When I was "seriously" using C++ I created myself a bunch of flashcards (using the Quizlet app) to regularly test myself (spaced repetition) on various C++ idio

When I was "seriously" using C++ I created myself a bunch of flashcards (using the Quizlet app) to regularly test myself (spaced repetition) on various C++ idioms and rules; such as when to implement which copy/assignment/move constructors and the correct patterns, how to use std::forward correctly, the footguns in various types of casting or initialization, etc. I recently had cause to start using C++ again and went over the cards after about a year break. It was depressing how few I could answer correctly. C++ is great if you're great with it, but that takes a __lot__ of effort, and it can be a minefield otherwise.