Arimaa

Possibly the most daunting challenge any game designer could set himself is this: to design a new game with the rules simplicity but strategic depth of classic abstract strategy games like Chess and Go. Those games have been refined over hundreds of years and pondered by millions of people; for an individual to create anything remotely as deep is -- well, not impossible, but clearly astonishingly hard.

And yet, with Arimaa, the Syeds seem to have succeeded.

Arimaa is played on an 8x8 grid, like Chess, but four squares (each square exactly 3 in from the two closest sides) are "traps" which are the only mechanism for eliminating opposing pieces. As in Chess, pieces are set up on the two board-edge rows on opposite sides of the board, but there is no predetermined arrangement of pieces; players may place them in the available squares however they desire.

Pawns are replaced by "rabbits," and the main way of winning is advancing one of your rabbits to the opponent's board edge. Pieces are ranked from weakest (rabbits) to strongest (the elephant); each player has one elephant, one camel, two horses, two dogs, and two cats. On your turn, you may make four moves; moving any piece orthogonally counts as one move, and you can move a single piece four squares in any combination of directions, or four pieces one square, or anything else that adds up to four.

Pieces can "push" or "pull" opposing but weaker pieces that are adjacent, that is, either moving into a weaker piece's square and pushing it into the next square in the same direction, or moving away from the weaker piece and pulling it into the square vacated. This counts as two "moves", however. It can also be used to eliminate an enemy piece by forcing it to move into a trap square.

A stronger piece also "freezes" a weaker enemy piece if adjacent, meaning that piece cannot be moved--unless another friendly piece is also adjacent, in which case it is unfrozen. Similarly, a friendly piece adjacent to a trap square makes that square safe for you, so that if you move or are forced into it your piece is not eliminated.

You can also win by eliminating all opposing rabbits, or if the opponent can make no legal moves.

One of the design ideas behind Arimaa is to devise a game that is far harder for computers to play than Chess; with no fixed starting positions, position lookups become far more difficult, and the combination of the "four moves" rule along with the push and pull options means that there are far more potential actions a player may make on his turn than in Chess, making brute-force look-aheads computationally much more complex. Strategy, however, demands the same kind of pattern-recognition and understanding of force projection that Chess does, so it is not any more difficult for humans, who excel at this kind of thing, to play.

The game can be played with a standard Chess set, using King as Elephant, and so on; you can play online against either computer or live opponents (linked above); and Z-Man Games has recently released a nicely designed boxed set (also linked above, box cover show at upper left).

If abstract strategy games appeal to you, it's well worth a look.