text:
Can white do better versus the Sicilian Defense by avoiding an early d4?
Given that 1.d4 is said to produce better results than 1.e4 and about half of all 1.e4 games involve the Sicilian Defense, could a simple idea like avoiding trading the d pawn for black's c pawn in the Sicilian be used to produce better 1.e4 results?  Perhaps after 20 or 30 moves the d pawn will come in handy after all!

From the sidelines, most theoretically sound are those with Bb5. You can look at them, if it suits your style.

I'm not sure if "can white prove an advantage in the anti-sicilians" is answwerable in Stack Exchange format (or at all).

It's not the "trading the 1.d4"-pawn that causes the losses.

If you're strong at tactics, after you've played 1.e4, playing an early d4 to open up the game puts the burden of defense on Black to defend against these. Generally when you've played 1.e4 in an opening, your goal should be an early if sound d4 as well.  The same is true for Black after 1..., e5, i.e. to seek an early ..., d5 when sound. Playing a Closed Sicilian gives Black more time to build up a defense. And since Black generally plays a lot of early pawn moves in the Sicilian, that also gives White a time advantage which he can try to exploit tactically by an early opening-up of the game.  But as someone else has pointed out that Larsen had claimed, the standard "d" pawn for "c" pawn trade is giving up a center pawn for a less valuable off-center pawn, which can be positionally suspect. If you're well versed in the Sicilian lines and good at tactics, playing the standard early follow-up d4 would still seem to me to be the better course of action though.  Conversely, the Closed Sicilian may be better suited to someone who is not as strong tactically but plays a strong positional game.

All the main lines against the Sicilian are the open Sicilian.  This opening of the center gives white better attacking chances against black's lack of development.
Larsen claims that playing d4 is a positional mistake, allowing black to exchange a less valuable wing pawn for a center pawn.
Spassky played the closed Sicilian with great results.  And there are many anti-Sicilians which claims to give white the advantage.  The Grand Prix is the most fun, but I personally prefer the KIA.
The main difference between the open and closed Sicilians is the number of moves before the attacking begins.  The open offers more tactics right from the start.  The closed allows both players to finish developing before any attack really develops.
The real answer is that neither is necessarily good for white.  Since every line of the Sicilian is so heavily analyzed, the advantage goes to the player with the better knowledge and comfort in the positions.

There's also the Alapin Variation, where White aims to replace his d pawn with his c pawn instead of taking back with the f3 knight.

"The main difference between the open and closed Sicilians is the number of moves before the attacking begins" this is wrong. The main difference is how Black's plan change, and accordingly, White's plan as well. Also wrong that "The open offers more tactics right from the start".

The Alapin is considered an anti-Sicilian.With the open Sicilian, the pieces come into contact sooner, and therefore the attacking and the tactics start sooner.

You are certainly far from being the first person to raise the question. Alekhine, in his Collected Games, recommends in the notes to one game that White should play 3.Be2, but in all of his other games he actually plays 3.d4. There is a book called the Chameleon Sicilian by Andy Soltis that points to certain advantages of 2.Ne2, retaining the options of d3 or d4 depending on how Black responds. For example, if Black expects d3, and combines ..e6 with ..g6, then d4 becomes very strong. On the other hand, if ..d6, then d3 leads into lines where Black usually goes for ..d5.
One of the remarkable things about Chess is the balance inherent in the initial position. Typically White keeps a small but tangible advantage ("normal opening advantage") for about 20 moves, and nothing much has ever changed that. One could define the statistically best moves but in practice psychological comfort is more important. (and high winning percentages sometimes attach to the moves that strong players adopt versus weak opponents.)
As has been pointed out, avoiding d4 can cut down on the amount of book learning that is needed, but that cuts both ways. Strong Sicilian players just need to know one good reply to each of Whites offbeat attempts.

If you see in Chessgames.com then you can see the below openings e4 c5 Nf3 d6 which is pure Sicilian Najdorf in the Opening Explorer then you would be seeing the winning percentages of White Najdorf Winning Percentage
Now you can see that with d4,c3,Nc3,Bc4 white has the maximum percentage win even though the most number of games are with d4.
You can delay d4 if you find convenient for yourself and make some other move. What I feel is that you do not have a liking for Open Sicilian and want to deviate. So it is not a difficult choice either. There are other lines where different ideas also come into picture and honestly these Lines are easier to understand than open Sicilian .

What ELO threshold have you set? There is no way the second most played variation is 3.Bb5+ at hight level.

@GennaroTedesco Ask the people running chessgames.com. These are the raw stats from their database, and the Rossolimo has actually been a pretty popular guest at high-level games from time to time. It isn't really unsound, and I have a hard time seeing why there would be "no way" that it's the second most popular third move in the position.

Well, no opening is "unsound" if played well. I was just objecting that it is by no means the second choice at GM level, that's why I was asking whether you had selected particular ELO thresholds for the query.

@GennaroTedesco Ok then, after 1.e4 c5 2.Nf3 d6, which is the second most played move at GM level after 3.d4? There aren't that many popular candidates.

Bb5+ is definitely a choice but name me a top player till date who has ignored playing 3.d4 in Sicilian Najdorf . d4 has been the most popularised move till date . The real taste of Sicilian lies in d4 from White .

The practice of top players may not be very relevant to the participants on this site. We may learn from them but cannot aspire to imitate

Honestly the players of ELO 2100 plus and above also prefer the Open Sicilian.


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Please critique my game (Caro-Kann, Fantasy variation)
I'm an avid player of the caro-kann, yet I recently came across the Fantasy Variation for the first time. Although I won, I wanted to post my game for review:
[FEN ""]
[White ""]
[Black "Bad_Bishop"]

1. e4 c6 2. d4 d5 3. f3 Qb6 4. Nc3 dxe4 5. fxe4 e5 6. Nce2 {I knew we came out of book here, but I didn't know how to exploit it. I ended up trading pawns as my e-pawn was hanging} exd4 7. Nxd4 Bc5 8. c3 (8. Nde2?? {This simple line is interesting, as it shows the pressure on white's game even at an early stage} Bf2+ 9. Kd2 Qe3#) Nf6 9. e5 Bg4 {This move helps develop my queenside, as well as trading down against the isolated d-pawn} 10. Be2 Bxe2 11. Ngxe2 Nd5 12. Rf1? {White begins a kingside attack when his king is still stuck in the middle} O-O 13. h4 Nd7 {I wanted to open the centre and attack white's king. This move aims to either win the e-pawn, or provoke e6} 14. e6 fxe6 15. Nxe6 Rxf1+ 16. Kxf1 Be3? {My eyes lit up when I saw the possibility of a knight fork on e3, but there is no way to force it. My thinking here was just to lay a cheapo trap and hope for the best} 17. N2d4 (17. Bxe3?? Nxe3+) N7f6 (17...c5 {Immediately after playing 17...N7f6 I saw 17...c5 instead, but I don't think it works here} 18. Nxg7 Kxg7?! 19. Qg4+) 18. g4? Bxc1 {OK, it turns out 16...Be3 wasn't so poor, as I can remove the defender of g4 and win a pawn} 19. Qxc1 Nxg4 20. Qg5 {From this stage of the game, white is treatening mate, so almost all of the following moves have to be checks} Nde3+ 21. Ke2 Qxb2+ 22. Kd3 g6 23. Qe7 {I missed this move, as I thought white would play 23. Rg1} Qxc3+ {Forced, intending to trade queens and win a pawn} 24. Ke4 (24. Kxc3 Nd5+ {White should have opted for an inferior endgame rather than letting his king be pulled up the board}) Nf2+ 25. Ke5 (25. Kf3 Nd5+ {This shows the difficulty white is in. He either faces mate or large material losses}) Nc4+ 26. Kf4 (26. Kf6 Ne4#) Qe3#

My questions are:

How could black have played better?
I played 16...Be3 as a 'cheapo', which my opponent didn't fall for. What would have been better than 16...Be3?

The official name is Maróczy Variation. :) I wonder where that Fantasy name is coming from.

@toscho: The line has also been called the Tartakower variation too.

Tartakower in the CK is 1.e4 c6 2.d4 d5 3.Nc3 dxe4 4.Nxe4 Nf6 5.Nxf6 exf6.

What was wrong with 15...Bf2+ ?

@bof: Nothing wrong with 15...Bf2+ that I can see. The best response would be 16. Rxf2 Qxf2+ 17. Kd2 Rf7 when white has a tough game.

Not 17...Qe3+ & 18...Qxe6 ?

@bof: If black remains in white's camp then there are better mating chances. I'd prefer to keep the tension here, but each to their own.

You'd rather be up the exchange and "keep the tension", than be a whole rook up?

@bof: yep, but I like to make my opponents to squirm :-)

@fuxia: “Fantasy Variation” is the (only) name given to this opening in MCO12 (published in 1982), so the name has been around for a long time, though I don’t know where it originated. It seems to be the usual name nowadays. (GM Alexey Bezgodov, who has written a book on it, calls it the Extreme Caro-Kann - but that’s his own name, and very recent.)

On move 6, I'm not really sure why White didn't just play Nf3. After that, Black should play exd4 Qxd4 followed by (after Qxd4 Nxd4) just Bc5.
After Nce2, well surely exd4 makes sense, but I think Nf6 should have been considered, attacking the e4 pawn. Notice that anytime dxe5? is played then you have Bc5, with that mate threat that you already diagrammed (Bf2+ Kd2 Qe3#), so therefore you didn't have to give up the tension so early with dxe4. Nf6 develops and attacks e4 which is a critical point (a critical point is an unprotected piece/pawn or a piece/pawn with the same number of defenders and attackers on it. A critical point can also be a king or just like in the caters somewhere where you have weak squares and stuff. Attacking critical points is a key concept in torturing opponents or putting pressure in strategic chess).
By the way, I think Be3 is a medium good move... You are establishing a piece on the enemy's third rank or your sixth rank, which can be so strong in some middlegame positions that it is worth sacrificing an exchange for that piece and a pawn or something. The only other move I can think of is Re8, because there is a critical construction on the e-file with 2 knights on the e-file.
A critical construction is a rank, file, or diagonal where there are 2 or more pieces in opposition or just like a lot of pieces (regardless of color) on the same rank/file/diagonal. Critical constructions are very good for finding important tactics or defensive tactical resources that can involve double attacks, skewers, interference, etc. Therefore I think Re8 instead of Be3 makes a lot of sense. You are creating a lot of tension on the two knights and activating the rook.
Here is a sample line. 16...Re8 17. Nxc5 Nxc5 18. Nd4 Qa6+ 19. Kg1 (all other moves like Kf2 and c4 are just a worse version) Qd3 20. Bd2 (Qxd3? Nxd3 and now you are attacking 2 critical points which is the b2 pawn and c1 bishop, and you can take advantage of the critical construction on the second rank with Re2. On top of that, your knights easily get to the sixth rank or other strong squares) Ne4 21. Be1 Qe3+ 22. Kh1?! (Kh2 is just more accurate) Bxf2 23. Qxf2 and this should win, and all of White's lines were backed up by an engine.
P.s. On move 18 you missed ...c5, removing the defender of e6.
P.s. I think understanding critical points is something you mind as well learn anyway, and a technically possible answer to how you could have played this better. I think the opening was fine but you should have played Nf6 instead of exd4, because Nf6 develops while attacking a critical point which is e4, and you have a strong critical construction on the c5-g1 diagonal and tactical pattern if dxe5 which allows Bc5 and stuff.

On move 5, capturing with the knight is what I would've done. On move 6 as white, I would have pushed d5, ..cxd5 7. exd5 leading to an obviously good position for white. Move 8. defending with the bishop would put a counter attack on both attacking pieces and making an exchange in the center of the board means the black queen would run with free development. Using this you can point out some errors with black as well.

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What is the minimum number of pieces needed in a chess set to account for all possible promoted pieces?
How many pieces would be needed in a chess set where all possibilities for promoted pieces are included if pawns are no longer used after they promote?

I was playing a game on my phone called "Really Bad Chess" the other day and would love to have this set IRL :) Probably doesn't fit in a reasonable box really nicely though.

Let's count.
Starting set

2 rooks
2 bishops
2 knights
1 queen
1 king
(8 pawns)

Max promotions

8 rooks
8 bishops
8 knights
8 queens

Total
In total you would need 40 pieces and 8 pawns for each color, so 96 units for black and white together.
Edited to bullet format to "look" better.

Yes so 96 total pieces for white and black when including pawns as pieces.

No, just 64, right? Because 8 white and 8 black rooks, 8 white and 8 black bishops, 8 white and 8 black knights, and 8 white and 8 black queens. 8*8 = 64. Or did I misinterpret your question?

8 rooks or 8 bishops or 8 knights or 8 queens (for one side) so for both sides are 64, each promotion yields only one piece. But in practical games it is hard to promote all 8 pawns for each sides.

@SorinSolberg You need to add the starting set too (i.e. you need 10 rooks, 9 queens, etc.)

Oh of course... Okay I see.

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How do I get Stockfish to show notes like it does on Lichess?
I want to write a program to stop a chess game if Stockfish decides that checkmate is unavoidable for a player as a learning exercise. I downloaded Stockfish for Mac and it gives what it thinks is the best move but I can't figure out how to get it to show those more specific notes

Stockfish is an UCI chess engine, so you shouldn't mess up with the engine. You will need to write a new chess GUI.
Useful links:

https://www.chess.com/forum/view/general/chess-engines-amp-gui-uci
How do I use the analysis output of a UCI engine?
What is the optimal way to use Stockfish programmatically?
How to get position evaluation with UCI?

I have no problem writing a new GUI, but I am incapable of rewriting Stockfish. I'm asking how to integrate Stockfish with whatever program I write so that it gives me those specific notes

@DrewRightenburg The links give you idea how to integrate your GUI with the UCI protocol. My links are accurate and good. Please note your question has been asked several times here.

For example, the second link tells you how to use UCI output for detecting checkmates. The third link is about connecting UCI engine with your GUI.

You can't. Stockfish is just a chess engine and engines dont have such functionality.
Those notes are created by Lichess application not by Stockfish. Lichess manipulates engine outputs to deliver sophisticated functionality.
If you like you can develop an application of a chess engine for this kind of feature using Stockfish or any other engine. UCI protocol (which is a standard protocol for engines) can help you developing such application.


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Countering The Wayward Queen Attack
I'm a new player =I just started playing again after an over 10 year hiatus. I'm (sadly) in the 600s.
I've been studying openings and I seem to do better in games where I can use the Italian game or Ruy Lopez. However, there's a strange game that I continually lose a slow and painful game against and it's the family of plays that have the queen out causing havoc early. In particular, the [Wayward Queen Attack][1] has been at the heart of every game I've lost in the last 3 days.
I mostly contribute this to my lack of piece development out of fear of losing pieces to a queen. How should I counter it?
[1]: https://en.wikipedia.org/wiki/Wayward_Queen_Attack "The Wayward Queen Attack"

It might help if you could show us one of your games so we can see what you're doing wrong. I don't know what the proper tags are for this question, but the Italian game tag can't be right, your question is not about the Italian game.

See also https://chess.stackexchange.com/questions/4553

First of all, despite the stigma attached to early queen moves Nakamura has played the white side of 1. e4 e5 2. Qh5 several times in top level play, so it is a move you should treat with respect.
The best approach is probably to play moves like 2... Nc6 to protect the e pawn, 3... g6 to kick away the queen, then Nf6, Bg7, castles to get your king safe. Then if the white queen is still in the middle of the board try and attack it with your pieces.
Then you are in a normal game and if you blunder pieces because of your low rating then consider that your low rating is probably because of your poor tactical ability. To correct this you need to work on tactics. Learn about pins, forks, skewers, discovered attacks, etc. and do lots of puzzles to try and improve.

I have played against this opening in many blitz games online and I think it just amounts to unnecessary  loss of tempo for white because because black can play  1.Nc6
protecting the pawn and also developing the knight.
After white played Bc4 threatening mate on f7 black chases the Queen by playing g6, usually  the Queen moves to f3 still attacking f7 then you can develop your other Knight by playing Nf6 white usually replies with c3 preventing Nd4... black usually has a good game after that.

I believe that 2...Qe7 is reasonable approach especially for beginner. It protects the e5 pawn; it protects the f7 square: less things to worry about. Black development plan would be something like this: Nc6, g6, Bg7, Nf6, 0-0.

Here's a great little trap where when you can try trapping their queen. The only out of the trap is accepting a queen exchange .

I have never lost against this and only a handful of people have tried it on me.  Straightforward development does the job very nicely.  Be patient and just play positionally and black will get a good game.
Nc6 protects the pawn.  Threatening Nf6 attacking the queen and gaining the initiative.  White could try Bc4 to get a mate but P-g3 stops that and white has a misplaced queen and trouble developing the king side horsey as well as it could have been.

Since White wants a scholar's mate, I will run over a sample line.

e4 e5 2. Qh5??? Nc6 3. Bc4 g6 4. Qf3 Nf6 5. Qb3 Nd4!

Simply kick White's queen around while developing.

Just play 1.e4 e5 2.Qh5 Nf6 3.Qxe5+ Be7 and you have a fine game, except for having one less pawn, which means nothing in the 600s. For that matter, the computer evaluates this position as an even game, meaning that Black has full compensation for the pawn.

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Improving my ability to scan the board
This seems like a silly noob question...but I am a silly noob. Sitting at around 600 (and floating there in both tactics and in 30 minute games) I've noticed I give away material or extend the game considerably sometimes because I just don't see the moves needed.
I know that the trope I read all the time is "tactics, tactic, tactics", and I have been doing tactics for around an hour or so a day in addition to my daily games. I've noticed significant improvement in my ability to see attacks and play smart - but my problem seems to consistently be missing important moves for pieces. Especially in regards to 2 and 3 move mates.
One thing I do is I look for pieces under attack, and start to evaluate moves from there. If no pieces are under attack, I look around the board at pieces that I can improve their positions on. My issue seems to be target fixation:
[FEN "r4rk1/p1p4p/1p6/3pP3/P3nppq/1Q2PP2/4K1PP/R4BNR w KQkq - 0 0"]

Here, the actual move is to move the queen in for a mate in 2, however my first instinct is to notice the queen is protecting a square I can put my knight on, and guarantee a capture of their rook at h1. I don't think I made a terrible move, however it appears I have trouble spotting these easy mates. Additionally, sometimes I fixate on the check and put pieces in peril unnecess
Is there a way I can scan the board more effectively? Or does it come down to just getting beaten down over and over again in tactics until I learn to see them?

You can't mate in 2 here because the king is in check and has to move. Qf2+ Kd1, Qd2# is not possible

@AnthonyPham Aye. I think he misplaced the white king. If he's on e2, then we do have a real mate in 2.

It doesn't really matter whether you see Nf2 or Qf2+ first (although I'd expect the check to jump out) -- the point is to keep looking until you've found both.

Skill in chess is all about pattern recognition. You are doing the right thing with the extra tactics training, and as you said, you can definitely see improvement, right? Unfortunately, that is a slow process with no easy shortcut.. but don't worry, if you follow the path you are on, you will be able to spot a mate like in your example easily one day.
In fact, you already do see patterns ("Enemy rook trapped by own knight and pawn, I can win it with my knight on f2"), which is good. Your main problem is that your "map" of patterns is still very incomplete. And of course, it is only natural to focus on a pattern you see immediately and which is already favorable for you, instead of one that you don't know by heart yet. As said, the right priorities will come with time as you fill the blank spots on your map.
It is a good idea and might accelerate this process a bit if you try to get into the habit of ALWAYS calculating all possible checks each move. Especially point blank checks with a queen are rarely a bad idea (this is a pattern too, one that you want to have higher in your priority list). In all honesty, your example isn't that obvious a mate to see at first glance as you might think. The king first looks to have a lot of space to flee to on the queenside. My instinct in a real game (where you don't get told that there's a mate in 2 now) would probably be something like: "Let's see.. point blank check! Always good! Let's do that. Now, before I move, let's check his escape. d1 and d3 (pattern: point blank queen checks only offer 2 escape squares in the way a knight moves). Hm. Kd1 is an obvious mate (pattern: king at border, queen can move right next to him and is protected there), but d3 is kinda out in the open, which is bad when I only have 2 pieces to attack him further. But wait! The pawn on d5 covers c4 and e4! These are the escape squares from a queen check on d2, so this actually is mate, too! Cool."
Long story short, when I start calculating Qf2+, I don't see the mate either, it only becomes obvious after a few seconds of calculation. Hopefully you can draw some hope from that - you are only missing some links, not the whole chain ;)
So, keep up your work, focus a bit more on calculating forcing moves (checks), and you should be fine. Good luck!
PS: I am assuming the white king should actually stand on e2, otherwise your example makes no sense.

Yeah that was an error on my part. I copied this from chess.com, may not have been the mate in 2 I thought... Haha. Thank you for your advice. I really appreciate it.

@rec You still have the mate in two but it's just that you can't have the king there

An initial assessment of material is always a good idea, followed by subsequent layers of assessment: possible tactics, pawns structure, piece activity, etc....
I usually look at my side as say to myself: Q-M-M-M-R-R (M being minor pieces - no other distinction at this point); then the opponents side: Q-M-M-R-R...In this case, I'm up a piece so trading down is my major strategy - any move I make should fall within this theme.
And yes, being beaten over and over again initially is a part of the process, sorry to say.

Playing regularly, and playing a lot of games, will normally improve your sight of the board.  Constant practice is a method for improvement in chess as in other disciplines.  The more positions you see, the more familiar you will become with them and start recognizing familiar patterns.  In the position you have shown, you should immediately focus on the weak f2 square, and you should be looking for mate or a check first rather than just winning the rook, since ending the game quickly if possible should be a priority. The move 1..., Qf2+ leads to mate in two no matter where the white king goes, either to d1 or d3, by 2..., Qd2#.


text:
Countering the Horowitz Defense
Since my last post I've successfully learned how to counter the wayward queen attack, and now I've run into an interesting opening that I don't immediately lose to, but I feel I can play against better.
Typically as white I like to play the Queens Gambit. Being still new I stick to what I know. A VERY VERY common opening for black against the queens gambit in the 700-900 range (on chess.com) seems to be the Horowitz Defense.
[FEN ""]
[StartPly "6"]

1. d4 e6

Generally, I tend to continue with the queens gambit, moving 2. c4. My justification being an early deployment of his dark bishop would give check but theres plenty of (safe) ways to mitigate it and continue to develop my pieces. However, I feel there's strategy here I don't see. I haven't searched chessbase yet (will do that tomorrow) but I don't usually see this opening in club games.
Is there a better counter to it than 2. c4, are there specific master games I can study?
thank you!

Related question from Black’s POV.

Both sides have made one simple and useful developing move. Any further simple and useful moves will keep the game in known terrritory.. There is a wide choice, apart from 2. c4. For example 2.e4, 2.Nf3, 2. Nc3, 2. g3, 2.e3. 2.f4, 3. Bf4,etc. Basically Black is letting you play almost whatever you want to play.

I was not familiar with 'Horowitz-Defense' what made me read this post. After I saw the full line which is 1. d4 e6 I was pretty sure you missed most of the variation, haha! Personally I don't really like it, what kind of analysis can we do at move 2? As a beginner you should.n't really be concerned about openings that much. Anyway you got a very nice answer from Evergalo below

Since you are playing the Queen Gambit, 2.c4 is indeed the most logical way to continue. The main answers, 2...d5 and 2...Nf6, should fit in your repertoire anyway. The alternative is to go for 2.Nf3 first.
Move order finesses
Black's move order bears three subtelties:

You are offered a choice to switch to a French opening with 2.e4. This is probably your opponent's secret hope and since you are a 1.d4 player, you will probably not want to go down that road even though 2.e4 is of course a good move - unless you are fond of playing against the French defense.
After 2.c4, Black can bring the game to original territory with 2...Bb4+. This is a decent line, but not overly dangerous, and you can handle it with general rules (develop, avoid doubled pawns, castle...) if reaching an equal position suits you. Or you can learn a bit of theory about it, although at 700-900 level there are a lot of more important stuff for you to study.
If you want to avoid it altogether, you can start with 2.Nf3. Then 2...d5 3.c4 is back to QGD, with an early Nf3, which might or might not suit you depending on your favorite line of Queen Gambit. Note that 3...Bb4+ remains a decent option for Black.
Dutch players often start with 1...e6 to provoque 2.c4 and reduce their opponent choice: after 1.d4 f5 White often goes 2.g3 or 2.Nf3 and plays c4 only a few moves later, or even plays subvariations like 2.Bg5 or 2.e4, but after 1.d4 e6 2.c4 f5 those options are lost. If you play an early 2.c4 against the Dutch anyway, you won't mind those shenanigans at all, otherwise 2.Nf3 might once again be the solution.

Finally, some Black players also intend 2...b6 or other rare moves you should not be too worried about.
Conclusion
1...e6 is a decent move that plans to reach normal positions while limiting your choice. Those move-order subtelties are interesting when building your repertoire, yet they should not worry you too much until you reach a level around 1800 or so.
The natural alternative for a Queen's Gambit player is between 2.c4 and 2.Nf3; both have pluses and minuses. If it fits your usual way of playing in the QGD, go for 2.Nf3 first before 3.c4 and go for standard, QGD-like development: that avoids 2...Bb4+ tricks and requires less specific work on opening lines that shouldn't be your biggest concern right now.

What do you think about 2. e4?

@rec : 2.e4 is obviously a good move, it will land you in French defense territory. Very fine if you like this opening, but it not the choice of most 1.d4 players.

I am not very well versed in these openings, but is 1. d4 e6 2. c4 c5 also an idea for black to reach some Benoni? Can white avoid such options with a different move order? (At least 2. e4 c5 would seemingly make less sense for black, and avoid a Benoni.)

Well, when you play 1.d4 it is hard to avoid Benoni altogether. Even 1...c5 is possible. The move order 1...e6 and 2...c5 is rare, I see no advantage in it compared to the standard 1.d4 Nf6 2.c4 c5 3.d5 e6. If you want to avoid Benonis, you can reach an English type of position after 1.d4 e6 2.c4 c5 3.Nf3, when Black will take on d4 sooner or later, or play 3...c5 reaching a Tarrasch (which is no problem for a queen's gambit player).

Black can also employ 2...b6 for an Owen's defence.  1...e6 also dodges the Trompowsky.

If you are happy playing the white side of a French Defence then I would play e4. If black is playing e6 because he wants to avoid some white QGD lines then this could make him unhappy.

I think most players using the 1...e6 move order are French aficionadoes, and few White players starting with 1.d4 will enjoy facing it.

@OlivierPucher Starting with e6 is a good way of getting a Nimzo or a safer Dutch. It is usually played as a move order device.

BrianTowers : Absolutely. But this move order device is almost exclusively used by people who are not afraid of playing the Black side of a French defense... Most of them will play 1...e6 regardless of White's first move.

Black may be able to play the Bogo-indian, The QID, the Nimzo-indian, and such openings. I suggest that you learn the theory of the French and play that.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
What are some good books or articles on how to play coffeehouse chess?
A coffeehouse style is what players who work hard to improve their skill at finding the objectively strongest moves in a position, having taken account of the objectively strongest moves available to the opponent, often disdain. Used by hustlers, by some recreational club players, and by many who play friendly blitz games, it is about playing what works in practice, in games with short or no time controls and which may be but are not necessarily played for money.
It includes playing moves that set traps that for some reason the opponent is likely to fall into. For example a classic example of a coffeehouse opening by Black is the Blackburne Shilling Gambit, 1 e4 e5, 2 Nf3 Nc6, 3 Bc4 Nd4. If White plays 4 0-0, 4 c3, 4 Nc3, or 4 Nxd4, he can get an advantage, whereas Black hopes that he will play 4 Nxe5, grabbing the pawn, after which he gets walloped by 4 ... Qg5, perhaps in the line 5 Nxf7 Qxg2, 6 Rf1 Qxe4+, 7 Be2 Nf3 mate.
But coffeehouse is not reducible to tactically trappy play and can be more subtle psychologically. For example if facing the line in the Alekhine Defence 1 e4 Nf6, 2 e5 Nd5, 3 c4 Nb6 White plays 4 a4, that move is not objectively weak but if it is played with a view to influencing Black to believe that White is weaker than he actually is, as if he were prone to lashing out aggressively with lots of pawn advances even when objectively unsound, it would be coffeehouse.
I would appreciate recommendations of titles not just on trappy coffeehouse openings, but on any aspect of how to play strong coffeehouse.
One book on coffeehouse is John Healy's Coffeehouse Chess Tactics (2010) and there is also John Emms's The Survival Guide to Competitive Chess (2005). What other titles are there?

What's coffeehouse?

Sorry - give me a few minutes and I will edit to define the term.

Why is this question getting downvoted?

Authors don't write books aimed at coffeehouse players. There's little to no no market for them.

Some do - see the titles I've edited to mention.

Maybe it's not exactly "coffeehouse" but Simon Webb's excellent Chess for Tigers is all about finding what works rather than looking for objectively best moves. From page 2 of the 2nd edition:

Next time you sit down to play a match, ask yourself what is your aim in playing. Are you aiming to play the best moves? Or are you playing to win? There is a difference. Many players aim merely to play the best moves, objectively speaking. They never succeed, of course, but that doesn't stop them trying. But chess is not a science — it's a game, a struggle between two mortals who make mistakes, deceive themselves and each other, get tired, allow themselves to be distracted, and altogether have no hope of attaining perfection at the chess-board. If you want to become a Tiger, you must forget about playing the best moves and concentrate on winning.

Hikaru Nakamura wrote Bullet Chess; One Minute to Mate, perhaps not entirely what you had in mind. Ive not read it. Apparently, from Amazon reviews, some people liked it.

Any of the SOS books (Secrets of Opening Surprises) can be useful guides to lines effective in coffeehouse play.


text:
Longest number of moves that have been identical in two independently played games on record
Are there any recorded examples of two chess games that were identical till the end?
If the answer is no (which is most likely the case), what is the longest number of moves that have been identical in two independently played games on record?

A long time ago I played a game where we agreed to a draw on move 30 or something, where we were following a complicated line from a certain opening book where in the end everything comes off. Turns out we both had that same book.

I'd say the second question is interesting even if the ansewr to the first is "yes"

There are Several reasons for identical games:

The fact that we databases and computers allows us to find the best move in known positions. (if both players knows the theory in the same level - it might lead to a known draw).

Hence some players might follow a known game between two great players, which might result with identical games.

The fact that there are known traps, might lead to to the same trap (when one player knows the theory and the other fall in the trap)

In this case, the game might end after the player fall in the trap.

In same cases, following a theory might lead to a lose as in the below story about Vishy Anand:

Vishy Anand loses in 6 moves after following a known game
[White "Zapata"]
[Black "Anand"]

[FEN ""]

1.e4 e5 2.Nf3 Nf6 3.Nxe5 d6 4.Nf3 Nxe4 5.Nc3 Bf5?? 6.Qe2

Anand resigns

The story goes: reaching the position after white's 5th move,Anand
  recalled the publication of the game Miles-Christiansen,in the
  Informator(a highly respectable chess journal),which went 6.Nxe4,Bxe4
  etc....Impressed with the ease with which black had drawn in that
  game,Vishy decided to try it himself.But,after 6.Qe2,black just loses
  a piece.
Now,how could both Miles and Christiansen have missed such an
  obvious move???? The answer is........they didn't!!That game had been
  agreed drawn in advance.Something the Informator had not revealed.At
  the board,Miles did see that Qe2 was winning,but remained the
  gentleman,and avoided playing it.It is said,that he did spend some
  seconds polishing the e2 square with his finger,untill Christiansen's
  face had the appropriate shade of red,whereupon Miles took on e4.

Two Identical games
Here you can find

Two identical games for the first 28 moves

A Lopukhin vs Alexander Semeniuk (1975)
Yakov Estrin vs Hans Berliner (1965)

48 Moves - Both Haugen (2523)-Fernandez (2437), 2010, and Bross (2587)-Efremov (2574), 2011, reached the same position after 48...Qd7+:

This is my source for the below Answer, in this link you can find more identical games.
[Event "Uxbridge Int Alekhine"]
[Site "Uxbridge ENG"]
[Date "2010.02.17"]
[Round "8"]
[White "Rudd, J."]
[Black "Gormally, D."]
[Result "1/2-1/2"]
[ECO "B90"]
[WhiteElo "2286"]
[BlackElo "2479"]
[PlyCount "18"]
[EventDate "2010.02.13"]
[EventType "tourn"]
[EventRounds "9"]
[EventCountry "ENG"]
[EventCategory "2"]
[Source "Mark Crowther"]
[SourceDate "2010.03.01"]

[FEN ""]

1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 6. Be3 Ng4 7. Bc1 Nf6 8.
Be3 Ng4 9. Bc1 Nf6 1/2-1/2

Another Game:
[Event "ch-SUI"]
[Site "Lenzerheide SUI"]
[Date "2010.07.16"]
[Round "9"]
[White "Jenni, F."]
[Black "Kurmann, O."]
[Result "1/2-1/2"]
[ECO "B90"]
[WhiteElo "2542"]
[BlackElo "2449"]
[PlyCount "18"]
[EventDate "2010.07.08"]
[EventRounds "9"]
[EventCountry "SUI"]
[Source "Mark Crowther"]
[SourceDate "2010.07.19"]

[FEN ""]

1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 6. Be3 Ng4 7. Bc1 Nf6 8.
Be3 Ng4 9. Bc1 Nf6 1/2-1/2

Another Game:
[Event "Moscow Dvorkovich Memorial"]
[Site "Moscow"]
[Date "2009.09.11"]
[Round "4"]
[White "Gansvind, Valeriya I"]
[Black "Pisakov, Ilia"]
[Result "1/2-1/2"]
[ECO "B90"]
[WhiteElo "2226"]
[BlackElo "2331"]
[PlyCount "18"]
[EventDate "2009.09.08"]
[EventType "tourn"]
[EventRounds "13"]
[EventCountry "RUS"]
[EventCategory "4"]
[Source "ChessBase"]
[SourceDate "2009.11.03"]

[FEN ""]

1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 6. Be3 Ng4 7. Bc1 Nf6 8.
Be3 Ng4 9. Bc1 Nf6 1/2-1/2


text:
What happens if a strong chess engine plays with itself many times?
If a strong engine (eg. Stockfish) plays with itself many times (say, 100 times), what will be the outcomes in terms of the following:

What will be the proportion of draws? Will there be wins/losses? If so, what could determine wins? Will it tend to be predominantly white (because of opening advantage) or just random?
Will all the games played be along a narrow repertoire? Will there be diversity in games played?

Have you tried setting up an engine match to answer these questions yourself? I'm not a Stockfish user, but Fritz allows engine matches.

http://tests.stockfishchess.org/tests

has information on exactly what you want. They are self-playing tests for improving the Stockfish code base.

The draw rate is roughly about 60% - 70%. There're lots of wins and losses. I believe white has more wins but it's not shown on the page.
Chess engines aren't perfect, they do make mistakes. If SF makes a bad move at move 20, the same algorithm might find the win a move later (21) because it can search deeper and further.

With best settings and same opening moves, the results should be the same every time. Not very interesting.
Only variation that might occur is if search depth vary due to time limit and random dips in processing availability.
With different predefined openings white is expected to win up to 6% more often (opening advantage). This might vary from engine to engine and restrictions put on that engine (search depth/time).
If you google it, there have been some Stockfish vs Stockfish games played and most of them seem to end in a draw. But I can't seem to find any extensive statistics.

Lot's of statistics (too many!) in my answer!

There is some inherent randomness in at least some of the chess engines: https://chess.stackexchange.com/questions/19482/randomness-in-engine-play

If the results were the same each time, then as soon as someone won once they could just play the same moves and never lose against the engine again (for that color).


text:
Game analysis: What would motivate a human player to sacrifice White Knight at move 10 in this game?
I am a beginner player (rating on Lichess.org around 1550). While analyzing one of my own games (pasted below), Stockfish calculated that a Knight sacrifice at 10th move is a good idea. I tried playing through the position after the Knight sacrifice, and white is able to regain a minor piece after ~10 moves, and it possibly worsens Black's position after ~10 more moves (but I'm not so sure about that).
But, my question is: is it possible for a human player to recognize that a Knight sacrifice at move 10 in this game is going to benefit White? Is there a simple heuristic thought process that can help a player recognize that the position after 10. Nxe5 is beneficial for White?
(My chess knowledge level: trying to play without hanging pieces. No knowledge of openings or positional games or any formal theory)
The game is as follows:
[fen ""]
[White "White"]
[WhiteElo "1585"]
[Black "Black"]
[BlackElo "1354"]

1. e4 e5 2. Nf3 Qf6 { C40 King's Pawn Game: McConnell Defense } 3. Nc3 c6 4. Bc4 h6 5. O-O Be7 6. d4 d6 7. d5 c5 8. Nb5 Na6 9. c3 Qg6 { I am surprised that Stockfish thinks a Knight sacrifice Nxe5 is better here. Let me see how that line goes.... } 10. Re1 (10. Nxe5 dxe5 11. d6 Bh3 (11... Bd8 12. d7+ Bxd7 13. Nd6+ Kf8 14. Nxf7 Bc6 15. Nxd8 Qxe4 16. Nxc6 Qxc6 17. Qh5 Qc7 18. f4 e4 19. f5 Nf6 20. Qg6 b5 21. Bf4 Qd7 22. Bd6+ Qxd6 23. Qf7#) 12. Qf3 Be6 13. Bxe6 Qxe6 14. dxe7 Nxe7 15. Rd1 O-O 16. Rd6 Qc4 17. Na3 Qa4 18. b3 Qe8 19. Nc4 Ng6 20. Be3 Rd8) 10... Bh3 11. Bf1 Bf6 12. Qa4 Bd7 13. b4 c4 14. Bxc4 Ne7 15. Nxd6+ Kd8 16. Nxb7+ Kc8 17. Qxa6 Bg5 18. Nd6+ Kd8 { Here White missed a mate in 1 with Qa5 } 19. Nxe5 Qf6 20. Qb7 Qxd6 21. Nxf7+ Ke8 22. Nxd6+ { Black resigns. } 1-0

I think some reasonable expectations are in order. First, very few humans can calculate 10 moves ahead in a complicated position. Those that can can only do it after years of obsessive practice. There is no way for a beginner to do it, and there is no rule of thumb to help. Second, the computer will choose the move that is 1 centipawn better, even if the variations that follow are insanely complicated. it does not care about such things.

Another thing: before worrying about missing Nxe5 you should concentrate on seeing that after 11. .... Bf6?? 12. Nxd6+ wins two pawns and the game. :)

Study chess puzzles to develop pattern recognition -- DAILY!

I am quite certain that it is possible to find this move for a higher level chess player.
This has little to do with calculation depth actually. Yes, the engine is able to look 10 moves ahead and conclude that White is going to win his piece back in most or all positions resulting from the sacrifice. But for a human player, all that matters is if he can "see" (recognize) the right pattern. Concrete calculation only follows to make sure that this pattern is actually winning (and most of the work is done in the first 3 moves, instead of 10). Unfortunately, there is no easy heuristic blueprint (else we would all be GMs), most of this ability to "see" comes from experience. However, there are a few hints:

First of all, White has the more active position (he has castled already, his pieces are much better developed (to active squares), and he has some space advantage), so he should generally put himself in the mindset of the attacker, not the defender.
Looking at the developed pieces in particular, the knight on b5 is very strong and puts pressure on c7 and d6 - and from the latter could attack f7 as well - which also happens to be in the scope of his bishop on c4.
His queen and other bishop are ready to attack as well, but for now, there are pawns in the way. A friendly one blocks the file for the queen, and a hostile one defends f4 from the bishop. Nxe5 will help in both cases, but that alone does of course not justify a sacrifice.
Now the crucial part is to switch focus from attacking d6 to occupying d6. Important features that make this pawn advance really strong all by themselves (aside from the fact that passed pawns on the 6th rank are rarely a bad idea): Black's bishop on e7 will be attacked immediately, and Black has not castled yet, so d7+ is a very serious threat.
Additionally, all of White's pieces gain activity: The bishop on c4 gets freed, the queen gets additional scope along the d-file, the knight on b5 gets additional safety on c7 and without a black pawn on d6, the ones on c5 and e5 become very vulnerable to the other knight and bishop.

So, White's position would be overwhelmingly strong - if only the black pawn on d6 did not exist. A GM will probably see this immediately. For us normal folks, maybe that is the mental exercise you are looking for: If you "sense" that you have an advantageous position that possibly allows some tactics, check the important pieces and pawns (not the one on a6 obviously) of your opponent and judge the position with them missing. Once you have found a keystone, the actual calculation often is not that difficult. You just have to find a way to deflect the pawn/piece you identified as holding your opponent's position together, leading you to look out for moves like Nxe5.
Now in this case, the real calculation would merely amount to:

Bh3 counter attack - easily defended by Qf3, even adding pressure on f7 at the same time
Bxd6 - you can simply retake, regaining your piece while maintaining a good attack
Black retreats his bishop (e.g Bd8) - you can continue with d7+, and after Bxd7, d6 is open for the knight. At this point, you may have to calculate 2-3 additional moves, but really, if you have arrived here, you have done most of the work already.
Additionally, Tony Ennis' idea around f4 is worth having a look at, too.
Last but not least, you always have to consider that Black can refuse the sacrifice. Well, then Nxe5 either just won a pawn (probably the safer choice by Black) or has opened another attack angle after ...Qxe4 - you can now play Re1 with pressure along the opened e-file on an uncastled king.

As a contrast, list of reasons why people tend to overlook opportunities like this:

They are too occupied with the last move of Black (Qg6) that threatens Qxe4 and focus solely on the defense of that threat. End of list.

In all honesty, I still belong to that group too. Hindsight is 20/20.

As an FM Nxe5 is something that I would have considered in a tournament game, but would have missed in a blitz game. Many GMs would see this in a blitz game.
Black is behind in development with a king in center in a closed position. This is such a fleeting advantage for white that drastic measures must be considered.
The hard part is seeing Nd6-f7 after d7 clearance.
Second hard part is that a human player might play 11. ... Bf8?! after d6. White is down a piece for a single pawn with no immediate mate visible, but black king is in center and black is ridiculously undeveloped.
So white should be winning.
Now you have to see that after tempting 12. f4 black looks completely busted
12. ... Qxe4 and now you have to see that 13. Bd5 is winning
But again, black might play 12. ... Bd7 13. fxe5 0-0-0 this should be easily winning for white but they are still down a piece!
So calculating this position in my head at move 9. I would not be sure whether to play 14. Nxa7+ or 14. Rxf7 or 14. Bxf7 or maybe something else.
However, I would have to trust my instincts and prune this whole line as bad for black.
With practice and study you develop a sort of spidery sense on what moves to consider.
The concerns that Annatar listed should happen near instantly at 2000+ level.

I'm only 2000 ELO but Nxe5 seems an obvious candidate move to me. But I would have rejected it due to Bf8, wrongly thinking that Black was hanging on.

I'm a lofty USCF "B" player. So take my words with a pound of salt.
I would never think to play that move. But what does it allow?  The f-pawn is unblocked. After 1. f4 exf4 2. Bxf4, White has developed another piece and the Rook on f1 is looking at f7. Now White can think about d6, which doubles up on f7. Black has a threat of Bh3 and Qxg2#, but that won't happen.
My Stockfish also chose that move. That does not mean a beginner should have found it. Moves like that require a degree of technical vision that would be uncommon in a person who isn't a master.
[FEN "r1b1k1nr/pp2bpp1/n2p2qp/1NpPp3/2B1P3/2P2N2/PP3PPP/R1BQ1RK1 w kq - 1 10"]

1.Nxe5 dxe5 2.f4 Bg4 3.Qe1 O-O-O {If he takes the pawn, he won't be able to castle after the Bishop recaps} (3...exf4 4.Bxf4 O-O-O 5.Nxa7+ Kd7 6.Bb5) 4.fxe5 Kb8 5.Bf4 {Note the potential discovered check, and how this affects the f7 square. White's position is full of goodness} Ka8 {Run away! Run away!} 6.d6 {This pawn is a monster. Imagine when White supports it with a Rook...} Be6 {The d-pawn must be destroyed. Black is willing to pay the piper.} (6... Bg5 7.Bxf7 Qxf7 8. Bxg5 {discovering the Queen}) (6... Bf8 7. Qg3 Bh5 8. Rae1 {and here Black is so knotted up he wants to sacrifice the g-Knight on e7 but I would play Qxg3 though Stockfish says it is far worse}) 7.dxe7 Nxe7 8.Qe2 Bxc4 9.Qxc4 Qe6 {White has regained the sacrificed material and is having a splendid game.}

If human player  can't calculate 10 moves ahead, the player might use his/her feeling based on the experience he got.
Sacrifice like 10. Nxe5, get the initiative, open the game, and allow the d-pawn to start attacking.
The answer for the question is the sacrifice justified?

Might be objective (what a great computer chess engine will analysis)
Subjective - how will you use it against your current opponent

It is interesting that several chess engine gave different result for the move 10. Nxe5

cpuchess - using GarboChess gave: -1.37
lichess  - using Stockfish  gave: +1.7
thechesswebsite - gave -1.6

Note: Unfortunately I don't have access to any professional chess engine right now.

It was a temporary sacrifice. It enabled the knight on b5 to run amok through Black territory, and get both bishops for the two knights. Black ended up with an isolated e pawn, and vastly inferior mobility in the variation.
White in this game played "better" than a beginner. Maybe it was his "best" game, but if he keeps it up, he'll be an intermediate at least.
Capablanca (a world champion) did a similar thing in one game, and won.


text:
Unfamiliar with this move notation
I'm not even sure what to call this one. I'm reading Caro-Kann Defense: Advance Variation and Gambit System by Anatoly Karpov.
In the first chapter karpov mentions a move order:

e4 c6
d4 d5
f3

So far so good - the gambit system. Then he mentions black has a few continuations. The one that I'm not sure how to put on my board is:

...de
fe e5

I've never seen the notations de and fe used before. I thought they were for captures but it's very clear karpov is using normal capture notation (with 'x') throughout the book.
How do I understand this notation?

de = dxe4 and fe = fxe4

Sounds like inconsistent editing of the book.  Your thoughts are correct -- they are captures

de and fe are normal pawn captures. There is no contradiction in writing de and NxB and Nxe5. The "x" is optional.
It would be unusual and inconsistent to write 4. BxNc6 and 4. ... Nc6 in the following -
1. e4 e5 2. Nf3 Nc6 3. Bb5 Nge7 4. BxNc6 Nc6
but if we put it in fen then it works -
[FEN ""]
1. e4 e5 2. Nf3 Nc6 3. Bb5 Nge7 4. BxNc6 Nc6

Note what the latest FIDE Laws of Chess say about this -

C.9 When a piece makes a capture, an x may be inserted between:
C.9.1 the abbreviation of the name of the piece in question and
C.9.2 the square of arrival. Examples: Bxe5, Nxf3, Rxd1, see also
  C.10.
C.9.3 When a pawn makes a capture, the file of departure must be
  indicated, then an x may be inserted, then the square of arrival.
  Examples: dxe5, gxf3, axb5. In the case of an ‘en passant’ capture,
  ‘e.p.’ may be appended to the notation. Example: exd6 e.p.

(Italics added for emphasis)

how kind of FIDE to let me use the x

As well as books, video presentations a lot of times presenters will say "d e" instead of saying "d takes e"
I am trying to provide you with another example of its usage...it appears rather commonly in spoken word as well as text.


text:
How do computers play three-check chess?

How do computers evaluate three-check chess positions where the first side to check the other side three times wins?

How do they value the first and second checks?
It looks like the position evaluations would be tricky but it also looks like three-check chess would be an easier game to solve than standard chess.

https://github.com/ddugovic/Stockfish

Very active development, this is the Stockfish version used by lichess.
What you need to do is search this macro:

#ifdef THREECHECK

Evaluation function:

https://github.com/ddugovic/Stockfish/blob/master/src/evaluate.cpp

Checks are given extra bonus unlike normal chess:
    if (pos.is_three_check())
        score += ChecksGivenBonus[pos.checks_given(Us)];

pos.checks_given gives the number of checks already done. ChecksGivenBonus is an array of bonus values.
The bonus values are:
  S(444, 181),  // first check
  S(2425, 603), // second check

444 is the bonus for opening/middlegame, and 181 is the bonus for endgame. The bonus for the second check is much greater.
I'm not sure positional evaluations in three-checks is tricky. I can see the parameters have changed, king safety improved, but the overall structure is identical to regular chess.

I have been working on the aforementioned code of Stockfish for three-check chess, so I will try to summarize the most important evaluation changes (in terms of Elo gain) we made compared to standard chess. As was mentioned before, apart from these changes the evaluation is very similar to normal chess, with only some parameter tweaks.

Bonus for the number of checks:

In the middlegame, one check is worth about 2/3 of a minor piece, whereas the value of two checks is around 3 minor pieces, but such positions usually are highly dynamic, so they are hard to evaluate statically.
In the endgame, checks are not worth that much, since material is much more important. One check is worth about a pawn, two checks correspond to a bit less than a minor piece.

Much higher bonuses/penalties for safe/unsafe king positions, e.g., for the number of attacking pieces or for holes in the pawn shelter.

The king safety evaluation is also scaled depending on the number of checks the opponent has already given, so that king safety is more important if he is close to giving the third checks.

Piece values slightly differ from standard chess. Pawns are worth a bit less in the middlegame, since dynamic factors like open files are comparatively more important, and rooks are more valuable in endgames, since they can easily threaten to give check if only few pieces are on the board.

Regarding the second part of the question, I think that evaluation is tricky in closed positions, because it then is hard to evaluate imbalances regarding the number of checks and material. If the position is highly tactical, then the search should usually be able to resolve inaccuracies of the evaluation.
Solving three-check chess most probably is easier than for standard chess, because games tend to be shorter. One important point is the game theoretical value with optimal play. If white can force a (relatively short) win, then a proof might be feasible, but if it is a draw with optimal play, then the required proof tree would probably be much too big.

Thanks for weighing in. Not sure why your answer wasn't selected as best.


text:
What is the highest number of pieces from one side that can be involved in a checkmate?
What is the highest number of pieces from one side that can be involved in a checkmate? "Involved in a checkmate" is defined below.
A non-king piece is involved in a checkmate 'if removing it from the checkmate position would change the position to one which is either not checkmate or is illegal'.  The king is involved in a checkmate if it is the only piece of the checkmating side that attacks one of the other king's escape squares.

Does it count as an "illegal" position if the position itself doesn't violate the rules, but there is no possible way to get there in a legal game?

Yes indeed, any position which can't be reached in a legal game is illegal.

My original thought was that the limit was nine pieces; one for each of the 8 squares around the king, plus one for the mating check on the king's square.
[FEN "8/2K5/8/3Pk3/2P2PPB/3P2P1/2N5/8 b - - 0 1"]
[startflipped ""]

But, as someone pointed out in a comment, pieces can become "necessary" even if they aren't controlling one of those squares.  If the Black pieces don't have to be "necessary", then we can have a board where all White pieces are "necessary" for below to be a legal checkmate position.
Although, seven of them are just preventing check. The rest do the actual job of checkmate.
[FEN "3b1q1q/1N2PRQ1/rR3KBr/B4PP1/2Pk1r1b/1P2P1N1/2P2P2/8 b - - 0 1"]
[startflipped ""]

If black pieces are allowed, this is not the limit! You could have a situation where the check-mating piece needs to be protected from capture by blocking pieces. For instance in your example you could place  a black rook on f1 and say a white pawn on f2. Without the pawn on f2 it would not be checkmate, because black had Rxf4.

@user1583209 Hmm, good point...

As mentioned above, pieces could be required to block pieces from capturing the checkmating piece. They could also be required to block a piece from blocking. Another idea is to have a piece which pins an enemy piece which could block or capture the checkmating piece. You could also have a discovered check by a piece, for example a bishop in the corner, where the piece moving out of the way is needed because the position would be illegal without it.

Here is an example where removing a piece would make the position illegal due to castling rules: [FEN "7R/8/8/7b/8/5P2/3R4/2KR3k w - - 0 1"]

Here is another example involving en passant in which the pawn on d6 is needed to make the position legal.  The last move in the game involved removing a blocker which was in the checkmating piece's line of attack:[FEN "8/R7/3Pk3/6K1/5P2/B3N3/B3R3/1N6 w - - 0 1"].

Interestingly, in the example [FEN "8/R7/3Pk3/6K1/5P2/B3N3/B3R3/1N6 w - - 0 1"], removing the b1 knight after removing the d6 pawn makes the position a legal checkmate again.  In the following en passant example, removing any piece or pieces messes up the checkmate or is an illegal position: [FEN "8/4K3/2kP4/8/N1Q5/8/6B1/8 b - -"]

Here is a solution with all 16 white pieces, all mandatory for checkmate, without promoted units and without needing to protect the white king from checks. If you remove any white piece but the king, the position is still legal but not a checkmate anymore. Moving the wK to a random square (say, h1) would also destroy the mate.
QNr1R1b1/P1BpnP2/3P4/qP4Pr/Rn2kP2/1N4PB/2P2K2/8 w - - 0 1

Last move is Nc6-b8# or d5-d6#.

Here's another way to involve all 16 White units. This time the check is orthogonal.
[Title "All 16 White units in the mating-net"]
[fen "r2N1R2/1p2pn2/PBB1P3/Q4kPP/8/5nPK/PNPP1R2/q1r1b3 w - - 0 1"]
[StartFlipped "0"]

1.

wNd8 stops Ke6; wPg5, Kf6; wPh5, Kg6; wBc6, Ke4; wPg3, Kf4; wK, Kg4;
wRf8, N7e5;
wPa6, Rxa5; wBb6, b5; wPe6, e5;
wPa2, Qxa5; wNb2, Qe5; wPc2, Rc5; wPd2, Bxa5; wRf2, N3e5.
Legality: Perhaps wPa6 did bxPa and wPg5 did fxPg. (Or perhaps one of them captured [bBc8].)

Here is another 16-piece set, in which I strived for economy. I chipped down to 5 Black pieces; three less than @Evargalo, for whom I must thank for their matrix. I've also incorporated a new reason for needing a piece.
[FEN "QB1rR3/P1NPnN2/1P6/1rP5/4k3/1PP3PB/qRKP4/8 w - - 0 1"]

Here is a list regarding why each piece is needed.

wKc2: Guards d3.
wQa8: No checkmate.
wRb2: Without it, the position is illegal.
wRe8: Pins bNe7.
wBb8: Prevents bRxa8.
wBh3: Guards f6.
wNc7:  Without it, the wQ's check is impossible, and thus the position is illegal. It is impossible for c6xd7+ to have been the last move, as that would require one too many captures.
wNf7: Guards e5.
wPa7: Prevents bQxa8.
wPb3: Prevents bQd5.
wPb6: Prevents bRb7.
wPc3: Guards d4.
wPc5: Prevents bRd5.
wPd2: Guards e3.
wPe7: Prevents bRd5.
wPf3: Guards f4.

Maybe a further task could be to have all the wP on their original files...


text:
Can anyone recommend a free strong and good chess engine for endgame?
I am looking for good and chess engine for endgame but unfortunately when I test engine with competitive chess players in online,it fails with calculation ability. Please recommend apart from fish family chess engines.Please note I have made ground search in google. thanks for your time

What's so bad about the fish engines?

@Annatar. I do not have any conflict with fish family.I love it. I use multiple chess engines in GUI so I already possess fish family thats why thanks for your time

Stockfish with Syzygy 6-man tablebase.

thanks for immediate answer.I am looking for engine apart from fish family.

Houdini and Komodo with Syzygy 6-man tablebase... @Ram

Thanks again for quick answer both are commercial any luck for free and open apart from fish family.

@Ram: At least one of them offers older versions for free.

Current top engines almost have no problems with endgames, with the exception
of some fortresses, so either one of the best 3 will do just fine.
Years ago it was possible to beat top chess engines even in simple pawn endgames, but not anymore.
Tablebases improve engine play with a small amount of elos, depending on time control and the set used. 5-men would add +5-15 elos, 6-men up to 30, so this is still something, but nothing to marvel at.
7-men would do fine job, but still only commercially available.


text:
Getting the most out of chess books
I have a bunch of chess books that have been given to me on my favorite openings. I usually try to do a few games from them after I play my daily games and go over how I could improve with a chess engine.
However I feel like I am not getting the most from the books, and my coach hasn't really helped me yet understand how best to use them. Keep in mind I'm still a beginner, I'm hovering in the 800-900 range.
It comes down to I think a few things I don't get:

Many books I have just jump straight into games and talk about this or that variation, or another game, or their thoughts on the move. None of them discuss the ideas behind why those moves are good ideas, which I think is key in helping me understand. For example I watched a video of Karpov explaining some stuff on the Queens gambit that fundamentally improved my play because I was told the motivation behind the ideas.
I only have one program or chessboard available to me at any given time. Most books talk about variations in the middle of discussing a mainline. This is hard for me because I follow that line, then have to reset my board to follow the mainline until the next variation.

How do you guys handle these two problems? I feel like it's just like math. Once I learned to read a math text I got so much more out of it and became better. I think I can greatly improve my performance by understanding how to study a chess book effectively.

Sounds like you are reading the wrong books.

i think opening variations might be the wrong material to study for you. I'd recommend tacticts and endgames instead.

None of them discuss the ideas behind why those moves are good ideas,
  which I think is key in helping me understand

That's correct, the explanations are key. Opening books that don't give the ideas behind the moves along with typical middlegame plans are almost worthless. You might as well throw them away. If they don't give much more than just the moves and evaluations then you would be better off with one of the many databases.

Most books talk about variations in the middle of discussing a
  mainline. This is hard for me because I follow that line, then have to
  reset my board to follow the mainline until the next variation.

That's very conscientious of you. Most of us would follow the variation in our heads partly because we can but mostly because we are lazy. Once you get good you will be able to do this too. If you become very good indeed then you will be able to play the whole game in your head.

I recommend the free version of Chessbase software to easily look at multiple variations. I find it easier than using a physical chess set.

Doing it in your head is vital practice for tournaments where you are not allowed to analyze by moving pieces.

Keep in mind I'm still a beginner, I'm hovering in the 800-900 range.

Do not read any opening book. Rather concentrate on tactics. For this I wold recommend for example the book "Learn chess tactics" from John Nunn.
Just an example there are many similar books that are good to, but this is the only one I know. Simple tactics do not have many deep variants so this problem would be solved too.
For the opening I would recommend just to consider the following: Save your King (do not get mated early), develop pieces, occupy the center. If your level has improved and your opponents do not fail on simple tactics, than you can go and learn deep opening variants.
Furthermore I wold recommend long calculation time (at the very least 15 minutes better is much more like 2h or even daily chess), so that you are able to calculate the tactics deep enough.

I do tactics but a lot of them just aren't real. I have been pulling tactics from books and use chessbase as well. I generally play 15 | 10. I don't usually play blitz

He is right, forget openings now. Study middlegame tactics and play 1000 blitz games before studying anything else. This will give you essentials. Then you will be ready for endgame and strategy studies.

I've been advised against playing blitz except for fun. It builds bad habits. Minimum 15 | 10 to have enough time to dig deep. I don't go into openings deeply - but I absolutely needed a small repetoire against 1.d4 and 1.e4 for both black and white to have any chance at developing things properly. I plan on using Chessbase 14's tactical trainer more.

A player at your level should establish an understanding of tactics first. Quickest way to achieve this is blitz. Then you can dig deeper.

You can use software like Droidfish (on Android) or SCID vs PC to record multiple variations without losing your place. Another upside of this is that you can then store the variations as a PGN for later study and/or practice with a PGN player like iChess.

Once you get to the point where you can finish a game without leaving a piece somewhere you opponent can just take it for free, start with a couple of collections of older games. Logical Chess: Move by Move by Irving Chernev is a good place to start. The book is a collection of older master games, with an explanation given for every move. Follow that up with Chernev's The Most Instructive Games of Chess Ever Played. After you finish those two books, the other books you have should be easier to follow and will make more sense.

The simple correct answer is get better books that match your needs.
At your level you need opening PRINCIPLES not openings per se. And a lot more practice with fundamentals.
Also do tactics like https://chesstempo.com/chess-tactics.html  .
And study simple endgames.  First principles and then problems/studies.  Include basic mates as well as K+P and K&R endings.   Then move to more complex endgames.


text:
Why does ChessMaster recommend 24. Rg3 in this position?
I reached this position when playing against ChessMaster's cyber personality Laura. The engine recommends the line starting with 25. Rg3:
[FEN ""]
[White "Bad_Bishop"]
[Black "Laura"]
[StartPly "48"]

  1. d4             Nf6
  2. Nf3            c5
  3. d5             d6
  4. c4             Qa5+
  5. Bd2            Qa6
  6. Qc2            Bg4
  7. Nc3            Nbd7
  8. e4             Bxf3
  9. gxf3           h6
 10. h4             e6
 11. O-O-O          Ne5
 12. Be2            exd5
 13. exd5           Be7
 14. f4             Ned7
 15. Rhg1           Kf8
 16. Rg2            Ne8
 17. h5             Bf6
 18. b3             Qa3+
 19. Kb1            Bxc3
 20. Bxc3           Ndf6
 21. Rdg1           Rg8
 22. Bf3            Qa6
 23. Qe2            Qb6
 24. Re1            Qd8 25. Rg3 b5 26. cxb5 Nc7 27. Qd3 Rb8 28. Ba5 Qc8 29. a4 Qb7 *

To me 25. Rg3 is not intuitive and I did not consider it all in choosing a move. Granted, in the line that ChessMaster recommends, black throws away a pawn, but my question is, what is the purpose behind 25. Rg3 and why is it the best move?

In your bolded text, did you mean Rg8 or Rg3?

All of White's other pieces are placed well except the Bishop on f3.  If Black moved the a8 rook back and forth then White would probably like to play Rg3, Bg2-h3, and maybe Rg3-e3.
Simply put Rg3 increases the scope of the rook and the bishop.

It seems like e3 is the square that the Rook on g3 is heading for - after moving the Bishop on f3. (somewhere out of the way) This gives the g3 Rook certain access between the two f-file pawns.
The idea is to allow both Rooks to work together on the e-file.

This is a very complicated position.
No obvious winning plans. White has the bishop pair and much more space, but the
f2,f4 and h5 pawns are all isolated, and black is very compact and defends everything.
Stockfish shows +300cps advantage, but is not able to convert until maybe move 25 or so, frequently even reaches fortresses.
So, I am not certain what this position is: it might be a white win(I hope so), but it might also be some kind of fortress position.
In order to be certain one way or another, one needs deep analysis, which might take a couple of days.


text:
How do I respond to an arrogant beginner?
I played a skittles game (no clocks, arbiter etc.) against a beginner who did a lot of trash talking, which I didn't rise to. Here is an example of the conversation:

Beginner: I'm going to beat you easily!
Bad_Bishop: I'd like to see that. I play at quite a high level. Do you want a refresher on the rules, such as en passant and castling?
Beginner: No, I know all that already
Bad_Bishop: OK
Beginner: I'll take white. They always win!
Bad_Bishop: Hmmm...
Beginner: [Part way through the game] How do knights move again?
Bad_Bishop: In an 'L' shape
Beginner: [After being checkmated] OK, you won, but I took 2 pawns and a knight!
Bad_Bishop: Hmmm. Do you want to play a different game?

My questions are, should I have handled this beginner's trash talk differently? How?

I didn't keep a scoresheet, but this is what I remember of the opening:
[FEN ""]
[White "Beginner"]
[Black "Bad_Bishop"]

  1. b3             d5
  2. Na3            e5
  3. Nb1            Bc5
  4. d4             Bxd4
  5. Kd2            Bxa1
 *

During the game, I think ignoring the trash talk and letting the moves speak for themselves is fine. After, I would probably avoid playing with such an annoying player again for a while, unless necessary or there are signs of a change in attitude. I'd be more lenient if we are talking about a six-year old. :-)

Offer to play for money.

A good question for InterPersonnalSkills.SE ...

I act humble so in case they demolish me I can fall back and act normal

A much better way of handling it -

Beginner: I'm going to beat you easily!
Bad_Bishop: Of course you are.
Beginner: I'll take white. They always win!
Bad_Bishop: [Emphatically] Always! [pause, then with a note of doubt in your voice] Even when you are black?
Beginner: [After being checkmated] OK, you won, but I took 2 pawns and a knight!
Bad_Bishop: You were just so, so unlucky. [As you push the black pieces over to his side and start setting up the white pieces on your
  side] My turn as white.

I would add: "I can't believe it! I beat you with my left hand!"

"Beginner: I'm going to beat you easily!" "Bad_Bishop: Would you please solve this captcha first?"

This isn't about chess. It is about manners. I would explain to the youngster than this isn't Call of Duty. Trash talking is not acceptable.
"Young man, are you aware you're being rude to me?"
"uh, what"
"There is no trash talking in chess. There are only moves and they speak for themselves."

From experience, I would have done something like this:

Beginner: I'm gonna beat you easily!!
Bad_Bishop: Maybe, maybe not, anything can happen in chess ;)
Beginner: I'll be white. They always win!
Bad_Bishop: They don't win all the time ;)
Beginner: [After being checkmated]Ok, you won, but I took 2 pawns and a knight!
Bad_Bishop: True, but did you learn anything from this game, that's what's important. :)

If it is an online server you played the person on, avoid playing the user.  There are better beginners to spend your time playing with out there.
If it is in the club, hard for me to say.  Avoiding the player at the club, regardless of how the player acts,  may give an unwanted reputation change but maybe not.  Maybe people would be understanding, not sure.  I typically in interactions like that(be it chess play or not) I assume conservatively and avoid the trash talking, take everything they say as a joke and brush it off.  You gain nothing doing anything else as far as I am concerned.
They are obviously insecure about their game that they resort to trying to affect your mental game play by trash talking instead of making good moves on the board. Only the moves on the board win.
I have no tolerance for that type of etiquette/sportsmanship. As a lower level/rated player myself we should be grateful a higher level player agrees to play with us.  We only get better when we play people who are better than we are.

IMO this is a subjective question.
Personally, I would start capturing his pieces one by one by forcing moves making sure I have a overwhelming material advantage before I make his king run all over the board, only to be choked in the center.

Just because someone is making a fool out of themselves, you don't have to be an even worse sportsman.

It is not worse sportsmanship.  People are allowed to choose their strategies, no? That's why I said it was subjective, retorts to arrogance are different for different people.

There is no need to humiliate your oponent. To paraphrase Baltasar Gracian, “A wise man can learn more from his enemies than a fool from his friends”.


text:
Practicing tactics
I have been floating around the 800-900 tactical rating on chess.com for a while. A few things I've noticed

For a beginner I'm having giant swings in rating based on if I get a series that I can identify or not. It's not unusual in a single session for me to see a swing of up to 150 points between 820 and 970.
For the tactics I fail on, I feel discouraged because repeating them doesn't teach me anything. Many of them have 3-5 steps that if I spend more than the alotted time I don't get any points, and if I fail I lose even more points.

I don't feel these types of tactics are instructive to tactical beginners.
Is there a better source of tactics? I feel entirely discouraged with these giant swings where I feel like I'm getting it, but I'll miss a sacrifice or something two moves in and be completely obliterated in rating. My strategy of doing each tactic I fail 3 times to get the idea doesn't really help.
What can I do here to improve? More tactics is obvious but how do I improve seeing so far down the road?

Are you well acquainted with some of the most common tactical themes in chess, like forks, pins discovered attacks etc.? Otherwise that is a good place to start for you.

@Scounged I am, though I am a little weak on some tactics like desperados and such. But yes, I have a good command of the basics. My problem seems to be seeing the "middle moves" to create the situation two or more moves down the line.

Don't care about the time in the tactics and also do not care about the "rating" for your puzzles - these two factors just make you guess instead of analyze the position. Focus on solve every puzzle correct no matter how much time you spend and just make your moves when you are 100% sure it is the correct solution. That way you will improve both in puzzle solving but also in your general play.
What time control do you play on chess.com ? At your level you shall focus on the longer time controls e.g no bullet or blitz,
Maybe you also should start to study some basic theory ?

I generally do 15 | 10 or 30 minute games. Sometimes I will do 5 | 5 for fun because generally the person who spots the tactic first wins. I'm currently reading How to Reassess your Chess by IM Silman

First of all, don't worry about your rating. Particularly beginners will have large fluctuations in rating and in the end who cares about that number anyway?
Regarding tactics training, doing online puzzles is a very good way. Many websites offer these for free. I like the ones on lichess, because they are taken from real games and therefore tend to be a bit more realistic/messy than composed problems. However as a beginner you probably prefer cleaner problems focusing on just one or two motifs. But in any case, any good website will present you problem close to your level so that should not be a problem.
When you solve these puzzles (or fail to solve), I suggest to not stop there, but analyze each puzzle a bit more.
Particularly you should figure out which tactical motifs are relevant in this puzzle. Chesstempo can help you here, as once you solve (or fail to solve) a problem it will show you the motifs as "tags". Make sure you can see all of the motifs in the solution.
Another thing you can try is to take the starting position and remove all pieces from the board that are not necessary for the problem. This will give you a cleaner/clearer image of the tactics.
The aim of tactic training is to store certain patterns (positions of relevant pieces) in your brain and associate them with a tactic. You only store the relevant pieces, not the complete position, because this way the patterns are re-usable for many situations. As an example, a simple pattern could be: two pieces on the same row, two squares apart (e.g. on d5 and b5). This pattern would be associated with a "pawn fork".
When you solve puzzles later, you can quickly check whether the problem matches any of the stored patterns. Often it will match more than one, giving you more than one candidate move.
At this point it is time for concrete calculations in order to find the best move among the candidate moves and also to make sure that the tactics works (that there are no defenses). This involves for instance checking whether there are any additional pieces (compared to your stored pattern) that defend essential squares or whether the opponent has intermediate checks, etc.
In summary my suggestion is to:

do tactics puzzles (online or on computer or from books) and analyze them
try to find and name all the tactical motifs in the puzzle
remove pieces from the problem to get a clearer picture
memorize the relevant piece positions
re-check whether the tactic works

Thank you for your detailed feedback. How do you suggest I handle multiple move tactics? I bought two more structured tactics books to start there but I find it so difficult sometimes to see the idea 3-5 moves ahead unless I'm explicitly told to keep looking.

@rec What do you mean by "multiple move tactics"? Multiple motifs or just that the motif is longer than a single move?

Generally on tactics where the motif is one to two moves away, such as a distraction or removing the defender, I do fine. There are numerous instances of tactics on chess.com that require 3-4 moves of setup on something like a smothered mate. I find it difficult to look this far ahead, especially on messy boards.

@rec the only tip here is “practice”. You need to develop pattern recognition. A few moves will “jump out at you”, for the more difficult puzzles you’ll need to calculate the likely sequence for a few of these. After a while you’ll “see” longer sequences. At my best I’m 2000+, but tactics is still the thing that can swing wildly because if you don’t practice your pattern recognition skills deteriorate quickly. If you say you’re weak in strategy, study that too. Many great tactics arise from good strategy so learn principles like “capture to the middle” and see how they surface in tactics.

I've only made it to 1500 on chess.com, but here are some suggestions I found helpful.
For "tactics theory", you could consider reading a book such as Winning Chess Tactics which goes over each basic tactical theme systematically.
I also recommend CT-ART (available as a mobile app for $10 from the Google or Apple app store, or as desktop software from Chess King). Level 10 (the easiest) in particular consists mostly of composed problems which focus on a single motif at a time. Practice it repeatedly until you can spot the basic motifs quickly. Level 20 is also great practice and it starts combining motifs a bit more. The higher levels are probably too hard at this point. I find that level 30 is already harder for me than chess.com's puzzles rated 1600.
One advantage of CT-ART over chess.com as a learning tool is that if you answer wrong, it shows you the refutation, and it gradually gives you hints as you try again.
Within chess.com itself, you can try using the analysis feature that becomes available after you answer the puzzle. It can help you figure out why certain moves don't work, especially when the move you tried was wrong and you can't see why no matter how hard you try, but also when you guessed correctly but aren't sure why some other move didn't work.

Could you share a link to the CT-ART website?

I've edited my answer with a link. If you have a Android or iOS device, you can also search the corresponding app store.

The site chesstempo.com has tactics training puzzles you can try, but you might benefit from a more structured approach.  1001 Winning Chess Combinations by Reinfeld is cheap and organizes the tactics by theme.  Encyclopedia of Middle Games is more advanced but also by theme and is a must in my opinion.

I will look into both these. I think the problem I'm having is "creating" the tactic by looking a few moves ahead and seeing exactly what I need to do. This may be because I'm still weak in the "theory" of tactics - but I'm not sure how to improve that part.

I have 2200+ tactics on chess.com and I found two things to be the most useful:

Take your time. Really solve the puzzle, even if it takes time. You will naturally get quicker as you get more familiar with different tactics. Don't worry about the points.
http://www.chessimo.com/ is an absolute killer app for mobile (maybe for desktop as well), where they start with very easy tactics and repeat, repeat, repeat until you memorize them well. This is what took me from probably 1400 to 1800 in my tactical strength.
Bonus item- don't get discouraged and try to do it daily. I saw massive improvements after about 2 weeks rather than straight away.

Don't pay too much attention on your rating right now. As far as I can tell, you are having troubles identifying key "motifs". Even if you do a hundred problems your tactical ability won't improve ( your pattern recognition might improve though).
http://www.chesstactics.org
This site might be the thing that you are looking for. The author goes into detail explaining the reason for the occurrence of a particular tactic and how you can find them on the board.
Good luck.


text:
Making the best use of a coach?
Currently I pay for lessons, and I surely see value. I've gotten from the low 600s to being able to give USCF 1200s a run for their money. It's not much, but it makes me pretty happy.
But I feel like a lot of coaching sometimes is just random topics with a lack of structure. I usually bring 5-7 games to my coach and we go over them, followed by extra things I should study to improve my weaknesses. I also bring up stuff I have read, for example in How to Reassess your Chess to get clarification.
Is there anything more I can do to better utilize my coach?
Thanks!

Analysing one of your own games with a coach is one of the most important parts of work for a coach. To maximize the analyse-training effect you should always annotate your games before giving them to your coach. The reason for this is, that it makes it more easily for your coach to spot your weaknesses and therefore give you the right material to study. (very important if you don't live commentate all of your games in a meeting while going through them)
For your rating i would prefer a split of training time like this:

65% tactics
10% openings
15% endgames
10% positional & strategical plans

In the beginning this will often look some random topics with a lack of structure, but normally it isn't. (the percentage ratio will change when you get better)
From my coaching experience the book "How to Reassess your Chess" is far too complex and difficult to understand for your level. (i would leave it aside)
Also don't hesitate to ask your coach about topics you find uncomfortable. (e.g. how to play against this opening, how should i behave in positions like this one, etc.) -> He will get a feeling in which topics you are good or need additional training.
For saving time you should do tactic puzzles always on paper/in your mind, because in tactic puzzles it often takes more time to set up the board than to find a solution.

I think you are making good use of your coach from the sound of it.  Perhaps you are not studying the correct books for your rating.  And you should be heavy on puzzles and basic endgames; if your coach hasn't pushed you toward that there may be reason for concern.

I am certainly pushed towards tactics. No end games really. I don't hear very much about studying end games. Sometimes they come up in tactics however. I try to do around 20 minutes of tactics a day. Any more and I start getting burnt out setting up the board over and over again lol

This question is old now, but thought I would chime in on how to find a good coach.
You wrote: "But I feel like a lot of coaching sometimes is just random topics with a lack of structure."
You do not say what the rating of your coach is, but that lack of structure is a major red flag, and the sign of a not-great coach. Long-time coaches/trainers have definite lesson plans that can be tailored to players of different strengths. If they are just winging it every lesson, that is a sign it is time for a new coach.
Another important factor is that while many people want a GM coach, most players do not need a GM to train them, however, most professional trainers do nothing but that for a living, and usually are at least FM strength. In fact, many FMs or IMs can be much better coaches than many GMs, who just wing it since they work hard to have well thought out lessons.
Lastly, there are MANY places online nowadays that you can find very professional coaches for as little as $25/hour since they live in countries where that is a decent rate, but ask a lot of questions about whether they have formal lesson plans or just wing it. You can get a sense about that.
Chess.com Coaches
Lastly, here is my own tip about getting stronger: I cannot recall a tournament game between 1600 players that I kibitzed the postmortem that did not have an obvious missed tactic. I suggest immersion in chess tactics as I will describe in the next paragraph. I once took a 38-year-old friend, so not a super-young mind, from 1000 to 1850 ICC in three months doing this. He then stopped, and never got any better.
I recommend trying to do 50 tactics problems per day, spending no more than two minutes per problem, from the following books (eventually, you can use other books too):

“1001 Brilliant Ways to Checkmate”, 21st Century Edition by Fred
Reinfeld
“1001 Winning Chess Sacrifices and Combinations”, 21st Century
Edition by Fred Reinfeld

I know there are a lot of tactics books out there, but I love these two books because of how well they are laid out. You start with the mates book because the first chapter is queen sacrifices, so you have two huge hints: Mate, and give up the queen. I skip the last chapter on composed mates for now. As you are doing them, in pencil, mark each one with a number 1-5 as to how easy you found it, 5 being hard. You will read both books more than once. Again, try to do 50 per day. It is hard, but worth it.
I have been recommending this for over 35 years, but the method is very similar to the relatively new book "The Woodpecker Method", which was published in 2018.


text:
Failing to understand a pin from a tactics book
I've began going through, over the board, 1001 Winning Chess Sacrifices and Combinations - 21st century edition. This book is a great supplement to my last question on studying tactics, and I feel like I'm learning a lot from it.
One of the problems I'm having with this particular book is right out of the gate the tactics for pins are very difficult to see in a lot of cases for me.  Here is an example, problem 14:
[fen "r4rk1/p2nqppp/Qpp5/3p4/3Pn3/2N1PN2/PP3PPP/2R2RK1 w Qq - 0 1"]

To me one move was clear -

Nxd5

This move clears the way for the rook to enter and pin the knight to the queen. It's almost forced to take with the pawn to prevent the queen capture, the queen is on a pretty good square all things considered. Initially I had evaluated:

Qb7

But disregarded it as a first move because even though the knight is pinned to the queen

... Rfb8

Mitigates the attack immediately and forces the queen back - or so I thought. By having the rook perform the pin I'd be in better shape to mitigate that attack when I do 2. Qb7.
After:

... Rfb8
Nxd5 Rxf7
Nxe7+

Which seemed too easy to be right for this tactic and leaves the game at even money, which from what it seems is never the goal of a pin.
So from what I've gathered here I saw the pin at least. The problem I'm suffering from at the moment is how the solution plays out - the solutions don't really give great justification and there's a lot of moves here to consider it "solved":

Qb7! Rfc8
Nxd5! Qd6
Rxc6!!

From this I'm curious

Why 1. ...Rfc8 and not Rfb8, attacking the queen?
Why does black resign after Rxc6!!?
How do I study from this tactic book effectively? I'm getting a ton of them wrong even though I'm seeing the tactic, I'm unable to make the same moves in the tactic for black to make everything "play out right". I'm not sure when to consider a solution "complete".

I'm sorry if this is trivial, I'm working on fixing my over the board play by doing tactics and this book is incredibly difficult. Difficulty is great because its challenging but I'm only on problem 14!

To me one move was clear -

Nxd5

But after 1...cxd5 2.Rc7, although the knight is pinned for a move, Black can easily unpin it by moving the queen to d6, d8, e6, or e8.  In fact, the knight is not even fully pinned - Black could move it to c5 and force a queen trade.  You've sacrificed the knight for a pawn, and get no lasting pin.

Why 1. ...Rfc8 and not Rfb8, attacking the queen?

Well, after 2.Qxc6 Black has lost a pawn.  And after that move the d5 pawn is threatened twice and not defended, so Black must play 2...Nxc3 if he wants to have a shot at saving it. But now he's traded off a well-placed knight, and after 3.Rxc3, d5 is isolated and still needs a defender, and White will gain solid control of the c-file and will be up a pawn.
Rfc8 is shown here, not necessarily because it's Black's best move, but because in order to figure out how to proceed against it (and that Qb7 is a good move in the first place), you need to see the pin that Nxd5 exploits.  (And if this is based off an actual game, it might be the move actually played in the game.)

Why does black resign after Rxc6!!?

Because he's down two pawns, and White will control the only open file.  There's a threat of Ne7+ which limits Black's options in the coming moves.

What's really important here is that OP is focused on the wrong pin! It's not the Knight being pinned to the Queen that is the focus, it's the pawn being pinned to the Rook. The Knight on d7 isn't really doing anything. It isn't attacking any white pieces, it isn't defending any important black pieces, and it isn't one move away from attacking or defending either. Pinning a piece for the sake of pinning it isn't beneficial. You want to lock that piece in place for a reason (remove the defender, remove the attacker, or attack the pinned piece)

@ChrisG Thank you for your comment. If the pin isn't on the knight, then why does the queen move away from the pin on the A pawn? The A pawn doesn't seem to be doing anything useful either. The knight on D seems to be at least protecting a jump square at e5 the knight on f3 is current eyeing.

@rec I don't see a pin on the A pawn.  And yes, that knight is doing something by eyeing e5, but that's not why White pins it.

@rec First, the a7 pawn is NOT pinned. If it were removed from the board, white isn't attacking a piece, but is being attacked and would be forced to move his Queen (generally, pieces only pin to stronger or undefended pieces). Secondly, not all pins are created equal. Qb7 is NOT about pinning the Knight, it's about attacking the undefended c6 pawn. The black response Rfc6 is a bad response because it walks into a pin. Without the proper context from the book, it's hard to gauge, but it looks like a poorly designed tactics puzzle because black's best move doesn't result in a pin.

Regarding the question - how to deal with very hard tactics?
I'd suggest moving to an easier tactics book, where everything will be clear for you.
After you will finish that book, move to a more advance book, and you'll find that your tactics abilities are much better.
Below you can find a couple of possible continues after Rxc6 which shows why black resigned:

[fen "r4rk1/p2nqppp/Qpp5/3p4/3Pn3/2N1PN2/PP3PPP/2R2RK1 w Qq - 0 1"]

1. Qb7! Rfc8
2. Nxd5! Qd6
3. Rxc6!! Qxc6
4. Ne7 Kf8
5. Nxc6

[fen "r4rk1/p2nqppp/Qpp5/3p4/3Pn3/2N1PN2/PP3PPP/2R2RK1 w Qq - 0 1"]

1. Qb7! Rfc8
2. Nxd5! Qd6
3. Rxc6!! Rxc6
4. Qxa8 Nf8
5. Qxc6 Qxc6
6. Ne7 Kh8
7. Nxc6

The book in question is a mix of difficulties, but is mostly on the easier side.

@Ywapom I was under the understanding it's one of the best tactics books to learn from. Is there a better book I should be looking at or just continue to struggle and learn from the solutions? I do okay on tactics online and had zero problem working through Chess Tactics for Students, but I think a lot of online tactics are incredibly simple and compared to the one's in this book, the Chess Tactics for Students is almost too easy.

@rec I recommend giving yourself x amount of time on a puzzle and if you don't get it, just look at the answer.  Repeat the puzzle a day or few days later and see if you get it.   If you don't understand the answer to a puzzle (this happens for various reasons but should be rare), post here or just move on to the next puzzle.  The idea is to improve your pattern recognition; repeating a lot of puzzles on each theme until they sink in.

I think the key pin in this tactic is not the knight against the queen, but the c-pawn against the rook. If 2...cxd5, 3.Rxc8+ Rxc8 4.Qxc8+, winning the Exchange and a pawn while also keeping the initiative.
That said, 1...Rfc8 is hardly forced. Maybe it was the move played in a real game, like D M said. FWIW, Stockfish suggests it is a mistake (not even in the top five moves!), as it increases White's advantage from +1.5 to +3.0. Still, White can at least gain a pawn with what Stockfish considers best play, for example 1...Qe6 2.Nxe4 dxe4 3.Ng5 Qd5 4.Nxe4.
In the line you originally considered, 1.Nxd5 cxd5 2.Rc7, the problem is that the black knight can unpin itself by attacking the white queen with 2...Nc5! Both the white queen and rook are now under attack; the trade of queens is forced, which leaves White down a knight for a pawn. In other words, the sacrifice made on move 1 was for nothing.

You did well to recognize that Whites advantage has something to do with his control of the c-file and that to make anything out of that he has to open the c-file up. But when you say that one thing was clear, you were wrong, and it should not have taken so long to realize this. I suspect that you were drawn to Nxd5 "because thats the sort of move that you get in tactics books". This would be a very poor way of reasoning in a game. There you might still find Nxd5 tempting, but you would be less surprised that it did not work.
Probably you had another expectation because the position was in a book; you were expecting to gain a large advantage. When you looked at Qc6, either you did not realize the simple threat of Qxc6, or else you thought that was not enough.
It does seem that the solution was not well explained (not everyone has a high opinion of Reinfelds books). If you want to take it easy for a bit, I understand that there are some quite good chess books for kids, although Ive never looked into this.