Gin Rummy
Ten cards each against the computer, and you pick your moment to knock.
How to play
You each hold ten cards. One card goes face up to start the discard, and the rest sit face down as the stock. On your turn you take one card, either the unseen top of the stock or the face-up card, and then you put one card down. You cannot put back the card you just took off the pile.
Three or four of a rank is a set, and three or more of one suit in order is a run, with the ace low. Everything left over is deadwood: an ace counts 1, the picture cards count 10, and the rest count their number. Once your deadwood is 10 or less you can knock instead of a plain discard, and the round stops there.
Knock with nothing left over and that is gin, worth 25 plus everything the other player is holding. On a plain knock they first lay what fits onto your melds, and then either you score the difference or, if they end level or lower, they undercut you for 25 plus the difference. First to 100 points wins the match. If the stock runs down to its last two cards with nobody knocking, nobody scores and the same player deals again.