analysed openings in chess, and it has eighty chapters, B20–B99, set aside for it in ECO. 1... e5 leads to the classical Open Games, which includes openings like the Ruy Lopez, King's Gambit, Italian Game, Scotch Game and Petrov's Defence. Also in this opening, Black is ready to meet a d2–d4 advance with exd4. These openings are covered in chapters C20–C99 in ECO. 1... e6 is the French Defence, covered in chapters C00–C19 in ECO. Black's restrained response allows White to play 2.d4. This gives White a spatial advantage, with two pawns in the center to Black's one (after the usual 2... d5) and open lines for both of the bishops to black blocking in the light squared bishop and stopping it from developing. One or the other player will usually resolve the center tension, either by Black playing ...dxe4 or White advancing with e5. In the latter case, Black typically works to undermine White's pawn center with ...c5 and/or ...f6. 1... c6 is the Caro–Kann Defence, covered in chapters B10–B19 in ECO. Like the French, this is also considered to be a solid reply, but Black will often need to surrender control over the center (e.g., after 2.d4 d5 3.Nc3 Black usually plays 3...dxe4). On the other hand, the light-squared bishop will usually not wind up trapped behind its own pawns, as is common in the French. 1... d6 is usually played with the intention of playing the Pirc Defence (1.e4 d6 2.d4 Nf6 3.Nc3 g6, ECO codes B07–B09), a hypermodern defence in which Black allows White to construct a dominant center, with the intention of subverting it later. It can also lead to the Modern Defence, Pribyl System or Philidor Defence. 1... g6 is the Modern Defence. This is related to the Pirc Defence, which it can lead to. These openings allow White to build up a pawn center with 2.d4, but Black will develop the king's bishop to g7 and strike back at the center. These openings are covered in chapters B06–B09 in ECO, with the Modern Defence covered in chapter B06. 1... d5, the Scandinavian Defence or Center Counter Defence, is a direct strike at the pawn at e4, forcing the situation in the center. After 2.exd5 Qxd5 3.Nc3, however, White gains time by attacking Black's prematurely developed queen. Alternatively, Black can play 2...Nf6 (the Marshall Gambit), when White chooses between 3.d4 Nxd5 4.c4 with a