Gin Rummy

Goal of the game

Be the first to reach 100 points (or 50 in a short game). You score by ending a hand with less deadwood than your opponent.

Melds

• Set: three or four cards of the same rank (7♠ 7♥ 7♦).
• Run: three or more consecutive cards of the same suit (4♥ 5♥ 6♥). The ace is always low: A-2-3 is a run, Q-K-A is not.
• A card can belong to only one meld.
• Cards outside any meld are deadwood: ace = 1, 2 to 10 = face value, face cards = 10.

How it works

• Each player is dealt 10 cards. The next card, turned face up, starts the discard pile.
• First turn: the non-dealer may take that card; if they pass, the dealer may take it in turn; if both pass, the non-dealer draws from the stock.
• On your turn: take the top card of the stock or of the discard pile, then discard a card. You cannot discard the card you have just taken from the discard pile.
• You may knock when discarding if your deadwood totals 10 points or less. With no deadwood at all, it is gin.
• If the stock is down to two cards with no knock, the hand is voided.

End of a hand

• The knocker lays down their melds. The opponent lays down theirs and may lay off their deadwood onto the knocker’s melds (except after a gin).
• Knock: the knocker scores the difference between the two players’ deadwood.
• Undercut: if the opponent has as much or less deadwood than the knocker, the opponent scores the difference plus 25 points.
• Gin: 25 bonus points plus the opponent’s deadwood, with no layoffs possible. Big gin: all 11 cards form melds after the draw, 31 bonus points.

End of the game

The first player to reach the target total wins. Final scoring: game bonus of 100, box bonus of 25 per hand won; if the loser has scored no points, it is a shutout and the winner’s bonuses are doubled.

Controls

• Tap the stock or the discard pile to draw (keys T and D).
• Tap a card to select it, then tap it again or drag it onto the discard pile to discard it.
• Your hand is sorted automatically: each meld is outlined and your deadwood is always displayed.

About the AI

The AI always computes the optimal decomposition of its hand. From the Intermediate level, it estimates the value of each discard by the expected deadwood after the next draw. At the Expert and Master levels, it keeps a record of the cards you take, pass on or discard to estimate your hand (a Bayesian model), avoids discards that would help you and decides whether to knock by simulating hundreds of plausible opposing hands (including the risk of an undercut). It never sees your cards.