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arXiv · 2610.19558

The Two-Level Poset Game is PSPACE-Complete

Kengo Hashimoto
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Abstract

Poset games form a fundamental class of combinatorial games that includes classical games such as Nim and Chomp. Determining the outcome of a poset game is known to be PSPACE-complete even for posets of height at most three. However, the exact computational complexity of Two-Level Poset Game, played on posets of height at most two, has remained an open problem for over a decade. We resolve this problem by proving that Two-Level Poset Game is PSPACE-complete via a polynomial-time reduction from Avoid True on positive CNF formulas.

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Kengo Hashimoto. 2026-10-14. The Two-Level Poset Game is PSPACE-Complete. https://arxiv.org/abs/2610.19558

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