This is just waiting to receive a cease and desist from publishers.

Fair concern. Book2Course doesn’t redistribute textbooks or make them public — users upload material they already have access to, and the output is for private study, similar to notes or summaries. That said, I’m being careful about this and staying within fair use boundaries.

It's literally just puzzles which have to be solved through code. Solving puzzles is a very normal thing to do for many people

Never got that, I have plenty of "puzzles" to solve in work and life which have real outcomes. I guess Im too utilitarian to enjoy puzzles with ROI.