Vienna Gambit
Vienna Game
1.e4 e5 2.Nc3 Nf6 3.f4 d5 4.fxe5 Nxe4 5.Nf3 Be7
White plays f4, Black strikes back with d5, and a sharp center fight begins.
Fun fact: The original idea behind the Vienna Game was to play a delayed King's Gambit with f4. Source
Practice this lineThe idea
After 3.f4 d5 4.fxe5 Nxe4 5.Nf3 Be7, White has a pawn on e5 and the half-open f-file, and Black has an active knight on e4. This is the Breyer Variation, one of the main lines.
Plans for White
Develop with Qe2 to challenge the knight on e4, then d3 or d4. The pawn on e5 cramps Black, and the f-file gives White's rook a ready-made attack after castling.
Plans for Black
Keep the knight on e4 active, castle, and hit White's center with ...c5 and ...Nc6. Trading on c3 with ...Nxc3 is a common way to damage White's pawns.
Watch out for
For White, the e1-h4 diagonal. With the f-pawn gone, ...Qh4+ can be dangerous; 5.Nf3 stops it by covering h4. The Würzburger Trap arises after 5.d3 Qh4+, so that move order needs care.
For Black, the e5 pawn. It cramps Black's position, so it's worth challenging with ...f6 or by piling up on it once Black has castled.