Puzzle games like this, with a very clearly-defined but powerful ruleset where most of the challenge is navigating the massive possibility space, have to strike a difficult balance. If it's too easy, the game feels empty. If it's too hard, even if you can solve the puzzles you can't really understand why.

Tandis strikes this balance well. There are a few challenges where I had to use the hint functionality, but for most of them I was able to really dig in and understand why a particular sequence of transformations produced the output in question. It felt like playing with geometry, which is a great place for a game like this to land.