Giuoco Piano - Responding to 4...d6
(1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5)
To White's move 4.c3 in the Giuoco Piano, Watson (in "Mastering the Chess Openings" Vol 1) prefers 4...Nf6. (This develops the Knight to its best square, counter-attacks, and prepares castling.) But what happens if Black plays 4...d6?