"Two million, five hundred ninety-eight thousand, nine hundred sixty," Shiro says into the mattress.

"That's an awfully big number, Stephanie. We're going to start with a smaller one. Grab your chips."

He sweeps almost all of the cards to the side of the table. Three remain: a king, a queen, and a jack. He flips them over and gives them a wash shuffle, then slides them together into a pile.

Stephanie grabs her chips and leans forward, interested despite herself.

Sora pulls out a handful of his own white poker chips and stacks them up on the edge.

"We're going to play a game of poker, you and I. We'll strip out everything that makes poker complicated, leaving us with just the basics, and by the end of it you will understand the basic lesson of game theory."

The 'or else' is left unsaid.

"What are we wagering?"

"If you win, you learn what I'm about to teach you. If I win, you pay attention while I teach you what you're about to learn."

These two things are technically equal in value, and therefore valid wagers. She doesn't like it, but she nods anyways.

"Here are the rules. At the start of the turn, each of us gets one of these cards face-down and makes an ante of one chip. The first player either checks or raises one; if it's a check, the second player can check or raise one, otherwise they fold or call. Player one can call a raise, but once the pot reaches four the betting phase ends immediately. If both of us check or both of us bet, highest card wins. King beats queen, queen beats jack. Otherwise, if one player raises and the other folds, that player keeps the pot. Any questions?"

"How many chips are we starting with?"

"As many as you like. We're not worrying about the「M-ratio」for now, just individual hands."

M-ratio: something poker-related. Thank you Sora, very useful. She stacks out a handful of red chips, roughly the same number as Sora's white chips.

"Let's all have fun and play together!" she says with false cheer.

Sora deals each of them one card face-down, then slides his ante into the middle of the table. He checks his own card by bending the edge up by the absolute bare minimum necessary to read the symbol, then sets it back down and adds a second chip to the pot.

Ante up. Stephanie checks her own card. It's the jack. Odds of winning this hand: 0%.

"Fold."

Sora collects the pot, then deals another hand. He pays the ante, checks his card in the same fashion, then raises again.

"You can't do that! It's my deal!"

"I didn't say we would alternate. I'm going to keep acting first until we've played a few hands."

Nah, that's cheating. Sora forfeits.

"…Stephanie, how exactly are accusations of cheating arbitrated?"

Ah, now the shoe's on the other foot. Stephanie will savor the moment of superiority before answering.

"When you accuse a player of cheating you have to allude to how. Anything that violates the agreed-upon rules of the game is definitely cheating. Things that violate the presumed rules of the game… depends. If you're paranoid you can go around specifying that rock crushes scissors cuts paper covers rock every time you play, no one will hold it against you, but you can just say 'the game is Rock Paper Scissors' and that will do. It's not possible to redefine the outcome as 'rock tears paper, paper covers scissors, scissors stabs rock' midway through a best-of-three, even if you didn't clarify at the start."

She is speaking from experience, naturally. Everyone tries it at least once when they're little.

"You explained the rules of Idiot Poker as they differ, but there are still presumed rules like 'only you can bet using your own chips' and 'changing your call to a fold after showdown is not allowed'. No matter how fastidious you are about defining the rules of a game, there will still be some dumb edge cases that are covered by the presumed rules."

Again, this she knows from experience.

"There are also unwritten rules, which differ from presumed rules in that they're more ambiguous given the premise of the game. This is less of a problem for humans, since we can't use magic. Uh, if you imagine a chess game between two elves, and they didn't agree on a rule to not use magic, one of them could read the other one's mind and that may or may not be cheating. It would be a presumed rule in poker, that you don't know what your opponent's cards are, but chess doesn't have a presumption of secret information like that. The human equivalent would be… I don't know, maybe participating in a race after eating a magic berry that makes you run faster. Violating unwritten rules is usually not construed as cheating, so unwritten rules are often codified as written rules. If you subscribe to the 'collective cultural understanding' hypothesis of what constitutes cheating, it's possible that all the major chess tournaments specifically banning telepathy have made it so that mind-reading is more of an unwritten rule than a presumed rule for chess tournaments that don't ban it."

Human inability to use magic is a handicap on par with agreeing to only play paper, in Stephanie's opinion.

"What stops people from constantly accusing their opponents of cheating?"

"Nothing. It won't help if you don't accuse them of a particular type of cheating, though, and inventing rules violations can interfere with your concentration on the match." She pauses. "It's also widely believed that repeatedly making unjustified accusations increases the odds of future accusations of cheating going against you. I realize that from your perspective this sounds like a superstition, but from my perspective it's more of a 'we used to have good statistics on this subject but not anymore' and I don't know how to tell which of those is more true."

"Understandable."

Not having Wikipedia is inconvenient. Not having any of your scholarly records whatsoever must be a nightmare.

"Also if you get into a blowout argument with your opponent over the correct interpretation of the rules sometimes Tet shows up to make a ruling but that only happens once or twice a year, I swear."

Sora's Understanding of the Rules

1. Accusations of cheating must include details.
2. Explicit rules take precedence.
3. Obvious but unstated extensions of the rules are also enforced.
4. Unstated rules form a spectrum from 'obvious extension' (e.g. there must be a full deck of cards in the hand) to 'not an extension' (e.g. using steroids). The latter must be enumerated.
5. The crossover point on the spectrum is unclear but often involves magic.
6. Gaming the system is discouraged.
7. Tet has appointed himself the referee.

"Got it. Thank you for clarifying. As promised, you've won the right to hear what I'm about to say, so let's keep playing until I get around to saying it. Same rules, but this time I go first until we break to discuss."

Stephanie would tell Sora to shove his prize where the sun doesn't shine, if she had less of a self-preservation instinct. She collects the cards and deals another hand of Idiot Poker, quietly fuming.