What is Hex?

Hex is a two-player connection game invented by the Danish designer Piet Hein in 1942 and independently by the mathematician John Nash at Princeton in 1948. It is a favourite of mathematicians because it can never end in a draw: when the board fills, exactly one player has made a connection.

How to play

• Red and Blue take turns placing one stone on any empty cell.
• Each player owns two opposite edges of the board, marked in their colour. Link them with an unbroken chain to win.
• Stones are never moved or captured.
• Swap rule: moving first is a big advantage, so after Red's first stone, Blue may swap and take that opening instead. Blue's stone appears mirrored across the board so that the colours stay the same.

Strategy

• Learn the bridge: two stones that share two empty neighbours are connected, because an opponent can only block one.
• Blocking from a distance works better than blocking next to the enemy stone.
• The centre is strongest. With the swap rule, open somewhere that is neither too strong nor too weak.

Ways to play

• Against the computer: four levels. Wins raise your rating, which sets your place on the leaderboard.
• Quick match: an online opponent, with a computer player stepping in if nobody is around.
• Play a friend: make a private room and send the code or link.
• One screen: two players take turns on the same device.

FAQ

Can Hex end in a draw? No. A full board always holds exactly one winning connection. Nash's strategy-stealing argument also shows that the first player can force a win, although nobody knows how on large boards.

What is the swap rule in Hex? After the first move, the second player may take that opening instead of replying, which makes it unwise to open too strongly.

What board size should I choose? 7×7 for a quick game, 9×9 to learn properly and 11×11, the traditional size, for a longer one.