Gomoku

Gomoku ("five stones") is a two-player abstract strategy game played on a 15 × 15 (or 19 × 19 Go board) grid. Players alternate placing black or white stones on the grid intersections; the first to make an unbroken row of five (horizontally, vertically or diagonally) wins. The competitive tournament form is Renju, which balances the first-move advantage with opening restrictions.