Connect 4

Connect Four (also known as Four Up, Plot Four, Find Four, Captain's Mistress, Four in a Row, Drop Four, and Gravitrips in the Soviet Union) is a two-player connection board game, in which the players choose a color and then take turns dropping colored discs into a seven-column, six-row vertically suspended grid. 

The pieces fall straight down, occupying the lowest 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.