Victor Allis proved that black could force a win (see below).So a number of variations are played with extra rules that aimed to reduce black's advantage. An open row of three (one that is not blocked by an opponent's stone at either end) has to be blocked immediately, or countered with a threat elsewhere on the board.
Move 20 is a blunder for white (it should have been played next to black 19).
Black can now force a win against any defence by white, starting with move 21. Such long forcing sequences are typical in gomoku, and expert players can read out forcing sequences of 20 to 40 moves rapidly and accurately.
The second player next can select one of these three options: choose to play black, or to play white and place one more stone, or to place two more stones to change the shape and let the first player choose the color.
Black (the player who makes the first move) was long known to have a big advantage, even before L.
However, neither the theoretical values of all legal positions, nor the opening rules such as Swap2 used by the professional gomoku players have been solved yet, so the topic of gomoku artificial intelligence is still a challenge for computer scientists, such as the problem on how to improve the gomoku algorithms to make them more strategic and competitive.
Nowadays, most of the state-of-the-art gomoku algorithms are based on the alpha-beta pruning framework.The game is also popular in Korea, where it is called omok (오목 [五目]) which has the same structure and origin as the Japanese name. In the nineteenth century, the game was introduced to Britain where it was known as Go Bang, said to be a corruption of the Japanese word goban, said to be adopted from Chinese k'i pan (qí pán) "chess-board." Besides many variations around the world, the Swap2 rule (based on "swap" from Renju) is currently adapted in tournaments among professional players, including Gomoku World Championships.In Swap2 rule, the first player starts by placing three stones (2 black 1 white, if black goes first) on the board.Because pieces are not moved or removed from the board, Gomoku may also be played as a paper and pencil game.The game is known in several countries under different names.World Championships in Gomoku have occurred 2 times in 1989, 1991.