Black's K4(e5) pawn under attack removed the White QP on Q4(d4) to
simplify the centre. White castles - a rare gambit strategy rather than exchange
5.KtxP. Expect a 5..B-K2 reply.
W-Alt.
White Black
1. P-K4 P-K4
2. Kt-KB3 Kt-QB3
3. B-Kt5 P-Q3
4. P-Q4 PxP
5. 0-0