Nine Mark

Nothing to decide

Two hands are dealt, and the one closer to a total of nine wins. You choose which of the two hands to back before the cards appear, and after that the rules play themselves.

Counting to nine

Tens and court cards count nothing, an ace counts one, everything else counts its face. Only the last digit of the total matters: eight and seven make five, not fifteen.

The third card

Whether a third card is drawn follows a fixed table that neither side may vary. It is worth reading once, because it is the whole game.

The narrowest margin here

Backing the host's side comes to 1.06 percent and backing the other to 1.24. Both are among the smallest margins in any card game, which is why the game survives having no decisions in it.

The trap on the table

There is usually a third field offering a large reward for a level result. It carries a margin many times wider than the two main fields, and it is the only real choice this game asks of you.

Why cards are different

A grid draws afresh every round. A deck does not: every card that has already appeared changes what is left, so the odds move while the hand is in progress. That is the only family here where what you have seen tells you something.

Order of play is the whole game

In most card games the house acts last and knows more when it acts. The rules that look arbitrary — draw to sixteen, fold below a threshold, act before the fifth card — are all attempts to price that asymmetry.

Where the margin lives

A well-played card game has one of the narrowest margins anywhere: a fraction of a percent. Played carelessly, the same game can cost ten times that. The gap between the two numbers is the value of knowing the rule.

A caution about systems

Doubling after a loss does not change any game's margin. It changes the shape of the loss — many small wins and one very large loss — and the total expected result stays exactly where it was.