Philidor - Philidor counter-gambit - Zukertort variation
1. e4 e5 2. Nf3 d6 3. d4 f5 4. Nc3
White plays the king's pawn to e4. Black moves the king's pawn to e5. White develops the knight to f3.
Black moves the queen's pawn to d6. White pushes the queen's pawn to d4. Black advances the f-pawn to f5.
White transfers the knight to c3.