11 Jul 08
Hmm, I typed "difficult retro" on google. This was the first result:
I don't know how to set "illegal" positions in fen, so I will just write the pieces squares.
Pieces: Kc8, Kd6, Qc6, Rd8, Rf6, Ba8, Ne8, a7, b7
Colour the pieces. What was the last move?
I'm afraid it's too easy for you though, so I will look a bit further 😉
12 Jul 08
Originally posted by crazyblueBut in that one the idea is clear immediately (that white castles and thus proves that 50 moves were made without capture/pawn move).
how about this (unless you know it already, it will probably keep you busy for a while 😉):
[fen]nB3RbN/1kppppq1/1p4p1/1P3p2/Bp3P1n/4PrbP/2PP1rP1/R3K3 w - - 0 1[/fen]
white to move and draw.
12 Jul 08
1 edit
"Release the position"
In essence, this stipulation asks you to find how a given (usually quite tangled) position can be reached legally. So that it really asks for a proof game but without insisting on giving all painful details of a proof game. You "only" have to find the tricky maneuver that is required to lock everything the way it appears in the diagram.