Light to move after 21 discs, with 0 columns already full.
Connect four within 4 of your own moves. Exactly one column starts the win; any other lets the opponent off.
What the position is about
- forcing sequence — The solution is a series of threats, each one leaving the defence a single answer.
- diagonal four — The winning line runs on a diagonal, the hardest kind to see.
Finding the way in
In four-move wins, track which spaces become playable after each forced block; the final double threat often appears two rows above where you start.
Before you touch a piece, list every forcing move you have and every threat the opponent has; the answer is almost always on that short list.
Show the first move
Start with b5. Played out against the stiffest resistance, the whole line goes: b5 b6 e5 c6 d4 d5 d6.
Solve it and the next puzzle of the same game is one tap away. Your solved puzzles are ticked in the list, in this browser only.