Chess Board
[ECO code C23]
(CLASSICAL) BISHOP'S OPG. - Philidor Var.
del Rio Variation
White develops his King's Knight to KB3(f3) for control of Q4+K5(d4+e5), and enables castling.
Black develops his Queen's Knight to QB3(c6) to counter Black's KKt influence, keeping equality.
    White  Black	White  Black
 1. P-K4   P-K4	     6.	Kt-KB3 Kt-QB3
 2. B-B4   B-B4
 3. P-QB3  Q-Kt4
 4. K-B1   Q-K2
 5. P-Q4   B-Kt3
Example ends: Undo or Jump or Clear