I entered some weird mode: background went black, and can't select anything

I was copying and pasting with Ctrl-C and Ctrl-F (on a PC keyboard) and my view changed. The dark grey off away from the artboards turned black, my grid shut itself off, and I can't select any of the objects in my work anymore.

I've tried looking for solutions and played with a lot of the settings in the View tab, but nothing is reversing whatever I did. It's now affecting everything I open, so it's something I've done to Illustrator, not to that file.

Any ideas, folks? Thanks