Connect Four on 6 high, 7 wide grid, there are 4,531,985,219,092 positions for all game boards populated with 0 to 42 pieces. The game was first solved by James Dow Allen (October 1, 1988), and independently by Victor Allis (October 16, 1988). Allis describes a knowledge-based approach, with nine strategies, as a solution for Connect Four. Allen also describes winning strategies in his analysis of the game. At the time of the initial solutions for Connect Four, brute-force analysis was not deemed feasible given the game's complexity and the computer technology available at the time. Connect Four has since been solved with
Connect Four in a row of a specific color of discs. In 2008, another board variation Hasbro published as a physical game is Connect 4x4. This game features a two layer vertical grid with colored discs for four players, plus blocking discs. The object of the game is also to get 4 in a row for a specific color of discs. A "SpongeBob SquarePants" version of the game was released in 2009 for the show's 10th anniversary. The rules are the same as the normal version, only the chips have the faces of SpongeBob and Patrick on them. It was rereleased in