13. Online Aktivschach Weltmeisterschaft 2017: Unterschied zwischen den Versionen

Version vom 1. Januar 2017, 22:58 Uhr

	Weltmeister
	Titelverteidiger	Tasc CM 32 MHz Gideon 3.1
	Geräte	22
	Teilnehmer	15
	Partien
	Start	11.Dezember 2016
	Ende

Teilnehmer & Geräte:

Zur besseren Übersicht finden sich hinter den Geräten, die momentanen Elo Ranglistenplätze. Diese stammen aus unserer Aktivschach Elo Liste.

Die iSchach (ehemals Chessgate) Nicknames der Teilnehmer finden sich in Kursiv neben den Namen.

Teilnehmer	Geräte
Rüdiger - pato4sen	Tasc CM 14 MHz King 2.54 (Rang 9 - 2341)	Pewatronic Master Chess (Rang 40 - 2203)
Walter - mares	Tasc R30 V2.5 (Rang 6 - 2368)	Mephisto Atlanta 36MHz (Rang 17 - 2301)
Paul - paulwise3	Saitek Barracuda 40 MHz
Hans - sargon36	Tasc CM 32 MHz Gideon 3.1 (Rang 3 - 2377)	Resurrection Ruffian (Rang 2 - 2379)
Robert - star sapphire	Millennium ChessGenius Pro
Frank - frank_velbrati	Novag Star Diamond (Rang 46 - 2183)	Mephisto Milano Pro (Rang 51 - 2163)
Ruud - Ruud Martin	Reflection London	Revelation II Hiarcs 1% (Rang 4 - 2376)
Joachim - Jockel	Tasc CM 32 MHz Gideon 3.0 (Rang 8 - 2353)	Tasc CM 32 MHz King 2.2 (Rang 5 - 2376)
Tobias - goto34	Mephisto Genius 68030 (Rang 11 - 2335)	Saitek Sparc (Rang 41 - 2201)
Achim - achimp	Millennium ChessGenius 82 MHz
Bernhard - rodel	Fidelity Excel Mach IV (Rang 66 - 2125)
Guido - Mephisto Atlanta	Mephisto Atlanta (Rang 27 - 2266)
Franz - ferribaci	Millennium ChessGenius
Steffen - Diablo	Mephisto Berlin Pro (Rang 21 - 2283)
Udo - mickihamster	Mephisto Mystery 40 MHz (Rang 42 - 2200)

Modus

Modus: 9 Runden nach Schweizer System
- Sollten nach Ende des Turniers zwei Spieler den gleichen Punktestand aufweisen, bekommt der Spieler mit der höheren Buchholz-Zahl die bessere Platzierung.
Spielstufe: 30 Sekunden pro Zug
Turnierleitung: Rüdiger (pato4sen)
Turnierregeln

Runden

Runde 1

Reflection London	Ã¢â‚¬âCœ	Mephisto Berlin Pro	1 : 0
Millennium ChessGenius 82 MHz	Ã¢â‚¬âCœ	Resurrection Ruffian	0 : 1
Tasc CM 32 MHz Gideon 3.1	Ã¢â‚¬âCœ	Mephisto Atlanta	1 : 0
Pewatronic Master Chess	Ã¢â‚¬âCœ	Revelation II Hiarcs 1%	0 : 1
Tasc R30 V2.5	Ã¢â‚¬âCœ	Saitek Sparc	1 : 0
Mephisto Mystery 40 MHz	Ã¢â‚¬âCœ	Tasc CM 32 MHz Gideon 3.0	0 : 1
Tasc CM 14 MHz King 2.54	Ã¢â‚¬âCœ	Millennium ChessGenius	0 : 1
Novag Star Diamond	Ã¢â‚¬âCœ	Tasc CM 32 MHz King 2.2	0 : 1
Mephisto Genius 68030	Ã¢â‚¬âCœ	Mephisto Milano Pro	1 : 0
Saitek Barracuda 40 MHz	Ã¢â‚¬âCœ	Mephisto Atlanta 36 MHz	0 : 1
Millennium ChessGenius Pro	Ã¢â‚¬âCœ	Fidelity Excel Mach IV	0 : 1

Partien

[Event "13. Online Aktivschach WM"] [Site "schachcomputer.info"] [Date "2016.12.18"] [Round "1.1"] [White "Reflection London"] [Black "Mephisto Berlin Pro"] [Result "1-0"] [ECO "B18"] [PlyCount "67"] [EventDate "2016.??.??"] 1. e4 c6 2. d4 d5 3. Nc3 dxe4 4. Nxe4 Bf5 5. Ng3 Bg6 6. N1e2 e6 7. h4 h6 8. Nf4 Bh7 9. Bc4 Bd6 10. Ngh5 Bf8 11. c3 Nd7 12. Qe2 Bf5 13. g4 Bh7 14. Bxe6 Qe7 15. Bxd7+ Kxd7 16. Be3 Kc7 17. O-O-O Qe4 18. Nd3 g5 19. hxg5 hxg5 20. Ng3 Qd5 21. Nf5 f6 22. f4 Qxa2 23. fxg5 Qf7 24. d5 a6 25. d6+ Bxd6 26. Nxd6 Qd7 27. Bf4 b6 28. Nc5 bxc5 29. Nc4+ Qd6 30. Bxd6+ Kb7 31. Na5+ Ka7 32. Bxc5+ Kb8 33. Qe8+ Kc7 34. Rd7# {1-0 Matt} 1-0 [Event "13. Online Aktivschach WM"] [Site "schachcomputer.info"] [Date "2016.12.20"] [Round "1.2"] [White "Millennium ChessGenius 82 MHz"] [Black "Resurrection Ruffian"] [Result "0-1"] [ECO "E54"] [PlyCount "144"] [EventDate "2016.??.??"] 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. e3 O-O 5. Nf3 c5 6. Bd3 d5 7. O-O dxc4 8. Bxc4 Nc6 9. Bd3 cxd4 10. exd4 Re8 11. Ne2 Bd6 12. Bg5 Bd7 13. Qd2 Nb4 14. Ne5 Nxd3 15. Qxd3 Ba4 16. Qf3 h6 17. Bh4 Bb5 18. Rfe1 Ba6 19. Nc3 Be7 20. Ne4 Rc8 21. Red1 Rc2 22. Qb3 Rc7 23. Nc5 Qd5 24. Nxa6 bxa6 25. Qxd5 Nxd5 26. Bxe7 Nxe7 27. Rac1 Rec8 28. Rxc7 Rxc7 29. a3 Rc2 30. b4 Nd5 31. h4 Kf8 32. g3 Ke7 33. Rd3 f6 34. Ng6+ Kd6 35. Kf1 Nc3 36. Nf4 g5 37. Nh5 f5 38. hxg5 hxg5 39. f4 g4 40. d5 Nxd5 41. Nf6 Rc3 42. Ne8+ Kc6 43. Rxc3+ Nxc3 44. Nf6 Nb5 45. Ke2 Nxa3 46. Kd3 Kb5 47. Ne8 Kxb4 48. Nc7 Nb5 49. Nxa6+ Ka5 50. Nc5 Nd6 51. Kd4 Kb5 52. Nxe6 Ne4 53. Kd5 Nxg3 54. Nd4+ Kb4 55. Nc6+ Kc3 56. Nd4 a5 57. Nb5+ Kd3 58. Nd4 Ne2 59. Nxf5 a4 60. Ng3 Nxg3 61. Ke5 a3 62. f5 Nxf5 63. Kxf5 g3 64. Ke5 a2 65. Kf4 a1=Q 66. Kf3 g2 67. Kxg2 Ke3 68. Kg3 Ke4 69. Kf2 Qg7 70. Ke1 Qg2 71. Kd1 Kd3 72. Kc1 Qc2# {0-1 Matt} [Event "13. Online Aktivschach WM"] [Site "schachcomputer.info"] [Date "2017.01.??"] [Round "1.3"] [White "Tasc CM 32 MHz Gideon 3.1"] [Black "Mephisto Atlanta"] [Result "1-0"] [ECO "B09"] [PlyCount "88"] [EventDate "2016.??.??"] 1. e4 d6 2. d4 Nf6 3. Nc3 g6 4. f4 Bg7 5. Nf3 O-O 6. Bd3 c6 7. O-O d5 8. e5 Ne8 9. a4 Bg4 10. h3 Bxf3 11. Qxf3 Na6 12. Bxa6 bxa6 13. f5 Qb6 14. Qf2 Rc8 15. a5 Qd8 16. b4 Rb8 17. Rb1 Qd7 18. g4 gxf5 19. gxf5 Kh8 20. Na4 Qc8 21. Kh1 Rg8 22. Rg1 f6 23. e6 Nd6 24. Bf4 Ne4 25. Qe2 Rb5 26. c3 Qd8 27. Rg2 Nd6 28. Qd3 Qe8 29. Nc5 Ne4 30. Rbg1 Qh5 31. Qe3 Rxc5 32. bxc5 h6 33. c4 Kh7 34. cxd5 cxd5 35. Rg6 Ng5 36. Qg3 Qxh3+ 37. Qxh3 Nxh3 38. Rxg7+ Rxg7 39. Rxg7+ Kxg7 40. Be3 Ng5 41. Bxg5 fxg5 42. c6 Kf6 43. c7 h5 44. c8=Q Kxf5 {1-0 Aufgegeben} 1-0 [Event "13. Online Aktivschach WM"] [Site "schachcomputer.info"] [Date "2016.12.17"] [Round "1.4"] [White "Pewatronic Master Chess "] [Black "Revelation II Hiarcs 1%"] [Result "0-1"] [ECO "B23"] [PlyCount "132"] [EventDate "2016.??.??"] 1. e4 c5 2. Nc3 d6 3. g3 Nc6 4. Bg2 g6 5. d3 Bg7 6. Be3 Nf6 7. Nf3 Ng4 8. Bg5 Be6 9. O-O Nge5 10. Nxe5 dxe5 11. Be3 b6 12. Re1 O-O 13. Rc1 Re8 14. Qd2 Qd6 15. Rb1 Nd4 16. Rf1 Rad8 17. a3 a6 18. f4 Qc7 19. Rf2 c4 20. Rbf1 cxd3 21. cxd3 Nb3 22. Qe2 Nc5 23. f5 gxf5 24. exf5 Bb3 25. Qg4 Rd6 26. Ne4 Nxe4 27. dxe4 b5 28. Kh1 Rc6 29. f6 Rxf6 30. Rxf6 h5 31. Qxh5 exf6 32. Bh6 Be6 33. Rc1 Qd8 34. Rd1 Qc8 35. Bxg7 Kxg7 36. Rf1 Rh8 {Lg4!} 37. Qf3 Rh6 38. h4 a5 39. Qe3 Qc2 40. Rf2 Qa4 41. Kh2 b4 42. Rd2 Bb3 43. axb4 Qxb4 44. Kh3 Be6+ 45. g4 Rg6 46. Bf3 Qc4 47. h5 Rg5 48. Kg3 Qc1 49. Qf2 Qc8 50. Qe2 Qc5 51. Kh4 Qb6 52. Qf2 Qb3 53. Rd8 Qc4 54. Qe1 a4 55. Qe2 Qc7 56. Qd2 $2 Qb6 57. Ra8 Qg1 58. Qe2 Rxh5+ 59. Kxh5 Qg3 60. Qg2 Bxg4+ 61. Bxg4 Qxg2 62. Kh4 Qh2+ 63. Bh3 Qf2+ 64. Kh5 Qf4 65. Rg8+ Kxg8 66. Bf5 Qg5# 0-1 [Event "13. Online Aktivschach WM"] [Site "schachcomputer.info"] [Date "2016.12.30"] [Round "1.5"] [White "Tasc R30 V2.5"] [Black "Saitek Sparc"] [Result "1-0"] [ECO "E19"] [PlyCount "97"] [EventDate "2016.??.??"] 1. Nf3 Nf6 2. d4 e6 3. c4 b6 4. g3 Bb7 5. Bg2 Be7 6. O-O O-O 7. Nc3 Ne4 8. Qc2 Nxc3 9. Qxc3 f5 10. b3 Bf6 11. Bb2 d6 12. Rad1 a5 13. Ne1 Bxg2 14. Nxg2 Nc6 15. Qf3 Qd7 16. a3 Ne7 17. Rfe1 d5 18. Nf4 a4 19. Qe3 axb3 20. Qxb3 dxc4 21. Qxc4 Nd5 22. e3 Ra4 23. Qb3 Rfa8 24. Nd3 Kh8 25. f3 Qd6 26. Qc2 Bg5 27. Ne5 Bxe3+ 28. Rxe3 Nxe3 29. Qe2 Qd5 30. Qxe3 c5 31. Rd2 R4a7 32. dxc5 Qxc5 33. Kf2 Qb5 34. Bd4 Rb7 35. f4 Qd5 36. Bxb6 Qh1 37. Nf3 Rbb8 38. Rd7 Rc8 39. Bc7 Rg8 40. Be5 Rac8 41. Qd2 h6 42. Qb2 Kh7 43. Bxg7 Rgd8 44. Rxd8 Rxd8 45. Qb7 Rd2+ 46. Ke3 Rd3+ 47. Kxd3 Qd1+ 48. Nd2 Kg6 49. Qe7 {1-0 Aufgegeben} 1-0 [Event "13. Online Aktivschach WM"] [Site "schachcomputer.info"] [Date "2016.12.20"] [Round "1.6"] [White "Mephisto Mystery 40 MHz"] [Black "Tasc CM 32 MHz Gideon 3.0"] [Result "*"] [ECO "C59"] [PlyCount "101"] [EventDate "2016.??.??"] 1. e4 e5 2. Nf3 Nf6 3. Bc4 Nc6 4. Ng5 d5 5. exd5 Na5 6. Bb5+ c6 7. dxc6 bxc6 8. Be2 h6 9. Nf3 e4 10. Ne5 Bd6 11. f4 exf3 12. Nxf3 O-O 13. O-O Qc7 14. b3 Re8 15. Nc3 Rb8 16. Kh1 Bg4 17. h3 Bh5 18. Bd3 Nb7 19. g4 Bg6 20. Bxg6 fxg6 21. Bb2 Nc5 22. d3 Ne6 23. Nd2 Ng5 24. Kg2 Qd7 25. Nc4 Nd5 26. Nxd5 cxd5 27. Nxd6 Qxd6 28. Bc1 Ne6 29. c3 Rbc8 30. Bd2 Rf8 31. d4 Rxf1 32. Qxf1 Rf8 33. Qd3 g5 34. Rd1 Qa3 35. Qe2 Re8 36. Qf3 Qxa2 37. Qxd5 Qc2 38. Qc6 Nf4+ 39. Kg3 Re6 40. Qa8+ Kh7 41. Re1 Ne2+ 42. Rxe2 Rxe2 43. Qf3 Rxd2 44. Qf5+ Qxf5 45. gxf5 Rd3+ 46. Kg2 a5 47. c4 Rxb3 48. c5 a4 49. c6 a3 50. c7 Rc3 51. d5 {0-1 Aufgegeben} * [Event "13. Online Aktivschach WM"] [Site "schachcomputer.info"] [Date "2016.12.??"] [Round "1.7"] [White "Tasc CM 14 MHz King 2.54"] [Black "Millennium ChessGenius"] [Result "0-1"] [ECO "B19"] [PlyCount "162"] 1. d4 c6 2. e4 d5 3. Nc3 dxe4 4. Nxe4 Bf5 5. Ng3 Bg6 6. h4 h6 7. h5 Bh7 8. Nf3 Nd7 9. Bd3 Bxd3 10. Qxd3 e6 11. Bd2 Ngf6 12. O-O-O Bd6 13. Kb1 Bxg3 14. fxg3 O-O 15. Rde1 Qb6 16. Bf4 a5 17. Bd6 Rfc8 18. Ne5 c5 19. dxc5 Nxc5 20. Qd4 Ra6 21. Nc4 Qc6 22. Be7 Nce4 23. Bxf6 Nxf6 24. Ne3 Qc7 25. Qf4 Rb6 26. Qxc7 Rxc7 27. Rd1 Rc3 28. Rd8+ Kh7 29. Rd3 Rxd3 30. cxd3 Rd6 31. Kc2 Kg8 32. Rh4 Nd5 33. Nxd5 Rxd5 34. Kd2 b5 35. Ke3 Rc5 36. Kd2 Kf8 37. Rh3 Rg5 38. Ke3 Ke7 39. a3 a4 40. Ke2 Kf6 41. Kf3 Rd5 42. Ke3 Kg5 43. Rh4 e5 44. Rb4 f5 45. Rh4 Rc5 46. Kd2 f4 47. Rh3 Kg4 48. gxf4 exf4 49. d4 Rxh5 50. Rxh5 Kxh5 51. Kd3 f3 52. gxf3 Kg6 53. Ke4 Kf6 54. Kd5 Ke7 55. f4 h5 56. f5 h4 57. Ke4 h3 58. Kf3 Kf6 59. Kg3 Kxf5 60. Kxh3 Ke4 61. Kg4 Kxd4 62. Kf5 Kd3 63. Ke5 Kc2 64. Kd4 Kxb2 65. Kc5 Kxa3 66. Kxb5 Kb3 67. Kc5 a3 68. Kd4 a2 69. Ke4 a1=Q 70. Kf4 Kc4 71. Kf3 g5 72. Kg4 Qg1+ 73. Kf5 g4 74. Kf4 g3 75. Ke4 Qd4+ 76. Kf3 Qf2+ 77. Ke4 g2 78. Ke5 Qd4+ 79. Ke6 g1=Q 80. Ke7 Qgg7+ 81. Ke8 Qdd7# 0-1 [Event "13. Online Aktivschach WM"] [Site "schachcomputer.info"] [Date "2016.12.27"] [Round "1.8"] [White "Novag Star Diamond"] [Black "Tasc CM 32 MHz King 2.2"] [Result "0-1"] [ECO "D46"] [PlyCount "75"] [EventDate "2016.??.??"] 1. d4 d5 2. c4 c6 3. Nc3 Nf6 4. e3 e6 5. Nf3 Nbd7 6. Bd3 Be7 7. O-O O-O 8. e4 dxe4 9. Nxe4 b6 10. b3 c5 11. Bb2 Bb7 12. Qe2 cxd4 13. Nxd4 Nc5 14. Nxc5 Bxc5 15. Rad1 Qc7 16. Nf3 Rfd8 17. Bxf6 gxf6 18. Be4 Rac8 19. Bxb7 Qxb7 20. a4 Qe7 21. Kh1 Qc7 22. Nd2 Bb4 23. Ne4 f5 24. Nf6+ Kg7 25. Qb2 Kg6 26. h4 Qf4 27. h5+ Kh6 28. Kg1 Bd6 29. g3 Qg5 30. Kg2 Be7 31. Nd7 f4 32. Qe5 Rc5 33. Qc3 Rf5 34. Rd3 f3+ 35. Kg1 Qxh5 36. Qd2+ Bg5 37. Qc3 Rxd7 38. Rxd7 0-1 [Event "13. Online Aktivschach WM"] [Site "schachcomputer.info"] [Date "2016.12.18"] [Round "1.9"] [White "Mephisto Genius 68030"] [Black "Mephisto Milano Pro"] [Result "1-0"] [ECO "A39"] [PlyCount "129"] [EventDate "2016.??.??"] 1. c4 c5 2. Nc3 Nc6 3. g3 Nf6 4. Bg2 g6 5. Nf3 Bg7 6. d4 cxd4 7. Nxd4 O-O 8. O-O Nxd4 9. Qxd4 d6 10. Bg5 Ng4 11. Qe4 Bxc3 12. bxc3 f6 13. Bc1 Rf7 14. Qd5 e6 15. Qd4 Ne5 16. Ba3 Rd7 17. Rfd1 Nf7 18. Rab1 Kg7 19. Rb5 Qc7 20. e3 h6 21. Bb4 Qd8 22. a4 Qc7 23. Ba5 Qb8 24. Rbb1 b6 25. Qe4 Rb7 26. Bb4 a5 27. Ba3 Ra6 28. Qc2 Rd7 29. c5 dxc5 30. Rxd7 Bxd7 31. Bxc5 Qa7 32. Qa2 bxc5 33. Rb7 Qa8 34. Rxd7 Qc8 35. Rb7 Rd6 36. Qb3 c4 37. Qb5 Rd3 38. Bc6 Rd1+ 39. Kg2 Rb1 40. Qxb1 Qxc6+ 41. e4 Qxa4 42. Qb6 Qe8 43. Qc7 f5 44. Qxc4 fxe4 45. Qxe4 Qc8 46. Ra7 Qxc3 47. Qxe6 Qf6 48. Qxf6+ Kxf6 49. Rxa5 Ne5 50. f4 Nc4 51. Rc5 Nd6 52. g4 Ke7 53. h4 Ke6 54. h5 gxh5 55. Rxh5 Nf7 56. Ra5 Nd6 57. Ra6 Kd5 58. Kf3 Kc5 59. f5 Kd5 60. Kf4 Nf7 61. Re6 Kc5 62. Rf6 Nd6 63. Rxh6 Kd5 64. Rxd6+ Kxd6 65. Kg5 { 1-0 Aufgegeben} 1-0 [Event "13. Online Aktivschach WM"] [Site "schachcomputer.info"] [Date "2016.12.13"] [Round "1.10"] [White "Saitek Barracuda 40 MHz"] [Black "Mephisto Atlanta 36 MHz"] [Result "0-1"] [ECO "D42"] [PlyCount "116"] 1. e4 c6 2. d4 d5 3. exd5 cxd5 4. c4 Nf6 5. Nc3 e6 6. Nf3 Be7 7. cxd5 Nxd5 8. Bd3 Nc6 9. O-O O-O 10. Re1 Bf6 11. Be4 Nce7 12. Bg5 Bxg5 13. Nxg5 Nf6 14. Rc1 Nxe4 15. Ngxe4 b6 16. Qf3 Ba6 17. Red1 Rc8 18. b3 Qd7 19. Qg3 f5 20. Ng5 Nd5 21. Nxd5 exd5 22. Nf3 Rfe8 23. Ne5 Qd6 24. Re1 Bb7 25. Qf3 Rxc1 26. Rxc1 g6 27. g4 Rc8 28. Rxc8+ Bxc8 29. Qf4 a6 30. h3 b5 31. Kf1 Qf8 32. Qf3 Be6 33. Qc3 fxg4 34. hxg4 Qd6 35. Qc5 Qxc5 36. dxc5 Kg7 37. g5 Kf8 38. c6 Ke7 39. Ke2 Kd6 40. f4 b4 41. Kd1 Bf5 42. Ke2 Kc7 43. Ke3 Bb1 44. Kd4 Bxa2 45. Kc5 Bxb3 46. Kxb4 Bc4 47. Kc5 a5 48. Nxc4 dxc4 49. Kd4 Kxc6 50. Kxc4 Kb6 51. Kb3 Kb5 52. Ka3 Kc6 53. Ka4 Kd5 54. Kxa5 Ke4 55. Kb4 Kxf4 56. Kc5 Kxg5 57. Kd4 Kf4 58. Kc3 Ke3 { 0-1 Aufgegeben} 0-1 [Event "13. Online Aktivschach WM"] [Site "schachcomputer.info"] [Date "2016.12.21"] [Round "1.11"] [White "Millennium ChessGenius Pro"] [Black "Fidelity Excel Mach IV"] [Result "0-1"] [ECO "A26"] [PlyCount "92"] [EventDate "2016.??.??"] 1. c4 e5 2. Nc3 Nf6 3. g3 g6 4. Bg2 Bg7 5. d3 O-O 6. e4 Nc6 7. Nge2 d6 8. O-O Bg4 9. Be3 Qd7 10. a3 Bh3 11. Nd5 Nxd5 12. cxd5 Bxg2 13. Kxg2 Nd4 14. Bxd4 exd4 15. Rc1 Rae8 16. Qb3 c5 17. dxc6 bxc6 18. Qa4 d5 19. f3 f5 20. Rxc6 fxe4 21. dxe4 dxe4 22. fxe4 Rxf1 23. Kxf1 d3 24. Qc4+ Kh8 25. Nc3 d2 26. Nd1 Qg4 27. Qc2 Qh3+ 28. Ke2 Qxh2+ 29. Kd3 Qxg3+ 30. Kc4 a6 31. Rc5 Rd8 32. Kb4 Bf8 33. Ka5 Bxc5 34. Qxc5 h5 35. a4 h4 36. Qe7 Rd6 37. b4 Qf4 38. e5 Rd5+ 39. Kxa6 h3 40. Qe8+ Kh7 41. Qe7+ Kh6 42. Qf6 Qc4+ 43. Kb6 Qxb4+ 44. Kc7 Rc5+ 45. Qc6 Rxc6+ 46. Kxc6 Qxa4+ {0-1 Aufgegeben} 0-1 your web browser and/or your host do not support iframes as required to display the chessboard