This is a fantastic idea, except I would print some real code rather than a toy project. Unlike natural languages there's no way you'll be able to understand a piece of non-trivial code deeply without also being able to write it. And any developer reads many times more code than they write, if only because they have to re-read every time they want to modify anything.

Just make sure the code is linted and idiomatic unless you want the poor interviewee to be bogged down by a bunch of irrelevant details.