Followed opening principles, still lost, unsure what I did wrong.

I would probably follow Nxf7 with f4, trying to open up the file. In my opinion, I think one of White's central ideas in this position is to blast open the f-file.

My experience of the analysis engine on cheese.com is that it's appalling. It rewards development too highly, for starters. It changes its m,ind from one second to the next .... I think it evaluates fantasy lines as +12 imo.

10. f4 is correct, after which white doesn't need to speculate. I can't even see a reason for 10. b4 and yet up to that point white had played ok. Not perfect but not badly.

I think most engines are like that as they lack the long-term planning us humans have always had.

From now on, I will call the so-called Najdorf, the retarded hippo defense

Previous posters have made some very good points. I think the thing to remember at this point is that chess is an amazingly complex game; GMs have devoted lifetimes to its study. You have been playing for about 6 months, or so? For a beginner, your development in this game wasn't too bad.

I'm sure you have at least one book on openings from the nature of your post. It is very likely the book mentions a certain need for flexibility and that is something several others have noted.

When your opponent starts to make moves you may not have expected, this is when you should question why the move was made. What can it lead to? Or is it just a poor move? At this stage, any deviation may seem like a sophisticated move you're unprepared for (like h6). This is also when you may want to consider what you will do to counter it. This is where the flexibility arises.

Again, for anyone who has been playing for 6 months, even a year, this is much easier said than done! Just stick with it. Do some more reading, and analyze your games. Learn from your mistakes. And at this point there is still a lot of learning to do (and many more mistakes to be made).

Also, as at least one other person has noted, you probably should not have resigned so quickly. Give your opponent enough time and he, too, may blunder. I once played a game where my opponent blundered his Queen. He kept playing. Wow, I thought, I have this game in the bag and about two moves later, I blundered my Queen!!! Lucky for me the position was such that I was able to eventually promote another Queen and won. The moral is, at lower levels blunders will happen, by everyone. Give your opponent time enough to make a few. Good luck.

The point of 12.Nxf7 is that White's Ne5 is lost! 11.Qd3 accidentally took away the knight's only retreat square, so White is going to lose it. Under these circumstances, 12.Nxf7 is obviously the best move. because it opens up the black king and gives White attacking chances (and a pawn!) It really doesn't matter what the precise evaluation of the position is, 12.Nxf7 is clearly White's best move in the actual position

"... Hippos hold the murder high score in Africa. …" - CGP Grey

I suspect that FforEffort was trying to do a counter at this point.

I don't know... I still find them useful.

When I'm unsure what to do in the opening I try to develop another piece, keep control of the center, etc.

Sure, and I've lost to worse openings, but I still don't think it has a name, and it is like a silly version of the hippo.

"Opening principles works for beginners with rating <1000 only. "

Pretty much 100% wrong. Opening principles "work" for every player from 600-2880. Stronger players have a far better grasp of when exceptions apply and how to decide when two principles conflict with each other. And they are much, much better at concrete calculations. But the get their pieces out, make their kings safe, and fight for the center

Except when they play with Hypermodern ideas.

d6 is the best move since black can defend from the sacrifice well if he plays precisely.

11.f4, 11.f3, 11.Qd2 are all quite a bit better than 11.Qd3. 

Hypermodern opening are based on opening principles. When the opening principles are misunderstood as certain moves, which seems to be the case with the OP, then hypermodern ideas seem to violate them. When you understand opening principles as principles, rather than moves, you see that hypermodern openings aim at rapid mobilization, center control, piece coordination, flexibility, etc. They simply go about it a different way.

In the game, h6 wastes time and creates a vulnerability that White can exploit. Go back through this thread and read what the titled players have written. You'll see that.

Quite similar game from me , opponent doing king side attack.

My tips, " break the centre, when they do king side attack"

The opening principles are merely general, abstract guidelines to follow when we can't find a general or concrete plan (where to place the pieces and pawns to achieve something). It's also useful to be aware that opening principles can be more or less precise when there's little activity on the board, and quite imprecise when the contrary.

On your game: 2...h6 is a weak move, not of the kind that gets immediate punishment but of those which force to walk a narrow line thereafter. How? It doesn't oppose to the rival's conquer of space, wasting a tempo.

4.Nc3 is not bad, but as Black hasn't defined yet which pawn structure and piece disposition will he use, it's generally better to keep flexibility on the plans at disposal, such as conquer space on the Q–side (c2–c4, b2–b4, a2–a4) preparing an advantageous break, a faster punishment by breaking on the center (c2–c4, d4–d5 or e4–e5), or solidifying the center (c2–c3) as to open the game on, probably, the K–side.

5.Bc4 is an example of how general principles can misguide. Following them, there's no real difference between e2, d3 or c4 for the Bishop. Here, as Black is saying that he won't fight for space on the center but on the flanks (2...h6 and 4...a6), there was no need for 5.Bc4 when Black wins a tempo with b7–b5 or d7–d5. Much better was 5.Bd3, leaving c4 free for Nc3–e2 and c2–c4, or maybe to push the f–pawn and target on g6.

6.a4 g5. See, Black is that behind on development, that White shouldn't worry about flank pawn pushes as b7–b5 or g6–g5. Why? Because the more they advance the easier it will be –for White– to get pawn exchanges and open the roads which are now closed by the pawn structures on both sides. When opening roads, the one with more pieces on the area gets better chances; if not more pieces at the moment, then the one who can build up a superiority faster (fewer tempos) as to create piece activity using those roads... and this is where controlling more space, and tempos, get into play (both concepts that you missed on your post). So, a2–a4 wasn't really necessary, and g6–g5 lacks positional understanding.

7.Be3. General principles again. White has the advantage only if he uses the opportunity. And here goes with 6.0-0 intending f2–f4, the reason being Bxf4 in one move, assuming g5xf4, rather than Bc1–e3–xf4. For this White should prepare f2–f4 with Nc3–e2 and c2–c3, and decide which square for the Nf3 (probably e5). Now you may ask why f2–f4? Simple: As Black doesn't have static weaknesses or hanging pieces, it's all about the coordination of several pieces against appropriate targets, such as those difficult to defend (lack of defenders, lack of squares or roads to set up defenders, or high value target)... and here f7 jumps raising the hand, as the Black King will likely allow several tempo–free moves to the attacker. It's not difficult to foresee the battery Bc4–f7, Rf1–f7, Ne5–f7 and Qh5–f7, and the battery itself clarifies the concept of roads allowed or denied by pawn structures when White's f–pawn is denying (for the moment) key roads for four White pieces coordinating to achieve a strong activity.

The next moves had little to do with the logical course of the game when Black wasn't even aware of the crushing attack White could develop within a few moves, and White wasn't aware either... And I write this because we see Black weakening e6 by transferring the Bishop to b7 and later by d7–d6. At any rate, it would have been nice to see 12.Nxf7! followed by f2–f4, if only to demonstrate a concrete understanding of piece activity, material, space, time and pawn structures.