Opus Magnum. It's an optimization puzzle game. You have to assemble mechanical arms and other bits (that grab, swing, rotate, push, and pull) into contraptions that assemble resources that look like molecular diagrams. Optimization puzzles aren't unique but I felt like the pieces you build the contraptions out of in this game are pretty unique, the game is on a hex grid so rotation can play a big roll. Another interesting thing the game does is that to beat a level you simply have to accomplish a proper assembly, which in itself isn't that hard, but the game grades you on three different metrics (speed, size, cost) and gives you no overall score to tell you how much you should value each metric. In this way it is up to your preferences what you want to optimize for if anything. I had fun trying to minmax every stat separately on every level before building my "compromise" machine was not supposed to make big sacrifices in any field.

A lot of people have mentioned it but I definitely recommend Obra Dinn, haven't played a mystery game as unique and enthralling.