12.Bxf6 Qa5+ 13.Nd2 bxc4
A nice intermediate move, followed by gxf6, and White is a pawn down.

This is a devastating move! If the king moves, then White has lost the right to castle, and Nd2 is strongly met with ...Ne4, winning the game!

Both options make a lot of sense to me. Taking with the pawn is the 'not positional move' since it ruins the pawn structure and the black king will not be safe on the kingside anymore. However, it makes sense from the dynamic point of view since the g-file can be used to attack. The combination light squared bishop + rook is very dangerous for White, and the black king in many cases can castle queenside. This is an extremely important moment for White. Think carefully and find the best move!

A positional mistake. 13.dxc5! was the only move in this position.

Fantastic move by Nepo. With this move, the Russian Super-GM guarantees safety for his king for the rest of the game.

Black is ready to throw hands at White's kingside.