A silly game

Recently, thanks to mobbsy, I have been playing quite a lot of SpaceChem.

I suppose it's most like Peeko Computer on the BBC Micro, except that the machine model is multi-threaded (yay!) and lacks jump instructions (less yay); you're given a set of primitives with slightly awkward behaviour and a task to perform, and you have to write the best program to do the job. It seems that I can usually write programs that work, but they are much bigger and slower than the optimal ones whose existence is suggested at the end of the level; and the game doesn't tend to give you advice on style and efficiency.

See: large, slow acetylene and ammonia factories





I know that a lot of my friends play this; how does one build smaller, faster factories?