Not just a story, it’s a graphic novel

Brilliant has a bunch of math courses, up into calculus and other high-level math. It also has some gamification with points and daily streaks for completing lessons

Minute Cryptic has a daily cryptic crossword clue which is pretty fun. And they post video explanations for each solution, which is helpful for learning how cryptic crosswords work

I recently discovered Ben Eater, his videos about how computer hardware works are really interesting