Imbroglio (https://apps.apple.com/us/app/imbroglio/id969264934) is one of my favorite minimal purchase iOS games. I haven’t played it in awhile, but it’s a unique dungeon puzzle game where you place attacks as floor tiles on the board ahead of playing. There’s some consistent rules with ramping challenge, which made it super replayable for me. I loved trying different floor designs, finding strategies, and there’s a small progression system that’s fun. Hasn’t been updated in a few years, but it was a great design despite the rough appearance.