Gilmoy: 12.Ba3 looked odd. More amazing is that Sax apparently saw the looong-term plan of penetrating White's weak Q-side dark squares -- hence he promptly invites White to swap off the DSBs. Maybe 13.Bb2! to seize the long diagonal instead.
15..Qd4! must be the "avenue" in the title. She looks like such a target, but White can't find any better than trading down. With this move, Black won the race to <get vertical> -- the genius was to see that she isn't getting trapped. Thereafter, every recapture only drags Black's recapturing piece forward, locking in Black's 1-tempo lead.
16..Kg7!! is a sublime coda -- it's thematic for luft in any fianchetto after you trade off the Bs. Here, it's key to Black's coherent offensive strategy -- it gives Black's K a huge lead in the race to cross midfield on c. Meanwhile, White's K is still bottled up by his own Bg2, which is why White never got forward to penetrate Black's symmetrically weak Q-side light squares.
<al wazir>: After 26..Rd2 28..Kd7, Black has a whopping advantage:
- Black's R is offensive and forking, i.e. it paralyzes two White things (N+K), and blockades d, leaving White's third unit (R) with no life on e.
- Black's K can freely stroll up weak c. White's K is trapped east of d (and paralyzed anyways).
White must trade off the Rs just to relieve that pressure, conceding about three more tempi to Black's K. After 35.Kd1 White's K has managed to lose the field-position duel by <six vertical tempi> -- and White <preferred> this position because it sucks less than Black's Rd2.
Inevitably, Black doubles on the c-pawn and wins it. Six tempi will do that.