I'm playing in column 4 for two main reasons: 1) Defensively, my opponent has three Xs in a row horizontally at positions (1,4), (2,4), and (3,4). If they place a piece in column 4, they would complete four in a row. 2) Offensively, I already have two Os in column 4, so placing a third would start building a strong vertical threat. This move both blocks my opponent's immediate win and advances my own position.