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Old 2014-03-12, 13:54   #1
LaurV
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Default White 23

They moved wise: 22..f6

I think it is the best move they could do here. And according with the former analysis, I think we can safely take it. Maybe...
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Old 2014-03-12, 21:18   #2
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Not taking it will result in the opening of the center to their advantage.
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Old 2014-03-13, 02:42   #3
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Our deadline is [URL="http://www.mersenneforum.org/showpost.php?p=368817&postcount=132"]Wednesday, March 19 10:01 UT[/URL].

- - -

Here's something not yet in our analysis, IIRC:

After the pawn swap on f6, if the rooks are not involved, or have also been swapped, Black's dark-square bishop threatens to win a pawn via ... Nxd4 and ... Bxd4+. Here though, unless there's something more to complicate this, we interpose with Be3 and protect the knight while blocking the check. So the threat is Black's freeing of his position, not material gain.

For example, after
[B]23 exf6[/B] Rxf6 24 Rxf6 Bxf6 25 Bxh6 Nxd4 26 cxd4 Bxd4+ 27 Be3 e5 28 Bxd4 exd4, material is still even but Black has transformed his e-isolani into a passer in a queen-side pawn majority. Our N/d1 looks worse than Black's N/e7, and Black's B/c8 is unleashed.

So, we'd need to vary somewhere to prevent that outcome, perhaps with 24 Ne3 in the line above.

Maybe [B]23 ... Rxf6 24 Ne3[/B] Rxf1+ 25 Rxf1 bxc3 26 bxc3 h5 (if 26 ... Rb2 27 Nxc4) 27 Nxc4. But Black must have better moves.

- - -

Hey, [I]we[/I] have better moves!

[B]23 exf6[/B] [B] Rxf6 (or Bxf6) 24 Bf4 [/B]embarrasses Black's QR. If 24 ... Rb6 25 Bc7. So, [B]24 ... Ra8 25 Ne3[/B] g5 26 Bc7 (threatening 27 Nxc4 and 28 Nd6++) Ra7 27 Bb6 Ra8 28 Nxc4. If 28 ... Rxf1+ 29 Rxf1 and Black must defend carefully.

Last fiddled with by cheesehead on 2014-03-13 at 03:25
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Old 2014-03-13, 04:19   #4
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[QUOTE=cheesehead;368860]

[B]23 exf6[/B] [B] Rxf6 (or Bxf6) 24 Bf4 [/B]embarrasses Black's QR.[/QUOTE] Oops. I should've analyzed more carefully.

[B]23 exf6 Rxf6 24 Bf4[/B]
If 24 ... e5 25 dxe5 Rf8 (not ... Rf5 26 Ne3 or ... Rf7 26 e6) 26 e6 (not Ne3 g5) Ra8 27 Ne3 g5 28 Bc7 Ra7 29 Bb6 Ra8 30 Nxc4 and it seems like there oughta be a checkmate in here somewhere, but maybe Black can survive for a while with careful defense.
If 24 ... Ra8 25 Ne3 g5 26 Bc7 and so forth ...

[B]23 exf6 Bxf6[/B] 24 Bxh6 Rf7 (if 24 ... Nxd4 25 cxd4 Bxd4+ 26 Be3 and Black is down a knight for a pawn) 25 Bf4 Ra8 and Black is down a pawn. If 25 ... e5 26 dxe5 Bxe5 27 Ne3 Bxf4 28 Rxf4

Last fiddled with by cheesehead on 2014-03-13 at 04:36
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Old 2014-03-13, 05:44   #5
LaurV
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[QUOTE=cheesehead;368865]
[B]23 exf6 Bxf6[/B] 24 Bxh6 Rf7...<snip>...[/QUOTE]
This looks terrible for black, after 25 Ne4. They lose at least a figure. Better (for black) would be 24...Rh8, where we can exchange the bishops and we take another pawn in e6. Either way, it is still bad for black, they will lose the game for sure if Bxf6 - the king flank is gone, the center is gone, they have less material, queen side is blocked.

It is clear we have to take the pawn, as WMH said too. Their only way to go is [B]23...Rxf6[/B]. Here we have to work for our next (24) move. We can exchange the rooks and go for the pawn advantage, but this opens the center for them, they develop the bishop well. We can give the column and go for the pawn in e6, we can "block" with Bf4 (they are forced to move the rook from b8, and we get one more move), we can go for the pawns in b/c (I don't thing this is a good idea, let them blocked is much in our advantage now, as black has no much to play).

Here is where we have to work. So, 23.exf6 Rxf6 is the continuation 100%.
Then what?
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Old 2014-03-13, 13:16   #6
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24. Bf4 Rb6 or Ra8 25. Ne4 Rf8 26. Nd6+ Kd7 27. Nxc4
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Old 2014-03-13, 13:55   #7
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[QUOTE=WMHalsdorf;368884]24. Bf4 Rb6 or Ra8[/QUOTE]Not 24 ... Rb6 25 Bc7 and the rook is not merely Embarrassed -- it's Exchanged. But we must not let Black distract us at this moment: 25 ... Nxd4?! 26 Bxb6 (NOT 26 cxd4?? Bxd4+).

[QUOTE=LaurV;368866]< snip > This looks terrible for black, after 25 Ne4.[/QUOTE]Just to be clear, [B]23 exf6 Bxf6 24 Bxh6 Rf7 25 Ne4
[/B]
[quote]They lose at least a figure.[/quote]If 25 ... Nd5 26 Nd6+ Ke7 27 Nxf7 Kxf7 28 Bxd5 exd5 29 Bg5 (and the B/f6 is pinned)

[quote]Better (for black) would be 24...Rh8, where we can exchange the bishops and we take another pawn in e6.[/quote][B]23 exf6 Bxf6 24 Bxh6 Rh8 25 Rxf6 Rxh6 26 Nxe6 Rh8 [/B](to prevent 27 Rf8+ Kd7 28 Nc5+ Kd6 (if ... Kc7 29 Na6+) 29 Rf6+ Kc7 30 Na6+ Kb6 (and now the N/c6 is pinned) 31 Nxb8 or 30 ... Kb7 (and now the N/c6 is pinned the other way) 31 Nxb8 Kxb8 32 Bxc6 and we still haven't developed our N and R on our first rank)

Last fiddled with by cheesehead on 2014-03-13 at 14:51
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Old 2014-03-13, 14:52   #8
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I don't like this f6 move. What went wrong? We had the game in hand.

I squeeze my brains, what's left of it after a busy day at work, but can't get better that a draw. If they exchange the rooks in f1, they get advantage, maybe win. If we exchange the rooks in f6, we help them develop the king side, and all their pawns are more advanced than ours, so (almost) any exchange of pawns is in their advantage. We can not cover the rook, except with Nf2, Bf3, Bf4, or Ne3 (to make place to the other rook, if they exchange, but this will weaken our queen side). From all these moves, Bf3 is stupid, Nf2/Ne3 is "so and so", all are too defensive. The only move which seems "reasonable" is Bf4. It looks good and aggressive, but... [U]what if they don't move the rook[/U]? This version is very plausible, and if we get greedy and take the rook, it may be worse for us!

24 Bf4 bxc3 25 [U]bxc3[/U] e5 26 dxe5 Nxe5 27 Bxe5 Rxf1 28 Bxf1 Bxe5 29 Bxc4 Bf5 - clearly a draw (if we don't get jinxed and allow them to transform)

if 25 Bxb8 -> .. cxb2 Nxb2 Rxf1 Kxf1 Bxd4, now we must take Nxc4, otherwise we may not be able to stop that pawn from transforming, and they get the Rook back: Bxa1.

All in all, we have no material advantage and the position is spoiled, we go very fast to a draw. What the hack I am missing? It looked so brilliant few moves ago...

Last fiddled with by LaurV on 2014-03-13 at 14:57
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Old 2014-03-13, 15:48   #9
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[QUOTE=LaurV;368889]I don't like this f6 move. What went wrong?[/QUOTE]Nothing except that you're tired. Get some rest. :-)

[quote]We had the game in hand.{/quote]We still do. Get some rest :-)

[quote]I squeeze my brains, what's left of it after a busy day at work, but can't get better that a draw.[/quote]No, no, no, [I]you're just tired and have forgotten our positional and tactical advantages[/I]. Get some rest before looking again!

We still get at least two pawns -- they aren't in our hands right this moment, but they're positionally weak and Black can't hold them much longer. The pawn/c4 is a goner; we just have to swat a few pesky distractions by Black before we collect it in peace. The pawn/e6 is unsupportable against our resources.

[quote]If they exchange the rooks in f1,[/quote](after [B]23 exf6 Rxf6[/B]) [quote]they get advantage, maybe win.[/quote]No, swapping on f1 is no big advantage for them. If we retake with our king, then later ... Bxd4 is not with check. Get some rest :-)

[quote]If we exchange the rooks in f6,[/quote]([B]23 exf6 Rxf6 24 Rxf6 Bxf6)[/B]

[quote]we help them develop the king side,[/quote]No, no. We [B]eat[/B] their king side: [B]25 Bxh6 g5 26 Ne4 Kf7 27 Bxg5[/B] (not 27 Nxg5+ Kg6)

(to be continued)

Last fiddled with by cheesehead on 2014-03-13 at 15:52
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Old 2014-03-13, 20:05   #10
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[continued)

[QUOTE=LaurV;368889]all their pawns are more advanced than ours,[/QUOTE]... but the most advanced pawns aren't going further. Only their b- and c-pawns are "advanced".

If a knight is to defend c4, it has to get to b6 or d6, and that is either too lengthy or gets ambushed or is too costly to be a net gain. For the N/e7: ... Nf5 loses a piece (with check) to Bxc6+. ... Nd5 will get ambushed by Bxd5 or (after we move Ne3) Nxd5 exd5, Bxd5. Nc8 requires moving the B/c8 first. For the N/c6, it has to take a longer route such as N-d8-b7-d6 or Na7-c8(requires bishop move first)-d6

We could attack the c-pawn as soon as move 24 with Ne3, sooner than Black can defend it.

As for the b-pawn, an advance to b3 is a dead end: as soon as c4 falls, it's undefended except by a rook, and we can attack it twice with N&B or N&N combinations.

(OTOH, if we do stoop to take the R/b8 after Bf4, we may have to carefully plan how to handle the b- and c-pawns if we don't do bxc3 right away. Perhaps 24 Bf4 just won't be worthwhile after further analysis.)

[quote] so (almost) any exchange of pawns is in their advantage.[/quote]Not ... bxc3. We retake with bxc3 (Poof! there went one of their "advanced" pawns!), and the black rook on the open b-file has a curious problem: Even if it's not so "embarrassed" as to be forced to sit at a8, there's no useful safe square on the b-file for it!

We have b1 covered by our R/a1, b2 covered by our N/d1, b3 covered by our N/c5, b4 covered by our pawn on c3, b5 covered by our pawn on a4, and b7 covered by our N/c5, leaving only b6. A rook on b6 isn't very threatening, especially after our Nxc4 makes that one also rook-uninhabitable!.

Even if we were to immediately move our N/d1 ([B]23 exf6 Rxf6 24 Ne3[/B]), square b2 won't be safe for that rook. 24 ... bxc3 25 bxc3 Rb2 26 Nxc4 serves the eviction notice. If it tries to hang around with 26 ... Rc2, then 27 Be4 serves the [strike]eviction[/strike] Exchange notice.

[quote]We can not cover the rook,[/quote]Which rook? Covered why?

[quote] or Ne3 (to make place to the other rook, if they exchange, but this will weaken our queen side).[/quote]Ne3 does not weaken our queen-side, as explained above.

[quote]The only move which seems "reasonable" is Bf4. It looks good and aggressive, but... [U]what if they don't move the rook[/U]?[/quote]Then they lose the rook.

[quote]This version is very plausible, and if we get greedy and take the rook, it may be worse for us![/quote]We'd take the rook/b8 only after analyzing that it would be safe for us.

[B]23 exf6 Rxf6[/B][quote]24 Bf4 bxc3 25 [U]bxc3[/U] e5 26 dxe5 Nxe5 27 Bxe5 Rxf1 28 Bxf1 Bxe5 29 Bxc4 Bf5 - clearly a draw[/quote]But we won't be that dumb -- we will do something else earlier and never get as far as move 26 in that line.

[B]23 exf6 Rxf6 24 Bf4 bxc3[/B][quote]if 25 Bxb8 -> .. cxb2 Nxb2[/quote]No, 26 Rb1 is smarter there.[quote]Rxf1 Kxf1 Bxd4, now we [strike]must take Nxc4, otherwise we may not be able to stop that pawn from transforming, and they get the Rook back: Bxa1.[/strike][/quote]calmly play 28 Bd6.

[quote]What the hack I am missing?[/quote]Sleep :-)

- - -

It seems clear that our move 23 choice is

[B]23 exf6[/B] -- 5
else -- 0

but we have five days to analyze what's next.

Last fiddled with by cheesehead on 2014-03-13 at 20:56
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Old 2014-03-13, 20:32   #11
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The move f6 is a psychological move which is more likely to work in an over the board game than a game in this format. It takes a clear head to see that all it does is to take focus away from what we intend to do which is get the pawn on c4.
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