Thanks for the positive comments!
To be fair, a lot of the general ideas about trainings and providing clues, I kind of took directly from the Gumshoe system. But FIST inspired me to try and streamline it way beyond the mechanics that Gumshoe uses.
But you're probably right that ENIGMA could easily be tacked on to other game systems as well. It does lack fight mechanics, if combat was something one wanted in an investigation game.
The rest of the supplement is basically my attempt to wrap my brain around what qualities of a clue are useful to think about in game terms, and how clues can be organized in some way that's helpful to running a game. Probably thr organization at least owes some relation to my previous experience with D&D-adjascent "point crawl" mapping, and trying to outline process flow disgrams at work.