Second challenge: find the fastest position where white/black to move is mate, but the queens never move and the queens are not the mating pieces.
A queen (or any piece) can never be a mating piece unless it moves anyway. Read this thread (all posts 
): https://www.chess.com/forum/view/endgames/how-can-you-deliver-checkmate-with-a-king
It is possible though to specify that the queen does not attack the king in the checkmate position.
what about
This is an illegal proof game by FIDE law as the position is "dead" (no one can checkmate the other side) after 17. .. Kxe7 which terminates the game automatically in a draw. To get the final diagram legally you'll need to make the rook capture as the final move on e8!
This issue has recently been discovered by the retro-community though I've known it for 15 years. It caused problems in standard compositions which were drawn before the point designated by the author. I think they changed the rule now or are in the process of doing so. One of these days I'll look where they have gone with it. Probably the wrong way as they have a habit of doing.
Note that "dead positions" are a basic FIDE law (article 5.2.2) and not some weird "competition rule" or "Codex convention".
what about
This is an illegal proof game by FIDE law as the position is "dead" (no one can checkmate the other side) after 17. .. Kxe7 which terminates the game automatically in a draw.
True, and that was noted when this game was posted a couple of years ago. Article 17A of the Codex says "Unless expressly stipulated, the rule of dead position does not apply to the solution of chess compositions except for retro-problems." This being a retro-problem, the dead position rule does apply.
what about
This is an illegal proof game by FIDE law as the position is "dead" (no one can checkmate the other side) after 17. .. Kxe7 which terminates the game automatically in a draw. To get the final diagram legally you'll need to make the rook capture as the final move on e8!
This issue has recently been discovered by the retro-community though I've known it for 15 years. It caused problems in standard compositions which were drawn before the point designated by the author. I think they changed the rule now or are in the process of doing so. One of these days I'll look where they have gone with it. Probably the wrong way as they have a habit of doing.
Note that "dead positions" are a basic FIDE law (article 5.2.2) and not some weird "competition rule" or "Codex convention".
ohh okay! I did not even realize that
True, and that was noted when this game was posted a couple of years ago. Article 17A of the Codex says "Unless expressly stipulated, the rule of dead position does not apply to the solution of chess compositions except for retro-problems." This being a retro-problem, the dead position rule does apply.
Yes, I haven't been paying attention lately. This was changed in the 2015 Codex, it wasn't there before. The problem is that no-one cares to define what a retro-problem is - though some types are recognizable as retro by their stipulations. The weird part is that problems running into this issue can always be considered retro-problems for the simple reason that they ran into this issue. To find out what the author intended you first need to solve it and then reverse engineer that this was probably not a retro-problem! A questionable approach to rulings. Note that standard non-retro-problems need some retro-conventions as well, e.g. to find out about castling and e.p. right and who's on move.
Btw, all these issues could be resolved by introducing the habit to announce retro / non-retro type with the stipulation as soon as there could be the slightest doubt. And the author could use it to place compositions in a different category than would be assumed by default! Then a proof game such as this one could be treated as either a retro- or a non-retro problem.
Btw2, proof games are the least retro-type of all composition types anywhere! The retro-conventions are typically required to provide "choice rules" to fill in unknown states. But proof games are purely retro-analytical and have no unknown states whatsoever! Unlike standard two-movers or endgame studies which may demand access to retro-conventions! So proof games ought to be classified as non-retro with regard to the retro conventions. And then article 17A will save proof games such as the one discussed.
So we arrive at the retro-analytical "release the position" (which is a proof game) type by a detour. Typically the retro-conventions do NOT apply to the retro-analytical type. Nothing is known about states of castling, e.p. or who is on move. You have total freedom to retract whatever you like as long as it is "legal"! This is the place for proof games as well: retro-problems solved without retro-conventions and with pure Sherlock Holmes analytical deductions! Btw, Smullyan in his retro-books never assumed any "choice rules" for the unknowns. No conventions!
Second challenge: find the fastest position where white/black to move is mate, but the queens never move and the queens are not the mating pieces.
I found a few 4.5-move games but couldn't get it down to 4.0. Here's one where the diagram is reached via a unique sequence.
Annoying thing is that Black can even have a spare move...
Third challenge: find the fastest white/black mate where the pawns never move.
I found a few 4.5-move games but couldn't get it down to 4.0. Here's one where the diagram is reached via a unique sequence (diagram 1) Annoying thing is that Black can even have a spare move...(diagram 2)
The spare move exists and can't be denied unless you can shorten the proof game. But Rocky's last version can be undualed in an elegant alternative:
.
Here's a position EvinSung posted in the Illegal Position thread, presumably thinking it's illegal. How short a proof game can you find for it?
Just noticed a 4.5-move solution is possible with pawn moves only, including promotion mates!
Here's a position EvinSung posted in the Illegal Position thread, presumably thinking it's illegal. How short a proof game can you find for it?
It is illegal because the black king has no waiting moves after the pawns get into formation
Here's a position EvinSung posted in the Illegal Position thread, presumably thinking it's illegal. How short a proof game can you find for it?
It is illegal because the black king has no waiting moves after the pawns get into formation
Black king can come from b6:
Here's a position EvinSung posted in the Illegal Position thread, presumably thinking it's illegal. How short a proof game can you find for it?
Black king can come from b6:
This should give someone ideas.
Here's a position EvinSung posted in the Illegal Position thread, presumably thinking it's illegal. How short a proof game can you find for it?
It is illegal because the black king has no waiting moves after the pawns get into formation
Black king can come from b6:
Wow! I did not even see the possibility of waiting to capture.
My attempt.