I was in the middle of typing a long email message, and I must have inadvertently hit some key, because the screen turned black with white letters! I wanted to switch it back to normal, but I couldn't figure out how to do it. I asked chat about it, and I got an AI response that said to go to Settings and then Appearance, and then to switch from Dark Mode to Light Mode, but I didn't see anything that mentioned anything about Dark Mode or Light Mode!