the real world skill tree / directed acyclic graph
When I was twelve, it was suggested to me that instead of working ahead in normal math, I could go sideways and try to learn enough other math to understand the proof for Fermat's Last Theorem.
I still have yet to even read the proof. Maybe I could understand it now, maybe not.
A significant amount of the reason for this - as far as I can tell - is that I never had path. What other math do you need to understand to understand that proof? What math do you need to understand to learn that math in the first place?
As a friend observed recently, "it shouldn't be on the twelve year old to figure that out".
Some of this data is out there in the form of high school and college course prerequisites, but such data is not fine grained enough and too entangled with their paths to degrees.
The data is in skill.yml. Eventually I'll write up a visualization and personal checklist app...
This is free and unencumbered software released into the public domain.