Goodbye Zachtronics
I've found it difficult after starting to work full-time to fully enjoy Zachtronics games, since they use much of the same parts of my brain as my day job, but the sheer joy I got out of Zach's earlier games (SpaceChem, KOHCTPYKTOP, Codex of Alchemical Engineering) contributed a lot to my decision to work in software. I've experienced little else that scratches the "design itch" in such a pure and thoughtful way, whether games from other developers or actual software development.