Connect Four (Four in a Line)

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The game is played on a vertical hollow game board into which the players drop their tokens alternately. The game board consists of seven columns and six rows.
Each player has 21 checkers, yellow or red with yellow starts.
The winner is the player who manages to be the first to bring four or more of his playing pieces horizontally, vertically or diagonally in a line. The game ends in a draw when the board is completely filled, without a player has formed a four-line.