Is this position legal?

Sure, Black's knights just ate everything and then went back to their starting positions.

@ypiguh: what you can do with only one knight is amazing.

Easy enough to get three promotions for each side, so legal.

Here's one, for old times sake:

Legal or illegal?

Black's last move was Qd1xc2+ (or Qd2xc2+). The captured piece could have been a bishop or a queen. Retracting further, it seems that White would have to eventually retract g2xf3. This would release the rook, which would allow the cage to be freed. However, there is a problem with this. Black is missing 3 pieces, which is just enough to allow axb, dxe, and gxf. However, the h-pawn collision makes it rather difficult to promote it. It goes to the g-file. White, however, is missing 2 pieces, and if we retract gxf the LSB can't get out. Otherwise, the retrocage is pretty hard to unlock. I think it's illegal, but I'm probably overlooking something obvious.

I think I've seen [or solved] #1267 before, so I'll lay off of it now.

Interesting, I just made this, haha. Could I be recycling old ideas without even knowing?

Or perhaps I saw something similar in another composer's problem. I've solved so many that the names start to blur in my head.

I don't think that's legal. o.O

If this is legal, how did the bishop get into d3? o.O

On a different note, it's good to see you again BigDogg, and Remellion, and chaotic, and everyone else. I've been laying off retros (and these forums) for a while now because it was a huge time sink which I couldn't afford

Yeah, you and Rem are the best retro composers on here. When you're gone, we're down to one.

I used to compose occasionally, but now it's hard to think of good ideas that have not already been done. I think I enjoy solving more anyhow.

Hi shoopi! For something you just made it's as detailed as ever. Aside from a dual on 12-14 I count the last 18 half moves determined; legal. I particularly like the way that retracting bKa4-a3 is ruled out - tripped me for a couple minutes trying to solve in my head.

Perhaps it's recycled, perhaps not. What's a "theme" anyway? There are only so many things you can do with promotions, inventory and pawn paths.

Meanwhile here's an extra problem I made while trying to create the "SG50" ones. Aesthetically not so great so I left it unposted until now. Mate in 1.

I'm not a composer? Wait, I'm not.

Well, this is still a "is this legal?" thread.

White made 7 obvious captures, leaving one left. If d5 came from b2, then White needs two more captures (bxcxd and cxb as opposed to simply cxd), too much. So Black made a capture axb in order for b7 to "pass" through b5.

What was Black's last move? Not b6-b5 for obvious reasons. Not c6xb5 either because b5 came from a-file. Neither Kb6-a5 nor Kb4-a5 work because of White's Kc5. Ka4-a5 doesn't work because of double contact checks. Not R~xa6 either because Black has used the only capture available. So Black didn't make the last move and thus Black has the move, mating White by 1... d6#.

The position itself is clearly legal: retract -1. Ba2-b3 Ka4-a5 -2. Nb1-c3+ Ka5-a4 and Black is no longer retropat. Then remove Ra7 via top rank, remove Ra6, retract a6xNb5 and everything unlocks.

You missed a possibility: -1...Ra6, no uncapture. Evaluate that?

Whoops, correct. I missed -1. R~-a6 Ra8xa7+. I thought I couldn't retract R~-a6 because that's an impossible check. (Retracting -1... a6xb7 is clearly out of the question because too many captures necessary; I forgot White has one capture left to retract -1... Ra8xa7+ though.)

So, if that's the case, White captured 8 times, exactly everything. Black also captured 1 time, exactly everything. White's b-pawn didn't move out from its file, and neither did Black's b-pawn. But then Black's b-pawn couldn't get captured; White made no captures on b-file, and Black's b-pawn couldn't promote.

Wow this forum is back in track,

#1267: illegal. The pawn on f3 comes from g2 obviously. Black has lost two pawns and the bishop of the dark colours. Therefor must that pawn on f3 have captured one of the two pawns. That must be the pawn of the h-file. To go from the h- to the f-file must that pawn have captured the two missing pieces of white, namely the queen and the bishop. That implies that the queen on c2 has not captured anything. But that should have been, because otherwise was white already in check before the queen had made her last move. That is impossible, hence illegal.