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
Thanks for taking the time to look. My biggest focus right now is own Numerikos. I hope I can make a better math learning platform. Math games are fun too. There are some nice ideas in the examples you have shared here.
And examples of games is can power:
https://rupertlinacre.com/maths_vs_monsters/
https://rupertlinacre.com/breakout_maths/
https://rupertlinacre.com/maths_blaster/