I quite like this idea! Though I wasn't sure what some of the elements I made were. But I can see there's real logic to it, when I made a sapling, my first thought was water, I got a tree, then my first thought was fire, and I got charcoal or something. It'd be handy to have a tool tip when I hover over something, so I know what it is. I think swapping the left/right mouse button functionality would make more sense too, and lead to less issues with wasting a whole stack!