fxe4 loses to Bg4+. The tempting Bd4?! is met by e5! and if Bxc3 then Nxc3+ wins the queen back and white has no compensation for the lost pawns. After Qd4 Qxd4 Bxd4 Nf6 Rhe1, white’s two bishops provide a surprising amount of compensation. This was a tough one!
After Bxg5! Bxa8 can be met by Qb8! forking the bishops on a8 and b2 and winning two pieces for a rook.
White is absolutely lost after Qc4! He cannot castle, and Nb4-d3+ is coming (a3 doesn’t help due to the pin on the a-file).
Rxa4?? Qe8!, as played in Renet-Nunn European Championship 1989, drops a piece. Qxa6? Rh6 sets up a nasty discovery along the 6th rank with tempo, and gives black the initiative. h4?! while not losing, is a premature weakening of white’s queenside. Instead, Qg2! puts pressure on the d5 pawn (more relevant than either of the a-pawns) which can’t really be defended. White stands better and black would have needed to play precisely to hold the balance.
