5 ms·

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 availa

by 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).
  - JohnBooty 4y ago
    In hindsight, was that an official Namco/Bally-Midway thing? Or an aftermarket modification? I think that was common at the time... never heard of an official update to Pac-Man (but I could well be wrong) I know that Ms. Pac-Man removed the full determinism but that was a total conversion and it seems like you're talking about an update to the original thing
    - mikestew 4y ago
      In hindsight, was that an official Namco/Bally-Midway thing? Ya know, it was over 40 years ago and I'm going from memory. But now that you question it, and after a bit of reading, it would seem that the patterns just changed (as sibling comment states). All I know is, I showed up for a round of Pac-Man at the local 7-11 in Danville, IN after my part-time high school job, and the patterns didn't work anymore (or quit working after a point a few levels in, don't recall).
  - toast0 4y ago
    There's a (solder) jumper that was commonly adjusted for 'hard' mode where the level progression is a bit different (starts at a later level and skips a few early on), you can tell by where pac-man dies during attract mode. There were also hacked roms to speed things up; those weren't official, AFAIK.
- JohnBooty 4y ago
  They were hard codes paths. Not hard-coded paths, per se. It's more elegant than that. Each ghost has a distinctive deterministic movement algorithm based on Pac-Man's current position - some target the square ahead of him, some target the square behind, etc. That's why they seem so smart; it's like they're trying to surround/flank you. (If this seems underwhelming, I assume you it was a really neat trick back then - the ghosts had a level of personality and cunning not seen before. Combined with the cute, cartoony visual design of the ghosts themselves it was quite something.) http://gameinternals.com/understanding-pac-man-ghost-behavior http://gameinternals.com/understanding-pac-man-ghost-behavio...
bluGill 4y ago
The 8 bit Atari measured electrical noise to create random numbers. One of the io Chips had that ability. It was the only one that had real random numbers, which as a 9 year old was important to make me feel superior to everyone else I knew with Apple or Commadore computers. To be young again where such things were the most significant things in life...
jazzyjackson 4y ago
Here's a great talk on a few strategies used to fake entropy on the NES, Kevin Zurawel "Game Development in Eight Bits" StrangeLoop 2021 [0] To spoil it: Tetris does a sort of binary fibonacci sequence with XORs and bitshifts, Final Fantasy used a static lookup table it iterates through, and Contra counted idle cycles between drawing frames. [0] https://www.youtube.com/watch?v=TPbroUDHG0s https://www.youtube.com/watch?v=TPbroUDHG0s
alar44 4y ago
A good enough source of entropy is very easy for these games. Electrical noise, or player input for a few seconds is plenty as you don't need secure cryptography levels of entropy, you only need just enough to fool a human.

by simias 4y ago

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).
- JohnBooty 4y ago
  In hindsight, was that an official Namco/Bally-Midway thing? Or an aftermarket modification? I think that was common at the time... never heard of an official update to Pac-Man (but I could well be wrong) I know that Ms. Pac-Man removed the full determinism but that was a total conversion and it seems like you're talking about an update to the original thing
  - mikestew 4y ago
    In hindsight, was that an official Namco/Bally-Midway thing? Ya know, it was over 40 years ago and I'm going from memory. But now that you question it, and after a bit of reading, it would seem that the patterns just changed (as sibling comment states). All I know is, I showed up for a round of Pac-Man at the local 7-11 in Danville, IN after my part-time high school job, and the patterns didn't work anymore (or quit working after a point a few levels in, don't recall).
- toast0 4y ago
  There's a (solder) jumper that was commonly adjusted for 'hard' mode where the level progression is a bit different (starts at a later level and skips a few early on), you can tell by where pac-man dies during attract mode. There were also hacked roms to speed things up; those weren't official, AFAIK.
JohnBooty 4y ago
They were hard codes paths. Not hard-coded paths, per se. It's more elegant than that. Each ghost has a distinctive deterministic movement algorithm based on Pac-Man's current position - some target the square ahead of him, some target the square behind, etc. That's why they seem so smart; it's like they're trying to surround/flank you. (If this seems underwhelming, I assume you it was a really neat trick back then - the ghosts had a level of personality and cunning not seen before. Combined with the cute, cartoony visual design of the ghosts themselves it was quite something.) http://gameinternals.com/understanding-pac-man-ghost-behavior http://gameinternals.com/understanding-pac-man-ghost-behavio...

bluGill 4y ago

The 8 bit Atari measured electrical noise to create random numbers. One of the io Chips had that ability. It was the only one that had real random numbers, which as a 9 year old was important to make me feel superior to everyone else I knew with Apple or Commadore computers. To be young again where such things were the most significant things in life...

jazzyjackson 4y ago

Here's a great talk on a few strategies used to fake entropy on the NES, Kevin Zurawel "Game Development in Eight Bits" StrangeLoop 2021 [0] To spoil it: Tetris does a sort of binary fibonacci sequence with XORs and bitshifts, Final Fantasy used a static lookup table it iterates through, and Contra counted idle cycles between drawing frames. [0] https://www.youtube.com/watch?v=TPbroUDHG0s https://www.youtube.com/watch?v=TPbroUDHG0s

alar44 4y ago

A good enough source of entropy is very easy for these games. Electrical noise, or player input for a few seconds is plenty as you don't need secure cryptography levels of entropy, you only need just enough to fool a human.