Roll up, roll up for the OTF chess tournaments

[ad hoc]

[Spoiler]My workings.

The white king must have been the last piece to move as the black king is in check and any of the spaces the white bishop could have occupied would also have the king in check. BUT... The white king couldn't have occupied either of the two spaces between w B and b K as one is covered by two b pieces and the other is covered by the b K.

I'm stumped[/spoiler]

That's pretty much as far as I got (OR: the white king is on b3 and has just been placed in check by black. But there's no way that this could happen because it's in double check and there isn;t a way that this could have been a reveal check+check.)

[Wouter D]

If you require spoilers, let me know. For now, I'll assume that you want to puzzle on a bit.

[Sam]

I am stumped too.

Sam, I noticed you're waiting on the result of one game to determine if you make it into the final round of the sub 1200 tournament we're both in.

Bloody hell they're playing slowly, I assumed it had finished ages ago and I was out (I'm expected wesleyhoward to win, obviously). I see you did quite well over in the other group!

[Wouter D]

Partial spoiler ahead:

[spoiler]Levin is right that the white king moved last. So how could this double check that ad hoc alludes to have happened?[/spoiler]

[Wouter D]

Partial spoiler:

[spoiler]Most chess moves focus the action on two fields: a piece leaves the one field, and either moves to an empty field or replaces another piece on an occupied field. However, there are a few special moves where several fields are vacated simultaneously. Most of those are located on the back rank. And then there are others...[/spoiler]

[irony towers]

Yes, I had the sense of where this was going before your hint, and now I see how it fits. Nicely constructed.

[Wouter D]

For those of you who are still puzzling on, here is the solution: c3.

[spoiler]The situation given was this one:



To answer the question Sam asked: it can only be black's move. If white were to move first, black cannot be in check. That means that the white king must block the bishop, which it cannot do: on c2 it would be adjacent to the king, and on b3 it would be in double check by two black pieces, which cannot happen for reasons outlined by Levin and ad hoc.

So white made the last move. But which legal move could that be? The bishop is putting the black king in check, but itself cannot have moved into that position given the positions of the other pieces. So something must have been in the way and moved out of the way to make this check happen. And that something can really only have been the white king, moving away from b3 to somewhere else. So what makes this situation different from the situation described above and used to determine whose turn it is? Moving the king away from b3 to somewhere else has also removed additional material from the board.

To give the full sequence, we need to take back two turns. In this initial setting, the black bishop is on basically any other place on the a8-h1 diagonal (I'm going to denote it on h1 because I feel like it), and all other pieces that you see on the board are in the same position. Additionally, the white king is on b3, a white pawn is on c2, and a black pawn is on b4. The sequence that leads to our board is:
1: ...; Bh1-d5+
2: c2-c4; b4xc3+ e.p.
3: Kb3xc3+

So the en passant strike ensures that two fields are vacated simultaneously, which allows for the double check on b3.[/spoiler]

[Evariste Euler Gauss]

very nice!

[Evariste Euler Gauss]

In the 960 tournament that Wouter, Levin and I entered, chess.com have just taken their arbitrary and unpredictable rules on progression through rounds to a new level of absurdity. It's a 6->3 tournament which had two groups of 5 in the penultimate round. And, despite the rather obvious point that allowing 3 from each semi-final group through to the final would fit perfectly with the maximum group size of 6, the system is only letting 2 through, to (presumably) a final group of only 4. Harsh on Levin, whose progression to the final I thought would be secured by my victory over the other player who might have got 3rd spot. Wouter, I assume you never got a reply to your query about the misleading format specification?

[Wouter D]

Indeed.

[Sam]

That's a shitter.

Closing in on ending OTF 10 now, with me v Bored having just kicked off and thus the last game to be played is underway. That draw between Levin and EEG is spoiling an otherwise nicely diagonal symmetry in the result table of all 0s below the line and all 1s above it!

Alex is currently in Greece with very low internet time and phone battery (I talked to him briefly earlier today and he told me it keeps running out), so if we want to give someone else a chance of winning OTF 11 I'd suggest trying to get it started in the next couple of days so he times out of all his opening matches. I won't tell him if none of you lot do. But Bored and I have to finish first, of course ...

[Sam]

(Anyone else a bit irked that they've moved us down to Games, by the way? A year and a half ago I wouldn't have cared either way but now I think, 'Philistines!')

[Etienne]

We basically requested it.

[Sam]

I feel I should clarify that I was joking ...

I am currently in a king and queen vs king and queen endgame against someone who doesn't appear to realise that this is a draw, and keeps playing on. I'm the one putting them in check constantly (and they can't interpose their queen unless I do something really stupid), so I'm not sure what exactly they're getting out of it. Hoping for a brainfart on my part, presumably.

[Etienne]

Can't you just claim the draw after a few consecutive checks.

[Levin]

It's not a way of forcing a draw any more. Sam needs to trigger threefold repetition or the fifty-move rules.

I'm ready for a new tournament. My rating is far too high and I've no current games on.

[Evariste Euler Gauss]

I'll probably have to miss the next tournament, unless Bored's second OTF10 match against Sam takes 5 weeks or so. I'm off on a 3 week trip to Scotland and the Lake District with wife and daughter in a few weeks from now, back on Sunday 6 August, and it doesn't make much sense to be in a tourney when I'm away, what with the likelihood of limited signal/wifi, not to mention the need to engage in some quality family time on hols. If OTF 11 kicks off on 7 August or later, I'm in.

[Sam]

It's me against Bored. I'm sure we can drag it out a bit. (I'm off in three and a half weeks, but I'll be taking my tablet and computer so I ought to be able to make moves, albeit perhaps a bit more slowly.)

My opponent accepted a draw offer a couple of minutes after I posted that complaint last night. Clearly they're an OTF lurker ...

[Etienne]

I was quite chuffed with what I did in this game last night (on a board).
R x G7+ K x R
B - H6+ K x B
Q X Q.

Obviously my opponent didn't see what I was planning, not sure what would have happened if he'd play Kh8 instead of taking the rook.

[Sam]

OTF10 is over! Good game, Bored.

[Bored Of Education]

Thank you Sam but that was a much worse game than our first one in that tournament.

I have to say that I quite enjoyed this smaller tournament and I wonder if, for one tournament, we could have a two division tournament? Obviously, I would be in the lower division so it isn't a hassle for me but it would mean a shorter, quicker, closer tournament in both divisions. Also, with my ADHD, it means I can keep track of fewer games better.

[Sam]

I'd be up for that. Not sure how the division would be decided though (assuming Wouter doesn't just lump you and me in Div II and have everyone else in the top tier).

Given how long our games in these tournaments normally take, there's a good chance the next game we finish will be in person!

[Levin]

I don't think you can do divisions but what I have thought of in the past would be to set up a tournament with two seeded groups. Top 50% in each go to a final group and then have a person who isn't Wouter set up a "OTF XX Trophy" tournament with those people knocked out.

[Wouter D]

I don't think you can do divisions but what I have thought of in the past would be to set up a tournament with two seeded groups. Top 50% in each go to a final group and then have a person who isn't Wouter set up a "OTF XX Trophy" tournament with those people knocked out.

That sounds a bit harsh on my tournament directing abilities.

[Levin]

Sorry, it was purely that you can't direct two tournaments at the same time can you?