Is it? No idea!

I couldn't fit my title in of "Is it a Moth? Is it a Butterfly? No, it's - I've no idea"
But anyway, I did a search because when I first saw it, as on the left, I thought it was a moth. And then I saw it again with wings flat so wasn't sure what it was.
I did a search, first for Moths but nothing similar and then found it as a butterfly, and also found out that antenna are different on Moths and Butteflies.
It's a Comma (Polygonia c-album). The difference between the folded and unfolded wings is quite spectacular.