Illegal Position Contest!

I'm confused about whether you're saying the position at #7783 is legal or illegal.

I concluded that it's illegal, but would be legal if the e6 pawn were on f5, and was going to suggest that Leither post it that way in the Shortest Proof Game thread.

I first tried to explain how EndgameEnthusiast2357 thought it was illegal. Next I stated it was legal - in several ways - without explaining it. To leave everyone a bite at the cherry. Somebody will find one of those ways, not?

Btw, Leither wanted you to fall for the e.p. trap. But then you would first have to see the option of course!

The four ab pawns on the 4th and 6th ranks came from the cdef files and the e6 pawn came from g2 after two captures, regardless of whether one of them was an e.p. so I'm not sure what the e.p. trap is.

I can make a proof game with the e6 pawn still at f5, but I haven't found any of your several ways to reach the posted position. Before I look any further, I'd like Leither to confirm your suggestion that a legal position was deliberately posted to fool people into coming up with bogus illegality proofs.

I have now seen that my position is indeed legal. Black was supposed to be unable to promote all the pawns, but I had completely forgotten that two of them do not have to promote.

Alright then. I can swap the bishop for a knight to create a completely new illegal position. In fact, it is substantially different from my first one.

In your position at #7783, what were the first retractions for each side?

I thought I had figured it out, but realized I was still a move short. So I'm still working on making #7783 legal.

Don't see any substantial difference. Neither the knight nor the erstwhile bishop could have discovered check fron the c1 bishop. Or am I missing something?

It took me too long, but here is one way for #7783.

I suggested the opposite. He posted a diagram he thought was illegal but he hoped solvers would believe legal with the help of an en passant move. Composers always try to lure you into believing something that is untrue! His effort failed because (a) no solver detected the e.p. possibility in the first place (b) his assumption that the digram was illegal was wrong!

#7955 is perfectly illegal!

Yes, I misunderstood your suggestion. Now I'm hoping you'll challenge us to figure out why the new position is also legal. So far it looks illegal to me.

Edit - Just saw your previous comment, probably about #7795.

Yes, I was missing something (everything).

And the substantial difference beween #7783 an #7795 is that one is legal and the other isn't.

?

We aren't to #7955 yet, my post is #7805.

Oops! In that case we have to assume that #7955 is legal until it appears! Innocent until proven guilty

I predict #7955 will be a re-post by KieferSmith of the legal position at #7799.

P.S. That was my lame idea of a joke, since #7799 is illegal. White needs six pawn captures, and the capture at c8 makes seven, but Black is only missing six units.

Every time I try to make the position look more legal, I end up actually making it legal... I had originally been intending to post the version with the knight, but I thought it would look more spacious with a bishop instead, which made the position legal by allowing an alternate path for the black king.

Even after seeing the alternate path, I thought the position was still illegal because black wouldn't have enough captures to promote every pawn; not my intended idea, but I thought it saved me from posting something legal. Unfortunately for me, it turns out that black doesn't actually need to promote the a and b pawns.

try 7773

It's illegal even when the pawns on a4 and b6 are on a3 and b3. The number of tempi does not matter. It is possible to release 70% of the position but then there is still an "illegal island" in the upper right which can never be resolved