I think they're expecting a daily problem set like Advent of Code. This is not a set of problems to solve, it's a series with one release per day in December, similar to an Advent calendar.
If I were to write such a text, it would have a lot more about building intuition for advanced mathematical concepts. This intuition is extremely valuable, but missing from almost all advanced-level texts. On the other hand, it’s very difficult to put into words, and probably quite personal.
I submitted it, and the word “basic” is mine, because the author doesn’t really go deep into what I would consider “advanced” mathematics. It can be a good prerequisite for advanced things, though.
As elsewhere in the thread, I'd advocate for "basic higher mathematics" or "introductory higher mathematics" (which would make clear that it's for people actively studying math as a subject and not as a standard part of primary or secondary education, or a prerequisite in an engineering major or something).
The author says that this is largely aimed at high school students who are doing self-study, which is a realistic audience but not a context where a lot of people would naturally apply the word "basic". But this material is basic for mathematicians, I guess (although even a lot of mathematicians may not have quite as broad a knowledge of mathematics as the author does!).
If you have a third-party dependency that survived for 20 years. But what if you are trying to choose what to rely on today, and to decide if it will even exist in 20 years? Certainly none of the fashionable JavaScript frameworks will.
