Hex is a board game invented in 1942 by Peit Hein and John Nash.
The hex board is an 11x11 hexagonal tiling in a rhombus shape, like you can see in the image. Two players, Black and White, are assigned opposite edges of the board. The board is empty at the start of the game, and the players have to put the pieces, one by one.
The goal for each player is to establish an unbroken chain with the own pieces connecting the two sides of the board marked with the own colour.
How the game goes on
The color that every player will use is randomly choiced. The player with black pieces makes the first move.
Moves entails in placing an own piece on an unoccupied hexagon; placed pieces cannot be moved.
There is no limit for the number of pieces, so that players place new pieces until one of them reaches the victory.
The player who makes the first move has some advantage; between expert players, this advantage is almost definitive. In order to balance the options to win the game, the swap option is used: after the first move, the player who uses white pieces has the option to swap colors instead of moving; if so, the other player (the one who made the first move) has to make a new move, but from now on he has to use white pieces.
Play online with some other players
Play by yourself: hex
Wikipedia: Hex Game