## Friday, December 10, 2010

### Card Game: Xactika

I'm a fan of card games. Rook and Euchre were common activities growing up in my family (though I probably play both a bit too haphazardly). When I first learned about Magic: the Gathering in 1994, I quickly jumped on board and became an addict. Every time I find myself in Germany, I relearn how to play Skat. It was easy, then, for the Xactika box to lure me in by advertising "Calling all Euchre players!" (Note: this quote is likely wrong. I don't know where my box is anymore. Does anyone have the actual quote?)

Xactika is a card game with an amazing slice of combinatorics. In this game, each card has four different kinds of "shapes" drawn on it: balls, stars, boxes and cones. For each of these shapes, the card has either one, two, or three included. Thus, one card might have three cones, one ball, two stars and two boxes. No two cards have the same numbers of shapes. Thus, there are 81 cards in the deck. Each card also has a number which is the sum of all the shapes drawn on it. Thus there is one 4-card (one of each shape), four 5-cards (two of one shape, one each of the rest), all the way up to one 12-card (three of each shape). The example with three cones, one ball, two stars and two boxes would have the number 8. Having a knowledge of how many cards have which numbers of shapes becomes very useful during play!

Each card belongs to four different suits represented by the shapes on it (there are twelve in total). Our example belongs to the suits of Three Cones, One Ball, Two Stars and Two Boxes.

Xactika is a trick-taking game. The first player to start each trick chooses a card from their hand and picks one of the suits on that card as they play it. Everyone else must play a card in the called suit if they have one (or playing another card from their hand if they don't). The highest-numbered card played that follows suit wins the trick. In the case of a tie, the last-played card takes priority. Thus, if two 10's were played in one trick (and both followed suit), the second one would win the trick.

In some situations, you can be sure to win a trick. For instance, if I have the 10 with three balls, three cones, three boxes and one star, and I'm leading, I can play the card and confidently say "One star", knowing I'll win the trick; there are no other cards with that value (or higher) that only have one star!

However, it often happens that you don't want to win a trick. After dealing out all the hands, but before play begins, each player "bids" the number of tricks they think they will take. After the hand is played, each player scores points if they made their bid exactly, otherwise you lose points! Thus, you often play a card, intentionally hoping you will lose the trick. In this case, it's better to play a low-valued card and call the suit with the most shapes. A 6 with three of one shape is a great move; any other card in the suit will be above it.

Although this deviates a bit (again) from our topic of combinatorial games, this is an excellent card game with a real unique twist. After learning Xactika, I often would rather play that than other trick-taking games! The box does not lie; I highly recommend this for card game fans!

Note: My Faculty Aide, Ernie, found this excellent video, explaining how to play Xactika.

Have a great Winter Break! I plan to post again the week of January 16, 2011.