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This is an electronic take on the classic Connect 4 board game.
There are two players, player 1 is 'x' and player 2 is 'o'.
Player 1 is always human, and player 2 can be a computer or a human player.
The object of the game is for a player to get 4 of their gamepieces in a row,
either horizontal, vertical, or diagonal.
Game ends when either player gets four in a row or there are no more
spaces left on the gameboard.\
Run connect_four.rb to play