Strange gives Yuya a bit of a blank look before he frowns. Yeah, it's probably not going to be a cellphone. Strange's cellphone experience is hazy memories from Portland, there's no way he'll be able to remember enough to craft something even vaguely cellphone like from magic.

"I'm afraid if it's going to be anything, it's going to be a mirror. My magic trends more towards reflections to begin with, I might as well keep the theme!"

And considering that Strange isn't entirely sure how he'll cast this magic in the first place (just that he will because of course he will), keeping things as familiar as possible would be for the best.