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 the left and right sides of their standard 6 by 7 game board. The game plays similarly to the original Connect Four, except players must now get five pieces in a row to win. Notice this is still a 42-ply game, since the two new columns added to the game represent twelve game pieces already played, before the start of a game. In this variation of Connect Four, players begin a game with one or more specially marked, "Power Checkers" game pieces, which each player may choose to play once per game. When playing a piece marked with an anvil