From Wikipedia.org
Connect Four (also known as Captain's Mistress, Four Up, Plot Four, Find Four, Fourplay, Four in a Row, Four in a Line and Gravitrips (in Soviet Union) ) is a two-player connection game in which the players first choose a color and then take turns dropping colored discs from the top into a seven-column, six-row vertically suspended grid. The pieces fall straight down, occupying the next available space within the column. The objective of the game is to be the first to form a horizontal, vertical, or diagonal line of four of one's own discs. Connect Four is a solved game. The first player can always win by playing the right moves.
To play this game, simply run ruby play.rb to invoke the gameplay wrapper.
From The Odin Project: TDD Connect Four