[Retros] shortest proofgames of castling switchback

[Noam Elkies]

NDE> change the sequence 12 Re3 Qf3  13 Bh2 Qh3  14 g3  to
NDE> 12 Rg3 Qf3  13 Rg5 Qh5  14 g4,  giving this diagram:

MR> This still doesn't work, the position can be reached
MR> without black 0-0:

MR> 1.a2-a4 g7-g6 2.Ra1-a3 b7-b6 3.Ra3-h3 Bf8-g7 4.b2-b3 [...]

Argh -- so the extra move b3 at the end can't be entirely random.
Let's try Kf1 instead:

  r Q B . k . . r  hg-19.0
  p . p p p p . p
  n p . . . n p R
  . b . . b . R q
  P . . . . B P P
  . . . P . . . .
  . P P . P P . .
  . N . . . K N .  16+16

  NDE 17.vii.07

Thanks,
--Noam D. Elkies