Center is the strongest opening — it intersects all 4 winning lines (1 row, 1 column, 2 diagonals), maximizing threat space. Standard principled choice.

Taking a corner is the strongest response to a center opening, as it creates immediate threats and maximizes future winning opportunities.

Opposite corner (8 vs O's 0). This is the canonical reply in the center-vs-corner line — anything else (edge, adjacent corner) lets O fork. Forcing the symmetric defensive line.

Playing an adjacent corner creates a fork opportunity by threatening two lines simultaneously.

Forced block on row 0 (O has 0 and 2 — would win with 1 next). Note: Gemini called this a 'fork opportunity' but it's a single threat, not a fork. A real fork would require O playing 6 to threaten both 0-3-6 column and 6-7-8 row. From here, optimal play forces a draw.

I must block X's immediate winning threat on column 1 by playing at position 7.

Position 3 is the pivot — it's the only square contested by both players' last live line. By taking it, I (a) block O's column 0 (0-3-6) forever, and (b) create my own threat on row 1 (need 5 to win). O is forced to block at 5. Both moves rolled into one — clean simplification toward draw.

I must play at position 5 to block X's immediate winning threats on row 1 (3-4-5) and column 2 (2-5-8), forcing a draw.