Renju VCF #4996507 (7-move VCF)
To move: Black — find the move that forces a win by fours
Winning line
J7 → J6 → L7 → M7 → I8 → F11 → F8 → G8 → K8 → L8 → M6 → N5
Why this move works
The answer is J7. A seven-move VCF that forces White’s reply with a four every move (J7→J6→L7→M7→I8→F11→F8→G8→K8→L8).
The decisive M6 makes two winning points at once; White cannot cover both, and N5 completes five. Even over a long line, the key is never to let the chain of fours break.