Connect Four: count threats that survive the opponent's reply

In Connect Four, every move changes which columns remain playable and which horizontal, vertical, or diagonal threats become possible. Check for immediate wins and blocks first, then prefer moves that create two winning threats without giving the opponent one. Center columns participate in more lines, but tactical safety overrides general preference. Account for gravity when evaluating an empty square. For a dispute, include the full board, player to move, column sequence, dimensions, and win-length rule.