2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/31034We introduce a new family of one-player games, involving the movement of coins from one configuration to another. Moves are restricted so that a coin can be placed only in a position that is adjacent to at least two other coins. The goal of this paper is to specify exactly which of these games are solvable. By introducing the notion of a constant number of extra coins, we give tight theorems characterizing solvable puzzles on the square grid and equilateral-triangle grid. These existence results are supplemented by polynomial-time algorithms for finding a solution.25 pages, 33 figures. To appear in the book More Games of No Chance edited by Richard Nowakowski and published by MSRIDiscrete MathematicsComputational GeometryComputer Science and Game TheoryG.2.1; G.2.2; F.2.2; I.3.5text