"Well", the mouse said, "world is getting narrower every day. In the beginning it was so large, that I was full of fear, I ran and was happy when I finally saw walls to the left and right in far distance, but those walls kept approaching each other, that I finally reached the last room and there is a trap over there in the corner I'm running into." -- "You just have to change direction", said the cat and ate the mouse.
Franz Kafka, Translation by Frank.
What is mini-Xafka mini-Xafka
is a reduced version of a unpublished game of mine (Frank). It's "mini", since I used to play the game on a 63 squares board instead of the 37 used by the applet. You can play online against the applet below
The name of the game is reminiscent of Franz Kafka cause I sometimes get the same feeling of collapsing space while playing Xafka or reading his stories. The name is also derived from "Hex" cause of the hexagonal squares on the board.
I've been kicking arround with this game since about 1980. It's first versions were probably the first games of mine with written rules. Actually we were playing on chess boards then. mini-Xafka is
- ... a two players full information game.
- ... takes at maximum 38 turns till end.
- ... never ends in a draw.
- ... contains elements of moving game like chess.
- ... contains elements of pattern building games. like (nine men morris). Though patterns are defined implicitely by the rules.
- ... is IMHO essentially a territorial game like Go.
- Original Xafka also works with 3 players.
| The empty board
I know there are similar games arround, namely the recent Quivive
and Game of Amazons
. Of course I like mine best: Rules of Xafka
seem to be slightly simpler than the ones of similar games. Anyway play is hard and there is space for beautiful combinations. But this is what every game designer claims about his 2 player game ;-)
How to play
Rules of the game
Beside the board there is a "traffic light", a piece for every player (one white, one black). You also have to imagine the board to consist of parts which can be removed during play.
- Start with an empty but complete board, the "traffic light" is on yellow. Every player takes turns with his piece until one of them has no turn left. It will be decided during the game weather the player with no turn left is the winner or the looser.
- First turn consists of the black player putting its piece anywhere on the board, removing the corrsponding hex. From turn three pieces can only be moved in straight lines from their destination square. There are 12 straight lines going out from a Hex: 6 of the border and 6 over the corner. Note that your move has to go over squares, that have not yet been removed and may not end on a square, that is reachable by the opponents piece ( Play a few turns and use the "Easy" feature of the applet to learn about that rule ).
Second turn is done by white, he puts his piece on any square, not reachable by black. The corresponding hex is removed.
| Some hexes removed. White dots mark squares reachable by white, black dots squares reachable by black, gray for squares reachable by both.
- Now turns alternate . Players move their piece to any reachable square not reachable by the opponent. With every move the destination hex is removed.
- From the point when there are 11 hexes removed the "traffic light" is free (note the slight colour change). Instead of a piece move a player can now decide the goal of the game by setting the traffic light to either green or red.
T he selection of the goal is irreversible.
- Green says that the player whos turn it is and who hasn't got a move left looses .
- Red says that the player without a move at his turn wins
- Play ends as soon as one player runs out of moves. There are basically two differenct situations how this can happen:
W e used to call the latter a "short circuit" in German. The first one is the usual one. Of course it might happen, you run out of piece moves, but you can still decide the goal...
- The players piece has no adjacent hexes anymore.
- There are adjacent (and therefore reachable) hexes, but all of them are controlled (reachable) by the opponents piece.
You do not have to work out those to exercises play the game, its just in case, you want to!
The picture above (the one at Turn 18) depicts a forced win for black. Do you find it?
|The position to the left is a forced win for white. Actually it easy to sort out the loosers, but the winning variation is quite nice.
|In the righthand position black has only two moves. Looks easy? So the question is, does black win or loose?
|White can choose a goal and win immediately. Which goal?
|In the position to the right, white has only two moves left and seems to be in the smaller territory. In fact white can win!
|In this position both struggle for the little "appendix" f4g5. But Black has a unique winning move.
How to use the applet.
The applet is very easy to use. In the default mode, you simply have to click on the square
you want to move and your piece is moved there, the computer calculates its reply and replies. Click on the traffic lights
to choose a goal. Note that the piece of the player who moved last has a little red mark on it.
On downloading: The applet needs 10 files and about 55KB. If you see any diagrams on this page, you've allready downloaded a few of the classes, cause the diagrams are another applet and share a class with the playing applet!
- Watch the browser status line for any messages.
- Use the Reset button to start a new game.
- Use the <- and -> button to navigate a back und forth within a game.
- Use Calc! to force the computer to move. Hint: Use Calc! after Reset to have the computer start the game.
- Select the Easy checkbox to mark squares as reachable for black, white or both respectively.
- Use the listbox to choose weather the computer should reply your moves, play auto matically against itself or do nothing and act as a board only. See below for ponder .
- Use the other listbox to choose the average time consumed for pondering by the computer. The strength of the applet depends on computing time and the speed of your computer. On a fast computer with reasonable timelimit, the program is a tough opponent! This is mainly due to the small board size.
(Fullscale) Xafka against (skilled) humans is more interesting, cause humans migth choose to delay the decision of the goal for very long, forcing you to consider two ways of winning for a very long time. Also Xafka allows deeper maneuveres than mini-Xafka on one hand and more geometrical reasoning on the other hand.
This applet has been developed by FSN in 1998.
Both the applet and the game are © 1998 by Frank!
- Ponder -mode is for specialists: The computer thinks about moves, without actually playing it on the board. Even if you press Calc!
- Experts might want to look at the Java Console to watch some internal information about the programs thinking process. The Applet consists of a vanilla depth-first iterative negascout algorithm, with positional scoring, selective peaks on search depth. The positional scoring is based on only 4 boardparameters. It has been self trained with a special algorithm which is neither neural net nor A.L.Samuels checkers system, though slightly reminiscent of the latter. I want to implement hash tables some time. But this is all techie talk...
- Ponder ing, together with the console window is useful for analyzing positions.
- If you dont understand any information given by the applet, ignore it ;-)
Call for positions
If anyone has a interesting position or game versus the applet or versus another human, please send me a email and I will publish it on this page.