For those who prefer a single-player experience, or at least one to practice with to hone one's skills in preparation for a heads-up match against another human opponent, and if a little Japanese text won't scare you off, then give Taro Ito's GameDesign Flash implementation of Hanafuda a try.
If you're new to Hanafuda (Koi Koi), be sure to review the cards and the rule set for this very simple Japanese card game. The most difficult aspect of the game will be familiarizing yourself with the cards and the sets of value. Once that is done, however, you're in for an enjoyable card game that is very easy to play.
In this version, simply click on one of your cards to automatically capture the matching card from the board, or to discard it if there are no matching cards.
The rule set is similar to Bryon's multiplayer version, but there are several differences to make note of. The most significant difference is the relative insignificance of the sake cup card in the GameDesign version. Pairing it with either the moon or the blossoms light card has no effect. The other major difference is the Koi Koi dialog has the "Call" and "Koi Koi" buttons reversed, with "Call" on the right and "Koi Koi" on the left.
Beginning with the first month, January, and for each new hand, one of the dregs cards for the current month is shown on the right with your score. Whomever captures all four cards of that month during the hand earns 4 points, similar to completing a set. Most other standard sets are recognized with their standard point scores. There are no score multipliers used in this version, and if no one earns a score before all cards are exhausted, the player with more captured cards earns 6 points.
You begin the game with 10 points. Lose all 10 and it's game over; however, earn 50 points to win the game and turn on an alternate "face-up" mode. When playing face-up, you can see both yours and your opponents cards, as well as the next card to be turned up from the deck. Win that game and it's back to normal mode again.
Analysis: As usual, Taro Ito's exceptional game design talent shines through in this implementation. The artwork is crisp and gorgeous, and the interface controls are intuitive and very easy to use. I especially like the elegant single-click selection that works in most instances. For turns where a card matches more than one card on the board, only one additional click is needed to choose which of the two to capture. The downside to this method, however, is that someone just learning how to play doesn't get the benefit of highlighted matching cards. A simple mouse-over showing matching cards on the board would address this shortcoming easily.
I also enjoyed playing through a second time with the cards all turned face-up, as this allowed for a slightly different strategy and made the game seem fresh again. Overall, an excellent piece of work.