Players: Two - Also known as: Four in a Row, Four in a Line
Players take turns in marking squares on a grid subject to gravity. The first player to get four squares in a row wins.
The game is played on a grid with six rows and seven columns:
One player is 'O' and the other is 'X'. The players take turns in marking a square with their symbol, but the pieces behave as if subject to gravity. In other words, you can only put a piece in the lowest space in a column.
The first player to get four squares in a row, horizontally, vertically, or diagonally, wins.
In the following game the second player 'X' has won by making a diagonal row of four: