Zachtronics
A satisfying puzzle-programming-optimization game, so good that “zachlike” has become a genre. Highly recommended, but maybe superseded by Opus Magnum.
Back in 2011 I wrote:
Woo! This is my kind of game! Chemistry-themed puzzle solving via visual programming! The opportunities to feel clever are endless here. Optimization has never been so fun! The game also gets fiendishly hard (I haven’t finished it yet). My only complaint is that the boss levels seem to encourage inelegant solutions.