Project 2: Amazons


The game of Amazons is a simple but rather interesting board game, usually for two players. It was invented in 1988 by Walter Zamkauskas of Argentina, and originally called El Juego de las Amazonas (now a trademark of Ediciones de Mente). The board is a 10 by 10 chessboard. Each player gets four "amazons" (represented as chess queens), white for the player who moves first, and black for the opponent. Initially, the board is set up as in the diagram on the left of Figure 1.

Game of Amazons Basics

Figure 1. On the left: an Amazon board showing the standard numbering of squares, and the initial placement of the pieces. On the right: the board that results after the two moves d1-d7(g7) and d10-c9(h4).

Each move consists of two parts: first, an amazon of the appropriate color makes a chess queen move—any non-zero number of squares in a straight line horizontally, vertically, or diagonally with the restriction that the piece may not move onto or through an occupied square. Pieces are not captured in this game; the board keeps getting fuller. Next, the piece that moved "throws a spear" from her final position. Spears move exactly like pieces, and are subject to the same restrictions. The spear sticks permanently in the (previously empty) square in which it lands. That square is counted as being occupied for the rest of the game (so no piece or spear may move through it). For example, the right diagram in Figure 1 shows the result of two moves. From the initial position, white moved from d1 to d7 and from there threw a spear to g7. Then black moved from d10 to c9, and from there threw a spear to h4.

A player who has no legal move loses. For example, after black moves a7-a6(a7) in Figure 2, he will have used up all his moves, and white (who still has plenty of room) will win after his next move. Draws are impossible.

Amazons Lost Position

Figure 2. A lost position for black. After a7-a6(a7), black has no move


A square is denoted by a column letter followed by a row number (as in e4). Columns are enumerated from left to right with letters a through j. Rows are enumerated from the bottom to the top with numbers 1 through 10. An entire move then consists of the starting and ending position of the piece that is moved, followed, in parentheses, by the position to which the spear is thrown. Thus, d10-c9(h4) means "Move from d10 to c9 and then throw a spear to h4."


When running from the command line, the program will accept the following commands, which may be preceded by whitespace.

Feel free any other commands you think might be nice.


When an AI plays, it should print out each move that it makes using exactly the format

 * a1-c3(c6)

(with asterisk shown). Do not print these lines out for a manual player's moves.

When one side wins, the program should print out one of

 * White wins.
 * Black wins.

(also with periods) as appropriate. Do not use the * character in any other output you produce.

You may prompt a manual player for input using the form


where "..." may be any text. The grading scripts will discard any text from the beginning of a line up to a > character.

Your Task

Your job is to write a program to play Amazons. To run it in text mode, use the command

java -ea amazons.Main

to enter commands from the terminal or use

java -ea amazons.Main INPUT

to feed it commands from file INPUT.

The AI in your program should be capable of finding a win that is within 10 moves. The branching factor for Amazons is quite high at the beginning of a game, but rapidly declines thereafter. Therefore we suggest that you choose a maximum search depth for a move that depends on how full the board is. Experiment a bit to see what works. The autograder will allow 3 minutes for a fully automated game.

The GUI is an optional (extra credit) part of this project. We will actually do automatic testing only on the commands

java -ea amazons.Main


java -ea amazons.Main INPUT

Staff Program

The staff-amazons program on the instructional machines runs our solution to the project. This version has additional bells and whistles that you are not required to duplicate. It is not the standard for this project, just as example of a solution. In particular, your GUI (if you do it) need not look anything like ours. The autograder will use this program in some of its tests to check your program's output.


We have only provided a token UnitTest file; you can add additional unit test files and list them in UnitTest so that they all get run by

java -ea amazons.UnitTest

(which is what make check does).

The integration test program, test-amazons, is not part of your skeleton. We will be providing it slightly later. To run test-amazons, you'll use

python3 testing/test-amazons

to run through your program and

python3 testing/test-amazons

to run two programs simultaneously so that each one sends all of its AI's moves (such as "* c3f6(i6)" as described previously) to the other program. (Replace "TESTFILE" with the actual name of your test file.)

Each .in and input file should start with a Unix-style command for running a program, such as

 java -ea amazons.Main

(You will probably use just this command; the autograder will sometimes use this line to run the staff solution against your program.) The rest of the .in file is fed to this program as the standard input, except for lines that start with "*" in the first column, which are special instructions to the testing script.

A few other commands apply only to the two-argument form of test-amazons. They are intended to allow two programs to play each other.

The idea with these two commands is that one of the two scripts will, at a certain point, contain the commands

*remote move/win

and the other will contain

*remote move/win

so that the first sends a move from its AI to the other program, which then waits for a response from its AI to send back, and so forth.

For the remote commands, both programs should generate "wins" messages, and test‑amazons will check that they are the same.

The test-amazons script throws out any other output from either program except for properly formatted board dumps, as are supposed to be produced by the dump command described previously. You can see all the output by running it with

 python3 testing/test-amazons --verbose


 python3 testing/test-amazons --verbose

which will show all the commands sent to each program and all their output.

The test-amazons program will report an error if a program hangs or times out, or if it exits abnormally (with an exception or an exit code other than 0). Finally, if there is a file TESTFILE-1.std or TESTFILE-2.std, test-amazons will check it against the output from the program for (likewise for TESTFILE-2.std against the output for

Extra Credit

First get your program working, and then, if you feel the urge, try the extra-credit GUI (Graphical User Interface). If you do, the option

java -ea amazons.Main --display

should create the GUI. If you don't implement the GUI, this option should cause your program to exit with a non-zero code via System.exit(2). Your GUI does not have to look at all like ours.


Your final work must be your own, but especially on this project, feel free to get together with other students to discuss ideas and plan strategies. Of course, you should always feel free to consult your TA or me.

The board is an obvious place to start. We have provided suggestions for methods that you can use if you want, but you are not required to do so. We have structured the skeleton so that the different kinds of player (ordinary human at the keyboard using text commands, AI, or human using a GUI) are represented as different subtypes of a type Player, an example of how using OOP can cut down on pervasive conditional tests for types of player.