White offers the second pawn Danish Gambit style. As white I prefer Nxc3.
This is a solid defensive line recommended by Smyslov apparently.
Not in my book in this move order, although logical. The focus is f7 in conjunction with Ng5 but white has to be alert to the possibility of Na5
I came to the conclusion that this was pretty much forced. The light squared Bishop is the correct one to block in because of the defence of b7, and to keep alive the transposition into the main d6 line by Ng5 and Ne5.
This was a surprise as developing with Nxc3 and not taking the pressure off f7 seems more in keeping with gambit philosophy.
So after another think I decided to threaten Bb4 pinning the Queen and threatening both the Knight and e pawn.
Quite probably forced which means I felt that he may have considered all this in detail before playing Qxc3. I wondered if he was hoping to devalue the extra pawn by making it into a doubled pawn.
Following the plan although Stockfish claims dxc4 is more accurate.
5... Ne5xd7 6. Bb4xc3
Again stockfish claims dxc4 is much more accurate by nearly a whole pawn.
Now if B takes the Knight he gets d5 so I have to take the Bishop which doubles the extra pawn although, on the plus side, it is in a fluid 4v2 situation.