randomness (eg PacMan ghost patterns). Was this an intentional gameplay feature, or did the hardware lack a suitable source of entropy?

Lammy 4y ago
"This is the heart of the game. I wanted each ghostly enemy to have a specific character and its own particular movements, so they weren't all just chasing after Pac Man in single file, which would have been tiresome and flat." — Toru Iwatani, Pac-Man creator https://gameinternals.com/understanding-pac-man-ghost-behavior https://gameinternals.com/understanding-pac-man-ghost-behavi...
- nsxwolf 4y ago
  The ghost behavior is the real genius behind the game. Even if you don't realize it, your subconscious learns how each ghost operates and longer you play the more you learn how to exploit it.
- antiterra 4y ago
  Atari 2600 Pac Man is an entirely different game than Pac Man in the Arcade. It was incredibly unpleasant, even at the time. https://en.m.wikipedia.org/wiki/Pac-Man_(Atari_2600) https://en.m.wikipedia.org/wiki/Pac-Man_(Atari_2600)
  - theonething 4y ago
    Agreed, yet I remember my parents signing up on a waitlist to get the game for me because it was sold out everywhere.
- JohnBooty 4y ago
  In Pac-Man, each ghost has a distinct movement algorithm that is entirely deterministic. In Ms. Pac-Man, initially an aftermarket hack of Pac-Man, each ghost has its own distinct movement algorithm but there is some randomness. Interview w/ the creators of Ms. Pac-Man: https://www.fastcompany.com/3067296/the-mit-dropouts-who-created-ms-pac-man-a-35th-anniversary-oral-history https://www.fastcompany.com/3067296/the-mit-dropouts-who-cre... I'm not sure how they achieved the (pseudo-)randomness, but I don't think the Ms Pac-Man conversion added new hardware other than new ROMs? Not sure about that assertion.
  - yencabulator 4y ago
    Even something as simple as seeding a PRNG with current uptime goes a long way, when there's human input available. I challenge you to insert coin on the 1 millionth clock oscillation multiple times. Hardware entropy sources are more necessary for servers, or early boot-up.
deleted 4y ago
[deleted]
simias 4y ago
I can't answer for Atari but I know that games from that time would usually derive randomness from user input timings. There simply wouldn't be a readily available source of (good) entropy available otherwise and using a complicated algorithm to harvest it and "mix" it would be prohibitively expensive. And who cares for crypto-grade entropy in a game anyway? It's actually still common with much more recent games where there are viable strategies that involve putting the RNG in a known-state (for instance at init) and then performing very precise actions to trigger a normally random event with 100% certainty. Here's an example for Final Fantasy XII: http://www.fftogether.com/forum/index.php?topic=2778 http://www.fftogether.com/forum/index.php?topic=2778 Basically the strategy is that by using a "cure" spell several times in a row and looking at how much health it regenerates in the game you can guess the position within the RNG output sequence (that is fixed and resets when you power down the console). Then when you know where you are you can plan your actions knowing ahead of time what the RNG will output and whether it'll be favourable or not. I believe that what you observed in Pacman was however due to a primitive AI: each ghost would have a simple strategy and stick to it, making them predictable and non-random by design.
- nemo44x 4y ago
  Yes the movements in original Pac-Man were deterministic. There were books published back in the day that detailed the pattern you should take to beat each level. They were hard codes paths. There were a few variations and the only thing stopping you was your execution at higher and higher speeds. I got to the point on a Nintendo DS port of it where I could pretty much play forever (255 levels I think). Ms. Pac-Man didn’t have this as the ghosts were not deterministic any longer.
  - mikestew 4y ago
    Original, arcade cabinet Pac-Man got an update after a while that eliminated the deterministic patterns. I'm sure the owners of 7-11 stores across the U. S. rejoiced, as I was one of those taking up space for quite a while for the price of a quarter (of a U. S. dollar).
    - 4y ago
Miraste 4y ago
The ghost patterns in most Pac-Man gameplay are designed on purpose, but the directions they turn when running from Pac-Man once he’s eaten a pellet are intended to be random. From a broadly interesting look at the game’s internals (https://www.gamedeveloper.com/design/the-pac-man-dossier https://www.gamedeveloper.com/design/the-pac-man-dossier): “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.” I don’t know how the initial RNG works (the source is available online, but my Atari ASM skills seem to be lacking), but more modern takes sometimes use a linear-feedback shift register, as seen here: https://www.randomterrain.com/atari-2600-lets-make-a-game-spiceware-10.html https://www.randomterrain.com/atari-2600-lets-make-a-game-sp...
keyle 4y ago
Each ghost was designed to be more or less aggressive based on their colour. Red was always coming straight for you and you better be watching for that guy!
flohofwoe 4y ago
Pacman uses a pseudo-random-generator in the frightened-ghost movement (to pick a random direction at intersections - but only for ghosts in frightened mode). In general "randomness" and "balancing" don't work too well together. PRNGs in arcade machines and home computers often used a variant of xorshift since that's easy to implement in hardware, but most often this was just for noise generation in the audio chip.
deleted 4y ago
[deleted]

Some of the games appeared to not have randomness (eg PacMan ghost patterns). Was this an intentional gameplay feature, or did the hardware lack a suitable source of entropy?

Lammy 4y ago

"This is the heart of the game. I wanted each ghostly enemy to have a specific character and its own particular movements, so they weren't all just chasing after Pac Man in single file, which would have been tiresome and flat." — Toru Iwatani, Pac-Man creator https://gameinternals.com/understanding-pac-man-ghost-behavior https://gameinternals.com/understanding-pac-man-ghost-behavi...

nsxwolf 4y ago
The ghost behavior is the real genius behind the game. Even if you don't realize it, your subconscious learns how each ghost operates and longer you play the more you learn how to exploit it.
antiterra 4y ago
Atari 2600 Pac Man is an entirely different game than Pac Man in the Arcade. It was incredibly unpleasant, even at the time. https://en.m.wikipedia.org/wiki/Pac-Man_(Atari_2600) https://en.m.wikipedia.org/wiki/Pac-Man_(Atari_2600)
- theonething 4y ago
  Agreed, yet I remember my parents signing up on a waitlist to get the game for me because it was sold out everywhere.
JohnBooty 4y ago
In Pac-Man, each ghost has a distinct movement algorithm that is entirely deterministic. In Ms. Pac-Man, initially an aftermarket hack of Pac-Man, each ghost has its own distinct movement algorithm but there is some randomness. Interview w/ the creators of Ms. Pac-Man: https://www.fastcompany.com/3067296/the-mit-dropouts-who-created-ms-pac-man-a-35th-anniversary-oral-history https://www.fastcompany.com/3067296/the-mit-dropouts-who-cre... I'm not sure how they achieved the (pseudo-)randomness, but I don't think the Ms Pac-Man conversion added new hardware other than new ROMs? Not sure about that assertion.
- yencabulator 4y ago
  Even something as simple as seeding a PRNG with current uptime goes a long way, when there's human input available. I challenge you to insert coin on the 1 millionth clock oscillation multiple times. Hardware entropy sources are more necessary for servers, or early boot-up.

deleted 4y ago

[deleted]

simias 4y ago

I can't answer for Atari but I know that games from that time would usually derive randomness from user input timings. There simply wouldn't be a readily available source of (good) entropy available otherwise and using a complicated algorithm to harvest it and "mix" it would be prohibitively expensive. And who cares for crypto-grade entropy in a game anyway? It's actually still common with much more recent games where there are viable strategies that involve putting the RNG in a known-state (for instance at init) and then performing very precise actions to trigger a normally random event with 100% certainty. Here's an example for Final Fantasy XII: http://www.fftogether.com/forum/index.php?topic=2778 http://www.fftogether.com/forum/index.php?topic=2778 Basically the strategy is that by using a "cure" spell several times in a row and looking at how much health it regenerates in the game you can guess the position within the RNG output sequence (that is fixed and resets when you power down the console). Then when you know where you are you can plan your actions knowing ahead of time what the RNG will output and whether it'll be favourable or not. I believe that what you observed in Pacman was however due to a primitive AI: each ghost would have a simple strategy and stick to it, making them predictable and non-random by design.

nemo44x 4y ago
Yes the movements in original Pac-Man were deterministic. There were books published back in the day that detailed the pattern you should take to beat each level. They were hard codes paths. There were a few variations and the only thing stopping you was your execution at higher and higher speeds. I got to the point on a Nintendo DS port of it where I could pretty much play forever (255 levels I think). Ms. Pac-Man didn’t have this as the ghosts were not deterministic any longer.
- mikestew 4y ago
  Original, arcade cabinet Pac-Man got an update after a while that eliminated the deterministic patterns. I'm sure the owners of 7-11 stores across the U. S. rejoiced, as I was one of those taking up space for quite a while for the price of a quarter (of a U. S. dollar).
  - 4y ago

Miraste 4y ago

The ghost patterns in most Pac-Man gameplay are designed on purpose, but the directions they turn when running from Pac-Man once he’s eaten a pellet are intended to be random. From a broadly interesting look at the game’s internals (https://www.gamedeveloper.com/design/the-pac-man-dossier https://www.gamedeveloper.com/design/the-pac-man-dossier): “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.” I don’t know how the initial RNG works (the source is available online, but my Atari ASM skills seem to be lacking), but more modern takes sometimes use a linear-feedback shift register, as seen here: https://www.randomterrain.com/atari-2600-lets-make-a-game-spiceware-10.html https://www.randomterrain.com/atari-2600-lets-make-a-game-sp...

keyle 4y ago

Each ghost was designed to be more or less aggressive based on their colour. Red was always coming straight for you and you better be watching for that guy!

flohofwoe 4y ago

Pacman uses a pseudo-random-generator in the frightened-ghost movement (to pick a random direction at intersections - but only for ghosts in frightened mode). In general "randomness" and "balancing" don't work too well together. PRNGs in arcade machines and home computers often used a variant of xorshift since that's easy to implement in hardware, but most often this was just for noise generation in the audio chip.

deleted 4y ago

[deleted]