[Retros] "half" proof games

[Noam Elkies]

NDE> 1 f3 ... 2 Kf2 ... 3 Ke3 ...#  seems to have a unique solution.

R.Stanley> Are there any longer?

There are certainly no shorter...  There are other exmaples in 3,
such as  1 f3 ... 2 g4 ... 3 fxe4 ...#, and at least 4 and 5 look
possible as well, as in 1 g3 ... 2 Bh3 ... 3 B:e6 ... 4 f4 ...#
and 1 d3 ... 2 Bd2 ... 3 Ba5 ... 4 Bxd8 ... 5 Qc1 ...#.


> Can Francois check up to some number of moves?


... and likewise with White giving checkmate, and
with other notational options such BxQd8 for Bxd8?

NDE