I already shown it off on Mastodon, but I’m so pleased with getting this bug on video that I’m re-reporting it here! First, though, some background.
I’ve been looking into the various home computer ports of Pac-Man lately. One of the better ones is the one for Famicom/NES, probably because it was made in-house at Namco, which I presume because while it’s by no means perfect, it has ghost AI that much more closely matches Jamey Pittman’s definitive Pac-Man Dossier than the others. This is a bit more important than the other ports because, due to the relative familiarity (that is to say, inexpensiveness) of NES emulation at this point, Famicom Pac-Man is often put in compilations, especially in dedicated consoles, instead of the arcade game. In point of fact, the Namco Museum Archives Vol. 1 that’s available for various consoles uses the Famicom versions of all its games, not the arcade, and Pac-Man is one of the included games. To tell the difference: if the score, fruit tally and lives are to the right of the screen, instead of above and beneath it, and Pac-Man looks a little too big to fit in a maze passage, then what you have is an inferior home conversion.
How is it different? Well:
- The sound of Pac-Man eating dots is much worse, for starters, it never fails to bother me.
- More substantively, the ghosts have slightly different constants in their chase routines: it’s slightly harder to fake out the Pink ghost (Speedy/Pinky), and the Orange ghost (Pokey/Clyde) gives up the chase a little more reluctantly.
- The timing for scatter periods, relative the speeds of the ghosts, is a little off. Scatter periods are usually slightly longer.
- The speed of the game as difficulty increases is also a little off. In the arcade, the First Apple board (Level 5) marks a noticable increase in Pac-Man’s speed, but it seems to happen around the Second Orange (Level 4) on Famicom. Yes, that’s how much of arcade Pac-Man and its port that I’ve played-it could be subjective, but maybe it’s not.
- The bug that affects Pink’s and Blue’s (Bashful/Inky) AI when Pac-Man’s facing up doesn’t exist here.
- When ghosts enter Scatter mode, they don’t reverse direction. This makes the game easier (one less sudden reverse to throw you off) and harder (no obvious indication that the ghosts are scattering, and one less thing to throw them off from immediate pursuit).
- As the game advances in difficulty, in the arcade, on the 4th Key board (level 17), the ghosts won’t turn blue and vulnerable when you eat an Energizer, and instead will just reverse direction. And from the 6th Key (level 19) on, the ghosts will never turn blue again! NES Pac-Man instead gives them a very tiny bit of blue time, about a half-second’s worth. It never reaches a state where the ghosts become completely invulnerable.
And at last, the bug which I have confirmed. On the 10th Key board (Level 22), and every level thereafter, the ghosts will start out in an unusually long Scatter period. Their usual habit is to emerge from the box in the center of the screen and move to a corner of the screen, and circle there for a few seconds. Pink goes to the upper-left, Red (Shadow/Blinky) to the upper-right, Orange to the lower-left, and Blue to the lower-right. This period is called a “Scatter Mode” in the Pac-Man Dossier.
In most levels, presuming you don’t lose a life, the ghosts will enter Scatter Mode at exactly set three times: from the start, about 25-or-so seconds in, and about 30 or so seconds after that. These periods are usually five seconds long. There are some minor details I won’t get into-you can read the Dossier for those. These periods are lifesavers for intermediate Pac-Man players playing without patterns, as they are the only really safe ways to access the bottom passages of the board without getting trapped or wasting an Energizer.
Each Scatter Mode is only supposed to last five-to-seven seconds, but on Level 22 and after, all of the Scatter Modes last around 20 seconds. Here is the bug in action, demonstrated in Namco Museum Archives Vol. 1:
Why would this board be different from the others? In the arcade, the 9th Key (Level 21) is the maximum difficulty the game reaches. Any pattern that works on the 9th Key level will work for the rest of the game, all the way up to the kill screen on Level 256. It seems that, on the Famicom/NES version, after that level the game may not have data for the level to follow? But I haven’t looked at its code to know for sure. Maybe I should make that a future project.
