Opus Magnum
This is a work of art. The balletic movement of the steampunk mechanisms producing the elemental molecules is hypnotic. I absolutely love it. Like the other Zachtronics games, I'm no master and don't care to be. The completion of the puzzle is reward enough, I don't require perfection and rarely strive very hard to achieve that lower score, trimming cycles and parts until it is the picture of elegance. I find the pictures pretty elegant already and that's good enough for me.
As on other pages, I've arranged by visual complexity rather than game order, though they kind of go hand-in-hand.