FA-83424 / Card game rule engines / Member archive

Twenty-one against twenty-one is paid as a win · case 04

Non-natural 21 ties are paid instead of pushed.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Input [player_cards, dealer_cards, bet, doubled, from_split]. A natural is a two-card 21 not from a split. Player bust loses the stake (2*bet if doubled) first; both naturals push; player natural pays 3:2 on the bet; dealer natural takes only the original bet; dealer bust pays the stake; otherwise compare totals, equal totals push. Return net units.

Why this case matters

Card-game engines, scoring apps and online tables apply this rule automatically on every hand.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
settlement case 6	`10`	`0`	Failed

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