Lets discuss the aims of both players (their game plans).
When Bobby Fisher played Nc3 he was supporting his centre (developing his minor piece)
Wolfgang plays (the classical) B-b4 immediately putting pressure on E4.
Bobby (white) understands the COUNTERBALANCE EFFECT whereby, if the black bishop ever captures on C3, White will have a Powerful Black Squared Bishop and more pieces on the Kingside to mount a potential attack-generally speaking-of course!
E5 was only move for white as black was better after EXD5
Ne7 is played to get rapid development. Black is not preparing to Castle KIngside-He would be under enormous attack if he did.
Reason is ALL the Black pieces are on the Black Queenside!!
Bobby plays A3 because he wants to SET the terms of engagement and try to dominate the Black Squares on the board.
Here we face Chess Dynamics
White has the two Bishops and wants an OPEN GAME where the Bishops would be devastating.
Black wants to seek a Closed Position favouring his Hippity Hoppity Horses!
C5 is the ONLY move consistent with Blacks game plan for 'Balanced Counterplay'.NC6 would leave place with a Constricted Position with a Backward C-Pawn.
A4 gives white the option of occupying the A3 F8 diagonal for his Bishop.
Black Develops with fluid co-ordinated piece play
Blacks Play is Flawless. Black knows he can castle Queenside if necessary where it is difficult for white to get to the Black King. Meanwhile Black has possibility to attack the Centre with F6.
Black knows full well the position cannot be opened up at a time favouring the white bishop pair.Alas be mindful of these dynamics, because yes,even at this stage,both players consider how an endgame might play out.
Qd2 gives whit the possibility of Q-F4 or Q-G5
Qa5 Retort completes Blacks development in the classic style.He also clears his back rank and has a cxd option.
Black does not want an OPEN POSITION-he knows bobby's stealth and bishop endgame technique.HE declines any queen exchange CONFIDENT his King is safe.
F6 is logical and correct! Both players Kings are ALREADY on their Safest square with the option of running away from threats by castling either side.Classical forces are at play.
Bobby is Happy for the game to 'OPEN UP" favouring his two bishops
Black declines to open up lines of attack and pawn grab. The Black King is now secure, ready to throw the Kitchen sink at the white king.
Nh4 shows how 'Finely Balanced' the position is.
It looks tremendous for white-the white bishops ever so more effective.Can Black shut them down and How?
White has succeeded in ACTIVATING his Queens Bishop.
Black has an open HFile -Black rooks are slightly more active as a result.
PERFECT TIMING!! Q-F4 is PREVENTED!!
The 'KEY MOVE' without which Blacks position would be untenable.
CORRECT! not fxg Ne4 Q-F4 when E5
opens up ALL LINES on Whites King
Leaves C3 pawn loose and ACTIVATES the Black Position.
G4 is Truly a GrandMaster type sacrifice. Black wants to BURY the Bishop on H2 so its as effective as a pawn.And he will sacrifice a pawn to achieve his STRATEGIC OBJECTIVE!
Black wants to eliminate the threat of Fxg4.
He ENVISIONS a Stone wall type setup with his pawn on F6 on F4 and his Knight on E4 with Bishops of opposite colors..
Black now improves the position of his Bishop on D7 which frankly looked like a pawn .It had good defensive strengths, yet Black sees if he can eliminate the Bishop on F3 for his bishop the Knight can enter E4 with the Power of TEN!! Utter Dominance although a pawn down..Also a MATING NET forming.
Perhaps if Black had played B-H4 White 'MAY HAVE played K-F2 and if BxF3 GXF
Deadly Entry. Often in CLOSED POSITIONS with LOOSE PAWN STRUCTURE The Queen is Far more effective than Discombobulated castles.
Passed Pawns must be pushed is an old saying
This frankly looks like time scramble but I'm not so sure.