Preliminary Rules: May be modified arbitrarily at any point. Make your code flexible enough to cope with obvious changes, such as different board sizes and slightly different capture rules.
The game of Gothello bears some similarities to both Go and Othello. It is played on the intersections of a 5x5 board
by alternately placing dark ("black") and light ("white") stones
By convention, the 25 intersections are lettered a-e in the horizontal direction, and numbered 1-5 in the vertical direction, giving a unique name for each intersection, as shown above.
The players alternate in placing a stone on an intersection: black goes first. When a stone is placed in such a way that stones of the player on move plus the outer wall completely enclose, with no gaps, a group of the opponent's stones horizontally and vertically, the opponent's group is captured, and changes color to the color of the capturing player. A stone may be placed in any empty location on the board, except that placing a stone in such a way as to make the player on move form a captured group is prohibited.
A player may pass at any time, and must pass when no legal moves are available. The game is over when both players have passed (in particular, when all positions are filled). The winner is the player with the most stones on the board at the end of the game: draws are possible due to the restriction on placement discussed above.
black moves to capture at b3
capturing two white pieces
Note that the left wall was part of the enclosure.
In the position shown
the white stones at e4, d3, and e2 are "safe". Black cannot play e3 due to the capture restriction described above, while white may play e3 on any turn to complete the group.
Note that this is different from Go: here we have "one eye lives" rather than Go's "two eyes live" because of the differing capture rule. The rules here were chosen to work better on the smaller board, where it is difficult to create two "eyes".
In the (probably unreachable) position shown
the game is tied, and black is on move. However, black must pass, since the play at e3 is still illegal. White will play e3 and win.
As in Go, it is important to create "eyes" to make safe formations. As in Othello, it is important to build "walls" that the opponent cannot easily capture.
As with any two-player alternating game, creating multiple simultaneous threats is effective.
First player probably has a strong advantage: someone should build an opening book.
An endgame database would be very useful, as many stones may change hands in the last few moves.
Quickly computing and/or efficiently caching "groups" of connected stones for capture purposes may make a search go much faster.
