Thanks a lot for playing and for the feedback!
All the recipes are possible to get but for more complicated ones like metal you need to build the inputs in parallel, not one after another, because both inputs take 3-4 mutations to get to while most elements only survive up to 3 centuries. You're right that it might be frustrating if you don't know the recipe though. A timer is a good idea! Also, could be decaying sprites to illustrate the decay stage.
Thank you very much for the kind words!