Alekhine's defence - O'Sullivan gambit
1. e4 Nf6 2. e5 Nd5 3. d4 b5
White advances the king's pawn to e4. Black develops the knight to f6. White advances the king's pawn to e5.
Black transfers the knight to d5. White advances the queen's pawn to d4. Black moves the b-pawn to b5.