Renju opening pattern is a Renju position with 3 moves made. All debut classifications in Renju are based on patterns.
Restrictions on first moves The first move is black and must be played in the center of the board. The second move is white and must be played in the center 3x3 square. The third move is black and must be played in the center 5x5 square.
Openings classification Since the second move is to be played in the center 3x3 square, the white stone must be adjacent (vertically, horizontally or diagonally) to the first move. It is clear that due to symmetry any legal opening pattern will fall into one of the following categories: Indirect openings - 2nd move is diagonally adjacent to the 1st move Direct openings - 2nd move is vertically adjacent to the 1st move
Indirect openings
Due to symmetry there are 13 possibilities for the 3rd move as shown on a picture. 1st move is solid black circle, 2nd move is white circle, possible openings are shown enumerated. Brief evaluation for an old RIF opening rule follows. 1I (長星) (Chosei): mostly equal, slightly better for White 2I (峡月) (Kyogetsu): sure win for Black 3I (恒星) (Kosei): sure win for Black 4I (水月) (Suigetsu): sure win for Black 5I (流星) (Ryusei): slightly better for White 6I (雲月) (Ungetsu): sure win for Black 7I (浦月) (Hogetsu): sure win for Black 8I (嵐月) (Rangetsu): sure win for Black 9I (銀月) (Gingetsu): advantage for Black 10I (明星) (Myojo): sure win for Black 11I (斜月) (Shagetsu): slightly better for Black 12I (名月) (Meigetsu): advantage for Black 13I (彗星) (Suisei): sure win for White
Direct openings
Due to symmetry there are 13 possibilities for the 3rd move as shown on a picture. 1st move is solid black circle, 2nd move is white circle, possible openings are shown enumerated. Brief evaluation for an old RIF opening rule follows. 1D (寒星) (Kansei): sure win for Black 2D (渓月) (Keigetsu): sure win for Black 3D (疎星) (Sosei): mostly equal, slightly better for White 4D (花月) (Kagetsu): sure win for Black 5D (残月) (Zangetsu): advantage for Black 6D (雨月) (Ugetsu): sure win for Black 7D (金星) (Kinsei): sure win for Black 8D (松月) (Shogetsu): slightly better for Black 9D (丘月) (Kyugetsu): slightly better for Black 10D (新月) (Shingetsu): advantage for Black 11D (瑞星) (Zuisei): mostly equal, slightly better for Black 12D (山月) (Sangetsu): advantage for Black 13D (遊星) (Yusei): sure win for White
External links http://renju.net/study/openings.php - brief evaluation of different opening patterns http://renju.net/study/starting.php - opening process description for the RIF opening rule