Ryu Lopez / Spanish Opening, Berlin Wall defense.

? Passive, as it blocks the d-pawn and thus the queen's bishop. Opening theory suggests Nxe4 or Bc5.

The queen's bishop could've had a nice diagonal through b7, so I took a step to prevent that.

A weak move, only blocking Bg4. Bg5, b3, Nc3 or Re1 would've been natural moves here.

ok, but limits the mobility of the king's bishop. With the d-pawn missing it will take a bit of work to get past the pawn at e4, such as Nd7 and then f5. How aobut O-O or Bb7 ?

The idea was to go for the pawn at e5 by doing b3, Bb2, and Nc4. It's easy enough to block, though, with O-O, Re8, and Nd7.

?! Prevents Nc4, but the queen's side pawns become more difficult to defend.

Preparing to fight for the c4 square, and bringing the bishop to play.

? Loses two pawns for one after bxc4 bxc4 Nxc4, allows the white knight to enter play, isolates the c7 pawn and enables white to attack the e5 pawn.

? Loses another pawn.