Cliffs for now (it's intended as a running thread):

Opening with 1. Nf3,

i) is 1... d5 2. c4 d4 (reverse Benoni) playable enough to prefer 2. c4 to 2. d4?
ii) how to counter the Dutch (1... f5)?
iii) how to counter the Sniper (1... g6, 2... Bg7, 3... c5)?
iv) what to do after transposing to the Normal (5. Nf3) KID?

As I'm on a +70 chess.com corr rating upswing to 1838 after the ladder loss to BJJ, terrible thoughts about invincibility are starting to creep in, and that's when I should begin studying at least something

When I was 13-14, I read many middlegame and some endgame books, but never really did concrete opening studies until I started playing online this year. So, even though players are generally advised against obsession by concrete opening lines, I can indulge myself due to the above and the fact that I look for unexploitable lines instead of traps.

That 1. Nf3 was Carlsen's first move of the last championship was a factor in my choice if it, but more so was the fact that it's the best scoring first move in free databases (though its performance rating is the third best, excluding 1. Na3 that is 'crushing' over 22 games, as well as popularity).

I proceed to play 2. c4 against Nf6 and e6 and enjoy not delaying the d-pawn, rendering the Nimzo less useful as said below. I don't mind the (Petrosian) QID if it happens.

Notable Black responses that I'd like to discuss and that sometimes keep me awake at night are:

1... d5 leading to a close choice between 2. c4 and 2. d4

d4 allows to play highly theoretical and comfortable stuff, but it passes up on the opportunity to save a central pawn (that often becomes a target for Black when it comes to d4) and a tempo (which helps e.g. when Black plays 2... c6 and then makes a standard mistake of bringing the LSB out, which is exploited by cxd5, Qb3, Ne5, Bb5 and queenside destruction on light squares, usually without even summoning the DSB ).

c4, otoh, sometimes runs into 2... d4 - the Advance Reti - when White ends up playing a reverse Benoni. However, specifically for me, I feel it's not a bad thing because, playing the Sniper (1... g6, 2... Bg7, 3... c5) against almost any White setup, I'll sometimes find myself on the Black side of the Benoni as well (if White advances to d5).

We've actually discussed it to some extent in buffyslayer1's log, from where I'm x-posting:

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1... f5 - I've never faced it in practice (though I've faced 1... e5 once ), but it's safe to say that I'm clueless about White's plan against the Dutch and why the kingside fianchetto is its essential part.

1... g6 - here I might have a taste of my own Black medicine (the Sniper), which is a pain for White (it doesn't crush, but leads to dynamically equal positions).

The 'optimal' line 'suggested' by DBs is 2. d4 Bg7 3. c4 c5 4. e4 (moves 2-4 in any order obv) Qa5+!? 5. Bd2 Qb6 6. Bc3 Nc6! 7. dxc5 Bxc3+ 8. Nxc3 Qxb2!? which looks very drawish

4. d5 (Old Benoni) is also interesting, but alas Black has 4... f5! followed by Nf6 (which s/he of course doesn't have if playing Nf6 early), d6, Na6-c7, Rb8, b5. That's what I play myself as Black here. It seems to turn into a kind of Leningrad Dutch, i.e. White is supposed to play g3, Bg2, Nc3 to have the d5 pawn supported after it's undermined.

Black can do quite well with e6 instead of early f5 too, as witnessed by a Kramnik vs Topalov game (I'm yet to go through it).

Any ideas on improvements against the (unlikely) Sniper would be appreciated.

Most of the time, Black transposes to the Normal Variation of KID (as RoundTower mentioned, other popular KID variations are unavailable, but this one is just as good) - 2. c4 Nf6 3. Nc3 Bg7 4. e4 d6 5. d4 O-O.

I proceed with 6. h3 here, taking g4 away from Black's minor pieces, preparing my own kingside onslaught and usually not castling early, but are there fans of 6. Be2 or anything else here? If so, why?

Sorry for my tiring nooby questions, it's going to be a long-running thread Thanks in advance!

What sort of middlegame structures do you enjoy playing / want to get better at playing / etc.? I'm not sure the "What is theoretically best?" angle is practical at your level.

lol, you're like the most knowledgeable noob ever.

Oh, sorry for not answering to this valid question beforehand.

I'm more of a tactical player, though I'm not so likely to create a direct mating attack; rather, I look for loose or overloaded pieces. Alas I haven't been tracking how exactly I've been beating opponents, but it seems that almost every game was won by some fork, or pin/overload exploitation, or early pawn promotion threat. But how do I create such situations? I somehow do it , probably by concentrating pieces around some critical square.

When I see no weaknesses or imbalances in the position and the material is equal, I often have no clear plan and move pieces rather randomly, thinking about transitioning into an endgame that could be in my favour (e.g. knight vs bishop, good/bad bishops, iso/doubled/passed pawns, pawn majorities, king placement and so on). For that reason, I adore Slavs misplayed by Black - connected a&b passers are an easy game I especially hate KID for its closed nature, though other Indians are not so pleasant either.

I know that 1. e4 is an option, but it's hard to memorise the essential part of the open/semiopen game (especially Sicilian) theory (and hence I respond to 1. Nf3 c5 by c4, not e4). It seems to me that there are much fewer typical closed game structures.

Here's a nice blogpost about the 5. Nf3 O-O 6. h3 (Makagonov) KID (see also a holy wall of text in the description of the 2002 Chessbase DVD mentioned there). That's quite a tactical system. There's actually a ton of White blitz games in this variation posted on Youtube by Christof Sielecki aka chessexplained

It amazed me that, in 'Benko-style' Chessexplained's blitz #766 vs GM sauerkraut and in a similar Aronian vs Nakamura game at Sinquefield 2013, White castled kingside, but their kings actually felt very safe despite pawns being thrown on Black's short castle, Black pieces were so passive Is it standard? I thought that, even though Black's initiative is on the queenside, White's king is not in big danger anywhere and it's quite useful to keep the rook(s) on the h-file to break through there (as in blitz #659).

You could try out:

1. Nf3 d5
2. c4 d4
3. b4!?

3.b4 f6! is not all that great for White if Black knows his stuff. On the other hand, 3.e3 c5 4.b4 and 3.e3 Nc6 4.b4 are good times.

I guess you mean that the game could proceed like this:

3. e3 Nc6 4. b4 dxe3 5. dxe3 Nxb4 6. d4 e5!? 7. a3 Nc6 8. Be2 exd4 9. exd4 - White's development lead and (semi-)open lines compensate for being a pawn down.

yeah 6.-e5 is a good move, if Black plays too passively then White can end up with really dominating compensation

8.-e4 is interesting in that line too.

That's a bit too wild and offbeat to me

Regarding the 'Reti Slav' (that my opponents go for surprisingly often) 1. Nf3 d5 2. c4 c6 3. e3 Nf6 4. Nc3 with a somewhat delayed d4, Chessexplained has actually recently played blitz #1704 on the Black side of this line vs GM Jubilant.

The moves 4... a6 5. Qc2 g6 6. d4 Bg7 were all quite standard (though the seldom played immediate 6... Bf5 is the best scoring, namely, the most drawish), but then Jubilant played the rare 7. Be2 instead of the most common 7. Bd3, he seems to know his trade.

After 7... O-O 8. O-O Bg4!?, Jubilant's 9. h3 and the doubling recapture with the pawn (instead of doing this with the bishop as a gambit) seem to be the miss, 9. Qb3! (attacking d7 and defending c4) Ra7 10. h3 looks more precise.

CE's tilt in the last 1.5 minutes is priceless, deserves a Phil Hellmuth award

Speaking of, the back-to-back blitz #1705 also features a 1. Nf3 Slav (1... Nf6 2. d4 d5 3. c4 c6), with an earlier d4, but with (4.) Qc2 (actually the (near-)nuts) as well. After 4... dxc4 5. Qxc4 Bg4, Silvo's 6. Bg5!? Nbd7 7. Ne5!? with the intention to double pawns on the f-file is somewhat curious (6. Nbd2 is the most common, but the second most common 6. Nc3 looks better, gets a better grip on the centre), but CE shows that it poses no problems to Black while giving him a bishop pair. The best White can do there is exchange the knight for the LSB to get opposite colour bishops. The end is quite surprising too