I finally finished SpaceChem today. The last 2 boss battles where kind of anti-climactic I thought. Especially the last one, where it all boiled down to "how fast can you fuse Xenon to fire the laser". Still an amazing game, very satisfying to solve all of the puzzles.
Some of my solutions could be heavily optimized, but they work. Overal Spacechem was the best $5 I've spent on a game in a long time.