[ECO code C50]
White correctly declines 4.KtxKP?? (actually something of a trap) and instead gains a tempo by (for example) setting his Queen's Bishop's Pawn to attack Black's knight (forcing it to retreat or be exchanged by 4..KtxKt+ch, 5.QxKt). W-Alt.
White Black 1. P-K4 P-K4 2. Kt-KB3 Kt-QB3 3. B-B4 Kt-Q5?! 4. P-QB3
Example ends: Undo or Jump or Clear