Anderssen Defense

The idea

Black plays 2...Bc5, putting the bishop on its best diagonal before White can play f4. The main line is 3.Nf3 d6 4.d4 exd4 5.Nxd4: White gets a central knight and Black has quick development.

Plans for White

Take the center with d4, then develop with Be2 or Bc4, Be3 and castle. Trading Black's active bishop with Be3 or Na4 takes away Black's best piece. A later f4 is possible once White has castled.

Plans for Black

Develop with ...Nf6, ...O-O and ...Nc6, and keep the bishop on the a7-g1 diagonal. Black aims for a solid, active position with pressure on f2. Against Be3, keeping the bishop with ...Bb6 avoids giving up the bishop pair.

Watch out for

For White, playing f4 too soon. With Black's bishop on c5 aiming at g1, an early f4 can leave White's king unable to castle safely.

For Black, the bishop can be traded with Na4, giving White the bishop pair. Retreating it to b6 keeps it.