Nim is a purely mathematical combinatorial game placed here as the closest available neighbor rather than left as its own singleton category.
Alignment and Abstract Strategy Games covers games won primarily by achieving a line, connection or configuration of pieces, such as Connect Four, Gomoku, Hex and Tic-tac-toe. Nim, a purely mathematical combinatorial game, is placed here as the tree's closest available neighbor rather than left as a singleton, since it shares the family's no-chance, abstract-calculation character even though it is not itself an alignment game.