White is to play d5, then e5... the big black diagonal has to be exploited.

Don't agree; the g4 bishop is holding up black's pawn storm. Why move it to a better square?

... No comment

With the point that the bishop on b2 is now covering e5, just to clarify.

And get his other knight to d4 where (after dxe5,Bxe5) and then to f5 maybe?

I wonder what would happen now, were White to play 16.Nb5. Check it out: 16.Nb5!? Bc5ch! 17.Kh1 Qe7 18.a3 Be3 19.Bc1 Bb6 20.b4 a6 21.c5 Bxc5 22.bxc5 axb5 23.Qxb5 c6 24.dxc6 Nxe4! 25.Rab1 Nxc5 26.Bb2 ... a battle royal. True, this is no forcing line, and either side might well find ways to improve. For one thing, 16.Na4 might at once offer better prospects for White.

Black has the posibility of launching a strong attack with g4, opeing lines to whites king. For white it is harder to do the same on the other side of the board. So black has an advantage here.

White is behind by a pawn. he does not have a major space disadvantage, and he has the beginnings of a pawn storm brewing on the QS. While black may have a slight advantage white is nowhere near as badly placed as you make it seem.

I think white has to go for this. There's nothing for him on the kingside and the centre is fairly locked up. Where else can he play?

I agree with the other two kibitzers. White has a slight space advantage on the Queen's flank. He might as well see what he can make of it. See my previous comment to find at least some possibilities for White in attack.

True, but black might block this advance with a5, controlling the black squares. However 16.a3 seems a little slow.

Good move!

White might have tried a Knight sac, here, by 18.Bxe5! axb5(?) 19.axb5 Bc5ch 20.Kh1 ... and now: 20...b6? 21.Ra8ch Kb7 22.Ra7ch! Kxa7? 23.Qa2ch Kb7 24.Qh6ch Kb8 25.Ra1 and wins. Again, Black can certainly improve, but the attack white gets after 18.Bxe5 is very promising.

Hear, hear! Ionadowman is correct. In situation like this you can sometimes sacrifice a piece, if you get the open a line (or h-line if its on g5)

...but it doesn't really accomplish anything.

I don't know; with those two rooks bearing down, h1 is a much worse square than g1 if black can blow open the pawn cover. The two rooks would then mate the king immediately.

The Bishop is well placed here, but Black needs to place a reliable guard over e5.

For the moment, Black has held up White's pawn majority on the Queen's side. But his own pawns remain mobile on the other wing. Black could fancy his chances, here.

Qe7 feels stonger to me, with the intend of playing Qh4 somewhere in the future. On d6 the Queen is a little trapped behind its own pawn, although it may go to g6 or h6 perhaps.

'Reculer pour mieux advancer'. maybe?

That's hardly a retreat. a3 was not a good square for the knight. Besides White wants to avoid exchanges.

Good move, but I might have played a5 as a preparation first.