The Game of SIM
The game of SIM (for SIMple SIMmons, as one of my colleagues pointed out) is played by two persons on the six vertices of a regular hexagon using two colored pencils. Each player in turn fills in one of the 15 possible lines connecting a pair of the points. The player who is first to form a complete triangle (only those with vertices on the six starting points are considered) of his color, loses. The object of the game then is not to form such a triangle yourself and to force your opponent to do so.