Equal Material is Not Equality

This fun game emerged out of a rare 4. f3 Nimzo-Indian Defense. It illustrates how material equality does not mean positional equality. On move 21, the material is equal but the game is already decided. 

A quick word on the origins of this game. Sometimes for practice I play centaur-style (using computer analysis but making my own decisions) against a weakened (usually 1400-1600 ELO) computer. I try to understand the position and then guess the next move or combination, checking my computer analysis to see if I was right. If I'm way off, I explore why my ideas failed. Even if I'm right, I try to articulate why my plan makes sense.

Here is the game with annotations and some variations: