but the chessmasters that when left with a choice to either invent a new variation or follow a standard opening, choose the latter. There are dozens of different openings, varying widely in character from quiet positional play (e.g. the Réti Opening) to very aggressive play (e.g. the Latvian Gambit). In some opening lines, the exact sequence considered best for both sides has been worked out to 30–35 moves or more. Professional players spend years studying openings, and continue doing so throughout their careers, as opening theory continues to evolve. The fundamental strategic aims of most openings are similar: Development: To place (develop) the pieces (particularly bishops and knights) on useful squares where they influence the game. Control of the : Control of the central squares allows pieces to be moved to any part of the board relatively easily, and can also have a cramping effect on the opponent. King safety: Correct timing of castling can enhance this. Pawn structure: Players strive to avoid the creation of pawn weaknesses such as isolated, doubled or backward pawns, and . During the opening, some pieces have a recognized optimum square they try to reach. Hence, an optimum deployment could be to push the king and queen pawn two squares, followed by moving the knights so they protect the center pawns and give additional control of the center. One can then deploy the bishops, protected by the knights, to pin the opponent's knights and pawns. The optimum opening is ended with castling, moving the king to safety and deploying for a strong and a rook along a . Apart from these fundamentals, other strategic plans or tactical sequences may be employed in the opening. Most players and theoreticians consider that White, by virtue of the first move, begins the game with a small advantage. Black usually strives to neutralize White's advantage and achieve , or to develop in an unbalanced position. Middlegame The middlegame is the part of the game when most pieces have been developed. Because the opening theory has ended, players have to assess the position to form plans based on the features of the positions, and at the same time take into account the tactical possibilities in the position. Typical plans or strategic themes—for example the , that is the attack of pawns against an opponent who has more pawns on the queenside—are often appropriate just for some pawn structures, resulting