The Game of Sim is a paper and pencil game played by two players, Red and Blue, using six dots ('vertices') arranged in a hexagon. Players alternately draw a line between two dots. The first player to draw a triangle of their color between three dots loses.
The game cannot end in a tie. 15 moves is the maximum. If the game actually lasts 15 moves then the loser will actually complete two triangles at once!
An electronic version is available at: https://wideaperture.net/sim/.
Simmons, Gustavus J. "The game of SIM," J. Recreational Mathematics, 2(2), 1969, pp. 66.
Gardner, M. Mathematical Games, Scientific American, February (1973), pp. 108-112
E. Mead, A Rose, C, Huang, The Game of SIM: A Winning Strategy for the Second Player, Mathematical Report No. 58, 1973, McMaster University.
L.E.Shader, Another Strategy for SIM, Mathematics Magazine, Vol. 51. No. 1, pp. 60-62, 1978.