Showing posts with label Rybka. Show all posts
Showing posts with label Rybka. Show all posts

Monday, August 3, 2020

Jerome Gambit: Two Computer Programs Walk Into A Bar...

I put some work into maintaining this blog, but I never could do it without the ideas, analysis and games that Readers send me.

For example, here is an introduction and then some analysis that I recently received (thank you, Anastazja) concerning a chess game where Stockfish gave Fruit 1.2 "Jerome Gambit odds".
Interested in the Jerome Gambit, I decided to look into it a little bit. However since my own chess playing abilities are a little weak, and since I don't play chess myself and I am more interested in AI research (and that of course leads to chess), I decided to test it on some computer games. However, since the Jerome Gambit is a very hard line to hold as white, I needed to change things a little bit. Considering that you would usually play Jerome Gambit against unprepared opponents looking to surprise them, it in theory has no place in today's computer chess. Their deep search can easily spot tactics and not fall victim to early queen attacks. However it turns out, that if you look deep enough, even computers can be outplayed with the opening. In the game I wish to share, white managed to use the queen checks to create a blocked position with very long term plans, making it very easy for opponents to become overzealous. 
Since the evaluation of the top chess engine Stockfish is at -3.5 pawns black advantage and the same engine can't surprise itself, I decided to try something different. I put Stockfish as white and an old engine called "Fruit 2.1" as black. Fruit is an old engine, however it still is about 2800 elo in strength, which would put it near world champion level. Moreover, its strength mostly comes from tactical prowess, as engines back in the day were relatively weak positionally. One would think that the Jerome Gambit is a tactical line that looks for compensation in terms of attack on the king that is in the open, so an engine with superhuman tactics should easily hold it. It turns out that it's not so simple. 
The game is 150 moves long, however most of those moves are just "shuffling" moves waiting for 50 move rule to take effect. White of course wants the draw, as it's a piece down, however black doesn't want that to happen. Even though most of the game are "pointless" rook and king moves, the critical moments of the game are definitely very interesting in my opinion. 
Game starts in the Jerome Gambit Accepted position, after Kxf7. White develops its remaining pieces. This, combined with queen checks, has led black to a little chaos. Black tried to force the queen trade, however the little positional and development edges white gained earlier made it not so simple. When black finally got its pieces developed and queens off the board, the position was already blocked and white got its own fortress ready. 
After creating a blocked position, both engines just shuffled around for multiple moves. The "shuffling" starts at move 34.Rf2 and continues for about 100 moves. White, being a piece down, has held the position because black could make no progress. Black constantly looked for opportunities, however the preparation in the first 30 moves of the game has made it impossible for black to find any kind of an attack. 
First 50 move rule reset happens at [71]...axb4 and [72].axb4. This pawn exchange doesn't open the position however, so engines continue to shuffle around. It's on move [121]...Rxc6 that the game gains a new life. Fruit playing as black, sacrifices the rook for a knight to open up the position hoping for some kind of an attack. Black is still up in terms of pieces, bishop and a knight for a rook. White has one pawn more, however in engine games pieces are usually worth a lot more than pawns. It turned out to be a very serious mistake. White managed to showcase a beautiful temporary rook sacrifice that led to a creation of connected passed pawns which ultimately gave white the material back and ultimately won the game. 
This result surprised me. If a 2800 elo engine has fallen victim to impatience and being overzealous because of the material advantage, a human surely can too. I'm not an expert so I can't really evaluate the position after it got locked and I don't know how it would play out if it was two humans, however I can easily see humans sacrificing and going for even worse attacks way earlier. The mental advantage Jerome Gambit can definitely catch some humans off guard, however I would never it would happen to an engine as well.
When I raised the question of the exchange of Queens, I received

Fruit definitely wanted the queen exchange to happen at first, the king was still in the open and the checks could prove a little annoying, plus exchanging the pieces when up the material is definitely a good idea. After [10]...Qb4, Fruit expected [11].Qxb4, however Stockfish played the [11].Qb5 move. Even though Fruit wanted the exchange to happen, [11]...Qxb5 would be followed by [12].Nxb5 with an attack on the c7 pawn. The only way to defend that pawn is [14]...Ne8, however after [13].Bf4 the pawn is still most likely going to fall. Black's pieces are still not developed, the knight on e8 blocks the access to an open file for the rook (and the other open file is blocked by the king). Apparently the engine thought that it no longer has any time to trade the queens, as development is more important. Can't make the use of the extra piece when most of them are hidden behind pawns after all. White used all this crucial time gained that way to create a solid position which then turned out to be impenetrable.  
stockfish_20060616_x64_modern  - fruit_2.1
computer vs computer, 2020

1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. Bxf7+



4...Kxf7 5.O-O Nf6 6.Nxe5+ Nxe5 7.d4 
Bxd4 8.Qxd4 Nc6 



So far, following in the path of Demon 1.0 - Rybka 2.3.2a (0-1, 53) and La Dame Blanche 2.0c - Rybka 2.3.2a (0-1, 41) from the Torneo tematico GaJero00–A PC Intel Pentium 4 630 3000 1, in 2009. 

9.Qa4 Qe7 10.Nc3 Qb4 11.Qb5 d6 12.Qd3 Be6 13.b3 Rhf8 14.Bd2 Qd4 15.Rae1 Rae8 16.Be3 Qxd3 17.cxd3 Nb4 18.Rd1 Ng4 19.Bc1 a5 20.d4 Nf6 

21.d5 Bd7 22.f3 h6 23.Rf2 b6 24.a3 Na6 25.Rc2 g5 26.h3 Re7 27.Ne2 Nc5 28.Rc3 Rfe8 29.b4 Ba4 30.Rf1 Nb3 31.Ng3 Kg6 32.Bb2 Rf7 

33.Rd3 Nd7 34.Nf5 b5 35.g4 Nb6 36.h4 Nc4 37.h5+ Kh7 38.Rf2 Ra8 39.Kh2 Ra7 40.Kg3 Ra6 41.Kg2 Rf8 42.Rc3 Raa8 43.Kg3 Rfe8 

44.Rg2 Ra7 45.Rd3 Rf8 46.Rf2 Rf7 47.Kh2 Ra8 48.Kg3 Re8 49.Re2 Ref8 50.Rf2 Rb8 51.Kh2 Rff8 52.Kg3 Rbe8 53.Rg2 Ra8 54.Rh2 Rad8 55.Rf2 Rb8 56.Re2 Rf7 57.Rh2 Rg8 58.Rg2 Rd8 59.Re2 Re8 60.Rg2 Rff8 61.Re2 Rg8 62.Rf2 Ra8 63.Rg2 Ra6 64.Re2 Rga8 65.Rg2 Rf8 66.Re2 Rf7 67.Rg2 Rb6 68.Rf2 Rf8 69.Rh2 Rb7 70.Rf2 Ra7 71.Rg2 axb4 



The fifty-move rule states that a player can claim a draw if no capture has been made and no pawn has been moved in the last fifty moves. Fruit 2.1 assesses itself as better, and, although it can not figure out a breakthrough, it does not want to give up the 1/2 point.

72.axb4 Raa8 73.Re2 Ra6 74.Rg2 Rf7 75.Re2 Ra8 76.Rg2 Re8 77.Re2 Ref8 78.Rf2 Rb8 79.Rh2 Rg8 80.Re2 Re8 81.Rg2 Ra8 82.Rh2 Rd8 83.Rf2 Rdf8 84.Re2 Rg8 85.Kh3 Ra8 86.Kg3 Rff8 87.Rg2 Rae8 88.Rf2 Rb8 89.Rh2 Rbc8 90.Rf2 Rcd8 91.Rh2 Rb8 92.Rc3 Rb7 93.Rd3 Rb6 94.Rf2 Rg8 95.Ne7 Re8 96.Nf5 Rf8 97.Re2 Rg8 98.Rh2 Ra6 99.Rf2 Raa8 100.Re2 Rgd8 101.Rf2 Rd7 102.Rg2 Ra6 103.Bf6 Rf7 104.Bb2 Ra7 105.Rh2 Rb7 106.Rg2 Rb6 107.Re2 Rd7 108.Rf2 Rb8 109.Rh2 Re8 110.Rg2 Ra8 111.Rh2 Rf8 112.Rf2 Rg8 113.Rh2 Rdd8 114.Rf2 Rb8 115.Rh2 Rb6 116.Rf2 Rb7 117.Rh2 Rbb8 118.Ne7 Rge8 119.Nc6 Rb6 120.Rg2 Kg8 121.Rf2 



Black is bumping up against the 50-move rule again. Perhaps its programming has a "contempt factor" built in, that prohibits it to offer a draw in this kind of situation. Of course, one way to get by the 50-move rule here is to play 121...Nxb2. Instead, Fruit 2.1 sacrifices the exchange.

121...Rxc6 122.dxc6 Ra8 123.Rd5 Ra7 



I expected that Fruit 2.1 would continue with its sacrifice-the-exchange plan and grab the extra pawn, i.e. 123...Ra6, and if 124.e5, then 124...Nxe5 125.Bxe5 dxe5 126.Rxe5 Rxc6 and my buddy, Komodo 10, sees the position as even.

Stockfish now shows the kind of creativity we expect from Jerome Gambit players.

124.e5 Ne3 

This does not work, as Stockfish is ready for it.

125.Rxd6 cxd6 126.exd6 

Suddenly, the "Jerome pawns" make their appearance. Despite the fact that Black has two extra Knights, White is better.

126...Nd5 127.Re2 Ra8 128.Re5 Nxb4 129.c7 Na6 



130.c8=Q+ Rxc8 131.d7 Rd8 132.Re8+ Kf7 133.Rxd8 Ke7 134.Ra8 Nb8 135.Rxb8 Kxd7 



White is clearly winning, but some programs don't resign, they wait until they are checkmated.

136.Rh8 Na5 137.Rxh6 Nc4 138.Rg6 Bc2 139.Rxg5 Nxb2 140.Rxb5 Na4 141.Rb7+ Kc6 142.Rb4 Nc5 143.Rc4 Bd3



144.Rxc5+ Kxc5 

Black has an extra piece, while White has extra pawns, an echo of the position 100 moves earlier.

145.f4 Kd6 146.f5 Ke7 147.Kf4 Bc4 148.g5 Bg8 149.g6 Be6 150.fxe6 Kxe6 151.h6 Kf6 152.g7 Kf7 153.Ke5 Kg8 154.Kf6 Kh7 155.Kf7 Kxh6 156.g8=Q Kh5 157.Qg3 Kh6 158.Qh4 checkmate

Friday, July 24, 2020

Jerome Gambit: Looks Simple, But It Is Not


In the following Jerome Gambit (1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.Bxf7+) game, the same player from the previous post again tries his best against the "annoying" or "silicon" defense. The line the players explore looks simple, but it is not. 

Anonymous - Anonymous
1 move / 3 days, Chess.com, 2020

1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.Bxf7+ 



4...Kxf7 5.Nxe5+ Nxe5 6.Qh5+ Ke6 



7.f4 d6 8.fxe5 dxe5 



White has one pawn for his sacrificed piece.

Black's King is annoyingly safe in the center, but White will try batting him around a bit.

This defense was seen as early as the 1993 match between Micah Fisher-Kirshner and the computer program KnightStalker (an early version of ChessBase's Fritz, marketed in the US).

9.Qh3+ Kd6 10.Qd3+ Ke7 11.Qg3 Kf6 



Up until Black's last move, we have been following games where Black was played by computer programs Comet B50, Demon 1.0, Fritz 8, Junior 7, Knightstalker, La Dame Blanche 2.0c, Rybka (v.1 and 2.3.2a), and Zarkov 4.7. None of them chose the move in the game.

What's the problem with the move? Because Black does not want to give up a pawn (11...Kf7 12.Qxe5) he allows the Rook to come to f1, with a check that requires another King move.

12.Rf1+ Ke6 

What is going on?

Well, it's probably not a good idea for White to go pawn-grabbing with 13.Qxg7, as Black not only has the development 13...Nf6, with an even game, he has the sharp riposte 13...Qh4+, when 14.Kd1 Qh5+ 15.Ke1 Qg6 forces the exchange of Queens, and Black's development, activity and Bishop pair give him a clear advantage.

Because computers almost always see White as worse in the Jerome Gambit opening, they constantly look for drawing lines as "best", and, here, Komodo 10 offers one: 13.Qb3+ Kd7 14.Qb5+ Kd6 15.d4 Qh4+ (necessary to move the Queen, otherwise 15...Bxd4 16.Qd5+ Ke7 17.Rf7+ wins it) 16.Rf2 Bxd4 17.Qd5+ Ke7 18.Qf7+ Kd6 19.Qd5+, etc.

So, it's not surprising that White, instead, gives the enemy King another kick, even if it's not objectively the best move.

13.Qg4+ Kd6 14.Qxg7

This capture has its risks. The Queen would probably be safer on g3, but White is not seeking out safety.

14...Ne7 

Protecting the safe Rook. However, after 14...Qh4+ 15.Kd1 Bg4+ White's position would be a mess. 

15.d4 Bxd4 16.c3 

White is still playing with only a couple of pieces, but Komodo 10 rates him as having a slight edge, especially after the recommended return of a piece with 16...Ng6. The reasonable alternative, which Black plays, leads to a difficult position for the defender.

16...Bb6 17.Bg5 

You can almost hear White saying "Gotcha!"

17...Re8 18.Na3 

This Knight means trouble.

18...Be6 

Black needed to try 18...Bg4, but 19.Nc4+ Kc6 (other moves are worse) 20.Qf7 would force him to return a couple of pieces, i.e. 20...Bf2+ 21.Rxf2 b6 22.Nxe5+ Kb7 23.Nxg4.

White's next move settles everything.

19.O-O-O+ Kc6 20.Rxd8 Raxd8 21.Qxe5 Bxa2 22.Qb5+ Kd6 23.Rf6+ Be6 24.e5 checkmate





Thursday, October 3, 2019

Jerome Gambit: Some Seriousness

Image result for free clip art serious


Defending against a "refuted" opening like the Jerome Gambit is easy - until it isn't. It is not good enough to just play the "right" moves. The followup moves also have to be correct. And the ones after those. Until you get to the playing level where people look at your game and mumble "and the rest is a matter of technique", you would be well advised to treat the Jerome with some seriousness.

Wall, Bill - Anonymous
lichess.org, 2019

1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.Bxf7+




4...Kxf7 5.Nxe5+ Nxe5 6.d4 Bxd4 7.Qxd4 d6 



8.O-O Nf6 9.Nc3 Re8 10.Bg5 Kg8 



We have an ordinary Jerome Gambit position: Black has a piece for a pawn, and has prudently castled-by-hand, while White has pressure on f6, and hopes to get his "Jerome pawns" rolling with f2-f4.

11.Nd5 

An alternate was 11.f4, e.g. 11..c5 (or 11...Nc6 12.Qd3, as in Wall,Bill - Foman, Chess.com, 2010 [1-0, 22]  or 12.Qa4 as in Wall,Bill - U80, PlayChess.com, 2016 [1-0, 29]) 12.Qd2 Nf7 13.Rae1 Bd7 14.e5 dxe5 15.fxe5 Rxe5 16.Rxe5 Nxe5 17.Qe1 Ng6 18.Nd5 Be8 19.c4 Bf7 20.Nxf6+ gxf6 21.Bxf6 Qd3 22.b3 Re8 23.Qf2 b6 24.Bb2 Qe3 25.Qxe3 Rxe3 26.Kf2 Re8 27.Rd1 Ne5 28.Bxe5 Rxe5 29.Rd7 a6 30.g4 b5 31.cxb5 axb5 32.a4 bxa4 33.bxa4 c4 34.Rd1 c3 35.Rc1 Rc5 36.Ke3 Bb3 37.Kd4 Rc4+ 38.Kd3 c2 39.a5 Rc5 40.a6 Ra5 41.Kc3 Ba4 42.Kc4 Rxa6 White resigned, Komodo 5 - Wall/Rybka, Florida, 2018.

11...Ned7

Overly cautious, perhaps anticipating f2-f4. Better was 11...Be6, as in Wall,Bill - Guest4809124, PlayChess.com, 2013 (0-1, 41).

Now, White gets to pull off a small tactic. 

12.Qc4 Kh8 13.Nxc7 Rb8 14.Nxe8 Qxe8 15.Qc7 Ra8 



White has a Rook and 2 pawns for 2 pieces. Stockfish 10 says that is plenty enough for a clear advantage, but there is still work to be done.

16.Rad1 Qxe4 

Black cannot afford this pawn grab.

17.Rfe1 Qc6 18.Qd8+ Ng8 19.Re8 Ndf6 



A slip, but defense was difficult.

20.Bxf6 gxf6 21.Qxf6 checkmate



Nice.

Saturday, December 29, 2018

Jerome Gambit: A Positional Dance

I have struggled to appreciate the Human + Computer vs Computer Jerome Gambit games that Bill Wall has sent me, and this has slowed my presentation of some of them. (For an over-all look, see "Jerome Gambit: Centaurs".)

I suppose that I had expected a series of one-sided crushes, revealing brutal new Jerome Gambit refutations and uncovering scintillating dynamic defenses. It didn't turn out that way - at times the game looks like a positional dance. Let's take a look.

Wall/Stockfish - Crafty
centaur match, 2018

1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.Bxf7+ 



Okay, we all should be expecting a win for White - Stockfish is a higher-rated computer program than Crafty, and it is partnered with Bill, who is pretty knowledgeable when it comes to the Jerome Gambit.

4...Kxf7 5.Nxe5+ Nxe5 6.Qh5+

Bill played two games with White with Critter as his partner, two with Houdini, two with Rybka, and two wth Stockfish. Each time, he played one 6.Qh5+ game and one 6.d4 game. (6.Qh5+ scored 2 - 4 - 2, while 6.d4 scored 2 - 5 - 1.)

6...Ke6 7.f4 Qf6 

Interesting: Black avoids 7...d6, which I have called the annoying or silicon defense, because it annoyingly drains much of the dynamism out of the position, and because it has been a primary choice of computer programs.

The Database has 208 games with 7...d6, with White winning 54% of the time. Instead, it has 133 games with 7...Qf6, with White winning 56% of the time.  

8.Rf1 g6

Even computers like to kick the enemy Queen, but 8...d6, working toward development, is probably a little bit better.

9.Qh3+ Ke7 10.fxe5 Qxe5



White has to be careful here (he cannot castle, Black threatens the pawn at e4) and probably should not go into this line without some preparation. That is one suggestion that 6...Qf6 might have been a "book" move inserted by a knowledgeable human.

11.Qf3 Nf6 12.Nc3 c6

The computers tut-tut at this move, which keeps White's Knight off of d5 and prepares ...d7-d5, preferring the more complicated 12...Bd4. They still give Black the advantage after the text.

13.Ne2

Wow. This move has a tactical justification that comes from silicon thinking. Of course, now, 13...Qxe4? would blunder a piece to 14.Qxf6+. It takes a bit more work, however, to see that 13...Nxe4 is met by 14.d4 Bxd4 15.Bf4!?, when 15...Qa4+ 16.c3 d5 17.Nxd4 allows White to recover his sacrificed piece, with a roughly equal game. "Equal", as in mutually complicated; not "drawn".

Instead, a decade ago a couple of computers fought it out after the solid 13.d3 -   13...Bb4 14.Bd2 d6 15.d4 Qe6 16.O-O-O Ng4 17.d5 Qg8 18.Qg3 Ke8 19.dxc6 bxc6 20.Nb5 cxb5 21.Bxb4 Ne5 22.Rxd6 Nc4 23.Qg5 Nxd6 24.Qe5+ Qe6 25.Qxh8+ Kd7 26.Rd1 h5 27.Rxd6+ Qxd6 28.Bxd6 Kxd6 29.Qd8+ Black resigned, Fritz 8 - Fritz 5.32, D1N5TWD1, 2008

13...Rf8 14.d4

I (sort of) warned you about this move (and the next) in the previous post.

14...Bxd4 15.Bf4 Qc5

It was okay, instead, to take the e-pawn with 15...Qxe4 16.Qxe4+ Nxe4 17.Nxd4, as after 17...g5!? the game would resolve itself into a pawn-plus Queenless middlegame favoring Black with 18.Be3 Rxf1+ 19.Kxf1 d5.

Interestingly enough, 17...d5 (instead of 17...g5!?) would have led to a human game where White ground down his opponent: 18.O-O-O Bg4 19.Rde1 Kd7 20.h3 Bf5 21.Bh6 Rf7 22.Nf3 Re8 23.g4 b6 24.gxf5 Rxf5 25.Nd2 Ng3 26.Rxe8 Kxe8 27.Rxf5 Nxf5 28.Bf4 h5  29.Nf3 Ke7 30.Ne5 Kf6 31.Nxc6 g5 32.Bc7 g4 33.hxg4 hxg4 34.Nxa7 g3 35.Nb5 Kg5  36.Bxb6 Kg4 37.a4 g2  38.Bg1 Kg3 39.a5 Nh4 40.Nd4 Kf4 41.a6 Nf3 42.Nxf3 Black resigned, Vlastous 2344 - Daboa 1799, Chessmaniac.com, 2016.

Black is still for choice, but this is how computer games go - a small slip here, a slight goof there... it all adds up.

16.O-O-O Be5 17.b4 

Again: Wow.

Black is close to stabilizing his position with ...d7-d6, so White has to do something.

17...Qb5 

This doesn't work. The other (stronger) computers suggest 17...Bxf4+ 18.Qxf4 Qxb4, when 19.Qe5+ Kd8 accents Black's uneasy King and unfinished development. Stockfish 9 then likes 20.Nf4, while Komodo 9 prefers 20.Nd4, both leading to a balanced game, or the slightest edge to Black.

A decade ago, a computer vs computer game saw this continuation: 20.Rxf6 Re8 21.Re6 Rxe6 22.Qxe6 Qf8 23.Qe5 Qe7 24.Qd4 b6 25.e5 Bb7 26.Nc3 c5 27.Qg4 Bc6 28.Qf4 h5 29.Nd5 Bxd5 30.Rxd5 Rc8 31.Qa4 Rc7 32.Qe4 Rc6 33.Qa4 Qe6 34.c4 Rc7 35.Qd1 a6 36.Qe2 Rc6 37.g3 b5 38.h4 bxc4 39.Qxc4 Qf7 40.Qb3 Kc7 41.Qd3 Kc8 42.Rd6 Rxd6 43.Qxd6 Qf1+ 44.Kd2 Qg2+ 45.Kc1 Qc6 46.Qd2 Kc7 47.Qa5+ Kb7 48.Qd2 Qe6 49.Qb2+ Kc6 50.Qg2+ Kb5 51.Qb7+ Ka5 52.Qc7+ Kb4 53.Qb7+ Kc3 54.Qb2+ Kd3 55.Qc2+ Kd4 56.Qb2+ Kd5 57.a3 Qg4 58.Qb7+ Kxe5 59.Qc7+ d6 60.Qe7+ Kd5 61.Qb7+ Ke6 62.Qb3+ Ke5 63.Qb2+ Qd4 64.Qe2+ Kd5 65.Qg2+ Qe4 66.Qd2+ Ke5 67.Qb2+ Kf5 68.Qb8 Qd3 69.Qc8+ Ke5 70.a4 Qc4+ 71.Kd2 Qxa4 72.Qc7 Qd4+ 73.Ke2 Qe4+ 74.Kf2 Qd3 75.Qe7+ Kd5 76.Qe8 Qf5+ 77.Kg1 Kd4 78.Qb8 Ke3 79.Qb3+ Qd3 80.Qf7 Kd2 81.Qa2+ Ke1 82.Qa5+ Qd2 83.Qa1+ Qd1 84.Qc3+ Ke2+ 85.Kh2 Qd4 86.Qa3 Qf2+ White resigned, Fritz 8-Fritz 5.32/D1N5TWD1 2008

18.Nd4 Bxd4 

Have to get rid of that annoying Knight, but the exchange opens up dark squares in Black's position. White is now a bit better.

19.Rxd4 

19...Kd8

Black's two problems are related: uneasy King and under-development. In the game he works to move the King to a safer place. He should have chosen, instead, 19...d5, unblocking the Bishop that blocks the Rook - a standard defense ailment in the Jerome Gambit. Then, after 20.Bg5 Bg4 21.Bxf6+ Kf7!? 22.Qf4 Kg8, White will probably be able to untangle his pieces, with an edge.

The problem is that White has a powerful response to the text move. 

20.Bd6

Remember when the doctor told you "Okay, this is going to hurt  a bit"?

20...Qg5+ 

What else?

21.Kb1 Re8

White now has a forced checkmate in 17 (!), but it is hard to find any acceptible alternative for Black.

Perhaps you are used to seeing computers display their brutal tactical skills, and this game is a good example of how many "positional" games are underlaid by tactical themes.  

22.h4 Qxh4 23.e5 Black resigned



Simply brutal. The more you look, the more painful it becomes for Black.