What to write for a junior portfolio in C++?

Question

C++ / C#

Actually, the question is in the title. The direction is not important yet, I want to do everything and a lot, but there are no ideas. I'm waiting for ideas for programs, libraries, utilities, etc., of adequate complexity, of course

Answer 1

brainfuck compiler.

Answer 2

Isn't it better to show achievements - participated in olympiads, hackathons, etc., show a profile on github with your programs.