Chess Board
[ECO code C23]
(CLASSICAL) BISHOP'S OPG. - Philidor Var.
Side Variation
White's King is forced to remove Black's bishop on KB2(f2) and forfeits all castling rights.
Black's Queen on K2(e7) moves to the vacated QB4(c5) with check, for 6.P-Q4..QxB to gain a pawn.
	White	Black
 1.	P-K4	P-K4
 2.	B-B4	B-B4
 3.	P-QB3	Q-K2!?
 4.	Kt-K2?! BxP ch
 5.	KxB fcd	Q-B4 ch
Example ends: Undo or Jump or Clear