I spent some years only learning C++ from online websites and YouTube videos. I went over basic stuff like variables, functions, pointers, references, and so on, as well as OOP concepts like classes, operator overloading, inheritance, virtual functions, and so on, and I did some template exercises. But every time I move on to the next topic, I find myself forgetting what I learned before. Then I noticed that I needed to make software that covered all those C++ concepts (I know some programmers may have gone through this and decided to do what I'm going to do now).
I'd like to know if there is such a thing as minimal software designed to cover most of the C++ concepts that work together, and it must be small software; (not writing an operating system). I know this question sounds strange, but I'm going to give it a try and just want to gain some time if someone has done this before. Thank you all; I may be lucky if someone there designed such a thing.