Last month I wrote about Neal Agarwal’s web game Infinite Craft. Tom Fang wrote to tell me he’s created a dictionary of Infinite Craft elements, along with their uses and recipes. This got me thinking about the game’s mathematical structure. By “mathematical structure,” I mean something like how we make recipes and the metrics by which we might compare one recipe to another. For example, if our goal is to make Sandwich, we could do it like this: Wave = Water + Wind Steam = Fire + Water Plant = E...