The centre is the vital point
Lesson 8.1 promised that three-point shapes are undecided — here the promise is kept. A straight three or a bent three has exactly one point whose owner decides the outcome: the defender there lives with two eyes, the attacker there leaves the defender one eye forever. That double duty is why the point is called vital — it is the same intersection for attack and defence, so the fight is a pure race of tempo, not of strength. The typical punishment for ignoring it: you spend two moves building elsewhere, White spends one in your eye space, and your whole group is hostage for the price of a single stone. Black to play: pay the vital point now.