The game can also be played with black and white counters on a large board, such as a Go board.
In the basic game the first player has an advantage, so a number of rules have been introduced to reduce this:
- Overlines rule: Only a row of exactly five squares wins; rows of six of more, called overlines, do not count.
- Three and Three rule: A move must not simultaneously create two open rows of three squares (rows not blocked at either end by an opponent's square).
- Four and Four rule: A move must not simultaneously create two rows of four squares, whether blocked or not.
- These restrictions are sometimes only applied to the first player.