Budapest - Alekhine variation
1. d4 Nf6 2. c4 e5 3. dxe5 Ng4 4. e4
White plays the queen's pawn to d4. Black develops the knight to f6. White pushes the c-pawn to c4.
Black advances the king's pawn to e5. White captures on e5 with the queen's pawn. Black transfers the knight to g4.
White advances the king's pawn to e4.