XandO 1979

XandO is played on a 6x6 square grid. The game begins with the players taking turns to blacken four squares of the grid (two each). After that the players take turns to mark their symbols (X and O) in empty squares, with the option of blackening a square instead on their last turns.

Once the grid is full players score for consecutive lines of their symbols in any direction. However, while even numbers of symbols score positively, odd numbers (greater than one) score negatively.

A game consists of two rounds. In the second round of a game, the same four squares are blackened as were chosen at the start of the first round and the player who went second now goes first.