Amazons
The Game of the Amazons (often called Amazons for short) is a two-player abstract strategy game invented in 1988 by Walter Zamkauskas of Argentina. It is a member of the territorial game family, a distant relative of Go. It is played on a 10×10 chessboard (or an international checkerboard). Although the game uses pieces with moves like a chess queen, it is in no sense a chess variant. The two players are White and Black; each player has four amazons, which start on the board in the configuration shown at right. A supply of markers (checkers, poker chips, etc.) is also required.
Rules
White moves first, and the players alternate moves thereafter. Each move consists of two parts: moving one of one’s own amazons one or more empty squares in a straight line (orthogonally or diagonally), exactly as a queen moves in chess; it may not cross or enter a square occupied by an amazon of either color or an arrow. After moving, the amazon shoots an arrow from its landing square to another square, using another queenlike move. This arrow may travel in any orthogonal or diagonal direction (even backwards along the same path the amazon just traveled, into or across the starting square if desired). An arrow, like an amazon, cannot cross or enter a square where another arrow has landed or an amazon of either color stands. The square where the arrow lands is marked to show that it can no longer be used. The last player to be able to make a move wins. Draws are impossible.
Strategy
The strategy of the game is based on using arrows (as well as one’s four amazons) to block the movement of the opponent’s amazons and gradually wall off territory, trying to trap the opponents in smaller regions and gain larger areas for oneself. Each move reduces the available playing area, and eventually each amazon finds itself in a territory blocked off from all other amazons. The amazon can then move about its territory firing arrows until it no longer has any room to move. Since it would be tedious to actually play out all these moves, in practice the game usually ends when all of the amazons are in separate territories. The player with the largest amount of territory will be able to win, as the opponent will have to fill in her own territory more quickly. Scores are sometimes used for tie-breaking purposes in Amazons tournaments. When scoring, it is important to note that although the number of moves remaining to a player is usually equal to the number of empty squares in the territories occupied by that player’s amazons, it is nonetheless possible to have defective territories in which there are fewer moves left than there are empty squares. The simplest such territory is three squares of the same colour, not in a straight line, with the amazon in the middle (for example, a1+b2+c1 with the amazon at b2).
Computer Amazons
The large branching factor of Amazons in the opening and middle game strongly limits the search depth of full-width search programs. There are over 2000 possible starting moves on the 10×10 board, and although this number decreases quickly in the opening, there are several hundred legal moves during most of the game. Experiments have shown that as in most other games, search depth is strongly correlated to playing strength. Amazons seems to be a very suitable game for experimenting with selective search methods.
[from Wikipedia.org; "A gamut of games" by Jonathan Schaeffer; "Experiments in Computer Amazons" by Martin Muller and Theodore Tegos]