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A gin hand can be undercut · case 02

Going gin against a defender with zero deadwood hands the defender the undercut.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

Input [knocker_deadwood_cards, defender_deadwood_after_layoffs, gin, big_gin]. Deadwood: A=1, T/J/Q/K=10, others pip. Knocking above 10 is ["illegal", 0]. Big gin scores 31 + defender deadwood, gin 25 + defender deadwood (gin cannot be undercut). Otherwise if defender deadwood <= knocker deadwood the defender undercuts for 25 + difference; else knocker scores the difference.

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
knock score case 1	`["defender", 25]`	`["knocker", 25]`	Failed

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