Slipstream

Three selections out

The round begins with three equal selections on the table. Five cards will appear, three of them yours and two shared.

Pulling back

After the third card and again after the fourth, you may pull one selection back and take it off the table untouched. That is the only decision, and it happens twice.

The settlement

What remains on the table is paid against a fixed table of hands. A pair of tens or better pays; anything below that does not.

The pull-back is worth more than it looks

Playing all three selections to the end regardless costs several percent. Pulling back on a weak three-card start recovers almost all of it, and the correct rule is short enough to memorise.

Where 3.51 percent comes from

The reward table pays slightly below true odds on every hand, and the two pull-back points give back most of that difference to a player who uses them. Ignore them and the margin roughly doubles.

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.