rules.txt

Connect Four is a two player game with "perfect information." This term describes games where one player at a time plays, players have all the information about moves that have taken place, and all moves that can take place, for a given game state. Connect Four also belongs to the classification of an adversarial, zero-sum game, since a player's advantage is an opponent's disadvantage.

One measure of complexity of the Connect Four game is the number of possible games board positions. For classic Connect Four played 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 brute force methods beginning with John Tromp's work in compiling an 8-ply database (Feb 4, 1995). The artificial intelligence algorithms able to strongly solve Connect Four are minimax or negamax, with optimizations that include alpha-beta pruning, dynamic history ordering of game player moves, and transposition tables. The code for solving Connect Four with these methods is also the basis for the Fhourstones integer performance benchmark.

The solved conclusion for Connect Four is first player win. With perfect play, the first player can force a win, on or before the 41st move by starting in the middle column. The game is a theoretical draw when the first player starts in the columns adjacent to the center. For the edges of the game board, column 1 and 2 on left, and column 7 and 6 on right, the exact move-value score for first player start is loss on the 40th move, and loss on the 42nd move, respectively. In other words, by starting with the four outer columns, the first player allows the second player to force a win.







RULES (from original Milton Bradley game box)
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1. Decide who plays first. Players will alternate turns after playing a checker.

NOTE: The player starting the first game will play second in the following game.

2. On your turn, drop any one of your checkers down ANY of the slots in the top of the grid.

3. Play alternatives until one player gets FOUR checkers of his or her color in a row. The four in a row can be horizontal, vertical, or diagonal.