Finishing Things

On the last day of the decade,* it seemed appropriate to look at a rook ending that I played in my last bullet game of the year. A week ago I played a couple of bullet games, did well, and then decided I would try to get my bullet rating back above 1700. It required 160 games to achieve that feat. Along the way, I lost to a national master whose bullet rating was just under 1700. In the final game that lifted me over that milestone, I dropped a pawn early and was fighting for a draw well into the endgame.

Internet Opponent (1906) -- Stripes,J (1709) [A45]
Live Chess Chess.com, 30.12.2019

White to move

39.g5??

39.Rf7+- or Re5 or Rh7. White must protect the a-pawn to maintain the advantage.

39...Rb5= 40.g6

At first, Stockfish sees a slight advantage for White with a couple of alternatives, but as the search depth increases, the evaluation moves towards zero.

40.Rg7 Rf5+ (40...Rxa5 41.Kf2 Rc5 42.Kg3) 41.Ke1 Rxa5=;
40.Rxe4 Rxg5 41.Ra4 b6 42.axb6+ Kxb6 43.Kf2=

40...Rxa5 41.Rxe4

41.g7 Rg5 42.Kg1 a5 43.Kh2 Ka6 44.Kh3 a4 45.Rxe4 b5 46.Rg4

Black to move

Analysis Diagram

46...Rxg7 47.Rxg7 a3 48.Rg6+ Kb7 (or Ka7=; 48...Ka5 loses) 49.g3 a2 50.Rg7+ Kb6 51.Rg6+ Kb7=

41...Rg5 42.Re6

Black to move

42...b5

42...a5 43.Rd6
a) 43.e4 b6 44.e5 a4 45.Re7+ Ka6

White to move

Analysis Diagram

46.e6 (46.g7?? a3-+) 46...Rxg6 47.Ke2;
b) 43.Kf2 a4-+

43.Ke2 b4 44.Kd3 Rxg2 45.Kc4 Rg4+ 46.Kb3 a5 47.Ka4 Rg5

White to move

48.e4

48.Re7+ Kb6 49.Re6+ Kc5 50.Ra6 (50.e4 Rg3-+) 50...Kc4

White to move

Analysis Diagram

51.e4= (51.Rxa5?? Rxg6-+ 52.Rb5 Ra6+ 53.Ra5 Rxa5+ 54.Kxa5 b3-+)

48...Rg1 49.Kxa5 b3 50.Re7+

50.Ra6+ Kb7 51.Rb6+ Kc7 52.Rxb3 (52.Ka6++ Ra1+-+) 52...Rxg6=

50...Kb8

White to move

51.g7??

51.Re5= is the only move to hold the draw.

51...b2-+ 52.Re8+ Kc7

White to move

53.g8Q

53.Re7+ Kd6 54.g8Q Rxg8 55.Rb7 Ra8+ 56.Kb4 b1Q+-+

53...Rxg8 54.Rxg8 b1Q

We have reached an ending that I have attempted several times against the computer with mixed results.

55.Rg5

Black to move

55...Qxe4

55...Qe1+ is better 56.Kb5 Qe2+ 57.Ka4 Qxe4+

56.Rb5 Qa8+ 57.Kb4 Kc6 58.Rc5+ Kd6 59.Rb5 Qe4+ 60.Ka5

Black to move

60...Kc6

60...Qe2 finishes more quickly 61.Kb4 Qd3 62.Ka4 Kc6-+

61.Rb4 Qe1

61...Qd5+ 62.Ka6 Qa2+ 63.Ra4 Qxa4#

62.Ka4 Kc5 63.Rb5+

63.Rb2 is more stubborn

63...Kc4 64.Rb2 Qa1+ 0-1

Time was less critical than it might have been in bullet, as this game was played with a one second increment.



*I realize that some readers believe that the decade ends on 31 December 2020. This belief is grounded in mathematical consistency from the year 1. However, the notion of a decade is an artificial construct grounded not in mathematics but in human culture. Most people who are doing ten-year retrospectives are doing them now, not one year from now. The Western calendar has changed several times over the past two millennia. The years 1 CE and 1 BCE are rooted in speculative dating of events that more than likely took place four to seven years earlier. When the digit in the tens place advances to another number seems like the most logical time to reflect on the previous ten years, and that is what most people do.

Instructive Failures

In a ten minute game online yesterday, my opponent blundered away a winning position. Another blunder gave me the edge, but then I returned the favor. Later, I could have held the draw with a move that I rejected as losing. Instead, I played it safe and my opponent gave me another chance to win.

The errors strike me as instructive.

Black to move

Stripes,J (2000) -- Internet Opponent (2036) [B01]
Rated Rapid game LiChess, 19.12.2019

40...Re8??

Rooks belong behind passed pawns, but in this case, the rook becomes immobile.

40...Ra5!-+

41.Ra3= Ra8 42.Ra6

Black's rook cannot do much.

42...Kf8 43.Kg4 Ke7 44.f5 h5+ 45.Kg5 gxf5 46.Kxf5 Kd7 47.Kf6=

Black to move 

Black has more pawns, and they seem marginally better. On the other hand, White's rook is more mobile and his king is well placed. Black seems to have two clear ways to hold the draw: 1) hang on to the f-pawn, or 2) eliminate White's g-pawn.

47...Kc7??

1) 47...Ke8 48.Kg5 Ke7 49.Kxh5 f5 50.Kg5

Black to move

Analysis Diagram

Now, Black must eliminate the g-pawn. 50...Rg8+ 51.Kxf5 Rxg2 52.h5 Rf2+ 53.Kg6 Rg2+ 54.Kh7=

2) 47...Rg8

Eliminating the g-pawn immediately shows recognition that the game should be drawn. When a player had a clear advantage a few seconds earlier, the transition to understanding the game is drawn can be difficult.

48.Rxa7+ Kd6

White to move

Analysis Diagram

49.Kxf7 (49.Ra2 Rg4 50.Kf5 Ke7 51.Re2+ Kf8) 49...Rxg2 50.Ra5 Rg4 51.Rxh5 Re4=

Back to the game as played, and another instructive variation.

48.Kxf7+- Kb7

48...Kd7 is an interesting try.

White to move

Analysis Diagram

49.g4 is the only winning move. 49...hxg4 50.h5 g3 51.h6 g2 52.Rg6 Rh8 53.Kg7 Rc8 54.h7+-

49.Ra5 Kb6 50.Rxh5

Now, it is White who has more pawns. Moreover, White's advantage in number of pawns is decisive with a better king position.

50...a5 51.Rf5 a4

White to move

52.g4??

Throws away the win.

52.h5 a3 53.Rf1 Ra7+ 54.Kg6+-
52.Rf1 is also winning.

52...a3= 53.Rf1 Ra4 54.Rg1 a2 55.h5 Rxg4

White to move

56.Ra1

I looked at 56.Rxg4 and thought it was losing. However, White can hold against the queen. 56...a1Q= 57.h6 Qh8

White to move

Analysis Diagram

58.Rg7 White's pawn is protect by a fork. 58...Qxh6 59.Rg6+

56...Rh4 57.Kg6 Rh2 58.h6 Kb5 59.h7 

Black to move

Kb4??

Still playing for a win, Black loses.

59...Rg2+ 60.Kf6 Rh2=

60.Rxa2! Rxa2 61.h8Q+- 1-0

Black played on until I managed to win the rook.

Queen versus Knight

Winning with queen versus knight is an elementary skill, but it is easy to falter with the wrong plan. This morning, I struggled briefly with a position that resulted from misplaying a bishop and pawn versus knight ending that I found in Rashid Ziyatdinov, GM-RAM: Essential Grandmaster Knowledge (2000).

White to move

1.Be5

Obvious first move--trap the knight.

1...Ke7 2.Kc5 Kd7 3.Kb5 Ke7 4.Kc6 Kf7

White to move

5.d6 Ke6 6.d7

6.Bd4 would have simplified matters. 6...Nf4 7.d7 Ke7 8.Bc5 and attempting to occupy the promotion square leads to a quick checkmate.

6...Kxe5 7.d8Q Nf4

White to move

I reached this position thinking it would be easier than it was. It became clear that I could use some work on elementary skills.

Elements of the Game of Chess

After several efforts, then engine checking, followed by further practice, I began to see some patterns. I then remembered an old textbook that had some exericises, William Lewis, Elements of the Game of Chess (1822). In "Lesson One" (August 2017), I discussed the merits of Lewis's approach to elementary checkmates with the queen. Queen vs. knight is the next chapter in his book.

Lewis's first position is instructive, and his solution is very close to what chess engines reveal today.

White to move

Lewis
Queen vs. Knight, 1822

1.Qd4+ Ke6 2.Ke4

Black to move 

2...Ng6

Lewis gives the variation 2...Nc6 3.Qd5+.
The engine shows that 2...Nf7 holds out one move longer.

3.Qb6+

Lewis's technique takes one move longer than the engine's top two choices.

3...Kf7 4.Kf5 Ne7+ 5.Kg5 Nd5 6.Qd6 Ne7 7.Qf6+ Ke8 8.Qe6 Kd8 9.Kf6 Nc8

White to move

10.Qc6 Na7

10...Ne7 11.Qd6+

11.Qb6+ 1-0

Lewis treats his readers to two more positions. In both cases, White has a knight-winning fork on the second move.

White to move

My students will be seeing these positions this coming week.

Crushing Attack

In my coaching this week, I've been drawing on Encyclopedia of Chess Miniatures (2015),  by Branko Tadić and Goran Arsović. For example, one student who works with me individually chose the Queen's Gambit, and we quickly went through six games that began 1.d4 d5 2.c4 c6. This afternoon at an after-school chess club, the students chose the starting moves 1.c4 Nf6 2.Nf3 e6. It took me a few minutes to find a game with these moves, and they were played in a different sequence. The winning combination proved to be quite instructive.

Stefanova,Antoaneta (2546) -- Dzagnidze,Nana (2550) [A13]
Doha FIDE GP (Women) 6th Doha (7), 01.03.2011

1.Nf3 Nf6 2.c4 e6 3.g3 d5 4.b3 d4

White to move

Here I asked the students for suggestions. We continued looking for moves that White should consider.

5.e3 Nc6 6.Bg2 e5 7.0-0 Bg4 8.h3

A young chess player suggested this plan.

8...Bh5 9.g4 Bg6 10.exd4 e4 11.Nh4 Qxd4 12.Nc3 0-0-0

White to move

13.Nxg6

I suggested that pressure along the h-file might become a problem.

13...hxg6 14.g5 Nh5 15.Rb1

Black to move

15...Kb8

We looked at the possibility of playing 15...Nf4 here. The fork, 16.Qg4+, does not win a knight, but the pin gives White a tempo.

16.Bb2 Nf4 17.Nd5

Black to move

This position is given a diagram in the Encyclopedia. I told the students that I liked White's position, and they spent a fair amount of time trying to imagine the brilliant move that Black played. No one found it.

17...Rxd5 18.Bxd4 Rxg5 0-1

We spent ten minutes trying to stop checkmate. Nothing helped. Sacrificing the queen seems to delay, but not prevent the king's capitulation.

Playing Well

This game began at the end of July and finished two weeks ago. I spent a considerable amount of time playing it and am happy with my performance.

Stripes,J. (2242) -- Internet Opponent (2189) [D11]
Chess.com, 28.07.2019

1.d4 Nf6 2.Nf3 d5 3.c4 c6 4.e3

Why choose the second most popular move? In this case, my intention was to gain experience. I seem to recall also that my opponent's game history showed that he sometimes faltered against this line in the past.

4.Nc3 has been my normal move OTB, but I have played others.

4...Bg4 5.h3 Bxf3 6.Qxf3

I had the Black side of this position in two blitz games nearly twenty years ago, but this game was was my first experience from the White side.

Black to move

6...e6 7.Bd3

PowerBook shows a 62% scoring percentage for White.

7...Nbd7 8.Nc3 Bd6 9.cxd5 exd5 10.g4

Still playing the percentages. 66.7% for White.

10...Nb6

My opponent chooses an obscure move that has produced a handful of draws. The percentages no longer have any significance: too few games.

White to move

11.g5

11.Bd2 was the alternative and I examined four games where this move had been played.

11...Nfd7

Two previous games games have reached this position.

12.e4

12.h4 led to a win for White. 12.e4 led to a draw. However, 12.e4 looked more promising to me because the imbalance in the reference game seemed to offer better prospects for seeking a win.

12.h4 Qe7 13.Bd2 Nc4 14.Bxc4 dxc4 15.Ne4 Bb4 16.a3 Bxd2+ 17.Nxd2 Qe6 and White went on to win a long game. Dvirnyy,D (2543) -- Gomez,J (2492) Baku AZE 2016.

12...dxe4

12...c5 13.dxc5 Bxc5

13.Qxe4+

13.Bxe4 might be better, according to postgame engine analysis. I probably looked at it, but opted to follow my reference game. More often than not in my correspondence experience, my opponent deviates from a single reference game before I do. Sometimes the novelty is an error.;
My notes show that I considered  13.Nxe4 Bb4+ 14.Nc3.

13...Qe7

White to move

14.Qxe7+

I chose to continue following the reference game.

14.Be3 Qxe4 15.Bxe4 0-0-0;
14.0-0 0-0-0 would have led to an interesting battle, but I thought Black was better.;
14.a4 was also a move that I considered.

14...Bxe7 15.Be3 0-0-0N

Now we are on our own.

15...Rd8 16.0-0-0 Nf8 17.h4 Ne6 18.Be2 Nc7 White's isolani may become weak and it is hard to see how the bishop pair will prove advantageous. These moves were played in a game that was drawn after 69 moves, Likavsky,T (2494) -- Antoniewski,R (2510), Austria 2008.

16.0-0-0

16.0-0 strikes me as a candidate move, as does 16.a4 with the same idea: storm the opponent's castled king while withstanding the same from him.

16...g6 17.h4 Nf8

Even though we have departed from theory, this knight maneuver has been played before. It makes sense to bring pressure upon White's queen pawn.

White to move

18.Kb1

I was not sure how to proceed, so I made a waiting move.

18...Ne6 19.Be4

Is d4-d5 a threat? I'm not certain.

19...Nd5?!

I do not think that opening the c-file is in Black's interest. However, after this move my d-pawn becomes slightly less vulnerable, I may be able to use the c-file for my rooks, and Black also gets an isolated pawn.

20.Nxd5 cxd5 21.Bf3 Kb8 22.Bg4

I want to push my f-pawn

22...Bd6 23.Rd3 Nf4?

White to move

24.Bxf4

I happily give up the bishop pair for gain of a pawn.

24...Bxf4 25.Rf3 Bc7

White to move

26.Re1!

Black's f-pawn is going nowhere. I will get a pig.

26.Rxf7 Rdf8 27.Rxf8+ Rxf8 28.f3 looked drawish to me.

26...Bb6

26...Rhe8 27.Rxe8 Rxe8 28.Rxf7 Rh8 29.Be6

27.Rxf7 Bxd4

27...Rdf8 28.Ree7 Rxf7 29.Rxf7 Bxd4 30.Be6

White to move

28.Ree7 1-0

I like my position, but I don't think my opponent should have resigned so soon. I was rather looking forward to the endgame.

Positions from Recent Lessons

[T]actics flow from a positionally superior game.
Bobby Fischer, My 60 Memorable Games (1969)

My posting here has been sporadic lately. Between work and home maintenance, I've barely had enough time in the woods for hunting. As a consequence, there is no time for writing. Nonetheless, I've been teaching several individual students and running an after-school chess club. The positions below are from some classic games that were part of my instruction in October.

White to move

William Steinitz (still spelled Wilhelm at the time) did not make the computer's choice here, but it was a decisive move that forced matters. It also set up the theme for the next two positions. From Steinitz -- Mongredien, London 1862.

White to move

From Steinitz -- Mongredien, London 1863.

White to move

This was the position where Fischer made the comment in the epigraph above. From Fischer -- Sherwin, 1957.

Foolishness

One year ago, I won the Eastern Washington Open. This year, I finished second in A Class with 3.5/5.0. I won three games, lost one, and took my usual third round bye. My loss was to a young girl who I played in the first round last year. She finished with 4.0 and a tie for second place in the event.

I gave her an easy game because I engaged in some foolishness.

Deng,Lily -- Stripes,James [B43]
Eastern Washington Open (2), 28.09.2019

1.e4 e6 2.d4 c5 3.Nf3 cxd4 4.Nxd4 a6 5.Nc3 Qc7 6.Be2

Black to move

6...Bb4

I play this move because it has brought me success in blitz.

6...Nc6 is the normal move.

7.Bd2

7.0-0 Nf6 8.Qd3 Nc6

7...Nf6 8.Bf3

8.0-0 Nc6
(8...Bxc3 9.Bxc3 Nxe4 is a line that makes a virtue out of 6...Bb4, as in Fuchs,J (2197) -- Farago,I (2482), Nuremberg 2008, which Black went on to win after a long battle. )
9.Nxc6 bxc6 10.Bd3 a5 11.Qe2 d5 12.a3 Be7 Nezhmetdinov,R -- Furman,S/Moscow 1957, URS-ch was drawn in 31 moves.

8.Bd3 Nc6 9.Nxc6 dxc6

Black to move

8...Qe5?!

Emboldened by the odd placement of White's bishop, I put my queen where I knew she could be vulnerable.

8...Nc6 is simple and correct.

9.Nde2 Nc6

9...g5 at least makes sense.

10.a3

Black to move

10...Ba5??

10...Be7 11.Bf4 Qa5 12.b4 Qb6;
10...Bxc3 11.Bxc3 Qc7

11.b4+- Bb6 12.Bf4 0-1

I was home early.

Do Something Useful

While looking at an exercise in Imagination in Chess (2004) with one of my students, a part of the solution given stuck in my memory and then entered my consciousness while playing a rook ending a week later. The exercise was an endgame position from Polovodin -- Ivanov,A., Leningrad 1988. Paata Gaprindashvili commented, "Polovodin makes a useful move, while his opponent is denied such a possibility" (179).

Stripes,James (1851) -- Internet Opponent (1880)
Live Chess Chess.com, 20.09.2019

White to move

23.f4?!

This move exposes my king--probably not a good decision

23.Rc8 Rbd7 24.Rxd8+ Rxd8 25.Rc6 h6 26.Rxa6 Rd5

23...Rbd7 24.b4 g6

24...Rd1+ 25.Rxd1 (25.Kg2 R8d2+ 26.Kh3 Rxc1 27.Rxc1 Kf8) 25...Rxd1+ 26.Kf2 g5

25.R1c2 Rd4

25...Rd1+ 26.Kf2 R8d2+ 27.Kf3

26.a3 Rd3 27.R5c3

The game seems headed for a draw, but there are some things that can be tried.

Black to move

27...h5 28.Kg2 Kg7 29.Kf2 R8d7 30.Ke2

The king is a fighting piece. At this point, I felt that I could at least do something that offered my opponent problems or opportunities to go astray.

30...R3d4 31.h4

Black to move

31...Ra7?

And he went astray.

31...Re4+ 32.Re3 Red4 (32...Rdd4?? 33.Rxe4 Rxe4+ 34.Kd3 Re1 35.Kd4) 33.Rc6 Rd2+ 34.Kf3 Ra7

32.Ke3?

But I failed to capitalize on the error.

I could have played 32.Rc7 Rd7 33.Rxd7 Rxd7 34.Rc6 Ra7 35.Kd3

32...Rdd7 33.Rd3 Rxd3+ 34.Kxd3 a5 35.bxa5 Rxa5 36.Rc3 Ra4 37.Rb3

Black to move

37...Ra5?

Another error.

37...Kf8;
37...f6

38.Kc3?

Again, failing to capitalize. This move presents Black with a problem, but one that can be solved.

38.Kd4+-

38...f6?

38...Ra4 was the only move.

39.Kb4+-

Black to move

The fork is decisive.

39...Ra4+

39...Ra8 40.exf6+ Kxf6 41.Kxb5

40.Kxb5 Re4 41.exf6+ Kxf6 42.a4

It does not appear that Black has any way to stop this pawn. My game has become much simpler.

42...e5 43.fxe5+ Rxe5+ 44.Kc6 Kf5?

Black hastens the end by allowing a pin that forces rooks off the board.

White to move

45.Rb5 Rxb5 46.axb5 Kg4 47.b6 Kxg3 48.b7 Kxh4 49.b8Q

49.Kd5

49...g5 50.Qh2+

50.Kd5

50...Kg4 51.Kd5

51.Qe2+ Kh4 52.Kd5

51...h4 52.Ke4 Kh5 53.Kf5 g4 54.Qe2

54.Qb8 is a faster mate by one move.

1-0

Sometimes, it is helpful to simply keep playing chess in an equal position.

Fidelity Chess Challenger

Several years ago, my wife's uncle gave me an old stand alone chess computer, Fidelity Chess Challenger. Last night, I searched and found an instruction manual online for Chess Challenger 7, which appears to have the correct instructions. I played a game on its top level--level 7. Based on research presented in the HIARCS chess forum, I believe the device was manufactured in 1980.

In the image above, the machine has played its move as O-O-O by indicating that it moves its king from e8 to c8. That move puts my king in check.

In my game, I played quickly while also reading a book. On its top level, Chess Challenger requires several minutes per move for most moves. I was reading in another room, would read a page or two, and then check on the machine. I recorded the moves on another device that allowed me to quickly email the completed score to myself.

Chess Challenger played a decent opening, reached a winning position in the middle game, and then revealed substantial weaknesses in endgame understanding. It demonstrated understanding of exploiting a pin, and using forks. It also set a simple stalemate trap near the end of the game.


Stripes,James -- Fidelity Chess Challenger [C68]
14.09.2019

1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Bxc6 dxc6 5.d4

Probably a weak move on my part. I rarely play the Spanish Opening, and the exchange variation is not my usual choice when I do.

5...Bg4

5...exd4 6.Qxd4 Qxd4 7.Nxd4 seemed okay to me.

6.dxe5 Qxd1+ 7.Kxd1

This is the position in the photograph.

7....0-0-0+ 8.Ke2

Black to move

8...Bc5

This move struck me as odd.

8...Re8 9.Bf4 f6 10.Nbd2 fxe5 11.Bg3 Nf6 12.Rhe1 Bd6 (a later game continued 12...Nh5 13.Kf1 Nxg3+ 14.hxg3 Bc5 15.Nc4 Rhf8 16.Ncxe5?? Rxe5 17.Re2 Rh5 18.Rd2 0-1 Luptak,P (2086) --nZvarik,M (2245), Slovakia 2010.) 13.Kf1 Nh5 14.Kg1 Nxg3 15.hxg3 h5 Black won in 61 moves Aleksandrova,D (2015) -- Yilmaz,G, Albena 1977.

8...f6 9.h3 (9.Nbd2 Re8 10.h3 Bh5 11.Nf1 fxe5 12.Ng3 Bg6 13.Be3 Nf6 14.Nd2 Nd7 15.Rhd1 Be7 16.f3 Rhf8 White won in 54 moves Kieninger,G (2509) -- Rellstab,L (2478), Bad Oeynhausen 1941) 9...Bxf3+ 10.gxf3 fxe5 11.Bd2 Ne7 12.f4 exf4 13.Bxf4 Ng6 14.Bg3 Re8 15.Nd2 Bd6 Black won in 46 moves Babula,M -- Dobrovolsky,L, Brno 1969.

9.Be3 Bxf3+

This move does not exist in my database.

9...Bxe3 10.Kxe3 f6 11.Nbd2 Re8 12.exf6 Nxf6 13.Rae1 Nd5+ 14.Kd4 Nf4 15.h3 Bh5 16.g3 Ne6+ 17.Kc3 Bxf3 18.Nxf3 Rhf8 19.Re3 Nc5 and Black went on to win a pawn ending after a lot of middle game manuevering in Toumaniantz,R (2162) -- Duflot,S, Le Touquet.

If there was any sort of opening tree built into the software, it could have included moves from Lasker -- Pollock 1892.

9...Be7 My database shows four games with this move 10.h3 No other game in the database has this position. 10...Bh5 11.Nbd2 f6 12.Rhd1 fxe5 13.g4 Be8 and Black won in 42 moves Lasker,E -- Pollock,W, Baltimore 1892.

10.Kxf3

10.gxf3 might not be bad.

10...Bxe3 11.Kxe3 Nh6 12.h3 Rhe8 13.f4 f6

White to move

14.exf6??

14.Nc3 fxe5 15.g3 exf4+ 16.gxf4 Nf5+ 17.Kf3 Nd4+ 18.Kg3 Nxc2 19.Rad1 Black should win the ending;

14.g4! fxe5 15.f5 White's kingside majority is more dangerous than Black's queenside. Such endings, as I understand, are a principle reason for playing the exchange variation of the Spanish.;

14.Nd2 fxe5 15.f5.

14...Nf5+

I had underestimated this move, having mainly assured myself that I would not lose the rook on a1.

15.Kf2

15.Kf3 Nd4+ 16.Kg4 Nxc2 and Black wins material.

15...Rxe4

15...Nd4? 16.Nc3 Nxc2 17.f7 (17.Rad1 Rxd1 18.Rxd1 gxf6).

16.g3

I realized by this point that I was clearly worse.

16...gxf6 17.Nc3

Black to move

17...Re3?

I expected 17...Rd2+ 18.Kf3 Re8 19.Kg4 Ne3+ 20.Kh4 Rxc2-+

18.Rad1 Rxd1 19.Rxd1 Rxg3 20.Ne4

Black to move

20...Rxh3 21.Nxf6 Rh2+ 22.Kf3 Rxc2 23.Rg1 Nh4+

23...Kd8 24.Rg8+ Ke7 25.Ne4

24.Ke4

24.Kg4 Ng6 25.f5 Ne7 26.Nxh7

Black to move

This is the type of position I like putting in front of my students. Black is clearly better, but must find a plan to neutralize White's threats. For brute force calculation with limited depth, positional understanding is vital. Chess Challenger showed the weakness in its primitive programming at this point.

24...Rg2?

This move surprised me, as my f-pawn seems dangerous in the knight ending.

24...Ng6 Before playing Rg1, I had looked at 25.f5 Ne7 26.Rg7;

24...b5! avoids the checkmate threat and gives White queenside problems that cannot be met.

25.Rxg2 Nxg2 26.Nxh7

This move was not so much to grab the pawn, although useful, as to clear the f-file and control the promotion square.

26...b6

Chess Challenger's moves stopped making sense to me here. Prior to this point in the game, I had foreseen most moves.

26...Kd7 27.f5 (27.Ke5 Ne3 (27...Ke7 28.f5 Nh4) 28.b3 Ke7 29.Nf6) 27...Nh4 28.Kf4

27.f5

Black to move

27...Ne1??

This move is a game losing blunder that highlights that Chess Challenger is oblivious to the dangers presented by my passed pawn.

27...Kd7 or Kd8 are the only moves that do not lose. 28.Ke5 Nh4 29.f6 Ng6+ 30.Kf5=.

28.f6+- Nd3

28...Kd7 29.f7 Ke7 30.f8Q+

29.Kxd3

However, it is possible that the software saw 29.f7 Nc5+ 30.Kf5 Nd7 in which case the knight is still lost, but White does not yet have a queen and there is a lot of work to do to use the knight to convert a pawn minority into a passed pawn.

29...c5 30.f7 a5 31.f8Q+ Kd7 32.Nf6+ Kc6 33.a4 c4+ 34.Kxc4 Kb7 35.Qf7 Ka8!

I was impressed with the stalemate trap set here.

White to move

36.Kb5

36.Qxc7 b5+ 37.axb5 (37.Kxb5 stalemate) 37...a4 38.Nd5+-

36...Ka7 37.Qxc7+ Ka8 38.Ka6 b5 1-0

Chess Challenger made this move and then lit the "I lose" light.