Spirals corruption

SPIRALS

Level set	Chip's Challenge 1
Level number	88
Designer	Unknown
Password	WZYV
Hint	None
Chips required	12
Chips available	12
Time limit	400
MS
Bold time	304
Difficulty	*****
Bold difficulty	*****
Bold complexity	*****
Lynx
Bold time	304
Difficulty	*****
Bold difficulty	*****
Bold complexity	*****

Spirals corruption is a misnomer, referring to a copy of MSCC which shipped with the original Lynx version of Spirals, rather than the version edited to work with Microsoft rules. The difference is a single tile: at grid coordinates (29, 13), Lynx has a thin wall, but MSCC changes it to a floor. The difference is so drastic that the Lynx level was initially believed to be a glitch.

The difficulty in the original Spirals was apparently not noticed until after the initial release of MSCC. Although the level was altered to fix the issue, some early copies of Spirals — generally found in Windows Entertainment Pack 4 versions of the MS Chip's Challenge — made it into player hands before that happened.

Background

The change in difficulty comes down to a change in the behavior of walkers.

In Lynx, when a walker hits an obstacle while trying to move, it will choose a random direction and try to move that way instead. Crucially, it will choose any random direction, including the direction it's already facing. Thus, if a walker goes down a hallway one cell wide and hits a dead end, it only has a 1 in 4 chance of backtracking each tic. If more walkers are coming up behind it, there's a decent chance they will bunch up and bumble around for a while.

In MS, a blocked walker chooses a random open direction. A walker in the same dead end will thus immediately turn around and head back the same way. Even multiple walkers trapped in the same hallway will function akin to a cannon, shooting them all back out as quickly as possible.

The removal of the single wall changes a dead end to a corner leading into a T junction, providing a release valve that lets the walkers spread out into other parts of the level

Spirals also spawns walkers also more frequently in general under MS. When a new clone is created in Lynx, it only has a 1 in 4 chance of making it past the first corner after the red button; it's more likely to cause a traffic jam and prevent too many walkers from escaping into the level too quickly. In MS, a new clone will always take that corner, ensuring a steady stream of new walkers.

History

This corruption was first brought to the full attention of the public, although isolated reports had been made, on March 23, 1998, in a discovery by Erik Arfeuille:

There definitely was a bug in my chips data file. I used the chip's editor and the instructions given to me by Richard Field and was able to remedy the problem. If you have any knowledge of the Chip's editor: run it, load level 88 and check out square 29,13. On *my* Level 88, this square was blocked to the east by a thin wall! Level unsolvable. Via Richard Field's Chip's site, I learned that I wasn't the only one with this problem. Nobody knows why only some Chips.data files are corrupted in this way.

Ruben Spaans attempted the corrupted level, and found it could indeed be solved with a Texas-size portion of luck, reporting a time of 300. The full text of his theory is quoted as follows:

...I believe [my "corrupted" Chips.dat] is not corrupted. The only difference between [it] and the ["normal"] one ... the blocked spot above the exit on level 88. I did a file compare, and this is the only difference... What's makes this a bit interesting, is that level 88 on both the Lynx and Commodore 64 is exactly like my "corrupted" version... Somehow the walkers aren't as aggressive on the C64 as on the PC, and therefore level 88 isn't at all impossible on the C64 (I haven't played the Lynx version, so I can't speak for that one). My theory is that Microsoft converted all the levels from the Lynx, with too [little] playtesting. Later they discovered that level 88 was way too difficult, so they patched it. Surely you know about all those non-working trap buttons and clone machines, so apparently they slipped up on many levels. But that's just my theory about level 88.... For the technical minded, the level 88 difference in [is?] at byte offset $EC5C in the Chips.dat file. The blocked square version ("corrupted") contains the byte $09, while the open square has the byte $00. So everyone with a hex editor can fix their file.

Since this time, the corrupted version's bold time has reached 304, achieved with turning 3D U 2D 4R 3L at the intersections, and with at most three moves lost. Though still significant, the luck needed is not tremendous, particularly if the player is a bit mindful of how many walkers are created in the first moments of the level. If they see less than ten walkers before picking up the second computer chip, then their chances of at least completing the level are decent. As for fixing a corrupt level, instead of using a hex editor, edit the level in a level editor.

Walkthrough

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See also

• Not All The Bugs Are Yellow: Alice Voith's analysis of the then-known glitches

References

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