Chess Opening Theory/1. e4/1...e5/2. f4/2...exf4/3. Nf3/3...g5/4. Bc4

= King's Gambit Accepted, 4.Bc4= With 4.Bc4, White ignores Black's pawn advance in favor of development. Black can now either continue his development with 4...Bg7 or attempt to unseat White's knight with 4...g4.

Theory table
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1.e4 e5 2.f4 exf4 3.Nf3 g5 4.Bc4