Renju

Renju is a professional, tournament-regulated variant of the abstract strategy board game gomoku, played on a fifteen-by-fifteen grid of intersecting lines on which two players alternately place black and white stones, aiming to be the first to form an unbroken line of five stones horizontally, vertically or diagonally. The game originated in Japan, where journalist Ruikou Kuroiwa gave it its name, meaning connected pearls, in the newspaper Yorozu chouhou on December 6, 1899. To offset the first-player advantage that plain gomoku gives to Black, renju imposes forbidden moves on Black alone, including certain double-three and double-four formations and any line of six or more stones, while White can win either by completing a five in a row or by forcing Black into one of these forbidden moves. Casual games typically last five to thirty minutes, while tournament games under slower time controls can run several hours.