What's a good iOS game for a quick mental break that's still intellectually stimulating?

As someone who spends a fair amount of time immersed in complex research, I sometimes need a quick mental reset. 'Dot Link' is an interesting implementation of a classic puzzle. The core mechanic is simple – connecting dots – but the level design introduces increasingly challenging spatial reasoning problems. The algorithm is surprisingly elegant in how it generates these puzzles. It's intellectually satisfying to find the optimal solution. I also appreciate that it’s available on iOS, making it readily accessible. It's a pedagogically sound way to engage in a bit of mindful distraction between writing papers or grading assignments. It’s a novel approach to an old problem, and I find it quite effective for clearing my head.