I can't help myself: every time I talk about design, now, I fall into explaining the way I see MDA so that we can be on the same page, using the same terms. To be honest, I only even reference the first two pages, where they define these three terms:
- "Mechanics describes the particular components of the game, at the level of data representation and algorithms."
In a video game, this covers not just the code but also all the assets. In a board game, this category includes the rules as well as the physical pieces. To me, this is a clear and distinct category -- no more mushy fuzzy "is this a mechanic" "what is a mechanic" etc.
TBH I think that to call any individual thing a "mechanic" is sort of misleading and confusing, because is an entire movement system a "mechanic", or is the jump button a "mechanic"? They nest within each other and flex and flow. If I say something is a "mechanic", it's just a convenient label describing any thing or group of things which are part of the game's mechanics.
- "Dynamics describes the run-time behavior of the mechanics acting on player inputs and each others' outputs over time."
Later the PDF (linked at top) more explicitly includes player actions and tactics in this element. This is the game as it's played: the events that occur, the choices its players make, the resultant situations that arise.
I like to think of this as my favourite category, the one I want to pay the most attention to; it's what first defined games as distinct from other formats. It's not that reading a book has no dynamics: turning a page is a dynamic. But innovating on dynamics are part of the mainstream artform of games, and I think that's fascinating.
- "Aesthetics describes the desirable emotional responses evoked in the player, when she interacts with the game system."
Replace the word fun completely, because fun is highly variable between individuals. Rather than ask "is the game fun?" or "why isn't this fun?", consider instead what emotional response you're hoping for. Instead start to ask "why doesn't playing this feel good?" or "why doesn't playing this feel RIGHT?"
I stumbled upon MDA when I was trying to figure out a definition of "game mechanic" which I agreed with. This was the best one because it didn't present a singular definition in a vacuum, but in the context of this little framework. I like this definition because it tells me what a game mechanic isn't.
Hopefully you find this useful too.