A trap in the Vienna Game

If Black plays symmetrically against the Vienna Game (1.e4 e5 2.Nc3) with 2...Nc6 3.Bc4 Bc5, White can set a nice trap with the primitive 4.Qg4! threatening 5.Qxg7. This is surprisingly awkward for Black to meet: 4...Bf8 is obviously unattractive, 4...g6 is weakening, and no one wants to move their king with 4...Kf8 (ugly, but perhaps best). The most plausible move, and indeed Black's most common move, is 4...Qf6?, meeting queen move with queen move and counterattacking the pawn on f2. However, White gets a large advantage with the shocking 5.Nd5!, threatening both 6.Nxf6+ and 6.Nxc7+. Since the queen can't defend g7 and c7 at the same time, and 5...Bxf2+? would be met by 6.Kf1!, winning material, 5...Qxf2+ is forced.

After White's also forced reply 6.Kd1, White's king is surprisingly safe, while Black's is in trouble. White again threatens both 7.Qxg7 and 7.Nxc7+. 6...g6!?, hoping for counterplay with 7.Nxc7+ Kd8 8.Nxa8 d5! threatening White's queen and bishop simultaneously, is met by 7.Nh3! Qd4 8.d3 (threatening 9.c3, trapping the queen) Bb6 (8...d6 9.Qf3) 9.Qf3 (threatening 10.Nxb6 axb6 11.Qxf7+ Kd8 12.Qf8#) d6 10.c3 Qc5 11.b4, winning material, as in Emms-Hawkworth, where future grandmaster Emms upset his higher-rated opponent:

Instead, Black usually tries to meet both of White's threats with 7...Kf8. Then 8.Nh3 forces 8...Qd4 (8...d6? 9.Nxf2 Bxg4+ 10.Nxg4 wins a piece), when 9.d3 threatens to trap the queen with 10.c3. The following games well illustrate White's possibilities: