Thank you! Noticed you're interested in similar areas. I've also previously done some work on maths problem generation. Similar to letterpaths, the core lib can then be used to power games/other educational apps. As I'm sure you've found as well, It's surprisingly difficult to generate random maths problems aligned to a curriculum! Core lib is UK-focussed: https://github.com/RobinL/maths-game-problem-generator

And examples of games is can power:

https://rupertlinacre.com/maths_vs_monsters/

https://rupertlinacre.com/breakout_maths/

https://rupertlinacre.com/maths_blaster/