Abstract
The game of nim, with its simple rules, its elegant solution and its historical importance is the quintessence of a combinatorial game, which is why it led to so many generalizations and modifications. We present a modification with a new spin: building nim. With given finite numbers of tokens and stacks, this two-player game is played in two stages (thus belonging to the same family of games as e.g. nine-men’s morris): first building, where players alternate to put one token on one of the, initially empty, stacks until all tokens have been used. Then, the players play nim. Of course, because the solution for the game of nim is known, the goal of the player who starts nim play is a placement of the tokens so that the Nim-sum of the stack heights at the end of building is different from 0. This game is trivial if the total number of tokens is odd as the Nim-sum could never be 0, or if both the number of tokens and the number of stacks are even, since a simple mimicking strategy results in a Nim-sum of 0 after each of the second player’s moves. We present the solution for this game for some non-trivial cases and state a general conjecture.
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Notes
It is a well-tempered (fixed-length) scoring game as defined by Johnson (2014).
A colored version is available at http://arxiv.org/abs/1502.04068.
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Acknowledgments
We thank the anonymous referees for their brilliant work.
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Eric Duchêne: Supported by the ANR-14-CE25-0006 project of the French National Research Agency
Urban Larsson: Supported by the Killam Trust.
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Duchêne, E., Dufour, M., Heubach, S. et al. Building Nim. Int J Game Theory 45, 859–873 (2016). https://doi.org/10.1007/s00182-015-0489-3
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DOI: https://doi.org/10.1007/s00182-015-0489-3