Winning requires that the player achieve five of his/her pieces in a row or removal of five of the opponents pairs (or both in the same move), in any of eight directions including diagonals.

A pair is taken when a player makes a move that places his/her piece in such a way that the opponent's pair becomes blocked on both sides.  Only pairs can be taken from the board.

Pairs are not lost by moving into already blocked arrangements.

Aside from being weary of loosing pairs, immediately defending against an "open three" by blocking either end avoids loosing 2 moves later.

An open three looks like .OOO. or .O.OO. in any direction. Watch for multi-directional open three's.