For the Slav and Semi-Slav Powerbook 2021 the ratings average was set at 2400. 1.76 million games from the engine room of playchess.com met this threshold, to which were added over 80 000 games played by humans.
Slav and Semi-Slav Powerbase 2021 is a database and contains a total of 10 610 games from Mega 2021 or the Correspondence Database 2020, of which 1030 are annotated.
Petroff Defence Powerbase 2020 is a database which contains 4821 high class games from Mega 2020 and the Correspondence Database 2020, of which 648 annotated.
The major part of the material on which the Petroff Defence Powerbook 2020 is based comes from the engine room of playchess.com: 260 000 games. This imposing number is supplemented by another 11 000 from Mega and from correspondence chess.
The major part of the material on which the King's Gambit Powerbook 2020 is based is sourced from the engine room of playchess.com: 30 000 games. Another 3500 games from Mega and from correspondence chess have been added to this corpus.
King's Gambit Powerbase 2020 is a database and contains a total of 2531 games from Mega 2020 or the Correspondence Database 2020, of which 112 are annotated.
The Ben-Oni Powerbook 2020 consists for the greater part of engine games (44 600), to which has been added high-value material from Mega and the Correspondence Database (23 600).
The Benoni Powerbase 2020 is a database and contains a total of 5955 games from Mega 2020 or the Correspondence Database 2020, of which 796 are annotated.
The Volga Benko Gambit Powerbook 2020 is based on over 21 000 games from the engine room of playchess.com and also 12 000 games from Mega 2020 and the Correspondence Database 2020
Volga Benko Gambit Powerbase 2020 is a database and contains a total of 4056 games from the Mega 2020 and the Correspondence Database 2020, 307 of which are annotated.
The greater part of the material on which the Rossolimo/Moscow Powerbook 2020 is based comes from the engine room of playchess.com: 226.000 games. This imposing amount is supplemented by some 25 000 games from Mega and from Correspondence Chess.
The Rossolimo-Moscow Powerbase 2020 is a database and contains a total of 8111 games from Mega 2020 or the Correspondence Database 2020, of which 575 are annotated.
The Pirc Defence Powerbook 2019 (including the Modern Defence) consists for a greater part of engine games (160 000), to which has been added high value material from Mega and the Correspondence Database (46 000).
Pirc Defence Powerbase 2019 is a database and contains a total of 8423 games from Mega 2019 or the Correspondence Database 2018; of these 709 are annotated.
The Queen's Indian Powerbook 2019 has a tree structure which is based on a mixture of over 350 000 complete chess games played in the Engine room of playchess.com and the best games played by humans (50 000).