Positional game
A positional game is a kind of a combinatorial game for two players. It is described by: During the game, players alternately claim previously-unclaimed positions, until one of the players wins. If all positions in formula_1 are taken while no player wins, the game is considered a draw. The classic example of a positional game is Tic-tac-toe. In it, formula_1 contains the 9 squares of the game-board, formula_3 contains the 8 lines that determine a victory (3 horizontal, 3 vertical and 2 diagonal), and the winning criterion is: the first player who holds an  entire winning-set wins. Other examples of positional games are Hex and the Shannon switching game. For every positional game there are exactly three options: either the first player has a winning strategy, or the second player has a winning strategy, or both players have strategies to enforce a draw. The main question of interest in the study of these games is which of these three options holds in any particular game. A positional game is finite, deterministic and has perfect information; therefore, in theory it is possible to create the full game tree and determine which of these three  options holds. In practice, however, the game-tree might be enormous. Therefore, positional games are usually analyzed via more sophisticated combinatorial techniques. Alternative terminology. Often, the input to a positional game is considered a hypergraph. In this case: Variants. There are many variants of positional games, differing in their rules and their winning criteria. Specific games. The following table lists some specific positional games that were widely studied in the literature.