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A defense beginning with e4, e5, Nf3, and ...d6, supporting the e5-pawn with a compact structure.

A compact system in which Black supports an advanced central pawn and places a knight behind it.

A Philidor system in which Black places both knights around two central pawns that support each other.

An aggressive reply to e4 and Nf3 in which Black plays ...f5 and offers pawns to attack the center.

A countergambit in which Black answers e4 and Nf3 with ...d5, offering a pawn to open the center and gain time.

The reply 2...f6 to 1.e4 e5 2.Nf3, intended to support e5 but weakening the king and allowing a strong tactic.