I wanted to talk about a concept I’ve recently hit upon that I’m calling a mechanic’s “shape”. To do that I have to introduce a few prerequisite concepts, but first, a caveat. I don’t believe in a grand unified theory of game design. Instead, I take a view that’s closer described as “there are many facets to truth.” So, when I say that I need to define what I mean by mechanic in the first place, I’m not claiming to have a perfect, complete, or final definition of the term. I can only bring up the parts that are currently on my mind here.
To me, a game mechanic is a rule, strategy, behavior, or convention that governs some sort of activity or sub-activity in a game. It has a domain that it applies to—where it fits in the entire system of mechanics. A simple mechanic might be “when you hit someone with a weapon, you roll that weapon’s damage dice and inflict that many hit points of damage.” The mechanic tells you what its domain is or the activity that it applies to—in this case, hitting someone with a weapon. It also tells you what to do when that thing happens—roll damage and reduce hit points.