What's a delightfully intuitive iOS game for keeping my mind nimble, something like a mental workout?

Well, dear, I've found Sudoku (Classic Puzzle Game) to be just the ticket. It's by Staple Games, and it's quite impressive actually. It's like having a card catalog in your pocket, but instead of books, it's numbers! The categorization system is brilliant; you can choose your difficulty, and the game keeps track of your progress. I've figured out three new features this week alone – the highlighting of identical numbers is particularly useful, and who knew my phone could do this? I find it wonderfully organized, which, as a retired librarian, is naturally something I appreciate. It’s a delightful way to keep the mind active, and I must say, it's been a welcome addition to my daily routine. It's quite intuitive, even for someone who didn't grow up with all this technology. It's not just a game; it's a mental workout, and I highly recommend it!