A tractability gap beyond nim-sums: It's hard to tell whether a bunch of superstars are losers.

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Title: A tractability gap beyond nim-sums: It's hard to tell whether a bunch of superstars are losers.
Authors: Burke, Kyle1 (AUTHOR) kburke@flsouthern.edu, Ferland, Matthew2 (AUTHOR) ferlandm@dickinson.edu, Huntemann, Svenja1,3 (AUTHOR) svenja.huntemann@msvu.ca, Teng, Shang-Hua4 (AUTHOR) shanghua@usc.edu
Source: Theoretical Computer Science. Feb2026, Vol. 1062, pN.PAG-N.PAG. 1p.
Subjects: Game theory, Computational complexity, Games
Abstract: In this paper, we address a natural question at the intersection of combinatorial game theory and computational complexity: "Can a sum of simple tepid games in canonical form be intractable?" To resolve this fundamental question, we consider superstars , positions first introduced in Winning Ways where all options are nimbers. Extending Morris' classic result with hot games to tepid games, we prove that disjunctive sums of superstars are intractable to solve. This is striking as sums of nimbers can be computed in linear time. Our analysis shows that the game Paint Can is intractable and also yields a new intractable game, Blackout. We present web-playable versions of both games. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:In this paper, we address a natural question at the intersection of combinatorial game theory and computational complexity: "Can a sum of simple tepid games in canonical form be intractable?" To resolve this fundamental question, we consider superstars , positions first introduced in Winning Ways where all options are nimbers. Extending Morris' classic result with hot games to tepid games, we prove that disjunctive sums of superstars are intractable to solve. This is striking as sums of nimbers can be computed in linear time. Our analysis shows that the game Paint Can is intractable and also yields a new intractable game, Blackout. We present web-playable versions of both games. [ABSTRACT FROM AUTHOR]
ISSN:03043975
DOI:10.1016/j.tcs.2025.115656