Turnablock is a game for two players invented by John Conway. It is played on a 3 by 3 square board with 9 counters that are black on one side and white on the other.

The counters are placed on the board at random, one per square, except that the majority must be black uppermost.

Players take turns to reverse a rectangular block of their chosen size (e.g. $1 \times 1$, $2 \times 3$ or even $3 \times 3$).

The only condition is that the lower right corner tile of the rectangle MUST BE BLACK.

On flipping, black tiles turn to white and vice versa.

The Player, who turns the whole board white, wins the game.