The puzzle...

The initial chess position allows White to play 20 legal moves. Do you know what's the max number of legal moves in a given legal position? I recall it was something like 200+, but don't know the exact number. Any ideas?

I just found a position with 218 legal moves:

I think the max is 247 or something, but not quite sure :/

Vrom it is interesting. Though, it is not a legal position - too many White pieces.

Tunatin: I think it was b3-b2 just after check :). Right?

:)

I know one with 457 legal moves, but its a secret I can't share :)

the vrom one has too many pieces to be possible

mossman500: I don't think it is possible. You can have 9 queens only. And it must be a legal position.

yea

That position wouldn't ecure in a proper game.

its legal, no?

ITS LEGAL!!! White has his initial: King (of course) Queen Bishops Knights. The 8 extra queens are from pawns.

I doubt you could get the black king into that position without a mate or stalemate somewhere.  The white bishop would have had to been the last two moves but before that it doesn't look like there were any possible safe positions for the king (perhaps if a black piece were in front of it...seems improbably though).  Also not too sure how you could turn 8 pawns into queens, yet still have two black pawns left on the board.   It would be interesting to try and manage this puzzle though....

Clearly a drawn position.

I know this is an old post, but I think it's an interesting puzzle, and it is indeed possible!  Here's a solution in 72 moves, though I suspect there are shorter ones.  White to move next (and hopefully select one of the many checkmate options!)

1. a4 Nc6 2. b4 Nd4 3. c4 Nb5 4. axb5 d6 5. d4 Bd7 6. e4 Bc6 7. bxc6 e6 8. f4 Qd7 9. cxd7+ Ke7 10. g4 c5 11. bxc5 Kf6 12. cxd6 a5 13. d8=Q+ Kg6 14. d7 b5 15. Ra4 Ne7 16. Nd2 b4 17. f5+ Kg5 18. Bd3 b3 19. Rb4 a4 20. Rb8 a3 21. Rxa8 Kf4 22. Qc8 Ke3 23. Kf1 h5 24. gxh5 g6 25. fxg6 f5 26. exf5 e5 27. dxe5 Nc6 28. Qg4 Na7 29. Qg5+ Kd4 30. h4 Nb5 31. h6 Kc3 32. cxb5+ Bc5 33. Ndf3 Rg8 34. Be3 Kb2 35. h7 Ka1 36. hxg8=Q a2 37. Qa6 Bd6 38. Bb1 Be7 39. Ne2 Bf8 40. Nc1 Be7 41. Nd4 Bd6 42. Nde2 Bc5 43. Nc3 Bb4 44. Nd1 Ba3 45. Bg1 Bb4 46. b6 Bc5 47. b7 Bd6 48. b8=Q Be7 49. Qbb6 Bf8 50. d8=Q Be7 51. h5 Bd6 52. h6 Bc5 53. h7 Bb4 54. h8=Q Ba3 55. Qh2 Bb4 56. Qhd2 Bc5 57. Rh8 Bd6 58. Qh4 Be7 59. Qgc4 Bf8 60. g7 Be7 61. g8=Q Bd6 62. Qg6 Bc5 63. f6 Bb4 64. f7 Ba3 65. f8=Q Bb4 66. Qf3 Bc5 67. Q8d7 Bd6 68. e6 Bc5 69. e7 Be3 70. e8=Q Bd4 71. Qa3 Be5 72. Qxe5+ b2