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.

White has almost completed development and has a good knight on e5, but the b-file cannot be occupied. How to continue?

With this move, White fixes the pawn on c6, which is attacked by the powerful knight on e5. Black can barely move here!

3...Nf6 4.h4 and White enjoys a fantastic space advantage!

The difference between bishops is significant. Once we have played e4, the b-file is accessible for our rooks, and the c4-pawn is very weak. Black can only await a slow death. It's very important to note that the bishop on d6 is controlling the b8-square so Black cannot fight for the open file!