Gin Rummy

In gin rummy the whole contest is the shape of your own ten cards. Each turn you draw, from the face-down stock or the face-up discard, and throw one card away, working your hand into melds: three or four of a kind, or runs of three or more in one suit. Whatever fits no meld is deadwood, counted at face value with pictures at ten.

Knock when your deadwood is ten or less and the hands are compared: you score the difference, unless your opponent's count is as low as yours and the undercut bonus goes the other way. Knock with no deadwood at all and it is gin, worth a bonus and safe from the undercut. The board groups your melds for you and counts your deadwood as you draw, so the arithmetic never gets between you and the decision.

Knocking works as a mode rather than as a control on every card. Arm the knock button, then tap the card you want to knock with. With the button off, that same tap simply discards. The button appears only on turns when a legal knock exists. The other choice each turn is the stock or the card your opponent has just thrown away, and taking the discard tells them something about your hand. The computer weighs that cost rather than always taking the cheaper card. Your difficulty and your record stay in this browser.