Nefatavl (hnefatafl, tablut) is an old board game dating back to the age of the vikings, which is why it is also often known as "viking chess". The game is played on a board having 11 x 11 squares, and it simulates an attack on the king's castle. It is special in the sense that the two parties in the game, the attackers and the defenders, have two different ways of winning the game. The attackers are to try to capture the king of the castle, the defenders must try to help their king escape from the battlefield.
Several findings from the age of the vikings tell us, that they have been playing nefatavl back then, but there is not enough to give a sufficient description of the rules. So, the rules known today are influenced by various other sources as well, most importantly by the swedish archaeologist Carl von Linné, who in 1732 saw a game resembling nefatavl played among the Lapps of northern Scandinavia. It is of course highly unlikely that the rules are identical to the rules of the vikings, but that is the best we have. The archaeological magazine Skalk has published the rules in various languages, and it is also possible to buy reproductions of the game through the publishing firm Wormianum (pages in danish).
I have written down a set of rules as well, based on the rules published by Skalk. However, these rules are not complete enough to use as basis for a computer program. The problem is, there are no rules preventing the game from going on forever! In chess, a draw is introduced together with rules deciding when a game is a draw, without the need to play on endlessly, but I think the asymmetry of nefatavl indicates that there should be no draw (which is not described in the rules neither), either the king is caught or he is not. The problem lies in the fact, that both sides can play passively, preventing the other part from winning without one self attempting to win, so it is not feasible to introduce a "rule of termination" as the 50 move rule in chess, and then just declare one part victorious. The party playing passively must of course be punished. I have suggested a few expansions to the rules, but I have not yet decided which one to actually use, so for now there is no rule of termination in the program. If you have any suggestions or comments to this, please send me an e-mail.
The program, which so far only exists in a demo version (not all menus work) can be downloaded here. Unzip the file in an appropriate folder, and run "Demo.exe".
It is also my plan to build a server enabling play against other internet users, both as "correspondence" and as "blitz", where you can play online against another player. The server will be built on the same principles as my chess server, so check this page out from time to time, until something pops up!
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Last revised: 2006-04-12