Connect 4 (or Score 4, as it is known in some places) is a well-known two-player board game.

This app offers you the ability to play with a friend, as well as against an AI with adjustable difficulty.

How to play:
The two players take turns placing discs of their own color on the board by dropping them in one of the seven columns. On your turn, to drop a disc in a column, simply tap anywhere on that column.

The objective:
Each player's goal is to form a line of four discs horizontally, vertically or diagonally before their opponent does.