Elevens is a single-player card game where the key mechanic is adding card face values that sum up to 11. The basic layout is nine cards arranged in a 3x3 grid, with the next available playable card being stacked on top. The nature of the game means that individual stacks in this grid tend to loop in on themselves (9-2 repeating, for example), which is avoided somewhat cleanly by the rule that the face cards (K, Q, J, but not A, since you need that to add to 10) can be placed anywhere and must be covered immediately with the next available card. Or, that's how I learned to play it. the most popular version of the game I could find online works almost in the opposite direction, with cards being removed and replaced rather than being covered up.
I like this 9-grid, though, because it allows me to do something else with the card numbers. After every game, I add up the values of the topmost cards in each row, column and diagonal.
you'll notice I have no clear reason for doing this. I'm not sure why I do either, But it probably has some form of useful application. If not for the amount of deliberate motion involved, I guess it could be used for divination of some kind. That was what I had in mind the first time I did it, but with no real way to categorize the numbers it's basically just a sequence of symbols. I don't know, I'll come up with something later.