 Other semi-open games have been studied but are less common; see Semi-Open Game for details.The openings classified as closed games begin 1.d4 d5.The move 1.d4 offers the same benefits to development and center control as does 1.e4, but unlike with King Pawn openings where the e4-pawn is undefended after the first move, the d4-pawn is protected by White's queen.