[merryocha]

When I was a kid I used flashcards to memorize the multiplication tables up to 12 and it allowed me to do very rapid mental math from that point on, and I still can to this day. It was useful for math quizzes and tests in school but it's also useful for life in general. Going up to 16 might be even better.

I use the Livio English Dictionary to look up words when I read on my tablet and I noticed one day that it keeps a search history, and I got an idea to make an Anki flashcard collection consisting of all the words I've needed to look up while reading. Despite being an obsessive reader my entire life I still regularly encounter words I'm not 100% certain about. Reading itself has spaced repetition built right in, assuming you quiz yourself and then follow up with a dictionary.