My mobile game interests are all over the map. Right now I'm playing two games that are each fun and addictive in their own way:
1) Mystery Mania (you play an adorable [third-person] little robot that goes from room to room in a mansion uncovering a mystery - a little like Samarost, in that you have to do things in a certain sequence to advance from one room to the next; easier than Samarost but not too easy)
2) Algerian Patience Solitaire - 'cause sometimes a card game hits the spot! For a card game, it's challenging. I think you can find free online versions if you're interested in learning how to play.
I got both of these from the App store on my iPhone.
Recently, I've also played Crostix, which I liked, but it was a little glitchy.