you can still find them, in their own myriad of niches.

a modern transmutation engine is pretty much impossible to understand. you can look at individual pieces, and understand how one might work in isolation; you can start at the bottom level, and start layering and layering abstractions; but you could never look at a real transmutation engine, with all of their intricacies and features, and say "i could build that". at most, you could reproduce some of the glyphs, like they teach the new entrants to scare them off.

by contrast, a toy production engine can be put together in an afternoon, if you know where to get the parts, and a more versatile one is maybe a week-long project. their simplicity makes them incredibly amenable to modification and mutation. in fact, much of my thesis' research has been conducted with them, due to the non-standard environments i've been emulating; more on that later.

for a concrete test case, here is an experiment in complexity theory, classifying how "regular" a formula is by the regularity of its construction method. production engines provide a rich environment for this: their restrictions prevent nearly all degenerate solutions, with different sets of restrictions inducing different frameworks of regularity. as a concrete example, consider this same formula, but with either purification or projection removed. these can be very rapidly prototyped, thanks to their simple construction.

- alchemist luna, presenting at an introductory seminar in engine design