Minimax algorithm implemented via a Tic-Tac-Toe variant using a 6x6 grid where 4 in a row wins.
See ledsworth.com for more details about the algorithm and a live/playable version.
Below is how I spawn/run a game from within IRB. It's not user friendly....But it works.
load "./tic_tac_toe_variant.rb"
game=TicTacToeVariant::Game.new(true)
You can them call game.make_move %sq% to get started (e.g. game.make_move 0).
The key is knowing the squares, 0 for upper left, 35 for lower right.
The algorithm will play it's move and then display of the board state. You can then make your next move.