Connect Four.

## Description

\- It is a popular chess game, easy to learn yet hard to master.
\- It is well-known over the world since many years ago due to its unique design.
\- There are 3 difficulty levels for you to choose, proper for everyone.
\- Or you may just play it with your friends.

Game rules

The board has 6 rows and 7 columns, each player can have a maximum of 21 pieces, two pieces of green and red;
After the start, players take turns to put their pieces into the board, the pieces will automatically drop to the top of the current column;
When a player first with four or more pieces in the horizontal, vertical or oblique direction connected into a straight line, the end of the game, the player victory.
After the board has been full, no players successfully put four pieces into a straight line, the game is the end of the bureau.