Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bc4/3...Bc5/4. c3/4...Nf6/5. d4/5...exd4/6. cxd4/6...Bb4

= Center Attack =

6...Bb4+
The bishop must move, and move it did! White has three options to block the check.

7. Bd2 is a natural blocking move. Black can either trade and break the center with 8...d5, or immediately take with 7...Nxe4 which leads to complicated variations and the sacrifice Bxf7+!

7. Nc3 is another natural blocking move, but hangs the e4 pawn. This is the Greco Gambit, where White then castles and allows the loss of a pawn for development.

7. Kf1 is not usually played, as White can no longer castle and hangs the e4 pawn. For the pawn, White gains initiative and attacks Black. Black has to find only moves to keep advantage.

Theory table
'''1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. c3 Nf6 5. d4 exd4 6. cxd4 Bb4+'''