You cannot not copyright an idea, but you can copyright the implementation of an idea.
I mean, if you can just copyright an idea, then the best way to get rich is to just become a science fiction writer, copyright all the ideas you come up with, and wait for people to invent it.

You cannot copyright the idea of "a guy meets a girl and they fall in love", but you can write a love song and copyright it. You cannot copyright the idea of "an app that makes fart noises", but you can (but please don't) make an app like that and then copyright it.