Janet Miles, CAP-OM (janetmiles) wrote,
Janet Miles, CAP-OM

About Spider Solitaire

Another question from my friend.

D: How familiar are you with the Windows card game "Spider"?

J: Fairly; I play it in Windows, and I'm very fond of Pogo's version, Rainy Day Spider Solitaire.

D: Windows version is the only one I'm familiar with, and I thought of asking you this because once-upon-a-while-ago you tipped me to a bunch of 'insider info' on FreeCell, so I thought you might know. I have come to the conclusion that Spider *must* be rigged, somehow, because logic tells me that otherwise a rules-violating situation would at least occasionally occur, which it doesn't.

J: Oh? What kind of rules-violating situation?

D: There are 10 columns for cards in the game, and one is not allowed to 'deal' from the draw pile if any column is empty. Why/how is it that it *never* occurs that there are less than 10 cards in play at one time, given that 13 cards are transferred 'out' once a suit is completed? I.e., if there were only 9 cards left in play while a draw pile still existed, it would be impossible by the rules of the game to deal more cards.

J: Huh. Let me think about that.

You know, I've never thought of that; I've always just left cards on the table so that I'd be able to make the final deal. Let me see what happens, if I can get it down to that.

D: A more precise description of what I've encountered that had me thinking of this: for the sake of clarity, let's identify the 'dealt' cards as being "on the board", the un-dealt cards as "the draw pile", and the completed suits as "discards". I have been in situations where there were no remaining face-down cards on the board, and maybe somewhere between 15 - 20 cards face-up, but not sufficient to complete any suit for the discard pile. Given that the remaining cards to complete those incomplete face-up partial suits *do* exist in the deck, why is it that I've never had between 14 - 22 face-up cards on the board and been able to complete a suit from them -- thus leaving fewer cards than needed to make the next deal?

J: That's a good question. I'm not sure how to set up the combinations / probabilities to figure it out.

D: Anything more than 22 cards, and there'd still be 10 left to fill each open column with at least one card.


D: Challenging little problem, no? {grin}

J: Indeed. And I'm still not sure how to set up the combinations to figure it out.

D: Nor how much math would be involved in assuring that every deck order the game starts with won't ever result in that situation, regardless of how the cards were played.

J: Also true.

D: And yet I can't believe that the game exists without something in place to prevent that possibility. Simple logic isn't enough to explain it away, and in fact it's logic that raises the question to begin with. But while I can see the Windows programmers inventing a new game of solitaire, I can't see them pouring in the hours needed to prevent what seems to be mathematically possible combinations from occurring which would, in essence, 'break the game'. They didn't bother preventing unwinnable 'deals' in FreeCell, after all.

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